Number 1 Dumbest HVAC System Mistake (Whoops)

[@YubbieNubbins]

Matt, you have an audio source playing from your overlay video at 10:10.

[@86abaile]

Yeah, really irritating. I couldn't focus on either audio source and pretty much missed everything he said.

[@gg-gn3re]

​@@86abailesubtitles seem to majority be of the louder talking so at least you can get one of them

[@tealkerberus748]

Quality control on the vid should have caught this. Thank you for flagging it - I though some other tab on my machine had started playing without cause!

[@kevinstenger4334]

The entire hvac industry is in crisis these days and most builders aren’t even aware of it. Any stupid mistake you can think of when it comes to hvac can be found in just about every spec house in America. It’s hard to say which one is most common but “don’t know”, and “don’t care” is very prevalent in the industry. Even the good guys that are trying to do a good job are typically years behind the technology. I’m an electrician but I generally do my own hvac work because it’s so difficult to find anyone that’s any good. A friend of mine is a builder and a recently completed home he built had problems with the hvac before the house was even on the market. On the 4th time he called his contractor back to fix it he demanded the owner come out also. The owner discovered his guys crossed up the refrigerant lines for the upstairs and downstairs units that were side by side outside. Three service calls on brand new systems and they never figured it out until the boss came out the 4th time. This is one of the top rated companies in the Chattanooga area.

[@gg-gn3re]

There's no way of saying it without being mean.. the dumbest laborers go into the hvac field (and roofing). Not to say they're all like that, certainly not the engineers either.. but a lot of them know zero and care zero. They only care about sqft and what btu goes in it with their extremely simple table. Don't care about insulation, climate, or anything else.

[@scottmason2094]

32 years I’ve been doing HVAC and the biggest HVAC mistake I see is not sizing equipment or ducts properly

[@KPHVAC]

I totally agree!! In my area just about every home has a single 14" or 16" round flex return duct. Even on homes that need 4 or 5 ton systems. We are constantly adding a 2nd return.

[@calebpruitt7235]

Same here. Tons of undersized duct and oversized equipment

[@sparksmcgee6641]

Yep. Just worked in a county and city that doesn't even require manual D or L. All the contractors just wanted to do it the way they always do instead of the design. Only a 1800 sf entry level house.

[@sparksmcgee6641]

​@KPHVAC flex returns😢😢😢 And now that masters are so big, even on entry level, it's good to make sure one is there.

[@tylerbogaard375]

I work as a mechanical engineer who designs commercial HVAC systems and another very frustrating issue is the way that newer HE equipment has to back down airflow for certain modes. For instance, on a ton of furnaces, the airflow for heating mode is way less than in cooling mode. And the issue isn't that you really need that much more CFM to provide adequate heat, the issue is all of the ductwork is getting sized based on that max airflow the unit would provide in cooling mode. So if it then goes into heating mode pumping out 2/3rds of the CFM it was, now the lower airflow doesn't reach the furthest ends of the duct runs. It's extremely frustrating.

[@leephil100]

Another dumb mistake in HVAC systems is when the supply vent to a room or office is right next to a return. This causes the far end of the room to be at a different temperature. Also the closeness of the supply and return is a feedback/short circuit causing inefficient loop of the supply going directly to the return. Do a smoke test right next to the supply to see how much goes directly to the return vent.

[@joecushman6030]

You are 100% correct. Even years ago as a HVAC contractor I would reject prints showing extensive ductwork and systems in unconditioned attics. I pissed off a lot of architects and builders asking why they continue to do something so stupid, but they never got it. All of those McMansions built in the northern climates most likely have miles of leaky ductwork in the attic. They would never consider my suggestions to install 9 foot ceilings within the envelope and build a soffits. Today they are still building the crappy houses they built in the late 1990’s. The mold spots on the ceilings from sweating ductwork it proof it was a dumb ass idea.

[@jeffa847]

@@joecushman6030I don't know what's it was like in your area but in my area the HVAC contractors themselves are just as stupid I say "the HVAC contractors" instead of "most HVAC contractors" because so far I have yet to find one that's not. I'd love to find a HVAC contractor like you who would not only want to do something right and know how to do it right but would be willing to risk pissing off a builder or architect to insist that it was done right.

[@alantittle299]

In an industrial application your comments are 100% relatable. I was about to hire on to design a line of housing mounted a/cs, essentially vertical PTACs. When we looked at the cold air delivery and return they were side by side. I came up with a universal design in my sleep and jumped on CAd at 2 a.m. I split the evaporator ports, or in a requested broad flat design f used a high speed scroll fan to blow hard into the electronic cabinet to mix to the max with the electronics we were cooling. Then most machines condenser side was cross flow to minimize that short circuit. Maintenance people raved about the logic and serviceability of these machines and became preferred. I helps launch them for 5 years. Year 7 they were one of the top 50 fastest growing companies. These set of features and attention to cool design had our machines in the top tier of performance.

[@mikelliteras397]

We have codes in Florida that makes you separate them. I go over the code unless there’s no choice. 3ft is the minimum

[@tealkerberus748]

@Navy1977 I'd like to know this too. I'm figuring supply in the middle of one side of the ceiling, shaped to throw to both sides, and return down low on the other side of the room. But if there's something wrong with that I'd like to know *before* I start building my next house!

[@jamesharder5643]

Regarding the frost line…I’m currently doing a self-build 11 miles north of North Dakota. My building inspector was prepared to accept my attached garage on a 48” grade beam sitting on a footing. He required my covered patios to be on a pad that was at least 8’ below grade as the patios are not heated and frost could work its way down below 4’.

