Your HVAC specs might be COMPLETELY wrong: Manual J Training

Check out Corbett and Grace Lunsford at ‪@HomePerformance‬
homediagnosis.tv/
Subscribe and follow my Podcast on Apple or Spotify!
Apple: apple.co/32AOwgU
Spotify: spoti.fi/3FXNg4X
Sign up for our twice-weekly newsletter:
buildshownetwork.com/newsletter
To sponsor a video or advertise with us visit:
www.buildproductions.com
Want to learn more about building? buildshownetwork.com/
Build Show Network on Instagram: / thebuildshow
Huge thanks to our Show sponsors Builders FirstSource, Polywall, Huber, Rockwool & Viewrail for helping to make these videos possible! These are all trusted companies that Matt has worked with for years and trusts their products in the homes he builds. We would highly encourage you to check out their websites for more info.
www.bldr.com/
www.Poly-Wall.com
www.Huberwood.com
www.Viewrail.com
www.Rockwool.com

[@thezfunk]

I finally got a new furnace and AC installed. I went with the young guys who just started their own company who did the actual load calcs for my house instead of just eyeballing it based on 'experience' or the old system. I had a 4 ton AC and 88,000 BTU furnace. Everyone else wanted to replace with a 4 ton with a 110,000 BTU furnace. The guys I went with asked me details on the house, what improvements have I done, what insulation have I installed and witnessed installed. What air sealing have I done, etc. They sized me at 60,000 BTU with a 2 ton system. I was really, really skeptical since they were the outlier but they showed me the numbers. It helped they were the cheapest since they were installing the smallest equipment. I had a 30 year old furnace and a 40 year old AC so anything newer would be an improvement and so far, everything they said has proven true. We'll see this winter but so far so good.

[@Onward1969]

There correct. I’m a HAVC guy and I learnt trades people hate doing calculations. They will do quick math but they won’t sit down and do the actual calculations. You fluked out and found the right guys.

[@potentialhvac6074]

What's the square footage of your house?

[@NINEx7x]

Can't recommend Corbett's KZbin channel enough, his house build is on a whole different level.

[@thetubekid]

Agreed. He does an incredible job!

[@HomePerformance]

Hey, thanks guys

[@andrewfischer556]

I’ve always enjoyed Corbett’s videos , they’re so helpful and informational and he’s such a energy geek like me. I’m surprised he didn’t get into more details about orientation at the house N,S,E, W. With the manual J software we can easily simulate how the heating and cooling loads change by virtually changing the orientation of the house. The exact same house facing north south east or west can require different heating cooling loads They can vary as much as 25,000 BTUs depending on which way the house is facing. This is why I recommend running these calculations before the architect and builder Have filed plans for the building permit. An energy and comfort conscious buyer owner might be willing to change the orientation of the house to reduce the energy level by 20%. Manual J software can even take into account roof overhangs and tree shading for more accurate results. For new construction is pretty rare to have tall meaningful trees close to the house. But for older homes in retrofits it’s very common and can result in a half ton more difference in the size of the condenser and coil. I was also surprised Corbett didn’t go into details about CFM versus BTUs. Manual J software can give a room by room breakdown of CFM’s delivered for heating and cooling season. This is a critical detail for the HVAC installer needs to use the maximum CFM of either heating or cooling. And make sure the ductwork and registers are sized properly to deliver this predicted CFM. Manual J software can also take into account whole house ventilation systems to deliver the desired ACH. It’s also important to note that anyone can learn how to design manual Jay reports with the right training. Builders can learn it and do it themselves. HVAC designers and installers can learn it and offer more value to the builders. More architects need to learn this technique as well. Most city and county building departments now require manual Jay reports before they will issue a permit for the house or a new HVAC system. And if I’m the owner or buyer I would like a thorough level of details and no more of this rule of thumb BS. Also he didn’t speak about zoning very much. Manual J software can and should also model zoning the house based on multiple zones for a single set of equipment. Or multiple sets of equipment per her house with each equipment serving one zone. Manual J can also be used for what if scenarios like, what if I used ductless split units versus traditional unitary equipment with sheet metal ductwork. They can also run what if scenarios showing flex duct versus metal duct. They can also show what if scenarios that show the difference with or without fireplaces and how many fireplaces. I use Wrightsoft manual J software. But there are a few others that are good including Elite. All manual J software Hass to know the ZIP Code of the building and uses that to get accurate weather data to predict heating degree days HDD and cooling degree days CDD. These are critical parts of the heating and cooling load calculations. The HVAC designer can vary whether you want to design to the 90 percentile (not recommended ) 95 percentile which is what I consider the sweet spot. Or the 99% percentile as Corbett went to in this example. You won’t take a big a hit designing to the 99% in a Matt Risinger new construction tight, energy efficient house. But 99% would be overkill in a retrofit of an older home.

