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# Learning heat loss calcs - looking for infiltration factors

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Member Posts: 7
edited December 2020
So I'm learning about heat loss calculations and boiler sizing etc. but I would like to be able to do that calculations myself manually before relying on a program or online calculator. I am finding it impossible to find the infiltration factor multipliers anywhere though. Can someone direct me to them? I don't mind if I have to pay for a download or book but I can't find it. I'm an ICI plumber but trying to expand my resi knowledge and skills to grow my own business. Thanks!

• Member Posts: 4,077
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This is how we used to do heat loss calculations in the "old days":
https://heatinghelp.com/assets/documents/110.pdf
Thanks to Erin, Dan and HeatingHelp for keeping this in their archives.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab
• Member Posts: 4,734
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Infiltration, that’s the wild west, unless you have a blower door. This is a basic fundamental, the taller the structure, the more infiltration. The older the structure, the more infiltration. It’s likely why the old-timers put these huge radiators in the front entry/hallway.
Gary Wilson
Wilson Services, Inc
Northampton, MA
gary@wilsonph.com
• Member Posts: 7
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This is how we used to do heat loss calculations in the "old days":
https://heatinghelp.com/assets/documents/110.pdf
Thanks to Erin, Dan and HeatingHelp for keeping this in their archives.

Thanks! There's a lot of old and roughly built homes where I am that I think this would be useful for. Is there any other resources you can suggest for learning about this stuff? I see reference to "Manual J" sometimes but I don't know what that is!
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This is how we used to do heat loss calculations in the "old days":
https://heatinghelp.com/assets/documents/110.pdf
Thanks to Erin, Dan and HeatingHelp for keeping this in their archives.

That one's too old, doesn't account for global warming. Neither does mine from the 80's.

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• Member Posts: 7
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Do you have a recommendation for where I can find something updated? Or even wheat to search for?
• Member Posts: 23,559
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Macro said:

Do you have a recommendation for where I can find something updated? Or even wheat to search for?

I think at @STEVEusaPA was joking -- the basic concepts haven't changed a bit, global warming or no. The only thing really lacking -- and easily accounted for -- is better insulation in more recently built or upgraded structures.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 15,764
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@Macro

Doing a few calculations manually is a good idea. Anyone can plug in a program and get results , but they won't know right from wrong.

Doing a few manually will give you an understanding of how it works.

Slant Finn has an app you can download that people use that is pretty good.
• Member Posts: 7,588
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Infiltration factor is always a bit of SWAG. The height of the building, location of the leaks, wind exposure and mechanical fans all play a factor.

A blower door test eliminates many variables. comparing past utility bills to heating degree days is also a good trick.

"If you can't explain it simply, you don't understand it well enough"
Albert Einstein
• Member Posts: 7
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@Macro

Doing a few calculations manually is a good idea. Anyone can plug in a program and get results , but they won't know right from wrong.

Doing a few manually will give you an understanding of how it works.

Slant Finn has an app you can download that people use that is pretty good.

I was having a look through it and it seems pretty comprehensive, almost too much for me! I'm not familiar with all the different variables you can choose from (wall types mostly) so I need to dig into it a little more.
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Some of the inputs to the heat loss are always a best guess. The r-value of windows and wall and ceiling assemblies are also a best guess.
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I just went through this myself.... As a DIY project mind you. Without learning too much, lol, I found this to be of help.

best of luck with your project.
• Member Posts: 558
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Take a look here, we went into detail on heatloss during the first few sessions of Taco After Dark, Summer School

Dave H.
Dave H