[@monteglover4133]

I agree with you 90% I’m a retired HVAC&R contractor from NE Illinois. I’d say that at least 80% of the systems are poorly built. We now live in Oklahoma and often visited our daughter who lived in Texas with all the supplies and returns in the ceiling makes the floor cold in winter. Many systems in the attic are very difficult to service mine is nearly impossible, as I’m 70 years old I can’t even service mine (trussed roof). A replacement system is planned. FYI our house was built in 1979

[@ryansport33]

So crazy that we still see most new builds built with fluffy stuff on the attic floor. Thanks for educating owners there is a better way!

[@SkilledLabor]

Those exterior ductwork pics are brutal! 😂

[@Seedavis397]

This is something that needs to be addressed with the builders not the hvac contractor. 95% of the time the builder does not offer the space for ducts to be inside the envelope and the hvac contractor doesn’t have a say in the insulation of the home.

[@ehsnils]

Which just indicates that building codes aren't what they should be. If ventilation ductwork had been specified in the code then we would have seen a lot less of this kind of issues.

[@kenbrown2808]

another dumb mistake is to let electrical and plumbing get buried in sprayfoam. it effectively prevents any repairs or modifications without doing major ripping and tearing. but having a slab in your crawlspace: incredibly good idea. it makes the subs' life much easier.

[@sparksmcgee6641]

Yeah but cost wise a good 15 mil barrier material I just about as good. Anything that keeps it clear is what us crawling around people appreciate.😊

[@kenbrown2808]

@@sparksmcgee6641 said like somebody who has never cruised around on a poured crawlspace slab on a mechanics's creeper.

[@davidhoover2446]

We built our house before I knew all this to do something about it. I would do it different now. But, I used aeroseal to make the best of it. Our house was being slightly pressurized and we had 120 cfm of total leakage on a new duct system. Now there’s like 15. It makes a big difference. The issue with it is that I have a fresh air system with a dehumidifier. The slow moving air through the ducts does heat up on it’s way through. But hey improvements can always be done later.

[@compactc9]

Here in te denver area we definitely have ic HVAC as well as slab on grade and crawlspaces. Though I am seeing more sealed attics. Only way I'd do a crawlspace is if I had it insulated and sealed like the "short basement crawlspaces" you've shown. Even had one customer tell me she had them pour a floor in the small crawlspace they had (mostly basement) because she felt the crawlspace with dirt inside the house like that was disgusting, and I agree. And as someone who works on machines for a living and for fun, I strongly feel machinery and mechanical systems will always remain in the best condition if it is all 100% in the same clean, conditioned space.

[@sparksmcgee6641]

Yeah some crushed and compacted stone is a little better in crawlspace because years from now adjusting the clearance is easy. A good barrier material over the rest of the dirt to the footer is worth it. Something 15 or 20 mill. You can walk or crawl on it

[@sparksmcgee6641]

I'm in Denver also, what trade are you in?

[@compactc9]

@@sparksmcgee6641 Central vacuums, so probably in the low voltage category, but I really specialize in the vacuums.

[@joelbovaird8011]

Another great video! It was an honor to meet you and Steve Bazek at the 2024 IBS this last week! Two great guys!!

[@henryperez8607]

Great information, but what do we do if our attack is outside the envelope? I see a lot of modifications: fans, foil on the rafters, foam panels on the rafters. What actually works and what’s a sham? Keep the great content coming!

[@MikeHarris1984]

Frost line in Phoenix. It's probably+3600 feet 😂😂. All slab on grade here! Almost all post tension slabs. Our attics are upwards of 160-190 during summer. When it's 120+ outside. So my ducts in my house built in 2019 are going from the handler to ducts in extreme heat and then dump into my house to cool to 74. We don't have condensation issues, but for the first few seconds when the air clicks on, you get a burst of HOT air. Also I run MERV13 only on my 9 air filters my home has. I don't have the dirty registers where it builds up brown dirt around each register. I wish I could have had a condition attic. But i am in a production builder home. So I'm stuck with what they offer :(

[@ehsnils]

I live in Europe and most of the office ventilation ducts are inside the inner ceiling with a "fake" ceiling below it to hide the ductwork. It of course makes each floor higher, but otherwise it's usually working fine.

[@j.h.684]

Love your channel. Thanks for all the expert analysis on the entire spectrum of building. My frost line is 48" in ND. Yup basement country

[@TheDroppedAnchor]

Before Matt and I moved here from Portland there were regional building codes. Not national. Of course, the South had its own and even more 'of course', Texas had its own. To say they were looser than the West Coast's would be correct. Love the webbing across the rafters to hold the rock wool in place. For a minute I was a New Orleans Residential Mechanical Equipment Inspector. I regularly measured the underside of the roof decking at 140°. The flex duct would almost always have serious droops. I found the installers were ignorant of correct installation methods. Most were willing or even eager to know the correct protocols. I was an inspector in 2017. I started studying the 2012 and soon we adopted 2015. I left before the tragic collapse of the Hard Rock Hotel but I knew all those guys.

[@sparksmcgee6641]

Yeah the biggest problem in the industry is whole regions that are trained by inspectors. Move back to where I grew up in a mid sized area and in 3 years I never met anyone worker, supervisor or boss that owned a code book or had read one. They're ridiculously priced but the ICC dropped the business model and dropped books to around a $100.00 Online for free you can read all the codes for free, thanks to an activists lawyer that posted PDFs of the building code for free and took it to the Supreme Court and won.

[@brianleeper5737]

Any knuckle-dragger can install flex duct in an attic, and that's exactly why it's done.

[@homeauthorityllc]

Never done right, though!