[@HomePerformance]

Right on, Andrew- honestly, this video could have been 3 hours long and we'd still leave some stuff by the wayside.

[@mattgirgenti3595]

I am smack dab in the middle of this so the timing of this video was PERFECT! I have a bunch of twists since I am comparing a VRF zoned solution versus a Geothermal (pond loop) solution. Apples and Oranges, BUT the both are viable and our personal long term goals come into play. Oh, and we are about to start a remodel of the 70's ranch house (vetting contractors now) and build a new office/in-law suite+garage workshop at same time. I am not sure I could add more if I wanted to (except solar and 2nd well, which is already in process. ha!)

[@davepetrakos475]

Corbett is a composer for the music in the mechanical room. One of The Best 38 minute videos. One take away is even though we need to plan on 100 yr flood, we don't really want to have huge equipment for the heatwave that seldom shows. With humidity it is more efficient for a slightly smaller system to run longer than a larger system cycling more frequently

[@boby115]

I’m glad he straightened Matt out about including the size of the conditioned attic. Matt always acted like he got that square footage for free (it’s not free ,you have to condition it); is it better than insulated ductwork in a hot attic ? Absolutely. So glad I live in an area where 95%of the homes have basements. Corbett did an outstanding job on explaining how manual J should work 👍. Ductwork design manual D is every bit as important as manual J . Size the ductwork correct, install the supplies in the area of the windows and install returns in every room but for the bathrooms and kitchen (Life will be good whether you have a single stage , two stage ,VRF or VRV).

[@Balticblue93]

I totally agree with everything you said. i just wanted to add that the Manual T and S are also becoming just as important to the equations. I have no laid my eyes on the Manual RS but it is coming. But as technology gets better, more expensive and more efficient; things are going to really change, and some information will be obsolete. My HVAC business doesn't do much zoning, but it looks like it will be going more in that direction. Living in Denver in a very arid climate has some major challenges with psychometrics amongst latent heating and cooling.

[@maurozammarano6651]

In terms of cost, what is better in zone 4a: mechanical and ducts in 1) a basement with a vented attic or 2) slab floor with an insulated roof?

[@boby115]

@@maurozammarano6651 , That all depends on the norm in your area. The norm here in the St. Louis Metropolitan area is basements. I have a 2500 square-foot ranch with a 2500 square-foot basement.80 % of the basement is finished ( bar, game room , media room TV, Office). unfinished section ( mechanical and workshop). Try to get that out of a conditioned attic. Forced air systems are the norm, gas furnaces where natural gas is available ; heat pumps, propane furnaces & mini splits out in the rural areas.

[@jamesphillips2285]

Up north where I live: the attic is generally left unconditioned to prevent snow melt and ice damming. Basements are very common though: so that is where you will find the ductwork.

[@Fulloctanegarage]

I own a new construction heating and cooling company that does primarily single-family residential. We start about 12 houses every day. Probably the biggest challenge that I have seen is getting accurate and current information from the builders about the product that they are building. We will often see that Building materials or processes have changed especially due to the supply issues of late. Situation is like not being able to get tech shield and so they just leave tech shield off houses for a couple months but they failed to notify anyone lol. We sent out builder survey sheets every six months to all of our builders every six months where they enter all the current specifics for all of the factors that will affect our HVAC load a.k.a. windows, insulation package etc. it’s always a work in progress. We run plot specific loads on every house that we do. Actually that’s probably another good point, using generic house plans and not taking into consideration the orientation of the home on the lot can make up to a large difference on a six or 7 ton home because of window exposures.

[@boby115]

Sounds like you’re home builders need more of an understanding about the numbers you need. If I were you I would set up a meeting to demonstrate the Wrightsoft software for manuals J & D so they could understand the importance of the numbers that you need, (Communication, education and understanding is the key). I know Matt’s understanding is a little better now that Corbett demonstrated manual J but manual D is also every bit as important (sizing ductwork, supplies in the area of the windows & Air returns in all of the rooms but for the bathrooms and kitchen).

[@D2O2]

@@boby115 If those builder(s) are starting that many homes a day, I am betting the level of caring isn't all that high.

[@bj820]

Is your heating and cooling company located in Los Angeles, Ca?

[@robertsmith2956]

Yea, I remember a guy trying to go cheap and copied the blue prints backwards. After the foundation was pored he realize the front of the house faced the mountain side, not the view over the city. Rather than start over he built it but the window calcs were way to high with them in the shade year round.

[@MegsCarpentry-lovedogs]

Wow! I came across his channel organically just by looking at passive home inspired building that emphasize air tightness and water....so wonderful to see your support with this man! 👍💯🇨🇦

[@CajunGreenMan]

This! is! perfect! I plan on installing my own geothermal system, and I am not trained as an HVAC repair man. This is exactly the deep dive into manual J that I've been wanting! Keep up the great work!

