Wall Information
Select the Wall Construction type that best describes your situation using the drop down list box. Carefully measure the length of each outside wall and, multiply by the ceiling height. Subtract window area. Record the total sq. ft. of exposed wall in the “Sq. Ft.” field. Enter the Temperature Difference using the drop down list box.
Ceiling Information
Select the Ceiling Construction type that best describes your situation using the drop down list box. Record the total sq. ft. of ceiling in the “Sq. Ft.” field. Enter the Temperature Difference using the drop down list box.
Floor Information
Select the Floor Construction type that best describes your situation using the drop down list box. Carefully measure the length and width of each room and multiply to calculate total floor space. You may also use outside wall dimension if practical. Record the total sq. ft. of exposed wall in the ”Sq. Ft.” field. Enter the Temperature Difference using the drop
down list box.
Infiltration
Enter the total cubic feet area of the building (square footage of floor times average height of the wall. Example: 2000 x 8 = 16,000) and the number of Fireplaces in the structure. Using the drop down list box, select the Infiltration Quality of the building. This is a subjective call on your parts. Consider the age of the building, overall quality of the windows and doors, weather stripping, etc., and use your best judgment.
Duct Gain or Loss
Select the Duct Location and Insulation that best describes your situation. Using the drop down list box, select the Supply Air Temperature that best describes your situation.
People
Enter the total number of people who generally occupy the building. Note: We use a 300 BTU per hour heat load per person.
Appliances
We assume a standard 1200 BTU per hour heat load for appliances. You may override this value if you feel it is warranted.
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May 21st, 2011 at 12:26 pm
I made a mistake on a calculation and could not go back to correct and had to do the entire processes over. In the past a correction could be made.
May 22nd, 2011 at 12:39 am
Hi Marvin, I will look into that. I plan some improvements on this soon too. Thanks for the comment.
August 8th, 2011 at 8:41 pm
Love the changes you made. I’ve been using your site for over a year. Thanks for saving me some much needed time!
August 19th, 2011 at 2:46 pm
where the heck am i supposed to put the house volume?
August 19th, 2011 at 3:26 pm
The volume is calculated automatically based on other information that was entered.
September 9th, 2011 at 12:19 pm
This appears to be potentially a good program to get an idea of Heat Gain Heat Loss using this calculator, however, when clicking on “Step 7:Show Report” an error message states “Please enter house volume”, but there is no place to enter it. James L. (#4) response states that it calculates it automatically base on the other information that was entered. It doesn’t calculate it at all. It will not allow one to click on “show report” without getting the error message. Is there a trick to this? I tried it on two different computers, one with Google Chrome and the other with Internet Explorer, with Windows Vista and Windows XP, but still no luck. Any suggestions? It appears to be an interesting calculator. Thanks.
September 12th, 2011 at 4:43 pm
There is no place to put house volume. What about question #4. Volume is 2112 cu ft.
September 19th, 2011 at 10:17 pm
HOW TONS REFRIGERANT FOR 1320 SQ.M.? AND HOW MANY TONS REFRIGERANT FOR 165 SQ.M. MODERATE TO HIGH HEAT
October 6th, 2011 at 4:23 pm
[...] need for heating or cooling is referred to as heating load. Take your climates worse day, when the temperature difference between outdoors and indoors is the [...]
October 13th, 2011 at 7:45 pm
[...] Click here to link to the Free Heat Gain Heat Loss Load Calculator by Mr. HVAC. This calculator is used to size heating and air conditioning equipment. Search for: [...]
November 30th, 2011 at 9:25 am
Regarding the “Please enter house volume” Message:
This error ocures when Volume Cubic Feet and Number of Fire Places are not filled in. See Step 3 Infiltration.
Enter the total cubic feet area of the building (square footage of floor times average height of the wall. Example: 2000 x 8 = 16,000) and the number of Fireplaces in the structure. Using the drop down list box, select the Infiltration Quality of the building. This is a subjective call on your parts. Consider the age of the building, overall quality of the windows and doors, weather stripping, etc., and use your best judgment.
I have noticed that on some computers these fields don’t display the way we designed them to. They can be hard to see because the formatting is not correct. I will have programming improve this error message and see what we can do about the formatting.
Thank you.
December 6th, 2011 at 9:14 pm
There are places to enter those values in Step 3. I wonder if there is an issue with a certain browser (not showing the the entry boxes). What browser are you using please?
January 7th, 2012 at 10:08 pm
For walls I live in Arizona so what would I use it usually stucco and what do you use for ceiling and roof when it is a flat roof house and the roof is foamed in?????
February 20th, 2012 at 1:34 pm
I see that 1200 is factored in on appliances. Is this a general rule of thumb? Do I need to figure out how many appliances I have that give off heat or do you allow so many BTU’s for each appliance. Gas range/oven, gas water heater, dishwasher, electric washer and dryer, refrigerator, computer.
February 20th, 2012 at 2:37 pm
This is a rule of thumb. It should be sufficient in most residential cases when there are no commercial appliances being used.
February 21st, 2012 at 9:56 pm
thank you so much but i am in a college class and we were ask to do a load calculation on a certain size room and this has helped so much, thanks
March 22nd, 2012 at 9:37 am
Florida Building Code Mechanical now requires heat and cooling load calculations to change out a system. Contractors have submitted your program for review. Code requires a ACCA approval on the program, do you have one? Please send notice of accepatance to me so I can accept these calculations.
Dennis Fischer
Building Official Edgewater, Fl.
March 22nd, 2012 at 12:09 pm
Hello Dennis. No we do not have ACCA approval. This heat load is based on their concepts and methodology but we have not asked them for a letter of approval.
April 14th, 2012 at 10:01 am
Nice program……..I am not sure what TIM for frame type. I used this since my frames were neither metal or wood.
April 15th, 2012 at 10:39 pm
First thank you very much for this calculator. It’s given me a great ballpark idea of what I need.
I did notice one small bug. If you choose “Duct Located In Conditioned Space”, the Duct Loss/Gain Factor in the calculation is set to zero. This in turn causes the final BTUs for both heating and cooling to go to zero. I’m assuming the Duct Loss/Gain Factor should go to unity in this case.
April 16th, 2012 at 9:08 pm
Enjoyed playing with your program and tweaking figures to see what effects it had on load/loss. Thanks!
April 16th, 2012 at 11:01 pm
is this load calculator availabel as a spreadsheet?
Thanks
April 29th, 2012 at 5:19 pm
No. Sorry it is not.