[@LaserFur]

Here in zone 8 the frost line is quite low, but 4 inches of foam sticking out 4 feet will prevent frost from tunneling under. It's also good to put foam insulation horizontally above underground pipes. Another problem is Central vacuum systems where the pipes or the unit is below the dew point and that leads to plugged pipes or plugged up filter.

[@frederickheard2022]

First thing we did after buying our house (built 1966) was insulate the bottom of the roof deck. The heat pump/ac in the attic is now inside the house. Better operation and longer life for our air handler. Gotta love it.

[@brickcitynetwork]

Bad video bad idea ..

[@frederickheard2022]

@@brickcitynetwork bad comment

[@brickcitynetwork]

@@frederickheard2022 Prove it ..

[@frederickheard2022]

@@brickcitynetworkYou know nothing about my house. You don’t know it’s construction, you don’t know my climate, you don’t know my mechanical systems. Making proclamations about my house when you know nothing about it is stupid. There: I proved it.

[@brickcitynetwork]

@@frederickheard2022 It’s only a few ways to properly construct a house .. If i install those mechanical systems in home then i sure know what they do in ALL HOMES, like your home is special, maybe you but not the home .. “Stop Wasting and Start Saving: Maintaining an Energy Efficient Home” is a book i wrote to help folks like you, so NO, nothing stupid over here

[@ecoheliguy]

Frost line reverses again as you head north. The permafrost is opposite, the surface thaws in the summer, and then freezes back down to the frost line in the cold season.

[@gg-gn3re]

What are you talking about, north vs southern hemisphere or something? Frost line in even north minnesota is 100 inches vs 5-10 inches in texas.

[@ecoheliguy]

@@gg-gn3re lol there is a lot more of the world outside the USA 😂

[@gg-gn3re]

@@ecoheliguyirrelevant. You going to answer or not?

[@marcfruchtman9473]

Very helpful. Thanks for the video.

[@mikelliteras397]

I would pull any AirHandler out of an attic if possible. The mildew is easy to kill. If you do the system right, you don’t have most of these problems. If you caulk the cans before setting them, you don’t get black ceilings. I put foam in the roof of the attic and the attic stays about 5 deg warmer than the house. People would rather have the closet space than spend a couple bucks a month extra. Those first ducts you showed, the awful light gray owlflex system and the black plastic systems were a first attempt that saved builders a lot of money over wrapped metal. The new R6 Mylar flex is so much better. People running the air too cold or with dirty coils will cause that mildew even with ductwork in a house. So can running it once in a while. There’s a lot of houses here in the Ft Lauderdale area that have 1ft attics. In a perfect world, the air handler or furnace, and the ductwork would be in the air conditioned space then you work back from there.

[@HubstepCamaro]

@10:22 missed opportunity to plug a heat pump Matt. No need for an exhaust and no “sealed combustion” (that will leak some day)

[@dapper-alien]

The picture of the southern crawlspace looks exactly like mine... The vapor barrier is thrown down over junk and dirt, and go figure, when it gets hot in the summer, I get condensation on the bottom of our metal AC duct junction box and the ducts themselves. My quick fix ideas are ( in order of cost ): Add a drip pan under the box where most of the pooling happens and pipe it outside with PVC, close the vents in the crawlspace and add a dehumidifier, take up the vapor barrier, grade the crawlspace so french drains actually work, add a sump pump, completely insulate/seal the space and redo it so it is more like a mini basement... all the options suck lol

[@jasonschultz9570]

@Matt Risinger I live in Texas and I have one of those attics you're talking about. I"m from MN and I'm really not a fan of how it's done down here. I want to improve it, but I have limited funds. So here are my questions. Would wraping the ducting with some fiberglass insulation help? Would building a room (conditioned space) around the HVAC equipment in the attic help? Would insulating at the roof line with foam or rockwool make the roof shingles get even hotter and shorter their lifespan? My shingles are only going to last about 12 years as is, even though their 30 year shingles.

[@sparksmcgee6641]

First of check your ridge vent if your shingles are failing. Or add more vents, I only use ridge vent because....... you can put ridge up on the underside of the roof as a DYI. Create a template for cutting slots in the board to wrap around the truss crosbraces. Many companies make foam boards at 24" and 16". I like loctite expansive foam, twice the cost and 5 times better than big stuff. Foam around all cuts and tape the seams. Remember your lower intake vents have to be seamed in the same One as the ridge roof vents so they function above your insulation. Two layers is tough but if you run another row horizontal and tape it that's great. Now that I think about it depending on how busy your truess are horizontal may be easier. Splurge on a hot knife because you have all those angle cuts. For 80-150 bucks you could place the board, sharpie the cut and slice it out with out moving. Insulation hand saws are what I use and they cheaper. Sawzall will blow out chunksas it pushes through even with a metal blade. You got it man, watch Craigslist and pick up sheets where you can don't wait until you have enough to do the whole thing if that will take a while. Oh and I use locktite adhesives think I used the X9 which is the MAX adhesive at HD. Check to make sure any glue you use is rated for foam or the solvent in the glue will break down the board and you'll have nothing. If you do it all at once and can find a foam adhesive go that rout it'll only for one can made 2 or 3 as a DIYer. So, Insulation hand saw. High grade, foam rated, construction adhesive. Swim shirt. Good at covering easy to wash. Rubber seal 3M respirator. The problem is all of the stuff you kick up in the attic. Rat,mouse,squirel, and bird waste can literally be deadly. Eye protection for nails sticking through studs in a constrained space. Go for it. Upgrades Hot knife Foam gun Foam adhesive

[@tealkerberus748]

I'd be insulating under the roof, and saving up for a nice clean metal roof when those filthy shingles eventually fail. Metal roofs are simple and durable and if your local government hasn't banned you from collecting your own runoff, a metal roof is the first step to having your own water that is safe to drink even when town water is toxic or stops running.