[@allanlindsay9414]

Having lived in a 1970 built house for the last 20 years where NONE of this planning work was done I can tell you that no matter the price point of the build this is critical and actionable information. For those viewers who are "just a homeowner" take these details and think about it carefully before you have your H-VAC (I'm in Illinois that's how we say it :) ) replaced. Maybe you need to have your duct system tweaked to avoid hot rooms and cold rooms. Maybe an ERV is worth the retrofit. Great information here.

[@HomePerformance]

Thanks Allan!

[@timdestasiohvac]

An encapsulated attic is not considered a conditioned space. It is a "semi conditioned" space because we are not trying to maintain 75/50. Even though it is inside the envelope, it should not be treated the same as the living spacr. In Wrightsoft, you can select the ceiling material as an encapsulated attic, set the roof deck R value, and the expected attic temperature (usually 85 degrees). There is a small transmission gain and duct gain from an 85 degree attic into a 75 degree space.

[@D2O2]

Yeah, and who wants to keep their living space at design conditions? Additionally, this is at the worst one hour of the day. Love to dig into the duct loading assumptions since manual D is likely not complete. I like how they quickly moved past increased cooling load as a result of decoupled slab.

[@hubercats]

Great video! Thank you. One comment follows: When discussing what I’ll call “effective square footage” I think what’s really important to convey to viewers is that it’s the volume of the house that gets heated or cooled, not the square footage. Given the volume of the house (cubic feet) one can then divide by the ceiling height (feet) to get an “effective square footage” (feet squared) which is what the Manual J calculators require. As a caveat, I’m not an HVAC specialist (rather I’m an electrical engineer) so I may not be thinking of this problem correctly. I hope this comment is helpful.

[@jefftee448]

Yea, you're absolutely right. I had that cubic area thought as well but I sort of questioned it considering the wealth of knowledge the both of these gents bring to the table.

[@seancollins5769]

That was fantastic! Thank you both

[@DaveCLL]

From what I've seen, many HVAC companies do not know how to handle a house with a conditioned attic. With a steep pitched roof a conditioned attic encompasses a large volume of air. This definitely influences the temperature in the house below the attic. This is largely overlooked by most Manual J calculations I've seen.

[@totallybonkers]

I thought Matt was going to say "Let's back up a second, you're not an engineer?" 🤣 Let's hear it for the musicians! They never cease to amaze me with their intelligence! I know many who moonlight in other professions and are the best at everything they do!

[@gracemcphillips]

Mysteriam ;)

[@DahEnforcer]

Music is so intertwined with math it is a natural crossover into may professions.

[@Nick-bc2lm]

I am one of the many in the humid south east Texas that has their duct work in a hot 140 degree attic. Been doing a lot of youtube, research, learning, and note taking. House needs a new roof along with a new efficient AC/furnace system. Didn't know there were 3 different run cycle units. Not my "forever home" so on the fence about a metal roof. Tonight, saw Matt's roof build with cool-vent panels. Will accept shingles or metal roofing. One thing I am for sure doing is spray foaming the attic. My folks had their 3 car garage spray foamed, and installed a mini split system. I'm sold on the foam and mini split. Will be adding one to my garage as well. Lots of good info. I have to find an auditor to do load calculations, someone that doesn't work for HVAC company. That way they can't tell ME what size of a unit I need to install. During these past hot few months, electric bill has been 400 bucks, for a single story house. So I am reading and looking to see what all I can do to make it low as possible. Changes are coming very soon. I am enjoying all this free info yall share. Down the road when I plan to move west, (centeral Texas) makes me really want to build a home so that its built right from the start.

[@carrabellicusp]

With Aerobarrier you can dial in the ACH60 to your target not a substitute for tight construction but takes the pressure off

[@MorryB]

Great timing, I just had a furnace installed today, lol. I previously asked the installer here in Canada about "manual J" and he didn't know anything about it. Maybe someone here knows what we use in Canada? There's some energy modelling software from NRCan called Hot 2000, but that seems like a lot to ask from a typical furnace contractor!

[@kaspergruszczynski9919]

HOT2000 was developed to enable the EnerGuide program in Canada and it can calculate a heating and cooling load for a home. We use it to determine an energy rating for a home for performance upgrade rebates and we tell customers to treat the calculated loads as approximations and that it's beat to get a more thorough calculation done when sizing loads. HOT2000 may be able to calculate a more accurate figure, but you'd need to dive deeper into the software then we do, similar to Corbett with his Manual J calculation. HOT2000 is also used for the NetZero program in Canada who make deeper use of the software.

[@garyhiland6013]

Corbett's video on HVAC static pressures is the best on youtube. Just finished the BS and Beer seminar in Kansas City last week and I told them they needed to get Corbett for next year's tour.

[@HomePerformance]

Aw shucks, thanks Gary!

