Vented vs. Ventless Attics - Cost vs Performance - surprising results

[@franklong6269]

1. IBC code requires vented attics with the exception of a licensed PE Mechanical Engineer designing a non-vented system. 2. In Arizona, nearly every home in the state has a vented attic. 3. In cold climates, vented attics prevent damage to the roof from ice dams and condensation buildup under the roof waterproof membrane. 4. Ductwork run through a vented attic does lose more energy than a conditioned attic; however, there are many ways to insulate ducts that are installed in the attic. As a licensed GC and a Civil Engineer, one of the methods I use is to have the main ducts installed close to the top of the bottom truss chord. Then, I blow in 14 - 20 inches of cellulose insulation to cover the ductwork. Also, most ducts in AZ are flex ducts. R-8 insulated flex duct is cheap, and you can add a higher insulation factor if you choose. This works extremely well and shields the attic ductwork from the AZ heat in the summer. No, it's not as "energy efficient" as Matt's house, but it costs a fraction (probably 1/8) of what Matt's house energy system costs. This system also doesn't require any maintenance. 5. Matt's sealed house HVAC system requires SEVERAL expensive filters to be replaced every year. Several of them have to be replaced every three months. That would drive me crazy and it probably costs at least a thousand dollars or more a year just for filters. 6. Not only does Matt's HVAC system require an exorbitant amount of maintenance, but the upfront costs are obscene. Matt probably spent $40,000 just on filter systems to circulate air in his house, and that doesn't include his heating/cooling systems and main ductwork. I am guessing that Matt spent somewhere around $80,000 for the engineering and installation of his sealed house HVAC system. Matt will never recover that upfront cost by energy savings of his system. 7. Matt is incorrect when he states that ductwork in the attic accumulates mold. That would depend on a lot of different factors. In AZ, nearly every home has ductwork in the attic. Obviously, if installing ductwork in the attic caused mold to form in the HVAC ductwork, major homebuilders would not be putting ductwork in the attic. In Texas, where Matt is, often some areas have high humidity. In those situations, then precautions have to be taken to prevent condensation from forming in the ductwork, WHETHER YOU HAVE A VENTED ATTIC OR A SEALED ATTIC - BOTH REQUIRE MOISTURE PROTECTION. While I don't deal with high humidity, but I have seen builders install whole-house dehumidifiers to prevent condensation and moisture buildup in the house. Having ducts in the attic doesn't magically [POOF!] cause moisture condensation in the ducts. If moisture condenses in the ducts, there probably are moisture and high humidity issues throughout the house, and they are not limited to the ductwork. 8. Sealed, airtight walls CAUSE mold growth in their interstitial space (inside the walls) if water somehow gets into the walls. Granted, with the advent of ZIP board systems, water penetration is not a problem, provided they are installed correctly. But what happens if you have a sloppy, lazy, sheathing contractor or a contractor who isn't trained well with sealed wall systems? It happens all the time. Then the chances of water getting into your walls and roof spaces explode exponentially, and if you have used closed-cell foam insulation in the walls and attic, you are screwed! If you design your roof and wall systems to be able to drain and vent any water that may get by the sheathing, then a poorly skilled contractor has less of an impact on your waterproofing system. Plus, building walls that vent at the exterior provides an additional layer of protection against water infiltration. 9. Not only is Matt's HVAC system incredibly expensive to purchase, it is also incredibly expensive to repair if it breaks down. Matt is using very high-end, cutting-edge tech, and using that tech to heat, cool, and filter the air in your home comes with a very high price. HVAC repair parts are not readily available; they are expensive, they have to be specially ordered, and not every HVAC contractor can work on complex, engineered HVAC systems. ALL of these factors point to sky-high repair costs for Matt's HVAC system when it fails, because every HVAC system fails over time. When I replaced my house's split system HVAC system (it's heated by gas and cooled by an AC unit), I chose a relatively simple two-stage Trane system. I could have purchased Trane's cutting-edge variable AC systems, but my HVAC contractor, who has worked with me on several projects, warned me that repairing them was very expensive. I checked into the efficiency difference between the luxury variable stage AC systems. Trane's specifications state that their variable speed AC units are only around 5% more efficient than their two-stage systems. Why? It's really pretty simple. My house requires a 5-ton AC unit, but I don't need that full cooling capacity most of the year. Trane's two-stage unit gears down to the equivalent of a 3-ton unit when the exterior temperatures don't require all of the cooling capacity of the 5-ton unit. Because my house is very well insulated, the AC runs at its lowest stage (the 3-Ton stage) almost all the time. Even in the hottest summers, my unit runs at the low-energy first stage most of the time. Only very rarely does it kick into the second-stage, 5-ton cooling mode. The point is, cutting-edge HVAC tech isn't always the best choice because not only does it cost a LOT more than established HVAC systems, it also can be incredibly expensive to repair. ANY licensed HVAC contractor can work on my two-stage Trane unit and repair it. They are relatively simple to diagnose and repair. The parts are reasonably priced, and most Trane vendors have them in stock. Variable speed units from Lennox, Trane, and other manufacturers require highly trained techs to diagnose and fix them, and they also require special tools. And all of that cutting-edge tech MIGHT save you 5% or so in actual cooling costs. It's just not worth the headaches. I don't really care if Matt promotes sealed, airtight homes; there's nothing wrong with the design of his home, provided everything is installed correctly and engineered. However, sealed homes do require an engineer to design them, and engineers cost money. The vast majority of home buyers cannot afford to spend $40,000 on air filtering systems and $1000.00 a year just on air filters. Most home buyers are struggling to get into a home. What frustrates me is that Matt seems to be grossly ignorant about alternate systems that have been thoroughly proven to work are very energy efficient, and cost a fraction of what his HVAC system and insulation systems cost. If Matt is going to present himself as an expert, he should first do his homework. The vast majority of people who are building a home would be better served to install a well-sealed home with a ZIP system with redundant drainage and venting in the walls and roof, and a vented attic with R-60 cellulose insulation. Insulate your walls to around R-30. Seal the penetrations into the roof and walls just as Matt's guest shows in this video. Install a Trane Clean Effects (or similar) air filtration system. You can wash your filters with a hose every three months on a Trane air filter system, and it will do a great job purifying and cleaning your interior air. Install a standard AC unit or heat pump that is energy-efficient, reliable, and easy to repair. On a larger home install a couple of super-efficient mini-split heat pumps at key areas of your home (they are very cheap and reliable). Then, use the huge amount of money you save for this established construction design and install a 10 KW solar system. Done correctly, you will have NO energy costs for your home, few maintenance issues, and you will be able to use as much energy as you want without always being concerned about how much your electric bill will be. If your standard heat pump breaks down, you will easily be able to find an HVAC contractor who can fix it, and the parts won't cost you an arm and a leg. Most of the time, your mini split heat pumps will be able to heat and cool the house, and you will hardly use your main central heat pump unit. That will greatly extend its life and save you even more money. In high-humidity areas, install a whole-house dehumidifier system to get the moisture out of the house. This is the smart way to build a cost-efficient home.

[@N-M424]

Can you provide the code reference for your point #1? You make a lot of great points. Matt's clients are very different than his YT audience. 99.9% of homes built in the US are NOT architecturally driven designs, they are economically driven designs. I agree that Matt seems to be very ignorant to a majority of products available in the market, instead he is only aware of those products that the sponsors want to showcase. Matt's house is a prime example of what you "could" do if money was no object. Spending the most money on materials and products does not equal the best house. So much can be accomplished by simply doing a better job with the materials already commonly used today and a little bit more tape and caulk, if builders cared. Builders only care when there is a financial motivation since they are trying to operate a for-profit business. If their clients don't care, why should they? You can tell a client that you build the best house in the world and it's got a 0.01 ACH50 and the air is so clean that we can assembly hard drives on the kitchen counter, blah blah blah. Do they care? Are they willing to spend the extra money? Most home buyers are just hoping to be able to buy a single home some day, they don't care about that. That is the real problem this nation faces. You make a great point about spending some of the money you save on solar. Once you can generate all the energy you need, who cares how energy efficient your house is? As with nearly all things, a balanced approach is best. Just because you can doesn't mean you should.