[@thebuildreview]

Great explanation video Matt 🙌

[@djpazzy]

Another informative video. Thanks Matt!

[@rickfetz469]

The house that I bought in Indiana had ductwork in it and the second floor was never cool enough in the summer or warm enough in the winter. I added on two story addition and added a second floor unit - and disconnected the first floor ahu from the second floor. This worked much better but not perfect. We added an attic fan and it brought the temp down from 140 to whatever the outside temp was and would turn off at 80 at night and come back on at 90 degrees. This worked even better but still not perfect until…….I replaced the second floor heat pump 15 years later. Our furnace guy discovered that the ductwork for the second floor unit was undersized and we had too much flex ductwork. He fixed the ductwork size and took out flex duct and not the system is wonderful! I would say the biggest mistake you can make with a HVAC system at least in the Midwest is under sizing the ductwork and putting too much flex ductwork in. He also installed a heat pump with a multi stage compressor and a variable speed fan. The advantage being in the summer it will dehumidify at low fan speed and low compressor for a longer time. I have never seen the fan on high ever in 100 degree weather. Big fan of the this type of unit…..

[@Stupefyyoursenses]

Matt, what do you think about ducted split units? I don't see them that much in the USA.

[@alberthartl8885]

Easy to do! Equipment is readily available. Change an existing furnace to an air handler. I put in over 50 systems in Southern California in the last 15 years. Fujitsu, LG, Mitsubishi.

[@marc-antoinerodrigue5703]

Our frost line here in eastern Canada, in Québec, is 4'-6'' minimum or 1500mm.

[@jasonkreps6434]

UV systems help with growth inside air handlers and ducts. Filtration very important too

[@sparksmcgee6641]

MERV 13 filters with an Amazon scheduled order for replacements. A few years ago no one even knew what MERV was. When my mom built a place 4 years ago I said I wanted MERV 20. 😅😅 Took me a minute to look at the ratings again before I realize that's a bit overkill. Example is medical surgery rooms are merv 18-20. There aren't any environments that use a higher rating for human occupation. 20 to 30 with is the top of the scale is pharmaceutical fabrication and it tops out at chip fabrication foundries that are MERV 30.

[@tealkerberus748]

This. UV comes in two sorts: the sort that causes skin and eye cancer but doesn't ionise indoor chemistry, and the sort that doesn't cause cancer but does ionise indoor chemistry. You can have the cancer-causing stuff inside a duct to kill off bacteria and viruses and the like and it will be fine so long as your skin and eyes are never exposed to it.

[@homeauthorityllc]

AeroSeal for leaky ducts - 40's, 50's and 60's houses in Northern VA usually leak 40 - 50% from the ductwork.

[@michaelmiller1109]

There is trade off in costs but maybe it makes sense to go with mini-split technology and get rid of the ducts altogether? In my imaginary dream home I would have a cassette recessed mini-split in every room with its own thermostat. Personal preference in temperature and shade from an outside object (tree) could play into the rooms preference.

[@skipbogard]

I've been considering mini-splits. However, there are some significant cons to them: (1) Expensive and messy to clean annually (2) Slightly flame-happy refrigerants (3) Toxic refrigerants [if one of your indoor mini-split systems should leak]. Right now, my heating/cooling is an outdoor pad-based gas package unit. I want to replace it with a heat pump when the Inflation Reduction Act rebates are available in my state. I'm thinking about tearing up interior walls to move my duct work out of the attic and crawl space where mine are now. The biggest problem with mini-splits is all that pesky water condensate that collects on the indoor coils, drips down into a collection tray, and then runs outside through long tubes. That water grows crap that has to be dealt with. Throw in the flammability factor, and it's been a deal breaker for me. I'd rather tear up my interior walls and move my duct work to inside the conditioned space, despite the cost. Mini-splits sure are efficient though! Some of the more expensive indoor units can be hung nearly flat on a wall with a piece of large artwork covering them. They are disguised to be large art pictures. Probably easier to clean & service than ceiling mounted indoor units.

[@sparksmcgee6641]

These pictures predate us having splits available in the US. A lot of people go that route now on older houses. But please for the love of God put a nice trim screen around it. A dishwasher mounted on you wall looks like crap and just a little homeowner work cam hide it.

[@sparksmcgee6641]

​@@skipbogardyou need to look at actual units on that fire risk they'll be rated as the same safety level as any other unit.

[@eDoc2020]

My imaginary dream home uses a hydronic loop and fan coil units. From a comfort (and aesthetic) perspective it's the same as mini-splits but all the piping is water instead of refrigerant. This has the huge benefit that the heat pump can easily be replaced without needing to modify each head inside the living space. You can easily have multiple heat/cool producing components on the same loop to meet changing needs and goals.

[@SomedayTooPulling]

Both here in South Central Kansas. R6 Rturn duct in attic, uninsulated or sealed metal supply trunk and ducts in crawl space. Built 1957.

[@rickfetz469]

Also to clarify we have ductwork in the attic but the furnace is in the garage for first floor and in a closet on the second floor. The attic fan works well - also a lot of my neighbors have whole house fans and they work really good until you have to turn the ac on.

[@HubstepCamaro]

Can you do a follow up video on why you recommend closed cell spray foam in the south now? That’s a big deal/very surprising!

