heatloss calc.

**phaedrus123** · 08-11-2011, 05:50 AM

slantfinn used to provide a heat loss calculation programme.they discontinued it a few years back.does anyone have access to this programme and if so would you be willing to part with it for a few days,i will pay all expenses,thankyou

**Tom Sawyer** · 08-11-2011, 09:51 AM

www.taco-hvac.com

You can send me a couple hundred dollars but the program is free.

**phaedrus123** · 08-11-2011, 03:42 PM

to funny,if i could i would send it.i tried to download that programme before but i have a mac and the programme is not compatable.i am no computer whizz .i tried wrightsoft to and the same result.i called taco and they said i needed some software to convert from windows to mac.im lost.now i was told from a friend a formula.it goes lxwxhx4 and that will give you the btuh for that room,what do you think.he says for years he has been using this formula.

**Tom Sawyer** · 08-11-2011, 04:09 PM

Not even close. The program figures insulation and construction R values, window and door area, infiltration and a host of other variables that you need to be accurate.

**phaedrus123** · 08-11-2011, 04:28 PM

the guy swears by it and says it is always pretty close.i know what you are saying about taking everything into account insulation etc,i even called slantfinn and they said they stopped making that programme a few years ago.anyway i am now looking at a hb smith boiler with an indirect tank,boiler co.says the boiler holds a lot of water preventing short cycling which will eliminate an ergomax been used as a buffer tank.what do you think.i know the right way to do it but am tight at the moment.thanks again for your help

**Dana** · 08-12-2011, 08:38 AM

Originally Posted by phaedrus123

the guy swears by it and says it is always pretty close.i know what you are saying about taking everything into account insulation etc,i even called slantfinn and they said they stopped making that programme a few years ago.anyway i am now looking at a hb smith boiler with an indirect tank,boiler co.says the boiler holds a lot of water preventing short cycling which will eliminate an ergomax been used as a buffer tank.what do you think.i know the right way to do it but am tight at the moment.thanks again for your help

How does the guy know it's pretty close- is he providing the post-installation energy use against heating degree days numbers, and demonstrating a very tight standard deviation over a few hundred sample cases as his validation of the methodology?

That kind of calc is pure crap. Yes, those methods are sometimes/often close when dialed for a particular location, if "close" means it's only 2x oversized on average, but never less than 1.5x oversized for the real 99th percentile design condition load.

The Slantfin freebie tool tended to shoot ~35% oversized on average (even more than that for very tight homes), but wasn't terrible. There are better heat loss tools out there. But if you have heating fuel use history on a place with known equipment it's pretty easy to put an upper bound on the whole-house heat loss at a given outside design temperature using simple math on fuel use against heating degree-day weather history, and the steady-state efficiency of the heating equipment.