[@erickessler6094]

Matt, Don't apologize for a long video! This was an amazing and critical subject with Corbett! Love ya bro, so keep these extremely practical videos with Corbett, Scott True, Steve and Jake for long format! Cheers, Eric 😊

[@TrainFlood]

One of the best videos you've ever put out. Thanks Matt and Corbett!

[@HomePerformance]

Wow, high praise for us both! Thanks Teo

[@davidhoover2446]

Really excellent information. Somehow on my house the installer really missed the mark. All the rooms cool evenly, but I never hit stage 2 and even at stage 1 70%, I rarely see 100% run time. I've slowed the fan and activated dehum mode to get more run time and dehumidification. I also now have a retrofitted ventilating dehumidifier.

[@bigpapa1470]

@Matt - In regard to the direction that a house faces, which is a good point as it relates to HVAC, but don't forget to look at your solar installation, even if you not installing one now. The roof type and orientation will play into the solar panel efficiency. You need to consider both...

[@taylorandersen6494]

This is amazing advice! I will definitely be doing this on my next project.

[@TagiukGold]

Thanks for this video. I'm so tired of rule-of-thumb bs, also with no testing or checking reality. The US would use 15% less energy with careful builders and smart architects.

[@hvac-r977]

You have to think about the AC cooling capabilities are getting lesser when people don’t care about their ACs and Freon leaking, etc

[@3nertia]

15% sounds pretty negligible though?

[@TagiukGold]

@@3nertia Depends on the upfront cost. In my climate, many energy efficient design and build upgrades have a 5 year payback for new construction.

[@RogerWilsonTodd]

Excellent info and impressive knowledge!

[@jepito29]

Real interesting, also Loved this type of long form/ in depth coverage of a single topic

[@CommonSenseFishing209]

One thing I'll say as a hvac business owner. With system sizing sucks big time if you put in one too small. Put one in too big and sure you'll have some issues but not as pissed off a customer as one who's home can't cool below 78 on 110 degree day when their neighbor can get down to 68 on a 110 degree day and both homes are similar. With that being said, don't be lazy. Do a load calc. But ways you can avoid screwing up load calcs is installing variable speed equipment and proper ducting. Also. When you do a load Calc for 99 degrees but we have like 40 days or more over like 105 this year in Central valley CA. Dry humidity. Don't want your system running too long. Dry the air out terribly.

[@HomePerformance]

Good points, fisherman

[@TennisFan2004]

I live in the Center Valley....26 days straight of triple digit heat means an insane power bill and me praying to the HVAC gods that my ac doesn't crap out. I just hope my ac hangs in long enough to insulate and generally upgrade my building envelope. My house was built in 1948 is leaky and maybe has a few inches of blown insul in the attic.🤣😭🥵

[@davidfleuchaus]

28:18 Uninsulated/insulated slab comment. I own an old house near chicago with a large uninsulated heat sink. Our basement has a 6" concrete ceiling, 12" thick concrete walls going down 8.5' below grade with only 6-12" of exterior exposure above grade. In the summer our house is almost entirely passively cooled. I can cool our whole house in the summer with a 5000 BTU window AC unit placed at the top of the stairs on the second floor. On the hottest days we turn on a second 5000 BTU window unit on the first floor. Someday I will insulate the top 3-4 feet of my foundation walls. Our ground temps average 54F +/-5F 8' below grade. So all in all some good tradeoffs.

[@HomePerformance]

Cool David- good to hear from you buddy

[@Balticblue93]

That is awesome and amazing all in one statement. Pretty incredible how different everyone's situation and home can be different. You scored on the sensible heat lottery!!

[@robertsmith2956]

but what does it do for winter when you WANT hot air, and the ground is 30 degrees? My first floor from the slab is nice and cool on the hottest days, while upstairs you could make a sauna if you spill water on the floor. I'm going back and forth about putting in a subfloor on the slab to level everything, but would I lose that nice comfort raising floor up 1" off it. I just found a defect with digital thermostats in the big freeze last week. Old coil spring thermostat was dead on heat. So bought a digital thermostat. Apparently the batteries only last about 10 minutes in the cold. Trying to diagnose the heater not working, and it kept shutting down low battery. Figured out almost two years ago when the transformer blew, it was probably the thermostat or the sequencer failure, I just replaced it adding in a fuse. Thought it was a lightning storm that did it, never thought to check the heat side, but both were dead apparently.

[@JoshuaRosaaen]

This is such a great build show style...thank you and looking forward t o more nerd level 16 stuff!!

[@ib2qwik2c]

Thank you!!!