[@sparksmcgee6641]

Insulation rating and life cycle in what is then an encloses space. It's tougher. All the carbon and chemical stuff is what they say is the reason. As costs have gone up the material cost is a lower portion of the install cost so it's gone from 3-50% more for closed to less than 20 a lot of times on residential jobs.

[@Expressitc]

Matt, what do you think about radiant barrier as a retrofit/remodel option?

[@jeffa847]

You stated it is more of a southern issue than a northern issue but I don't think that's true in the sense that putting ducts in the attic of an attic will trap heat in the attic and cause ice damning issues. Really bad ice damning issues if the builder also puts in 1,000,001 canned lights, doesn't seal the ducts as they go into the house well, leaves a portion of the main trunk line uninsulated in the attic, leaves a portion of the attic not vented at all -- and all on a house that didn't have proper soffit or roof venting to begin with So, that only leaves the question = when are you coming up to fix my house Matt? It would be a great video series - you could literally show the audience everything a contractor is not supposed to do. I've even got lots of issues I didn't list. Haha

[@markwyman1254]

This got me thinking. You only need r-4 insulation for ductwork in conditioned spaces. So if you encapsulated a crawlspace and cut in a dampened supply or 2, could you then use r-4 bubble insulation and not have to mess with r-8 fiberglass?

[@SeanLi-i7n]

What can you do if your duct work built is in the attic? I actually do not mind some cool air leaking to the attic or attic-air-duct not perfectly insulated and house not that air tight. Considering all the problems for an air-tight house if something goes wrong - moisture build-up, roof leak, water leak, shingles peeling off. Energy efficiency is not everything - got to have some compromise. I'd rather have a well ventilated roof and nothing attached to the roof-deck and sacrificing some energy efficiency.

[@scottbroadbent2086]

Western Houston suburb. I hate that the HVAC is in the unconditioned space in the attic. I go up there every few months and clean everything. I put HVAC access doors on my plenums which I open up and clean out as well.

[@Sarahd1324]

If your roof is a bit older (9 years) then rockwool sounds like a better idea than spray foam? Can it be done if you have a medium complicated roof instead of the most simple layout?

[@IAmKyleBrown]

Calling in from the Midwest here, I'm feeling t's just as prevalent in the North. So many houses have air returns on exterior walls. I've pulled one open during winter and there was nothing between the metal duct and wood siding! At least the air supplies tend to be on the interior.

[@Jcewazhere]

Whenever it's windy my bathroom exhaust flaps bang around like crazy. At my last house I could just hang a magnet from them and pull it off when I wanted to use the fan, but this new place has a 90 degree turn and plastic flaps so that trick won't work. Is there a quick/easy fix? I know I could tear the thing apart and put a stronger (or any) spring on it to keep it closed, but two problems. That's a lot of work, and it might keep the thing from working when I want it to. Suggestions?

[@alberthartl8885]

As a general contractor the most common problem I see is faulty ductwork. It is not that hard to get it right. Put the supply registers at the perimeter of the structure with the return near the center. It is really that easy.

[@michaelmcewan5074]

Open cell on the roof line tends to create humidity problems and the need for a whole house dehumidifier which consumes energy and adds cost of installation. Closed cell is the way to go on the roof line.

[@peteyou2325]

How many inches of closed cell foam would be required under the roof deck for a conditioned attic? I believe a conditioned attic is better than a vented attic in the south. Is insulation required on the floor of the attic if your doing a conditioned attic?

[@sparksmcgee6641]

Oh yeah vapor drive in the south. Permeability would be a big issue. I only use closed cell, usually rigid.

[@stephaneboisjoli1320]

When they installed my solar air heating system (yes, heat, not electricity), they put the ducts IN the "fluffy stuff", which there was tons because cellulose insulation is super cheap so you might as well load up on it - what else are you going to do with your attic? (just make sure you have the venting correct!!)

[@BillJBrasky]

What would you recommend a homeowner do if they unfortunately have ducting in an unconditioned attic? I have a 2-story with two air handlers, one for the basement and main floor and one for the 2nd floor. All of the 2nd floor air is run through the attic. I'm in Nebraska where we see the full spectrum of hot and cold temps. Do I just hose all the ducting with spray foam? Roof is built with standard trusses so making the space conditioned isn't really an option.

[@DTWCT]

Why can't you spray foam the roof for a conditioned attic? If not then yes spraying 1-2" on all the ducts is the next best bet

[@michaelsatterfield7944]

As an hvac guy. Please don’t spray foam your duct. Just wrap it with proper fiberglass insulation.

[@DTWCT]

@michaelsatterfield7944 reasoning? Fiberglass sucks. Especially in an attic where condensation is a concern. Or the possibility of rodents chewing it. Also the spray foam completely air seals the ducts so you're not losing conditioned air that you paid for to the outside

[@BillJBrasky]

@DTWCT it's my understanding that most asphalt shingle roofs aren't rated for an insulated deck so I'd probably have to build out a ventilated gap. Seems like a major pain in the ass with the trusses all in the way.

[@skipbogard]

@@DTWCT SPF insulation contains chemicals called isocyanates. Isocyanates: Rhymes with cyanide. All foams degrade with time, and especially with heat. Do you really want cyanide compounds in your attic? While I cannot speak for Michael directly, it kinda sounds like HVAC guys would rather not have to deal with cleaning up decomposed cyanide-based compounds it in the future when they go to repair ductwork. We've seen similar stories at least twice before: Chinese drywall (sulfur+water=>hydrochloric acid) and UFFI foam (Urea-Formaldehyde Foam Insulation). Amazingly, the building construction industry seems to find a new, seriously toxic building material to use about every 8-10 years. Two-part field-mixed spray foam is the new UFFI used in the 1970's and early 80's.