[@franklong6269]

@@N-M424 Here you go: 1202.2Roof ventilation. Roof assemblies shall be ventilated in accordance with this section or shall comply with Section 1202.3. Different climate zones require more or less venting. Here in AZ, every 300 SF of interstitial attic space requires 1 SF of venting. The code allows you to completely seal your building IF you have a Professional Engineer's design to do so. I have had some wealthy clients, and I guarantee you that THEY are not willing to spend extra money on HVAC systems most of the time. You have to get into the range of people who have hundreds of millions of dollars before you find a willingness to pay for the tech in Matt's house. What is even more amusing is that the rich people who do pay for highly engineered HVAC systems complain about the maintenance and repair problems they incur with them. It's not that they cost more to repair; they don't care about that. It's that they can't find HVAC contractors who know how to repair cutting-edge equipment, and they can't get parts for their equipment. As I mentioned in my first post, the average person today would be smart to build a more low-tech HVAC and insulation home and spend the difference on a solar system. I have designed and estimated a 10 KW solar system for my 1850 SF home and the cost for materials is approximately $20,000. With the AZ and federal rebates, the end cost of the system will be $13,000. Now, this is a Lexus system with a Sol-Ark 15K hybrid inverter that allows me to go off-grid if necessary. Most of the electrical for solar wiring is plug-in wiring, so they are not hard to install. Also, there is no sales tax on solar in AZ. The new hybrid inverters allow you to sell energy back to your electric utility, power your home directly from the panels during the day, connect several strings of different size panels, connect to an LP or gasoline backup generator, charge and monitor battery banks for nighttime power, automatic switching to battery backup if the grid goes down and more. And you can control and monitor all of the settings from your laptop. So, if you are reasonably handy and not afraid of some hard work, you can install solar for most homes for around $14, 400.00 which includes $2000.00 for a licensed electrician to connect to the grid and purchase permit plans. You made some great observations. Thanks for your comment.

[@franklong6269]

@@N-M424 One point to address your comment on American-built homes. The litigious nature of American society has literally forced American home builders to construct homes with amazing quality. Our system of construction has been copied by other nations because of its strength, its simplicity, its cost-effectiveness AND its energy efficiency. Today's mass-built tract homes generally have roofs that will last at least 30 years. They are structurally strong and often survive 200 MPH wind events (hurricanes). They don't require exorbitant amounts of maintenance. By code, they are required to be very energy efficient. They have very energy-efficient windows and doors. They have redundant water drainage systems in their walls (many builders use the ZIP system with wall standoffs under the sheathing (usually siding or stucco). This allows any water that gets by the exterior cladding to drain out the bottom of the wall through a metal "weepscreed" that keeps bugs, mice and pests out of the wall. The homes generally come with HVAC systems that will last at least 10 years (AZ is hard on heat pumps and AC units). And most of the builders have learned to implement quality construction standards in their homes because they have been repeatedly sued in the past. Conversely, it has been my experience that most custom homes designed by architects have a plethora of problems because they have not been built according to an established, proven system. Most Architects have no hands-on experience and are completely ignorant about quality control. They often spec materials that require huge amounts of maintenance, and they don't have a clue about how to design a structure that is easy to build and maintain. This does not include all architects. But most architects I have dealt with are borderline incompetent. It's easy to think that "architecturally designed" buildings are superior, but that is just not reality. I design my own homes, and when I design a home, I KNOW what details are necessary to safeguard the design from structural failure, water leaks, excessive maintenance, the correct details for sealing window and door penetrations and more. I have learned all of these details from hard-earned experience. Most Architects come out of college never having built anything.

[@Anytus2007]

I'm not an expert on overlapping code provisions, so I'm really ignorant here; why is the IBC provision relevant? IRC (at least 2021) gives a prescriptive pathway for unvented attic assemblies. It's a relatively detailed section (compared to most code provisions) that gives lots of rules about placement of air and vapor permeable/impermeable layers. I presume that no engineering is required for this prescriptive pathway, despite the IBC provision, but like I said I don't know much about this kind of overlap.

[@franklong6269]

@@Anytus2007 You have identified one of my frustrations with using closed-cell foam insulations. The answer to your question is PROBABLY different cities and states will have different requirements for the use of closed-cell and open-cell foam systems. Some cities/states may allow you to install a system without an engineering design if you use a licensed foam contractor. Some may require a licensed engineer’s stamped design. I suspect it would depend on how complex the project is. I am a licensed GC in my state and I have worked for some of the largest tract home and custom home builders. I have never seen a single builder use a foam insulation system in a residential structure. There are foam contractors here in several major cities near me, so it does get used. But because of the cost, the liability issues and the complexity of installation, most builders, including me, don’t appear to use it. I design my own homes now, and if I designed a home and specified closed-cell spray foam in the walls and ceilings, I would have to submit the plans without an engineer’s design and see if the city I was working in accepted the design or kicked it back. I simply don’t know what each city in my state requires or if there are state requirements. I suspect that if you eliminate the attic venting, they require an HVAC design to protect the city from liability issues, but I don’t know that for sure. City permitting agencies will often require stamped structural engineering designs for anything outside the norm because they are VERY concerned about liability issues, even though it's damn near impossible to sue cities. I would guess that this would mirror sprayed-in foam systems. Because they are so complicated and incredibly expensive to fix if they fail, the city and state agencies may require a stamped, engineered design to "cover their ass." You have to remember that a licensed foam contractor knows how to install foam systems but may or may not know how to design foam systems. The internet is proliferous with examples of foam system failures in homes. Using foam systems is great so long as everything you do in the wall and ceiling systems is PERFECT and you have ZERO leaks. The reality is that most walls and roofs have some leaks. But because most builders use roof and wall systems with redundant protection that allows water to drain off and/or evaporate, these small leaks are harmless. Now the idea that there are leaks in wall and roof systems is changing with the advent of moisture barrier systems like the ZIP system. Home designers have become MUCH more knowledgeable about using water-tight systems. But even with water-tight systems, redundant protection should be installed. Let me provide a real-life example of the dangers of using closed-cell foam systems. One of the post-frame builders I enjoy watching on KZbin built his family’s dream post-frame home. Since we don’t use post-frame designs in my state (or they are very rarely used), I was fascinated watching him construct his home. He’s a licensed GC, and he has built multiple post-frame homes - he is an expert in constructing these types of homes. He chose to use close-cell insulation in his walls. In his attic, he used fiberglass insulation. The home structure is wood, with a post-frame structural design. The exterior and the roof of the home are clad with metal siding. When he built his walls, he chose to not install a ZIP moisture barrier system. I corresponded with him through comments and recommended that he use a ZIP system as his shear panels because it would significantly increase the strength of the home to withstand tornados, and it would provide a second redundant water barrier in case any water got by the metal siding. He chose not to install a ZIP system, and he didn’t even use a house wrap moisture barrier because his foam insulation contractor told him that the closed cell foam would act as a moisture barrier. I warned him that this was a mistake, but he was doing almost all of the work himself, and he probably did not want to do ANY additional work. Fast forward, and after he got the exterior dried and the drywall installed, there was a several-month delay in getting materials. During this delay, heavy rain got through the metal siding on the walls and possibly the metal siding roof joints. Because he didn’t install a redundant moisture barrier, the water leaked directly onto the closed-cell foam in his walls. The foam got soaked because closed-cell foam is NOT waterproof, nor is it an effective moisture barrier. Their stunningly beautiful home had wet spots in the drywall all over the house. His wife was in tears. The contractor filed a Registrar of Contractor complaint against the foam contractor and hired a technical expert to diagnose why the house was leaking. He didn’t go into a lot of detail, but I am pretty sure that the foam contractor refunded him something like $6000.00 to settle the complaint. But really, in my opinion, it wasn’t the foam contractor’s fault. PROBABLY, the ROC inspector found the foam contractor partially at fault because he installed the foam wall system without a moisture barrier. In other words, the foam contractor misled the GC by telling him that the closed-cell foam will act as a moisture barrier. It was on his videos so the foam contractor probably could not deny he said that. This is stunning because the licensed foam contractor didn’t know that closed-cell foam is not waterproof. But here’s the key. This contractor, who is a pretty amazing GC, had to go through the entire exterior of the home and find every single place in the metal wall siding and roof panels and repair openings that were leaking. This must have taken a huge amount of time, and the GC probably was embarrassed because he didn’t show these repairs in his videos, though he did show one repair to his credit. I warned him again that because he doesn’t have redundant protection if a leak develops in his walls or roof, it will go straight to the foam and cause damage again. But at this point, he didn’t have much choice. Also, the GC didn’t mention any mold remediation, which can easily cost $40k - $50k. This is why I consider foam insulation systems to be treacherous, expensive and not worth the risk. If you are building a wood-frame home, I would suggest that you use 2” x 6” walls, and if you are in an extremely cold climate, use a ZIP board shear panel with 2” insulation on the exterior (that comes with the exterior moisture barrier). Install ½’ composite battens vertically on the walls and then install your exterior siding or stucco attached to the battens. Then use fiberglass or mineral wool batt insulation in the walls. That will provide an insulation factor of around R-50, and the water will never get to the interior. You will never have mold issues because any water that gets by wall siding (or stucco) will drain out the bottom or evaporate before mold can form. This system will probably cost less than using a closed-cell foam system in your walls and it is a hundred times better. For your ceilings, just use blown-in cellulose insulation and vent your attic. Use a modified bitumen barrier under your roof sheathing, like Grace Water and Ice Seal - follow the manufacturer’s instructions. You can insulate your attic with batt insulation, provided that you install an air barrier approximately 2” thick between the plywood and the insulation. Insulation contractors sell baffles that staple to your trusses to provide this air barrier. The air barrier must have eave venting and ridge venting. Insulate your ducts with at least R8, preferably R12 insulation. I hope that this helps you.