[@erickessler6094]

Matt, Corbett, This is a stunningly gr8 edu video! Thank you both so much ! At the 18:00 point, Corbett used SketchUp to create a simple depiction of the home. Outstanding! Wouldn't it be IMPORTANT at the same time ... If we included "Strategic Window Placement" & "Roof/Soffit Overhang," so we could also refine the roof overhangs with respect to the sun on various summer & winter scenarios? Energy Vanguard did exactly that for me on my Virginia home and we increases my front south facing dormer & porch overhangs. Corbett's AED points at 23:15 about west face windows will be especially critical for me on our new NC home design, with it west & water facing front-door side. 🤔 Thanks AGAIN for a brilliant video! Cheers, Eric

[@ParabellumX]

Corbett, you're a beast, bro. Love your channel. Subscribed less than 5 minutes while watching the first video I saw of yours. Please keep up the great detailed work that you seem to have a passion for; there are some of us who actually care.

[@HomePerformance]

Thanks so much man!

[@LucrStvn]

Amazing show! Thank you for this very informative video!!

[@Hard_7_Iron]

I did these calcs “manually” right outta college for about a year. It was interesting for 6 months. Then it was just tiring. I’m sure software has made this a lot easier.

[@scottperezfox]

Great video. I enjoy this format, podcast or otherwise.

[@brightboydesigns8325]

Great content. I wish more HVAC contractors would embrace the guidance set forth by ACCA (Manual J/S/D). Do keep in mind that Manual S is critical for AC sizing because the tonnage specs on most systems are rated at design specs that you would NEVER run your system at. Therefore, you have to use the extended performance data from the manufacturer to figure out the extrapolated ratings at 75F dry bulb and 62F wet bulb (at the ASHRAE outdoor temp for your location) for a few different cfm/ton (350/400/450) airflow settings (manual S will give you a formula for setting fan speeds based on data from Manual J) You shouldn't oversize by more than 15% for single-stage AC, 20% for dual-stage AC and finally 30% for variable speed AC. There are a lot of great training videos on KZbin from Ed Janowiak who is the head of education at ACCA. Search for his "What is Proper System Airflow" on the HVAC School channel.

[@seanpatrickrice]

I really wish that I had contacted Corbett instead of just watching his videos to run a manual J on my house. I did a lot of research and I ended up installing my own ducted mini splits… Trying to save money…. I’m still playing with trying to get it to cool as effectively as I want to this year… Last winter the heating was not perfect either. Hopefully I’ve been getting enough knowledge now that I can make the adjustments I need to, but I may need to call on Corbett or a local HVAC professional to help me.

[@HomePerformance]

Hey, sorry to hear Sean, but thanks for following :)

[@SLee-qb3xw]

Corbett is da man!

[@bdugle1]

Great info! I’d like to see the calculations for ACH 5 and ACH 0.8 as well as 2. Further, since I live in NW Wisconsin, how about the variations for cold climate. Just having some illustrations should let expectations be more reasonable.

[@TommyAlanRaines]

Great video! I have an issue with the online HVAC calculators, impart because the zoning/region maps they want people to pick from can be off. Examples say you live in Region 2 in upper north west Texas, but you live on the southern end of that zone were it can get to 110+ in the summer then you are actually more like Region 1 because of the summer temps.

[@jameyairmail]

I liked this. Thank you!

[@5starCA]

Great episode.

[@CybekCusal]

People should just pay your engineers instead of asking contractors to do it as part of the install. I do this same work commercially and interior loads are much more emphasized. For example he doesn't include any televisions or computers or guests. Also the ventilation rates look really low. I didn't see a bathroom exhaust fan. Etc. I would have added more detail on the interior loads. It makes a surprising difference. And yes lights will be on in the house lol.

[@jdrissel]

After watching these videos, I am torn between moving and leveling my house! AFAICT the only things right are the slab and that it is located where there is Google Fiber. Unfortunately there are copper pipes that were not deburred properly in or under the slab and the pipes are probably not in the right places...

[@HomesAtHeart]

I just did all my calcs in excel. It took a bit to put in all the formulas, but now I understand everything that goes into it

[@jeffprussack8171]

Do you have an Excel sheet you can share? Google drive link?

[@HomesAtHeart]

@@jeffprussack8171 for DIY try cool calc

[@ericbystrom]

Why not build tight and just install an ERV and mini splits only? How can we calculate size when using mini splits?

[@HomePerformance]

Great question, and I’ll be doing a video on this exact topic if you head over to our channel. Short answer- Man J has nothing to do with the equip, it’s all sbout the enclosure.

[@ericbystrom]

@@HomePerformance Thank you Corbett, just subscribed

[@rayfedorak4770]

another great show!

[@johnwhite2576]

Corbett[-decoupling slab can be important in summer though to prevent condensation

[@HomePerformance]

Maybe in an old home, John, but most of the ones who are watching channels like this have pretty solid humidity control these days.

[@georgemoomaw9437]

“The hottest day of the year in the summer”? Is that as opposed to the hottest day of the year in the winter? ☺ The Manual J has not changed much since I retired 30 years ago. I could use it to calculate the heat load done to within 5 BTUs. The problem was (back then) units were only available in one ton (12,000 BTU) increments. 2 stage units and VAS blowers were on the horizon nut not commonly available. Great video. Great advice.