[@CMbassin]

This video refers to heating and cooling? What about if you need to run an HRV or ERV fresh air or exhaust through some attic space? Does the same principle apply or not so much because the air isn’t really conditioned?

[@chriswilson7138]

Same really. I have an ERV in Dallas,TX and the temp rises a few degrees while passing through the ductwork in the attic.

[@CMbassin]

@@chriswilson7138 I’m in VT at the other end of the spectrum but my HRV duct passes through the attic for about 10 feet in a joist bay. I haven’t blown my insulation back in yet so since it rests against my ceiling vapor retarder so basically against my ceiling drywall I was wondering if I built an insulated box over the insulated duct then blew in over that maybe it would be a bit better than just the duct jacket.

[@manuelbustillos3925]

Crawl spaces are not as bad as attics. Just think about it ... Heat rises! I have seen as much as a 1/2 ton needed to be added based on a load calculation due to the ducts being located in the attic. In my opinion, the best option is to encapsulate the crawlspace and locate the ducts in the crawlspace with a downflow furnace located on the main level. Additionally, it may be possible to condition that crawlspace area by opening up a return and supply vent. this provides warm floors in the winter and prevents plumbing from freezing.

[@mattalbrecht7471]

If i were to build my house in the south (i live in texas. I bought an existing house), i would go with mini-splits just because too many cold and hot zines, and let everyone control the temperature for their spaces

[@austinc8176]

What do you recommend for someone with a dumb attic in Texas but not enough cash to pay for spray foam and a new roof?

[@utpharmboy2006]

i have a full size 4 corner basement under the same size 4 corner single floor home each level 2400 sq feet. basement is half garage/shop with the other half waiting to be finished. basement is mostly conditioned....in other words i don't have as many open vents but it stays a little cooler in winter and about the same as upstairs during the summer. all of my utilities and ducts run from the basement up. the only thing in attic are a few electrical lines for some ceiling fans and lighting. i love my setup. no nasty crawl spaces and no attics with ductwork and air movers attracting condensation. like matt ive been in miserable attics and nasty crawl spaces enough to know i was never going to build a house where i would ever have to be in either.

[@sparksmcgee6641]

The dream unfinished basement. Aaaaaaaah🎉🎉🎉🎉🎉🎉

[@utpharmboy2006]

@@sparksmcgee6641 yah it's good stuff🫨

[@charlessndenton]

When doing spray foam on crawl space walls, are there issues with termite inspections?

[@skipbogard]

Yes, termite companies are dropping their customers--even those with a 3"-6" termite inspection gap (required now by some local codes). There is an on-going battle between crawl space renovators and pest control companies. Many crawl space renovators are being rather vicious, blaming the termite pest control companies for using "outdated inspection technologies." Some crawl space companies claim pest control companies should be using magic technologies like high-powered stethoscopes to listen for termites, or use infrared scanning to locate termite colonies (sounds a bit like injecting disinfectant into your veins to kill off COVID). Close, but no cigar. There is no technology substitute for the visual identification of termite tubes ON A CRAWL SPACE WALL. Spray foam or foam insulating board covers & insulates a crawl space--muting termite colony sounds and attenuating thermal termite signatures. There are at least 10 or more videos on KZbin on the subject of termite companies cancelling customer termite bonds after encapsulating their crawl space. Then, there is this interesting story here in my hometown of Raleigh: "Beware of Termites in an Encapsulated Crawlspace" fcinsp.com/encapsulation Cutting to the chase: If you are buying a house that includes an encapsulated crawlspace, it is especially important that it is covered by a termite bond and that bond should not lapse.

[@MrItalianfighter1]

I have a 1957 built ranch. No basement, slab. My supply ducting runs through the slab to each room and my air returns are in the attic. So I think my setup is more efficient and the floors are warmer. The problem is that the supplies are not actually in ductwork, but jist open channels running under the slab with a pea gravel base, so I assume it has a ton of air leaks and probably not clean. I don't understand why they wouldn't have installed ductwork before the slab and because its under the slab, It would be very expensive and labor intensive to repair. My only real option is to seal the vents off with concrete, get a new furnace to blow up, instead of down, and run the ductwork in the attick. Either option sucks and I would rather get the ductwork under the slab sealed. Maybe run a sprayer through them and spray some sort of sealant. I can't find anyone that does that in my area. Thru all said without ductwork already there, they can't do it.

[@AdvancedesignServices]

Matt: I've noticed on a few of you more recent videos that on the outro you'll align "BUILD Show" with the music drop, which is an excellent touch. I will say that on the "OOOON" before the drop, breaking your voice has just been a little cringy. In the preceding 2-3 years, you'd add max emphasis on "OOOON" without breaking your voice like a 12 year old, and I think that's optimal: elevated vocal emphasis without breaking, then dropping the music in on "BUILD". Unsoliceted 2¢. It's a tiny detail, but knowing you're the detail wizard, I thought the input would be appreciated.

[@joer9276]

42” frost line in my area of NY. Some areas go down to 48”.

[@heytoast7129]

I apologize if this is a dumb question as I'm not a builder. But how much HVAC venting would be needed in an attic that's not venting to the outside?