[@Ed-jg3ud]

Have to say this is the first time I’ve heard this level of detailed discussion on how to do a vented attic properly where you design from the beginning (no load bearing interior walls, seal penetrations, run ducts under the air sealing drywall layer) for success. Would love to see more designs that showcase these techniques to do successful high level vented attics

[@jeremyjedynak]

This is the second time this week that I have seen a video on this topic, and never before. Steve Baczek, the architect mentioned in this video, has a separate YT channel and he just posted a video a few days ago about a Passive House project that he did years ago that had a vented attic with drywall immediately below with no internal load bearing walls.

[@billz4795]

A bit of caution jumping on " no interior load bearing portions". Barn examples are framed much differently in a series of structural bents, compared to standard 2 x as shown here. Additionally and more importantly are the structural requirements per the region - ie hurricanes, earth quakes etc.. So be mindful of the site specific requirements before selling yourself on no load bearing interior partitions. Yes it can be done - but specialized engineering and detailing is required.

[@Ed-jg3ud]

@@billz4795 agree 100%; but the ultimate take home IMO, is that if u plan it from the outset, design and engineer it from the beginning, it can 100% be done, and ultimately will perhaps raise construction costs slightly up front (less than a conditioned attic like Matt’s tho) but in the long run result in a much healthier vented attic that saves long term energy costs and avoids expensive roof repairs (ice dams, mold remediation etc). Seems like a no brainer to me if the aesthetic/functional design of the rooms in the house can accommodate that “no load bearing partition” requirement

[@rj.parker]

I agree with Matt that a sealed attic is best in the south when no basement is available. However Matt’s house may be too over the top for cost conscious buyers and builders. Matt highlighted a Central Texas Builder a year ago who seals it up for very little extra cost. Scott True out of Bastrop Texas. Search KZbin for “ LOW BUDGET Details For A High Performance BUILD” which is a two part Rissinger video.

[@billz4795]

@@Ed-jg3ud yes - it was great to see someone present alternatives facts to the " conditioned Attic. Most professionals know mechanical alternatives, ways to create "blanket envelopes " air barriers" etc . Without extending the envelope to include the"roof". Building science will advance, evolve. Choosing the fork in the road becomes difficult.

[@ErikPukinskis]

I love how Matt always tells people he's going to link to them below but never does 😆. Keepin' all that link-fu to yourself!!

[@jacobusdegroot7557]

Right?

[@billk65]

So true

[@JoniAntonio]

He has a aduio/video guy that does KZbin, Matt is not editing and uploading videos. With that said, his AV guy should watch his videos ^_^

[@Cotronixco]

If you don't like it, why do you love it?

[@SpringScapes]

I'm not sure what you mean, on this video there are 10 links below, or are they not considered links?

[@damianforeman5156]

Back when I was touring a bunch of model homes, the one thing that stood out to me is that every home that used spray foam insulation everywhere had almost no dust anywhere. Every other home with typical blown-in type insulation was quite dusty. That may be a big factor for those that suffer with allergies.

[@gssngr]

That’s true, cellulose insulation in attics can get a bit dusty and potentially make your home dusty. However, this video talked a lot about making a great air barrier between the attic and the house, essentially shooting for ~0 air leakage. If you have no air movement between the attic and living space, you also have no dust transfer. I know that’s the argument most builders would have about that topic, but in my area, I haven’t seen many of them actually doing that great of a job air sealing, particularly between the attic/living areas.

[@Care2WorldBuild]

Yup, seems like we have endless dust.

[@buick494]

​@@gssngr I am a remodeling contractor. I did my 1943 house my way. R-72 blown in insulation in 80% of my ceilings. The only exception was the master bedroom bedroom with vaulted ceiling were I used Dow polystyrene foam board with a radiant heat barrier. I have near ZERO dust in my house. I think any dust I really have is from my 10 year old boy and the dog coming in and out (leaving doors open) It's all about sealing up any holes prior to drywall. Rockwood in walls. So far highest heating bill for 1,500 sq has been $72.62. -5 F. Including a gas dryer, hot water heater and kitchen oven. Side: benefit is the house is dead silent. Also have whole house radiant heat barrier above blown in, stapled to roof joists.

[@VP411Designs]

@@gssngrgreat point, I was a bit lost on how Matt setup his attic to be inside the envelope to get the space conditioned! Can you offer any feedback or info that explains this? I think he said he put the foam boards built in with the 2 layers of the roof sheathing as his roof line with no cut Outs or ridge vents holes essentially closing off any air venting! As a texas home owner myself and customer designer for I get asked about this alot of How to use attic space or convert attic spaces but never understood how to do so!

[@robertlandis3378]

@@VP411Designsis exact house plans are available via builders first source you might be able to get more info from them.

[@Sylvan_dB]

Once we get the initial construction figured out to build a good building, we need to talk about what will happen to that building over the next 10, 20 and 30 years, and how we can build it to be maintainable and even modifiable such that the performance does not degrade over time. Talking about recessed cans that require constructing a box in the attic and extending the envelope over that box is great, but what happens in 3 years when the homeowner wants to add or relocate a can? I love the idea of no load-bearing walls, making it easy to remove or move a wall, but even just adding an outlet or a switch requires running some wires, likely breaching the envelope. How hard is it going to be to seal it up again? How hard is it going to be to teach everyone doing all that kind of interior work what needs sealing and how to maintain the envelope? For insulation the blown in cellulose is easy, quick and so cheap. But blown in cellulose tends to settle and lose R-value over years and decades. The rockwool batts in the conditioned attic are good unless/until physically damaged. The iso on the roof deck is pretty good, but can soak up water if/when there is a roof problem. I think putting the envelope on the outside of the house makes the most sense, and in future work it is pretty easy to understand that a hole to outside needs sealing. I'm still not sure if that will result in as durable a building as one that breaths, but I sure like that a sealed building keeps the bugs out a lot better!

[@bpduguard]

So, I like that Jake Bruton gives his perspective on homes that have to deal with both the cold and heat of climate zones that aren't Texas. My home is in Climate Zone 5. What NONE of the home improvement folks, not even Mike Holmes way up in Canada (side note: he'd be a great guest) have really tackled is the most cost-effective way to improve the insulation of a 1960s-era production home. Specificaly, the worst type of homes for the upper midwest: split-level or raised ranches. Please tackle this topic. Now, this spring, we're finally getting our siding re-done to include house wrap and insulation on most of the outer walls (they recommended working with someone else to insulate from the inside for the cast concrete walls), soffit vents, and pretty much everything that's not covered by siding will be wrapped in aluminum. We're hoping the next home improvements will be windows and doors, and then a new roof. When we do the roof, of course I want the F Wave Synthetic Shingles that the Stud Pack guys used (kzbin.info/www/bejne/rHqri5aihJdjl8k), but also the correct exhaust fan venting for all the bathrooms and replace the attic fan with a ridge vent. The ultimate dream for the attic is to move the access from a bedroom closet hatch over to the hallway. We don't store anything in there, it's just for maintenance and it's got blown-in cellulose on the floor and no insulation on the gable walls.

[@genes.1999]

Agreed! I haven't watched every video Matt R has put out, but it does focus on new builds where issues can be addressed in the design phase. Which is fine. However, whenever I watch these videos, I have to adapt it to my late 40's home or even a newer 2018 "production" home we recently purchased - where all the ductwork is in the attic! I'm wondering how I can improve this situation in a practical way...

[@jeffreyandrus6119]

I went with three ductless 30 SEER mini splits in my ICF house, NO crappy flex duct in an attic! 18 inches of cheap blown in pink fluffy in the ceiling R50. spray foam top plates and baffles, 360 bird block soffit vents and 72 feet of peak vents in low SRI standing seam metal roof over Sharkskin high temp membrane. The vision was build a yeti cooler under an easy up shade cover- house. Then add an ERV to breath it. 55 days of temps over 110 degrees in Phoenix last year, that's what I'm competing against!

[@msk3905]

But going mini split route means you have to look at three large rectangular eye sores on your wall…I’ll take the flex coming off metal mains in my attic every time

[@LincolnLog]

​@@msk3905there are ceiling cassette options you know

[@strategicactionservices2206]

I appreciate the honest and RESPECTFUL conversation. If only we could all do that.

[@AOHgoog22]

A+ wow! love this conversation i deleted all my attic HVAC ducts and central ac and went full mini splits heat pumps and few months ago CBS 1980s home built by commercial contractor built solid.! so 5 single heads run whole house in humid FL. next year planning to install small 4" ducted circulatory octopus to recirculate air around house thru all rooms with a 4" 20x20 near HEPA MERV 14+ media filter and UV light...electric bill already cut in half and house is so comfortable ...plus every room has insane power to move temp where ever i want within 5 minutes... need time to understand and design a fresh air intake and then air condition it because humidity in FL is rarely below 85pct need like a dehumidifier AC modular box to tap into ... awesome awesome conversation Thank You

[@Sylvan_dB]

That sounds nice! Many mini-splits can run in a dehumidifier mode. If that makes your house too cold, you oversized (spent too much) on cooling capacity. If your house is sealed tight (get a blower door test if you can) then you might need active air exchange with a heat recovery ventilator (HRV) but most likely you aren't that sealed.

[@davidmarasow731]

I have a 1930 house, mini splits work but always have high humidity, planing on sealing the house from outside with new windows. Hope it does the trick.

[@AOHgoog22]

@@davidmarasow731 hmmm ...in south FL ...so we are insane high humidity all of the time.... im confused bc i read peoples reports abiut minisplits havng high humidity issues...i was worried about that...but im curious ..please tell me what high humidity is to you.... i have my 20x20 garage with a 2ton mini and the doors have like 4"x 1/2" air gaps leaking and my garage humidity hits 37percent easy with a outdoor temp at 94 humidity at 80pct ... i can open door remove car and recover tmp humidity in less than 1 hour... > > > What size mini splits are you using.? What kind of ai leakage do you have in he walls and joints and outlets and pnetrations in general? IMO.. these mini splits shouls easily ove cmpensate for air leaks... mine are soo powerful...i get temp adjustment 3 degrees in less than 10 minutes even with living room with eight 4-foot sliding doors to the pool opening constantly all day and a 18' vaulted ceiling with open kitchen..that room has the only 2 ton.... separately... please note... i have 1 separate minisplit system in each room... NONE are shared to 1 compressor... Also mine are ALL cheap diy m r c o o l s like 750 after tax rebate all others are 1 ton ... i did all the work and the finish work interior so they look finished and clean without a single wall penetration..just popped thru ceiling drywall and out soffit

[@bobbray9666]

We built in zone 6a last year and almost all homes around here have basements, where the HVAC handlers go. We used Zip-R12 sheathing over 2x4 studs with closed cell foam for R-30 walls one a one story home. We had 2" of closed cell sprayed on top of the ceiling drywall and over boxes built over can lights and bath fans. Then blown fiberglass to R-60 in attic. The attic space is vented as usual. This was the best air sealing and insulation method we could come up with. I wanted to use mineral wool between wall studs (money savings and better sound reduction) but my contractor said the closed cell SF would add shear strength to the 2x4's with 4" nails coming through the 2-1/2" thick ZIP-R. Our blower door tested 75% below passing threshold.

[@lyonmccandless6161]

I’ve been considering something similar except I am contemplating doing the Zip sheating on the underside of our attic trusses, taping it all continuously to the edges with liquid flashing, and then an additional 2” closed cell spray foam. So every exterior surface has 2 means of air seal and insulation. My husband thinks it’s overkill but I think it makes sense

[@bobbray9666]

@@lyonmccandless6161 Probably overkill. 2" of closed cell spray foam is a vapor barrier by itself. The only advantage of your method is if you later go into the attic and accidently step between the trusses. You won't fall through like if it were just drywall. Probably better to staple plastic sheets to the underside of the trusses and spray foam directly on top of that if you want an extra vapor barrier. Will accomplish the same thing as taped Zip panels.

[@bobbray9666]

@Navy1977 Minnesota. Wimpy winter this year but cold weather payback will probably come next year as we transition from El Nino to La Nina next year. Not looking forward to -25F temps!

[@bobbray9666]

@Navy1977 That's a warm April day up here.

[@benhatcher2603]

One thing you didn't touch on is the added square footage of insulating the roof versus insulating the ceiling. Your R-value is per square foot and insulating the roof is adding 50% + more surface area depending on the pitch. For that reason alone, I'm with Steve, vent until it doesn't make sense to vent. Finding a way to run ducts inside the envelope as much as possible and minimizing the size of the unvented mechanical room would have been the more ideal solution.

[@miillersconstruction]

Great video man. I love what Jake is talking about with a continuous layer of drywall on the ceiling before framing interior walls. I also love what was mentioned about the "airtight" recessed lighting fixtures. Couldn't agree more with that.

[@Erik_MN]

I'm doing a post frame house with a vented attic following Jake's guidelines. No load bearing walls, minimal penetrations, all HVAC inside, continuous ceiling drywall. 40x40' the basic shell is up and I just ordered the wall insulation.

[@BuildItMakeIt]

I love the multiple ways to get the high performance. Plus the cost benefit trade off of basement vs attic. That is a great thing to keep in mind.

[@mpccenturion]

Matt -- God level info. Thank you so much! PS - my build - 30 inches of R5 styro. Gave me a guess at R 90++ in the attic. That was my build - based on the NRC R2000 info pack. Back in 94. Cheers!

[@BrianKrahmer]

Extreme insulation will most likely not be a good ROI

[@markrosenthal9108]

I'm a fan of unvented attics. I'm installing a hoist in a closet in addition to stairs so I don't have to carry stuff up the ladder for storage. The lack of blown-in insulation makes maintenance access from the attic easy. And besides energy efficiency, the lack of vents keeps the yellow jackets out of my unvented and conditioned attic.

[@russking63]

There is such a thing as a dry climate (most of the southwest US) where condensation in the attic is not an issue. HVAC systems in vented attics are completely acceptable and very common. Maybe not the most energy efficient option, but still cost effective. One problem I run into a lot is inadequate ventilation and the attic heat builds up and stays hot all night. In CA we also have something called high performance attics - vented attics with main insulation at ceiling, but also insulation under the roof deck acting like super duper radiant barrier.

[@steven7650]

One thing to bring up is separate venting the attic vs the assembly. Up here in climate zone 6 I sealed the roof, but will eventually have to vent the assembly because the albedo effect of snow will cause it to self melt once it's greater than 12" so you want to keep the roof surface cold to stop ice dams.

[@pacodefrancis7235]

Unvented "attic" (really what Matt has is a loft, as it's part of the actual house and thermal/air envelope) does not mean unvented roof. Roofs should always be vented, but that can done with a simple lattice made up of 2x4's built on top of the truss sheathing.

[@steven7650]

@pacodefrancis7235 You don't have to vent them in zones 1-4 but it increases the longevity of the material reducing the heat load so its best practice I would argue vs. a must like with snow.

[@ezosoro]

This was such an interesting conversation. Great example of how different cases call for different solutions and how both can be right for what is wanted or needed.

[@andrewkisner15]

Jake is very intelligent. He has the ability to simplify something that others would overcomplicate.

[@FreekHoekstra]

Good to see the nuance , that’s said a conditioned attic gets you almost another story worth of storage, for very little extra cost. Probably the most cost-effective way of increasing the square footage of your house, keeps the rats and the bugs out , and is easily inspect able so for me, its totally worth it. Although I'd add the sheetrock, which keeps it from getting dirty and makes it look infinitely nicer. Even if I did have a basement, I’d still want a conditioned attic main change I would due to matt’s is I would put up some drywall , to keep any dust from gathering. That basically makes it into a true room. the one exception is probably a truss, that might just not be worth it.

[@bobe5710]

Your first sentence: you mean "unvented" right?

[@FreekHoekstra]

@@bobe5710 I did haha, my bad.

[@functionalvanconversion4284]

You guys are fortunate to be building new. I work with existing problematic properties and everything you are discussing applies to the problems I see. Air seal, air seal, and air seal:) ERV create negative pressure that eliminates dust from that rockwool in the attic from getting in the hvac or rest of the house?

[@HonestEvolution795]

I love watching these attic videos… can’t explain why

[@shannalivingston1046]

We utilized this exact method in 2021 when we built our Nudura ICF dream home complete with Zehnder! Come on over, Matt!

[@Redwingster]

You used Matt's unvented method, or Jake's vented method?

[@allanmurphy7474]

The drywall air seal on the lid is a great idea for air sealing a house. The roof / wall intersections can be a challenge to get a good seal from the outside of framing unless you have a roof with no overhangs. the complete drywall lid shown in this video is a great solution. Cheers

[@Coleen_West]

Nice! Very Nice! -- QUESTION -- Jake didn't mention the most important issue with vented attics, from my point of view, and it is insects and rats etc getting in through the venting. I have yet to see an vented attic that didn't result, at some point in time, of bugs and rodents getting in through the eaves and vents and infesting your attic and then driving down through the wall cavities. PLEASE EXPLAIN EXACTLY how to stop that from ever happending on a vented attic.

[@Crusader1815]

After years in the trades, many spent in vented attics, and after living in homes with vented attics, I can say unreservedly that the way Matt's house is built is much better. With vented attics, you will almost always get critters and bugs and mold up there, and you can blow cellulose 3 feet deep if you want, but the wind will be penetrating it. In fact, the one thing I disagree with Matt on when building his house is where he puts the exterior insulation on the outside of the air seal. All insulation, even polyiso, and especially Rockwool comfort board, which is outside the envelope is compromised in its effective R value. Matt likes using the jacket analogy (where you blanket yourself with a jacket instead of stuffing fiberglass between your ribs,) but here's the sweater analogy: go outside on a cold, windy day wearing a sweater and see how quickly you get cold anyway, but put on a windbreaker over it, and you stopped that air movement and get the effective warming value of the sweater. I would do Matt's monopoly framing, but use a flash and batt strategy, with at least 2 inches of closed cell foam everywhere. That leaves no cold condensing surfaces to worry about. I know it's more expensive, but this is your home, and it needs to be done right.

[@nunyabidness3075]

What about SIPs?

[@CMbassin]

Lots of people here in VT use Zip R then flash and batt that so you still get that continuous exterior insulation but without having to build window bucks and all that.

[@Crusader1815]

@@nunyabidness3075 The drawback with SIPs is in expecting them to be structural. I would probably wind up with essentially self-constructed (S)IPs as my exterior insulation, with a plywood panel affixed directly to the studs for good shear strength, then 2 layers of Matt's Atlas panels, and ZIP or plywood+Aluma Flash on the outside, carrying the air barrier there.

[@nunyabidness3075]

@@Crusader1815 Is this just a case of not trusting the SIP manufacturer to make that top layer, or are you able to do it cheaper? Both?

[@Crusader1815]

​@@CMbassin This is a great solution without breaking the bank. The only drawback with ZIP-R is having the wood panels extended away from the studs, which lessens shear strength. I've noticed Steve Baczek using ZIP-R9 plus 2 inches of closed cell and then R15 Rockwool batts in a couple of his videos. Apparently not many people use ZIP-R12 because of the lessened shear strength and the need for longer nails/screws. The site-assembled IPs could let you use 3-4 inches of polyiso as your exterior insulation without a problem, except, as you noted, the need to also create window bucks. But having R50 walls that won't blow away in strong storms is not going to be cheap or easy.

[@timcervinsky]

I watched this twice and still wondering if I missed something. Every vented attic I've ever seen has always had a problem with insects and rodents. What are you doing to eliminate these problems?

[@dannylayton1106]

I believed in vented until I came to realize my storage, my HVAC air handlers and ducts and tankless water systems are in my vented attic. So now I have to figure out how to do a conditioned attic on a 60's ranch. Thanks for closing some doors and getting more focused.

[@detroitjohn4724]

Spray foamed the attic in July 2022. 130 degrees up there. Spray foam heats up when sprayed also. had box fans clearing out all the fumes that afternoon and a rest of the evening. the next day I went back up and the thermometer said 60 degrees! Fantastic ! It felt cool to say the least. And the A/C condenser started shutting off at 15-16 minutes ! Now saving money and the A/C will live longer. Sprayed the underside of the roof deck with CC.

[@semosancus5506]

I have a 60s hip roof. Can't get enough ventilation in that configuration. Sprayed roof deck with open cell foam.

[@alanjackson1015]

Great discussion of the pros and cons of both systems. Love this kind of back and forth

[@MakeMeThinkAgain]

Rockwool is a great option if there's ANY chance that it's ever going to get wet... or catch fire.

[@YIQUANONE]

I am in a high-fire WUI area and am rebuilding my house that burned down. Venting attics is more problematic than unvented attics. I am going with Rockwool because of the fire rating and it costs way less than spray foam and also too many risks to the downside of spray foam, like shrinkage, fire rating, inspecting, remodeling, access, etc. Built many high-end spec homes in the past 30 years, trusses are faster and cheaper but a nice stick-built roof to me is a higher-end construction method for many reasons. So it depends on what you want, track home or custom home. If you are building in a neighborhood with all houses are not valued high then might be better to go cheap if you want to get your money back at selling time, but in a high-end area, you will probably get your money back one way or another.

