Load Calculation Instructions

Heat Gain & Loss Short Form Instructions

These instruction are intended to help you use our HVAC Heat Gain and Heat Loss Calculator located here.

Our instructions assume you have some working knowledge of the Heat Gain and Loss process. If not, please see our blog post Heat Gain and Heat Loss Explained.

WE CANNOT PROVIDE TECHNICAL SUPPORT FOR THIS FREE UTILITY.

Please post any and all HVAC load calculation questions below. The website moderator and the HVAC community will answers your questions.

Step 1: Customer Information

Complete the customer information. This is not mandatory but helpful. This information will appear on your report.

Step 2: Temperature Difference

Record the inside and outside temperature and the difference. You may use any number you care to.

Step 3: Construction Details

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 part. 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.

Step 4: Additional Items

This space was provided to allow you to enter additional heat load values or other details.

Step 5: Heating, Doors and Windows

Select the Window Type that best describes your situation. Enter the total area of the window in the Area field by multiplying the height and width of the window. The last step is to select the appropriate window frame type. You may have multiple window types. If you have more than one of the same window types, add the total area of these window and enter this total into one field.

Step 6: Cooling, