heat loss/heat gain calculation

Empire_2

You cannot rely on anything , but a heat loss/gain program like "Manual "J" etc. But to ans. your question and this is only ballpark: Cu ft. X 5 air changes/hr./ divide by 60 min/ divided by 400cfm/ton. Note you have to have more than that for accurate calcs. N>S>E>W> exposure, insulation,.......The list goes on and on. Exmp. 2000 sq/ft. x 8 ft ceilings, X 5 air.chng./hr, / div by 60 min. / div. by 400cfm/ton = 3.34 ton.
Call a professional to do it right. You will save in the long run.... There are so many factors and I know you are a due it yourselfer, but this is not the area to skimp on....

greg_28

heat loss/heat gain calulation

I'm trying to size my home for central a/c.
If I used a heat loss calulator properly for a 10 degree design day and came up a 95k btu heat loss, what may be a good rule of thumb for converting this number to a heat gain. downstate NY area. Thanks for your help!

Mitch_4

3:1

rule of thuymb used to be 1/3 heat loss. But it is very inaccurate except on older places. Use a heat gain calculator for all the reasons listed inthe other post. exposure, trees, roof/ building color etc...

Mitch

Constantin

... how true...

... our home has a 1:1 ratio, according to HVAC-Calc. That is with 9 degree F conditions in the wintertime and 91 degree conditions in the summertime. Glass makes it possible.

GMcD

Heat gain calculation

Gotta do a proper heat gain calculation, just like the heat loss calculation. Heat gain from windows (solar + transmission), lights, people, equipment, ventilation load, latent load (de-humidification) and so on. Varies depending on amount of glass, solar exposure, etc. No shortcuts!!

John L

Mike T

In your calcs you mention cubic vol. x 5ACH div 60 min div 400CFM, what does the 60 minutes refer to

THNX

Empire_2

Reply

60 min... You are trying to figure BTU/Hr. Need the 60 min in the calc. Air changes can also change, but 5 is usually the lowest. This calc. comes pretty close to actual load but like I said it is only a Ball park figure.