Manual J Load Calculations 3D

In this 3D video, we show how to calculate heat losses and heat gains in a residential structure in accordance with ACCA Manual J, particularly a block load for an existing structure. We owe special thanks to Russ King, Ed Janowiak, Alex Meaney, and Adam Mufich for their contributions to this video.
Heat and Comfort Basics 3D: • Heat and Comfort Basic...
HVAC School Manual J Block Load Worksheet: hvacrschool.com/wp-content/up...
Kwik Model 3D: kwikmodel.com/
Air Conditioning Contractors of America (ACCA): www.acca.org/home
Load calculations require us to use math, and we can use Manual J software to do that work for us. However, we still need to obtain the data for the math in the first place; Manual J tells us which measurements we need to enter into the software for the load calculation. We can use Manual J to figure out block loads of an entire building or room-by-room calculations. Manual J may also be used in existing buildings or based on the plans of a new construction.
When gathering data from walls, we need to know the area and the R-values of each material making up the wall, including drywall, insulation, and exterior building material. Higher R-values indicate better resistance to conduction; we can control the material thickness and insulation to minimize heat conduction into or out of a structure. You’ll need to deduct the studs, windows, and doors from the R-value of a wall. Partition walls between other indoor spaces, like a neighbor’s home or an unconditioned garage, have different temperature differences (delta T) than an exterior wall.
To deduct the window area from the wall area, you’ll need to multiply the length and width of the wall and the length and width of the window(s) and subtract the product(s) of the window area from the wall area. The window will have its own calculated heat losses and gains due to its ability to allow for heat transfer via radiation. Heat gains via solar radiation will vary depending on the window placement and the time of day. We need to know the window size, material, framing, transparency number of panes, and placement of the windows to understand the U-factor, which is the inverse of the R-value; higher U-factors indicate higher rates of heat transfer.
Roof overhangs can reduce incoming solar radiation, so we need to account for the height and depth of roof overhangs in our calculations. We should also know the roof type, pitch, and color.
When accounting for exterior doors, we need to know the door size, material, and placement. We also need to know the elevation of the home and how many stories it is. The ceiling height and insulation (material and R-value) are also important for our Manual J calculations. Conduction also happens through the floors, so we must know about the material and possibly even the R-value of insulation (if applicable).
When considering the impact of ductwork on heat gains and losses, we need to factor in duct location, insulation R-value (often R4, R6, or R8), and leakage (due to heat gains and losses via convection into or out of the ductwork).
We also need to know if the air handler is in a conditioned or unconditioned space and how exhaust-only ventilation may be responsible for seasonal BTU gains and losses.
Household appliances add heat, and Manual J has a default appliance heat load of 1200 BTUs. Electronics also add sensible BTUs, and dishwashers or laundry appliances may also add latent BTUs. We can also expect higher latent BTU gains in homes where occupants frequently run faucets, do laundry, or bathe/shower. Occupants add heat loads when they breathe or their bodies give off heat, usually about 200 latent BTUs per hour and 230 sensible BTUs per hour. Account for occupants by adding up the number of bedrooms and adding one (e.g., we would calculate a heat load for four occupants in a three-bedroom home).
Appliances will not run all the time, and heat loads based on weather will vary throughout the year (and even throughout each day). There may also be more or fewer occupants than the load calculation accounts for at any given time, so we want to design homes to account for the most probable and common conditions, including the occupants’ lifestyle choices (see Table 6A).
Once we have the data, we can finalize our load calculations with ACCA-approved Manual J software, like Kwik Model 3D as shown. You can also use HVAC School’s Manual J worksheet. Then, we can move on to equipment selection in accordance with ACCA Manual S.
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Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschool.com/.

[@MattJMT]

Thank you Bryan for this great content!

[@teddycarter2618]

Man living in a rural and very diverse economic area in Virginia I get service calls to multi million dollar homes and also 50 year old single wide trailers. Can only imagine the range of J values I've probably encountered. 🫣

[@ahmedahmed-tv3nw]

thanks alot its very useful and nice animation

[@mehdibourha180]

Thank you Bryan for all the informations you provided for our community 🙏

[@JohnDoe-ej1lw]

Thank you HVAC school for this very good learning video 👍👍

[@AJservicetechAZ]

Can’t wait for other design concept videos from you guys! I really struggle to understand how duct design is approached and how Manuel D is applied.

[@sethmorrison9524]

Thanks!

[@je-niseghana7377]

There is always much to learn. Thanks for sharing.

[@timdestasio3367]

What a great intro to Manual J!

[@mhoush]

Awesome renderings! Thank you!

[@ducharmehvactraining925]

fantastic, thank you so much!