[@tillburn]

I feel like everything you are talking about here is addressed with a air tight full ICF build (wall, floors, ceilings), large spans without structural partitions, and when designed correctly all the HVAC, electrical, plumbing and other items are all with in the envelope. Leaving out the wood products where possible, water proofing and doing roofing material of choice cold framed or cavitied on top. The one issue I always see being left out of planning is LOW VOLTAGE, aka HVAC, lighting, networking, fiber, control systems, etc. Please do more videos on new construction low voltage ;)

[@VP411Designs]

This is awesome, great video! As a newbie and a fellow Texans, i would love to better understand how Matt did his attic, roof construction setup to see and understand the results of this setup! I hope Matt and his awesome team does a mock up video to show how this was done! Better to learn, ask questions to get best results

[@DaveCLL]

I'm glad that the added air volume burden of an unvented attic was mentioned. As a victim of an unvented spray foam attic, I have experienced this problem firsthand. During design, a Manual J was run, but it really did not encompass the huge amount of air volume under my steeply pitched roof. As a result, my hvac system was undersized and it struggles during periods of extreme heat or cold. Bottom line, I would never do an unvented attic again. Too many secondary issues to deal with.

[@bellaherna1]

Is your hvac system in your attic? We are trying to figure out how to accomplish a conditioned attic with a metal roof - manufacture says you have to apply directly to sheathing. I am very concerned about condensation.

[@alanjackson1015]

@@bellaherna1 Do what Matt did with his house. He has many videos on how he did all of the roof details.

[@bellaherna1]

@@alanjackson1015 What Matt did is cost prohibitive - I don’t know how people can afford to do what he did- the roof we were looking at is 26 gauge but requires us to install directly to sheathing so if we want to raise the roof off the sheathing the place we are working with said we would need to upgrade to the 24 gauge product which is double the cost plus the cost to do the perlins ??? Not sure what it is called but the wood strips on top of sheathing that allows the air gap.

[@LuminairPrime]

Somebody making a mistake and undersizing the HVAC isn't the roof's fault!

[@designiy]

I would love to see someone come up with a renovation/retro fit method for existing vented attics that take these details into consideration. To me, there always seems to end up being a hard compromise between access and air-tightness

[@thinde88]

So the vapor diffusion port is supposed to diffuse through 4” of foam and another layer of decking? I wonder what the combined perm rating of that is.

[@alanjackson1015]

Yes, and the decking on top of the iso is on strapping, so there is a continuous vent from eave to peak, on TOP of the insulation. And then with the diffusion port at the peak, the very small amount of moisture that will get in, drys to the outside. Joseph Lstiburek has some great articles and videos on that concept

[@johnwhite2576]

Nb !! Joe discourages diffusion vents anywhere near the mason dixon line!!

[@alanjackson1015]

@@johnwhite2576 From Canada, so no idea what the significance of the Mason Dixon line is! But I've seen several videos and articles where Joe talks about diffusion ports in Alaska. That is where one of the earlier non-vented roofs on a large project happened, and it was a disaster until they let the roof breathe through the peak. Not sure if the vid is on Matt's page, or another page

[@jacobecorder]

Sweet. This is what I did when I built my second story addition. One column in the middle and no interior load bearing walls. Then vented roof.

[@erfquake1]

Hey Matt, it would be great if you did an attic show in the Portland, OR climate zone: wet, dank, near-constant cold rain in winters, basically moss on the outside, mold on the inside. I'm wondering how much of this advice would apply to us. Thx! Love the channel!!!!

[@captsavage3049]

Matt- this is a great video. I’ve never heard this level of detail put into this type of comparison before. Thank you!

[@tylerwilliams3868]

I love your videos very informational but PLEASE make a video of us (30ys old home or less) of how we can help fix our insulation/ having a better performance home!

[@ThePowerful5]

kzbin.info/www/bejne/lZ-yemxvmtxog68si=JjYBY9Y0rqyaX8-K

[@spelunkerd]

With the most common defect in attics being inadequate air intake because soffits are too small and covered by insulation, has anybody looked at blowing outside air INTO the attic to enhance flow out the roof vents?

[@joelbovaird8011]

Great video as always! A lot to think about for sure. We're coming out to IBS in Las Vegas next week. I hope to get to meet you all!

[@afs3294]

Matt has it right. Any cost-savings of the well-executed vented attic need to account for the significant design penalties that come with it. Multiple soffits projecting below the ceiling, pancake lights are among the worst performing lights in the ceiling because they are too shallow, and the 8' ceiling height above grade is too short for new builds even in hallways (13:56-14:25). Taking advantage of bedroom/office/other living space in the conditioned attic space with the full stairwell is very valuable square feet in many urban/suburban markets.

[@ToddBizCoach]

Watch the video again for further instruction. There is no reason to have multiple soffits projecting below the ceiling if ducting is in hallways with 10’ ceiling height as described. You don t need to use pancake lighting with LEDs.

[@afs3294]

See 13:57 to 14:25. Soffits and 8' ceiling transitions in hallways to 10' ceilings in bedrooms. Not good. @@ToddBizCoach

[@matt45540]

We need a video on the best way to fix a uncondition attic from 10 years ago. Without going ventless.

[@jamprindle1]

Same here, we have a 1970's home with a vented attic and the ducts all over the attic. I'd love to see the best way to retrofit it.

[@ThePowerful5]

Have you checked out this video that Matt did last year?

[@ThePowerful5]

kzbin.info/www/bejne/lZ-yemxvmtxog68si=JjYBY9Y0rqyaX8-K

[@LuminairPrime]

@@jamprindle1 You would replace your HVAC with ductless minisplit heads wherever necessary, and you would gut your attic floor and air seal it tight with drywall patches and foam, and then you would re-insulate the whole attic with blown-in as thick as possible.

[@OliverDesigns]

This level of explanation adds value to the universe! Thank you!

[@Darthreloy]

What i hate about blown in cellulose is that its a giant heat battery in the evening. Sun goes down and for 3 hours your ceiling still radiates heat down on you from a two foot thick layer of hot cellulose on top of the sheet rock. So, dont go as elaborate as Matt, but still have a conditioned attic for great result.

[@jwristen24]

I can't stand vented attics.

[@snower13]

Insulation by definition has a low thermal mass. Materials with a low density, such as fiber insulation, have a low thermal mass.

[@Darthreloy]

I have blown in cellulose in my attic. My second year in this house I investigated the ceiling heat radiating down on us after dark. Up in my attic was this thick hot layer of cellulose that stayed hot for a couple of hours. So say what you want but I have one room with no cellulose above it and that room has no radiant heat coming down after dark. @@snower13

[@SuperAndrewpalmer]

As an HVAC Journeyman doing load calcs and duct design on new homes; it drives me nuts how poorly homes are designed for the allowance of duct to be installed.

[@RStout59]

My rule is "there are no rules when cooking". I trim whatever i feel like and render that for other uses.

[@KenYamaguchi-sg5zr]

A great comparison and discussion from two master builders. Thank you.

[@perrysebastian6928]

Good stuff! Not sure that cheap is the way to go, but the key points are the quality of the building envelope, no matter the configuration, and do not cross that envelope with conditioned air. The refrigerant lines make the heat exchange between the inside and outside, so putting any component of the airside part of that system on the outside of the envelope is just dumb.

[@HistoricHomePlans]

Another great video, Matt. Thanks. I still favor unvented attics for a lot of situations. But I have a question for you. Can you do a video that shows various ways to insulate an unvented attic, especially one that is made with pre-fabricated trusses? I know continuous rigid insulation above the roof sheathing is a good way to go. But what about other approaches?

[@cvally1]

you always had my respect now even more so humility is important in this life Well played Sir

[@scoobtoober2975]

Another tip of the day. Do not get too fine a filter on your furnace if that is your main source of circulation. It has to be closer to a merv 10 or less. You hurt flow. Or check flow. Then check flow when it's partially filled with dust. It made a huge different going to an 8 vs 13. Comfort is better in most of the rooms now. Semi-poor insulated home 1950's.

