Heatloss Calculations

John L

If a contractor uses the square footage method of heatloss,this is the most commonly used inaccurate method of sizing according to the Dept. of Energy.
How can he remember all the multipliers to use with all the different home he goes to, bearing in mind that home are like people, they are all different and have their own idiocyncracies. Do it once and do it right.

Adam Grant

Is there a reliable way to obtain a quick accurate heatloss calculation ? .Can a person measure the square footage and multiply by {depending on the type of construction]say 20 to 30 Btu a sqaure foot,to get a quick idea of what size boiler is required.

hr

Either or

sure quick is possible, but accurate requires a detailed room by room method with walls, windows, insulation R value included.

You can't have it both ways, my friend

hot rod

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Dave Yates (PAH)

sure is!

A reliable heat loss program utilizing Manual-J design formulas. I can run a normal home's loss/gain in 30 minutes (or less) if the phone doesn't ring(G).

Barring that: the doorway; curb; or finger method works (sometimes). Homeowners subjected to these three methods quickly learn a different version of the finger method where communicating their feelings are concerned. For some odd reason, they always choose single section boilers!

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Constantin

Allow me to inject my $0.002 as well

I'd invest in a program like HVAC-Calc, Wrightsoft, etc. to better understand what your heat losses are, where they are, etc. Using such a program, you can quickly determine how to deal with the problem of heating and cooling a structure holistically.

For example, it is usually a very good investment for new homes to receive more insulation/weatherization than the minimum standards the code allows for because additional insulation allows you to reduce the size of the heating plant, ductwork, AC, etc... There is a real domino effect that follows the reduction in heat gain and loss.

Without a heat gain/loss calculator, it is hard to sit down in front of a customer/GC and justify why they ought to appropriate their cash differently than they thought they would. The total building expense may not even go up, as some of the research/experience at building science corporation has shown. However, the operational expense is sure to go down.

I found HVAC-Calc to be quite intuitive, quick, etc. If you need just a heat loss calculation, you may even find slant-fin's heat explorer (free) to be sufficient.