[@drewgraham]

Awesome

[@MichelleShafer-cy9id]

38:21 38:21 Will be starting a building project this fall/winter. I had planned to put slab insulation… I’m understanding that I may not be doing the home justice by doing so for the summertime. I plan to wrap the house with rockwool comfort board… I’m curious if the insulation within the slab should be taking out of the equation or not… I live in central Missouri

[@jt5747]

Corbett "White Guilt" Lunsford made it on the Build Show! yay!

[@1227Masher]

When we built our production builder grade home - I asked for a manual J and they couldn’t produce one. When I pressed them for it - they told me they did one for the floor plan and not for my specific house. Now I know better. Doing a manual J for a floor plan and not a specific house doesn’t take into account for the location and orientation to the sun in the heat of the day. As a result - my hvac struggled in the July/August months…until I did Insulation 2.0. That actually made it to where my hvac could keep up. Would love to know what a manual j report would have said my house needed. I have a 3,100 square foot single story with a single 5-ton unit. When I build my retirement home I will be hiring Matt to come down to San Antonio to consult on the build to make sure it is done correctly.

[@LeanHVAC]

How did you do Insulation 2.0?

[@1227Masher]

@@LeanHVAC best advice is to search Matt’s other videos for insulation 2.0. Watch the video and do everything he recommends. It made a huge difference year round for us - but especially in the heat of the summer and coldest month of winter. My bills are consistently much much lower than my neighbors. Be prepared for a lot of work - especially if you have a large single story like me. Do it now during the winter months before the attic gets hot. Also as a best practice - I ran lights in my attic before I started so I had plenty of light to work. Also - I bridged the trusses with 2X4’s and plywood to make an easier time of getting around my attic.

[@TagiukGold]

Manual J is one of my top 26 favorite manuals!

[@HomePerformance]

It’s a classic

[@timothykeene5853]

I use Rhvac the program you are showing, but Florida requires a 405 form, which I have to use energy gauge program

[@HomePerformance]

Everybody's gotta get their kicks somehow I guess

[@1musicforme1]

Unfortunately the utility companies are requiring us to install at anything from a delta T 0f 70-80 degrees.

[@gar24407]

A little bit of a rant here. Dont that 1-1/2 ton of load lost on the duct prove mini splits are way more efficient. You dont have to insulate and cool the attic. So you dont only save a huge expense of extra insulation for the attic, but also save the loss of the duct (friction), but also cooling/heating losses. In theory you can kept the square footage of your manual J down, but also cut those loses alltogether. I am crazy here🤔🤔?

[@HomePerformance]

Interesting point, Gabriel- I’ve found it’s VERY difficult to get all you want from a home without a central duct system, here’s why: 5 Factors for Ventilation: How to Plan a Healthy Home kzbin.info/www/bejne/fICtaZmpdruIl6s

[@6incheels]

Good Video. Is the software updated to take into account the change of climate? Is there a place where I can get degree day data for my zip code?

[@HomePerformance]

No it’s not- that’s called design day shift I believe, and you can easily model it by changing temps yourself.

[@MatthewLiegey]

Good stuff gents

[@ecospider5]

For medical reasons the 99% calculation doesn’t work for us. So I told the installers we need the house at 72 degrees even if it is 110 degrees outside. Out of 4 quotes only 1 company acknowledged that. So they got the job. I’m really glad I did that 10 years ago because we hit 110 degrees lately.

[@peteaulit]

The 72* is not really the problem, it’s humidity management for those in humid climates because you reach dew point at 72 and risk creating serious issues. You’re ok if the house is properly dehumidified and right, and if done so, you might not even need to be at 72 due to lower humidity.

[@boby115]

If done correctly you should have no problem manual J & manual D . Manual J will use your geographical location . Size your ductwork correctly, install the supplies in the area of windows and install air returns in every room but for the bathrooms and kitchen. If you still have reservations go with a VRF or VRV System. Oversizing the system is not a very good remedy.

[@fredflickinger643]

I see a need for program which can ingest soft house plans to produce the 3D model, but most CAD based architectural products already have this capability, so is this just another learning and advancing curve for residential architects?

[@Ephbaum]

Where do you include the info about the amount of shade during what times of the day and how the home is placed on the lot vs the sun?

[@HomePerformance]

The orientation of the house facing, along with every window in the model, is critical info. Shade, including trees, drapes/shades, and even insect screens, is included in the model assumptions you can customize.

[@finalf137]

You got any Manual J Pro's you'd recommend in Austin?

[@MorryB]

He mentioned "Positive Energy" and has done videos with them before.

[@scha0786]

I use Trane tracer.

[@armandovillarreal6182]

Thanks for sharing this content. I can now take some load off! 😂

[@CC-kk8yh]

As an interior design student, I love learning about building technology. You can have the prettiest finishings inside but if it's not comfortable, safe, and healthy to live in, you're not going to enjoy it. How can people of more modest means (or even landlords or house flippers) access these home evaluations to even start planning a system for more efficient and healthy indoor air quality?