[@joniboulware1436]

I grew up in a flat roof slab on grade house. Ducting ran through a dropped ceiling down a hallway. Works very well, but with simple house designs.

[@Eric998765]

I'm going to have to go back and find the videos of Jake's builds. I wanted to do unvented but my building grew in size before we broke ground and now we have 54ft of roof line (upside down v) which would cost tens of thousands of dollars to spray foam, whereas blown in would be like $5000. I haven't really researched the air sealing and moisture details of vented though

[@bryantisaacs9811]

Maybe I'm missing something but why does @matts attic not need a vapor barrier. I think he said something about " if vapors get into attic he wants it the go upwards but the rest of the house has a vapor barrier?

[@timchestnut8531]

Any problem with wind blowing the loose insulation through the vents?

[@qwelve5848]

The only issue I have with those puck light replacing a can light is finding the same wattage and color replacement when one or two fail after a few years. It seems even name brand manufacturers chamge their designs and products quite often. Meaning you'll likely be replacement all of the puck lights when one fails if you can't get a matching one.

[@Hangovna]

So buy a couple extra spares if you're worried about it. I still have yet to have a $8 china fixture fail for the last 6 years

[@qwelve5848]

@@Hangovnagreat suggestion! This is something I have consistently failed to do, from keeping extra wood flooring, tile, backslash, shingles, etc...

[@DeuceDeuceBravo]

The other issue is that the light from puck lights sucks compared to normal cans.

[@Hangovna]

@@DeuceDeuceBravo not at all, they're up to 2000 lumens now for a 6". Even more for an 8" if you need more, which is easy to enlarge the hole in the drywall.

[@DeuceDeuceBravo]

@@Hangovna Lumens is not the issue. It's the quality of light and how the fixture distributes it.

[@drewtheelephant511]

would be interesting for the Build team / Arrow Building to do a renovations to 3 normal houses (meaning not built by a high end builder). 1 in climate 5 or 6 in the north east, 1 in mid climate maybe Iowa, and one in southern climate. the trick to do a cost comparison between a normal builder reno. using Home Depot rafters and crappy insulation to proper R level compared to prebuilt rafters and blown in. maybe vented is good for colder climates but unvented doesn't work in swampy Florida or Louisiana where the humidity would be too high?

[@jeremyjedynak]

All roads lead back to Steve Baczek! Not quite explicitly stated, but it sounded like Jake's builds typically have double drywalled "ceilings" with a gap in between, where the top one is just under the attic space acting as the air barrier, with minimal to no penetrations, and the lower one is the ceiling that people see when they look up from the floor that is beneath the attic. In some spaces, that gap is as small as a 2x4 for LED puck lights and electrical, and in other spaces (like hallways) the gap is much taller to allow for duct work. Is this correct?

[@jeremyjedynak]

In a vented attic, will "blown in insulation" get blown around from the air flow through the vented attic space?

[@MurDocInc]

@@jeremyjedynak Apparently, some builders/insulation contractors didn't put in rafter baffles/vents to direct air flow up and over the insulation. In that case, it will blow around with wind. If it's done right, wind won't touch it.

[@Sarahd1324]

I’d love to know how you take some of the existing Houston “McMansions” with vented attics and ductwork through them and the most cost effective way to retrofit that if there is a way to do it.

[@Byser]

I love these videos. Your videos really make me think about my next home build.

[@keithnoneya]

"Mechanical, ERV's" I'm not in the industry so I'm not sure what they mean. However those did not stop me from understanding the concepts of what you were talking about. Loved the video and the information presented. Thanks for sharing. Best Wishes & Blessings. Keith Noneya

[@LuminairPrime]

ERV means an air exchanger; a fan which blows air into the house, passing it through some material, passing by the air leaving the house, so the air from outside takes on some of the temperature of the inside of the house!

[@jimmyaber5920]

The nows needs some air exchange and if anybtrue range hood exhaust or bathroom exhaust is used then air needs a way in. The era is a air to air heat exchanger The air entering flows left to through right through tubular passages in a box where the exiting air is ducted to surround those tubes and flow up down. The incoming air will cool by passing inside air already cooled exitong to outside. In winter the heatflow reveres to let warm exitong air tobheat the cold incoming air. This make up air is where a significant leak of outside air comes into older homes where sealing was far less thorough.

[@davidjoly9816]

How are partition walls attached to the trusses with the continuous drywall? Are you using the slotted brackets or do you let the partition walls "float" free?

[@vinylcabasse]

i prefer old school can lights over puck lights for two reasons. if the bulb dies, you replace the bulb, not the entire fixture. also recessed lights have less glare because they are, recessed. puck lights or shallow canless put the light source right into your peripheral vision

[@joelkyle3310]

Such a great, detailed, explanation! Fantastic video!

[@omnizen]

Sounds cool (22:06), "Building Science Nerdery." "Nerdery" is actually in the Oxford dictionary, I just learned. Where have I been? Do you guys ever get into Earth Tubes and Cooling Towers? People living in the Sonoran Desert without electricity build their houses with onion shaped roofs (open to the ranch-style ground floor rooms, no attic, no ceiling, just underside of the roof), very efficient in evacuating hot air out the central roof vent opening and setting up passive air circulation. How about earth berming (like earth ships) and green roofs? It seems modern builders could be deploying a lot more ancient technologies that are highly energy efficient.

[@davidwashburn8695]

How are they building the interior walls at production pace? Also, how are the trusses be secured to interior walls?

[@richardmeiners6535]

In Kansas and Missouri, we have tornadoes, give me a basement any time, even if tiny, I want the shelter just in case. Also we often turn them into additional living space.

[@TimGGleason]

Remember, if you’re cold your ducts are cold. Don’t neglect your ducts, bring them inside.

[@raystormont]

Two great systems which is a achieve a great way to use building sciences to allow for the best outcomes for divergent owners and or users while not compromising on build quality and preformance. What's not to like? Ray

[@geraldlalonde5992]

I would like to see you guys build a house in northern Michigan, northern Wisconsin, northern Minnesota. I would like to see how this house can survive in our weather extremes.

[@billygilbert7911]

Great video. I'm in Washington with my ducting in an unconditioned crawl. Just seems like we should do better.

[@Thatsmessedupman]

My house is from the 50s with a truss roof mage from single 24 foot 2x4 truss!. Matt seems surprised by the concept of trussed roof.

[@loganfluegel925]

This video has me seriously questioning what I can do from a financial standpoint. Looking to build a new house next year, in climate Zone 5. I’m looking to do a finished basement, a first floor living space and obviously have an attic but struggling to figure out the cost of doing vented vs unvented, what do for an HVAC system. Both these examples Matt and Jake talked about seem like costly options ? Or am I missing something.

[@LuminairPrime]

The low-key point of this video is that ducts are bad, so get a bunch of minisplits, then it doesn't matter what you do with the attic!

[@loganfluegel925]

@@LuminairPrime thanks for the reply. I was actually looking into floor trusses and running duct through them, keeping it inside the enclosed living space of the home and not running anything in an attic.

[@snowgorilla9789]

From cold Canada this is a very interesting topic/conversation

[@scoobtoober2975]

@9:37 that framing knot is naughty

[@Tsvna-f8d]

1. Don’t you need the ceiling cleared and walls in for the rough framing inspection? 2. Do you need to finish the ceiling + primer + paint in order to have a true air barrier?

[@CannedHeat45]

Hybrid design could work too? For example Hypothetically building a 3000 sqf ranch, I could vent half the attic space and have the other half sealed with my mechanicals and some storage?

[@anndrake492]

In (crazy) California, vented attics, yes, giant open holes in the eves, are required on all houses.

[@stephensiler3854]

I had almost this exact argument with a friend building a house the other day.

[@kerryscott3287]

My house, a rancher with a walk in basement was built in the late 50’s. It is a leaky house, nothing is sealed, but the attic is like new. It heats up in the sun and cools off over night. It has gapping vents both ends that can move likely 50 to 100 cfm on a windy day. The home industry has created products, written them into code and these sealed MDF, OSB, laminated, and taped homes are disposable. My plaster, solid wood sheathed, red cedar shingle house has only had its roof replaced once. You’ll be replacing that roof ever 15 to 20 years. You have to build to code but code is to ensure trades and obsolescence for a mortgage so that you have to have a mortgage designed home. You have $100,000 of infrastructure to compensate for a more natural system that has been used for hundreds of years. Don’t get me started on those OSB 1.5 x 3” floor/roof trusses. These were invented to use garbage wood not to be better. I had to use an excavator to tear down a 100 year old barn because the solid wood, not kiln dried wood was so strong and tied without bolts and tack plates. What architects have created are disposable homes. I see McMansions abandoned for slight damage falling into the crawl space after 4 years.

[@bryonfaust5243]

Another excellent video!

[@robbed18]

How does someone get help in this regard? Just settled on a new construction with an hvac unit in the attic. A legacy fresh air intake via bathroom vent fan, last house had an Aprilair intake, so newer house with older mechanicals. My kid and mother both have severe allergies and asthma. How do I get an expert’s help, as most HVAC folks in my area are just focused on replacing existing units.

[@mil-specgarage55]

Don’t know why but I love this debate, literally think about at least once a month for the last couple years.

[@KevinBoss-u6g]

I live in Arizona and have a vented attic on my house. I must say I hate it. when the wind blows the attic pressurizes the the dry wall lid inside the house pops and cracks. the pressure in the attic is pushing down of the drywall lids causing the screws to pop through the drywall

[@AlexofAddison]

I had a 2005 built home in middle GA.. They did literally everything wrong per today’s standard. The return vent to the attic air handlers was basically a closet with a hole in the top. I still cringe thinking about it. I’ll never have a place like that again.

[@dougholcomb6851]

As a homeowner in climate zone 6a. I want to know what I should do with my attic. Vented? Sealed?

[@DouggieDinosaur]

I love it BUT . . . what about the reluctance of banks to approve mortgages for houses with conditioned attics? Their argument is inspectors can't determine if there's a leak in the roof because the insulation conceals it.

[@kevinhaskins6619]

Everything depends on the area you build in but for our climate, mini-splits make sense. They are more expensive per ton but once you consider all the construction details they eliminate, the cost is largely mitigated. And while your house is a cool science experiment Matt, it isn't a cost-effective model we can use to build affordable housing that uses best practices in building science. Vented attics work well if you just maintain the envelope at the ceiling and don't put HVAC elements up there. The attic access seems to be an area we could improve upon by making it external to the conditioned space. If you have nothing up there but the fluffy stuff, you put an external access point under an eve, and that eliminates one big hole between the conditioned space and the attic. Designing one simple venting system for the HRV/ERV and keeping everything out of the attic just makes sense because you can make design choices to cost-effectively air seal an attic if you do it upfront.

[@D2O2]

Yes! Matt's house is an experiment made possible by many donations from suppliers. Matt has always wanted to build himself a house based on the prescriptive approach laid out by Joe Lstibureck instead of a performance based approach. No consideration was made regarding how much insulation is good enough and where is the point of diminished return. We really shouldn't be looking at Matt's house as an example of how we should be building. Take for example, Matt insulated above his entire slab below his sub-floor. Sounds like a good idea, but actually hurt him in terms of cooling.

[@epiphany6]

In 5 years, maybe 10, we'll have a backlash against the minisplit everything philosophy. None of y'all have ever done an actual Manual S calculation - you're specifying a 30k BTU heat pump for a 30k BTU total house load. Then you put a 6k BTU head inside each 160 SF bedroom with a 2k BTU heating load. Except that heat pump can't modulate down below 12k BTU, so not a single one of those heads can actually modulate unless all of them are calling, and even then, the manufacturers don't actually disclose what's going to happen. Humidity issues, short cycling, etc... Ductless is an amazing solution to retrofit older homes. Amazing for a garage too. But, for new construction??? It's aesthetically horrendous, has far less ability to integrate with other air quality solutions (including that most ductless units offer poor filtration, have mold issues, require more cleaning / maintenance), and it turns out if you do your homework, they're all oversized. There are very few modern high-performance homes that actually have high enough heating (or cooling) loads for a ductless unit to go in a single room that has a door... It's always oversized. You know what Mitsubishi tells you to do about that problem, if you're smart enough to realize it's a problem? "Consider a small ducted unit with a small duct system for a group of rooms" Hmmmm

[@kevinhaskins6619]

@@epiphany6 That is a sizing design issue and you could make that argument against traditional ducted systems too. It is a valid point, but how many homes are built with pistol-whipped traditional HVAC units? I'd say most of them are sized wrong right out of the gate. Add to that that ducts leak, and their leakage rate isn't constant as the building ages. In terms of cosmetics, there are ever-expanding options for ductless designs. But I have no horse in the race. Both options will be around for the foreseeable issue and it is up to the professionals to understand the tradeoffs and pick the appropriate tool for the job.

[@afs3294]

@@epiphany6 agreed value for old retrofits and garages. Good IAQ requires a separate system, but ducted means it doesn’t have to be visible equipment. Also likely that the aesthetics will stay terrible for a long time based on how they are built/function. Nothing says cheap motel as fast as a mini split in the wall. It is the very first thing comment on when they see the wall in new builds.

[@sctexan5392]

Clarification please: if you have a basement to put your mechanicals in, vent, if not, then condition.

[@shannalivingston1046]

We used Jake’s vented method with slab on-grade, no basement in Northwest Wisconsin. It has/is working wonderfully! Check it out! It’s for sale! 1325 State Hwy. 27, Ladysmith WI

[@VernBigDaddy]

Equipment in a Texas Vented Attic = No Bueno. I build production homes in NB’s all FG Batt n Blow. Poly1, Poly2 do not get me to my 5ACH. My 30 Year old house in SA, emptied the attic of blow, I only have a duct board distribution up there. I pookied the crap out of it, bought a froth pack (2pcf CC) and put 2” over the entire distro box and every visible topplate/drywall connection in the attic. I have new windows and I went from tar paper and siding to osb & sprayed fluid applied flashing and LP smart. Left the original CT Batts in walls. 2.3 ACH Haven’t done a duct blaster. Now im worried that my 5 ton is too much and will fast cycle itself to death. Thats my story, sorry to be so to be so long winded. The moral is “more than one way to skin whatever it is your skinning”.

[@trenthaynes3461]

Long winded? I would have preferred if you have been longer winded and elaborated a bit on what you wrote. I'm not fluent in building or insulation lingo so a lot of whate you wrote is Greek to me.

[@VinceM797]

If tou have a vented soffit. Can it be cleaned with compressed air or something other than a pressure washer? Does even need to be cleaned out for airflow or does that have to be assessed in most cases?

[@CMCraftsman]

If using a product like Siga Majrex 200 which is an air barrier and a one directional vapor retarder, my brain tells me you should have it backwards on a ceiling that has a vented attic above so moisture can escape the house and into the attic to be vented away but hot humid air in the summer can’t come into your house from your attic. Or does it not matter because your ventilation system in the house is pulling that vapor out anyway and attic air doesn’t want to come into the house due to stack effect and moisture moving from high pressure to low pressure.

[@jrtoy704]

if doing mini split, how are you configuring your erv/dehum mechanicals without attic?

[@chipmhandle]

Just amazing! Jake I’m not far you. I’m in Kansas

[@martinpoulsen6564]

Run the VB on the trussess and strap it with upright 2x4"s underneath, with dense insulation for sound deadening in between, and you'll have as good as 0 penetration on the VB, outside of the fasteners, which either doesn't matter, as everything is pinched, or can easily be remedied with butylstrips.

[@trenthaynes3461]

What is "VB on the trussess"?

[@martinpoulsen6564]

@@trenthaynes3461 vapor barrier

[@wilmi79]

I’m going to move into a house built in the 60’s or 70’s. How do I find out if the ceiling is vented?