[@tunaman2200]

Thank you for this!! Been waiting for you to do these videos on the Acca manuals

[@pedrosolares3085]

Amazing work !!!!!! 💯💯

[@alaverdad.]

Thankyou so much for this information.

[@brianf2401]

Awesome video guys. Definitely going to be referring my students/contractors to this as a great intro to manual J

[@mandujano97670]

Thank you helpful information

[@realvanman1]

I did this for my home, before hiring a contractor for my install. He wanted to use a rule of thumb that, as usual, results in equipment that is too large. I’m very glad I had the knowledge to reign that in. Our A/C system is sized perfectly. The furnace he installed is too damned big, and he said that was their smallest model. Afterwards I found out that wasn’t correct. Damnit.

[@realvanman1]

@@blakeperson9189 Amen to that! He was a referral from a good friend, but turns out my friend didn't really know any better. Oh well. Both of our systems are still working, even if they're not as good as they could be.

[@boby115]

@@blakeperson9189, if he was putting bigger equipment in, he was probably expensive.

[@FiercefoxProductions]

If you’re such a helicopter homeowner why not get your license and do it yourself instead of criticize other ppl

[@eagletek1]

Great information

[@afitz676]

Awesome video. Looking forward to manual S.

[@HVACRTECH-83]

Thats a really nice looking ranch home

[@deoranferguson5657]

This is needed

[@KurtisSaiyo]

I think technically, uninsulated walls transfer heat mostly with convection, not conduction. Fantastic animation and narration. Very clear and concise!

[@reeves29456]

Great visual presentation! Mind sharing what software was used to create this?

[@tkacandes2052]

This is very well done - congratulations and thank you! I wish there was a very slightly simplified version I could send to homeowners so they can understand these concepts.

[@grashoprsmith]

❤ thanks

[@MetalDetectingwithCZkidd]

I use Wrightsoft. Easy to use and accurate. Nice vid.

[@ianegfp]

In this video, the R calculation for the wall was performed twice. Once with a total of 13.89 and a second time to obtain a total 4.89. Did anyone see why this was done? Also, I suppose as more and more households have pets, Manual J will provide some average numbers for cats and dogs. I think a pair of Labrador retrievers would probably huff and puff enough in a room during the summer to count as at least 1.5 persons.

[@deluxecool4149]

❤❤❤

[@potentialhvac6074]

So what was the tonnage for this house?

[@texture6]

Is this by Jack Rise?

[@HVACRTECH-83]

One thing ive been wondering for a while is if vaping in the space adds to the latent load. Its not really water vapor but is is liquid being vaporized and does stay in the space lingering for a very long time. Ive gone into homes where its just so cloudy inside you have hard time reading the clock on the wall lol. Im serious. I understand its not water vapor 100% but i wonder what some testing would show on the matter

[@MrHaydenJr]

Can you show how to properly size an a/c system from scratch... say i had a certain size evaporator, ho do i pick a condensor size, choose a given compressor size for the selected system? (Im building a camper van a/c system and would like to reuse the rear a/c evaporator with a 12v compressor, and undervan condensor) ive been watching you videos and i keep seeing reiterated how it work, and i understand that, but im still lost when it comes to sizing components...

[@amv_pure]

I thought Manual J was different, great video. What’s the name or certification for running diagnostics on a residential split HVAC system to make sure it’s not oversized, has possible static pressure issues, too much return air/not enough supply, duct leakage, etc. ? Would really appreciate it. Most HVAC companies just install, and quickly move on to the next job, and don’t test anything from what I’m seeing. Love this channel btw.

[@threestans9096]

yeah they tend to put the same size system that was there before. esp if the owner doesnt want to pay extra for a building load calculation done. you may be asking about “blower door tests” or just check up or load calculations blower door test- basically close your windows and front and back doors. and they attach what basically is a fan with a tarp on either side to make it airtight. Then turn on the fan and measure how much pressure it takes to keep balanced pressures.

[@amv_pure]

@@threestans9096 Most appreciated, I plan on buying a manometer soon to start playing around. You measure your return air and supply side, then do some math, and now you know if your system is operating correctly. That’s my goal. Thanks again.

[@neilcomparetto5282]

🍿

[@BillNickerson]

Who are the 3 avatars walking down the drive way ?

[@920HVAC]

#GFYM

[@thakingspodcast71]

Hello and don’t mind the channel name but my name is Mason and I am in the certificate program at my local community collage, And I Am Going To Be An HVAC Technician.

[@TonyRodriguez-ok2ix]

Acca approved software's

[@rickybrown6585]

Cray cray

[@kevinthomas26]

this didnt really teach anything lol

[@sheet-son]

The moment you get 5 minutes through and realize the statement "we wont cover the basics of heat transfer" was a damn lie.