[@HomePerformance]

If you just start doing math, everything gets clearer. Testing is also important. Start small, and you'll get more and more questions clanging around your head.

[@FreedomMath]

I am building my own home the reisenger way and got a useless manual J will be reaching out :) I also own mobile home parks and have been putting in 3.5 - 4 ton units in for 900sqft homes. I've been arguing with installer/prop manager for years. On the one hand these are the leakiest worst insulated structures, but it just seems impossible. I kind of want to buy a manual J for a 1985 mobile home just to settle this!

[@jasonbkau]

I own a 105 year old house with no insulation in Houston that is 1950 square feet with thirty single pane windows and HVAC in the attic with no radiant barrier and only gable vents. Two manual J from two different companies showed ~60,000 BTUs of cooling or a 5-ton. The 5-ton single stage A/C works great. A 900 square foot can’t possibly need a 4 ton..

[@boby115]

I can assure you it’s not manual J that’s the problem. Manuals J & D done properly and I will repeat done properly is the best tool in the design of a residential HVAC system. With properly sized ductwork, supplies installed in the area of windows and air returns in every room but for the bathrooms & kitchen, Life will be good👍.

[@HomePerformance]

Bring it, Damian!

[@donaldendsley6199]

Might be? I have a 3 ton heat pump in a 650 sqft condo. It was 20ºF last winter and the worst I did was a 50% duty cycle.

[@5starCA]

Can you guys explain the difference between a conditioned attic versus an encapsulated attic. My mech engineer says mine will be encapsulated even though well insulated at the roof because I don’t have actual vents cooling and heating the attic. I presume I’d need a thermostat up there too.

[@HomePerformance]

Short answer: every part of the home should be completely IN or OUT. If it’s IN, treat it like any other room, and put a supply and return pathway in.

[@johnhaller5851]

Humidity could be an issue with encapsulated. Since you don’t need insulated ducts if the HVAC system is in the attic, you don’t want them sweating in a non-conditioned attic, and you don’t want your roof rotting. Having a temperature difference or humidity difference between the attic and downstairs can lead to moisture issues which leads to mold.

[@jasonbkau]

@@HomePerformance I thought code doesn’t allow a return if you have another gas appliance in the conditioned attic like a water heater.

[@HomePerformance]

@@jasonbkau That mostly goes for atmospheric draft water heaters or induced draft furnaces- neither of which should ever be used in any home where airtightness is paid attention to. Massive problems coming whether you put a return in the room or not.

[@jasonbkau]

@@HomePerformance How about a dedicated minisplit for the conditioned attic? Insulate the attic roof with closed cell foam and insulate the attic floor with rockwool, hang the HVAC equipment, and then you get best isolation from a noise standpoint and don’t have return air sucking in rockwool fibers.

[@kimburlyz]

I seriously love this channel. So much helpful information. 👍🏼

[@timdestasiohvac]

Also Matt, do not bring the vent'g dehu supply into the HVAC return! I can send you some info from Santa Fe. Bringing it in before the evaporator coil significantly de-rates the AC's sensible and latent capacity. Bring it into a low static supply trunk!

[@SamuelBiller]

Is this the same as Santa Fe’s recommended configuration shown in their resources? We’ve just had a Santa Fe 120 installed in our home with the 6 inch fresh air input vented to the outside and the supply sent to the air handlers supply. I’m a little fuzzy on how they wired up the Santa Fe return.

[@timdestasiohvac]

@@SamuelBiller yes its what they publish. They recommend a dedicated return but they also approve of a short duct into the return plenum.

[@hkgonra]

I don’t understand why the temp the thermostat is set at is not relevant. I would never under any circumstances set my thermostat over 70. I keep it at 68 in the daytime and 64 at night in the summer,60 in the winter. Our manual j also shows 96 in my market but we had two weeks over the summer where it was over 100, I had to add window units just to be able to make it bearable inside my house.

[@thinkitthendoit3224]

how do you do this with an existing home?

[@HomePerformance]

Totally do-able, you just have to spend way more time doing ‘take-offs’- building a blueprint and finding the most accurate insulation values to assign to every surface of the home.

[@thinkitthendoit3224]

@@HomePerformance so you are saying from the interior, wall floor/basement and the parts that make them up?

[@HamidA-to8vy]

How the attic can be added to square foot and the load. It does not have walls, it is just a roof, no one live there

[@billwilljulz]

I’m no expert, but the thermostat setting is/could be different depending on the house. I preferred 69 in one house and 71 in another. It seems unlikely to me that HVAC design and install can directly nail down the exact thermostat settings the family will use. The number is unimportant. It’s the feeling that you adjust to. Maybe I’m wrong. Also, what if an elderly lady prefers the temperature at 78°? Should the design be customized and sized to that temp? When she passes away and the house is sold, the system is completely undersized for a new family. Maybe Corbett’s number is the avg. preferred temp of most people..