[@sparksmcgee6641]

Almost none because the unit and duct will heat and cool the area. If you want air filtration the standard is to put a return vent and supply vent as far away from each other. Just a return is an option if it's a old leaky house. If you're DIYing it get a 2"x8" saddle boot and a vent cover so you can control the flow. Or The Profesional way a tradesperson would do it is just cut a hole or two in the duct and never look at it again. Tradespeople don't have flexible duct in their house.😊😊😊😊😊

[@thenexthobby]

Matt, every roof will eventually leak unless you preemptively replace it. Replacing anything before it breaks is not usually sustainable. We should not be aiming for 100% reliability with today's tech. It's not realistic, not for a ROOF. :) You can foam an attic but now you're compelling the owner to replace the roof before it leaks -- somehow. On a schedule?? Rockwool is indeed the compromise here: It will let the eventual leak reveal itself before becoming catastrophic, and not harm the mineral wool. Also, where's the radiant barrier here? Assumed to be built into a fancier external sheath? Thanks.

[@jeffa847]

I'm not a builder but I'm with you. It seems like a lot of these designs work beautifully in theory (assuming the builder is very meticulous and has an excellent crew) - but get them out in the real world with ignorant and/or negligent homeowners and the untrained and indifferent contractors they hire to later come in and cut holes in walls and 'fix' things and you've got a recipe for leaks that will not dry out and not show themselves until there is catastrophic damage.

[@shubinternet]

@10:10 -- there's a weird audio overlay as part of the picture-in-picture display here. I think you want to correct that.

[@sparksmcgee6641]

Just worked in an area where none of the workers or inspectors knew what the rating was on the seam tape they were using. No inspector is getting in an attic to check tape.

[@jamesphillips2285]

According to google: the frost line up here in Edmonton is 2.5m (8ft) below the surface. Edit: checking a few more links: looks like it is around 4ft, but 8ft is specified for things like sewer to avoid freezing.

[@Radium3D]

For an attic situation could you instead build an insulated "box" around the ducting instead of insulating the entire attic, removing the insulation below between the ducting and the drywall? Our home in socal is 1970's and has the ducts in the unconditioned attic. It's also got dual whirlygigs and air vents all around under the eaves of the house though. It seems very dry in the attic. That said, I do think the soft mylar style ducts have quite a bit of loss with the thin insulation they have. I'd just hate to insulate the attic ceiling with closed cell foam and then down the road have any kind of roof leak... We have a relatively new roof installed, less than 7 years old, and it's solid, but I need to be able to inspect the wood.

[@gtg-inspections]

Matt, how about mini split ceiling cassettes?

[@scottturner4965]

Does a bathroom exhaust fan duct through an unconditioned attic cause condensation and microbe growth?

[@notmyname9876]

It all comes down to cost. Unless your client is wealthy, the cheapest way is to blow in fluffy stuff into the attic and used insulated ducts up there. For two story houses, using the crawl space works the same. With just a little bit of effort, the ductwork can be properly sealed to mitigate the air quality concerns. It's not nearly as good as the monopoly house framing technique you describe, but it's waaaaaaay cheaper.

[@conradrichard1492]

Metal, metal, metal!!! No flex through the first floor ceiling. I have seen flex duct in the ceiling become extremely brittle. Plastic holes and the insulation wrap exposed to the air flow. (I hate fiberboard for a similar reason, fiber glass in the air flow).

[@michaelsatterfield7944]

Thank you! Too many homeowners don’t want to pay for sheet metal duct and too many HVAC contractors either too expensive to do it or don’t even know how.

[@sparksmcgee6641]

So people don't use vent boots and bring the flex to or through the drywall????

[@conradrichard1492]

@sparksmcgee6641 they do use vent boots, but the inner liner of the flex pipe is plastic or a thin rubber. Over time, the inner liner will break down with all the hot and cold going through it, drying it out, over the years. The inner liner will become brittle and will start getting cracks and holes in it. These holes will expose the insulation wrap around the inner liner to the air flow. Metal is a better product. And this is only one reason. There are two other big reasons to go to metal and not flex.

[@elgringoec]

24" Frost line here. All ductwork within conditioned space. Built myself 30 years ago. Figured that out for myself. Common sense.

[@ScottMyers-j4s]

130F 70% RH is 117F dew point! NO WAY is it that high! Nonetheless, great video, thanks.

[@jonblakemore6454]

Yes. NOAA says the highest ever recorded is 95 degrees in Saudi Arabia in 2003. I expect more understanding from Matt.

[@KyleMackenzie]

Frost line for me in Southern New Hampshire is 48 inches.

[@mattalbrecht7471]

I have 10' ceilings, and all the ductwork is in the ceiling, which is a 14" truss - so lots of space for plumbing, ducts, etc

[@mpharr2]

How about those homes in the northeast with ducts & boxes are installed to LED commercial standards (no leakage)

[@mikecoombs3972]

Does it make sense to use closed cell foam on the rim joists of an older home?

[@sparksmcgee6641]

No or maybe if you're doing a new continuous insulation layer and it's incorporated. Air sealing is more important than insulation if you aren't doing the whole house. Rigid is waaaaay better than spray so use that anywhere you can.

[@mikejf4377]

Matt what is the cost to retrofit or remodel a house to those standards. I would have to replace all my outside sheathing and replace it with a insulated material, then cover that with the steel covering. Than the roof would have to be re-dun with a sealed covering then a metal roof and upgrade the windows which are original from 89 I think. How long to get a payback for this. You sell your house to one of the vultures owned buy a corporation it wont get all that. They'll will do the least to get it rented.

[@coryschaffhausen3048]

Frost depth in northern Minnesota is 60”, southern MN is 42”

[@sparksmcgee6641]

Yep, I'm in Colorado at 3-4 and once you go that far you might as well do a full basement. Even all the tract homes have them.

[@DuffyGabi]

Worse thing I’ve seen. Supplies run under the basement/concrete floor. Two different houses. Both took on water. Bred mold. Had to be abandoned.

[@scottmason2094]

On the concentric vent, you have the intake exhaust backwards

[@GordonKnight-x3m]

Frost line in southern Nevada is 2 feet.

[@donz327]

Audio tip for your next video: Isolate the microphone off of the table. Every time your hand hits the table, we get a huge bass thump in the audio. Otherwise, very informative video!

[@Scott-cu4ol]

why not use Mirex 200 over your rockwool in your attic? is it just not needed

[@berkleyman1]

Northern half of Minnesota 60" frost depth footings, Southern half of Minnesota 42" frost depth footings. Got to love to dig like a gopher on steroids.

[@agrarianelectrictractorco.400]

48” in southern Ontario

[@donbrutcher4501]

48" frostline Oswego Cty NY

[@TexasEngineer]

Builders don’t care. They put the HVAC where it is cheapest. A lot other times their ducts are too small. Remember the HVAC installer’s name is “Low Bid”. I have a 1.5 story slab on grade, cir 1977, and the attics were not able to be insulated. The HVAC sweated profusely. The problem was ths coil was too cold mainly because the fan speed was low. I did not understand that new replacement blowers would go bad. Then I replaced the air handler with not perfect results and reduced, but not eliminated sweating. I then replaced the outside unit with a RUUD 20 Ultra variable speed. The duct air temperature was warmer and the unit ran low, slow and long. I set it to run 40 minutute on low and then shift to high. The shifting to high speed takes care of the humidity issues the low speed causes. The sweating is gone and so is my high power bill. Variable speed to the rescue. I still agree with your video, but sometimes you can’t fix stupid and you have to find a way to live with stupid. Still living with stupid.

[@beardoe6874]

Alternatively you could use mini-split heat pumps to eliminate ducting. My personal kink is a single pitch shed roof that has the insulation, and a radiant barrier all within the height of the roof I-joists with a vapor barrier below and a vented air gap above. No attic to speak of and uses cheap blown in fiberglass instead of expensive spray foam or foam board. If it's sloped down toward the south, perfect for mounting solar too.

[@shannabolser9428]

Frost line 36 northern Indiana. Not putting duct work in my new build cause it is disgusting

[@ronsmith7739]

What we really should do is a "mechanical room" on the ground floor for HVAC and the roof / attic space designed for a conditioned attic / roof. And stop using the attic hot air.

[@sparksmcgee6641]

​@Navy1977yeah and that's better usually. Just sold an entry level new build at about $250sf so just the code requirements for access 12sf for an upright without the door swing requirements. So $3000 to put in a room. 6 to 9 k if it's for water heater ect... Way cheaper to just shift insulation to the roof. But customers don't want to pay for it.

[@l4xx03luyf6l0to]

My frontline is 6”.

[@natew2610]

My frost line in NYS is 50 inches.

[@woodturner1954]

I know another dumb construction move that only saves building time. Why can't small electrical lines like phone, internet be run through conduit in a orderly way. The last week or so I've had intermittent phone connection to my master bedroom. I'm thinking mice finally got to it. Built in 83' only had a phone in the kitchen and master bedroom. no doubt it stapled all through out attic and walls from garage where it originates. There's no way to pull new cable through. I know it would be added cost but if a house had a central closet everything routed to or from it would make for shorter runs. And maybe save someone like me 40 years down the road. Of course by then phones will all be wireless. Now I need to find a multi-phone answering machine with 2 extra wireless phones. I know rant, rant.

[@jeffa847]

I dealt with the same things including with wanting to bring coax through. SO stupid to staple it and not put it through conduit going up a wall.

[@skipbogard]

@suspicionofdeceit I use my old school phones to ring my lost cellphone when I can't remember where I left it! It's $10 a month more on my Google Fiber plan to tie my fiber to my existing (1990's) twisted pair phone loop running from room to room.

[@sparksmcgee6641]

You're literal 20 years behind. Media cabinet that goes on the wall ear where you're electric panel is. Everthing wireless from there, house phone if you want one, cellular booster, wifi ect... Only guy that loved tech that ran a direct line around the house and through the wall to a TV was a competitive gamer that couldn't have the millisecond delay from wireless. Look at the wireless home phones. They're expensive because only rich people had them 20-30 years ago, then everyone jumped to cellular.

[@kb5ulp]

Why not do away with ducts altogether and use a ductless mini split system?

[@sparksmcgee6641]

Cost, less functional and no direct airflow control for rooms with a delivery head. They have high pressure commercial ceiling boxes, but now you've hit a cost higher than tearing the roof off the house and redoing the whole thing.

[@nationsnumber1chump]

My split level has the ducts between upstairs and downstairs 🙂

[@alexanderjamieson7971]

4ft frostline where I live

[@usmarshall336]

And mold is not covered by any warranty or insurance company do not cover anything!! *Yes these are some great ideas but trying to convince customers to do this it is really hard to spend 30 to 75,000 extra to do all these nice amenities to make sure your HVAC system doesn't condensate.. when you've got five other companies dropping bids for something totally different and your 30 to 50,000 less ..

[@irsever]

This episode is brought to you by Kilz Mold & Mildew. Paint it white and you're alright!

[@smu4043]

There has to be a downside here. What is it? Roof shingles don't last as long??

[@scha0786]

Open cell spray foam on a roof deck????? That will allow moisture thru foam, sounds like a mold and rot issue in the future.

[@LincolnLog]

Strange he suggests it. Minimum is 1.5" CC to act as a moisture barrier then open cell over that is optimal

[@ashtonpalmer5035]

frost line 7' 11" deep