[@kgsails7102]

Usually the energy code dictates the temperature settings for designing heating and cooling systems and then you have an allowed safety factor. Usually you end up between sizes so you're then allowed to go up to the next available size equipment. This allows people to run the system warmer or cooler as they prefer.

[@MattPetrowsky]

Congrats to Corbett for the exposure. Schedule your Manual J with him now because his rates just got higher. :P

[@HomePerformance]

Haha thanks Matt

[@scorpio6587]

Nerd fan right here. I love this stuff.

[@josephfowler964]

I love that you called it both "H-V-A-C" and "H-VAC" - I'm from the Midwest and it's very rare to hear someone here call it "H-V-A-C", most likely because we're too lazy to spell it out every time... I know a lot of other places in the U.S do normally spell the whole thing out and to each there own but I've yet to see a compelling argument for either pronunciation being more correct... :P

[@HomePerformance]

I get the feeling H-VAC makes civilians think it has something to do with vacuums. Hence I always spell it all the way.

[@benjamintucker9829]

How about no ducts. My son and my neighbor built 2 houses with 6 mini splits each. Both houses are super insulated and a roof full of solar panels. Pretty much no electric bill

[@boby115]

If you’re dealing with slab on grade houses (no basements) then minisplits may be the way to go . Big heads mounted on the walls aren’t the prettiest things in the world and the units will lose their luster once the problems start occurring as they age (condensate pumps inside walls,unfishable line sets, retro fitting replacement heads because of design changes). But that will be the homeowners problem in 15 or 20 years, not yours.

[@MicahFunk]

What's everyone's FAVORITE manual J software?

[@HomePerformance]

As you can probably tell, I’m an Elitesoft user, numeric inputs only

[@MicahFunk]

@@HomePerformance the graphical part is all visualized in your head. It's like looking at 'The Matrix' and seeing beyond the numbers 😁

[@MerkDolf]

😀

[@robertduffy5805]

I'm a little disappointed Corbett didn't put that music degree to use and play us out with an original.

[@HomePerformance]

Sadly, I actually sang the entire soundtrack to the Muppet Movie as a technoballad at the end of this interview, but Risinger cut it out.

[@jsbrads1]

I think I can save him most of those two hours.

[@trp2413]

Dude hasn’t met my wife! She wants a 68 bedroom year round. 75 in the summer 🤣🤣🤣🤣🤣🤣

[@davidfleuchaus]

Until very recently most HVAC companies have put 99% of their attention on Heating and Air Conditioning and 0-1% on ventilation. No V in HVAC leaves you with HAC.

[@HomePerformance]

5 Factors for Ventilation: How to Plan a Healthy Home kzbin.info/www/bejne/fICtaZmpdruIl6s

[@marakevans3984]

All this Nerd stuff... *long snorting* Yeah... that's the good stuff. My brain is on FIRE! *flips back and forth through 40 page report*

[@onlyscience7120]

I can't believe people are still installing noisy, dirty and inefficient HVAC systems, all new constructions should have ductless inverters.

[@Z71hosestretcher]

Mine isn’t dirty or noisy. I’m curious, How do you efficiently and effectively clean the air with mini splits?

[@vandalorian8777]

He never answered the question. What does he charge?

[@Z71hosestretcher]

I thought he said 1-2 grand.

[@hollyrollu]

1. Rule of thumbs only lead to broken thumbs 2. Build to customer requirements. You will never win the " you should only set your air conditioner to 75⁰". It doesn't matter what acca wants, that argument has been lost in court. Bad advice. 3. Great observations on duct losses.

[@HomePerformance]

Agreed on #2, Holly- as long as the design pro has very clear and correct reasons for all the inputs, then there's no problem.

[@videos10]

Well that's not fair, you're using Corbet's video and knowledge on YOUR KZbin channel and you're getting compensation off views of Corbet's knowledge and experience. Tell me if I'm wrong.

[@HomePerformance]

Whoa, let me step in here and say it's an honor for us to be on a channel like Matt's. He has an audience roughly 20x bigger than ours, and has sent a bunch of new followers and clients our way. Collabs as successful as this one is are rare for us.

[@loganwallace911]

This might sound radical, but do you even need windows in a home anymore? Why spend all that money to install something that will just give you very low R values, When you could achieve the same view with external cameras and internal screens that you can turn on and off and achieve far superior insulation values? As a side benefit, nobody can see inside your house. Now you can still have the odd window or slider door, but you could eliminate a lot windows this way and could double as a security system.

[@HomePerformance]

Haha damn Logan- we need to make ladies happy too at least a little bit.

[@mediamalpractice1537]

Allow me to dumb this all down for possibly 98% of the people watching this. OK, hi I'm so-in-so and zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz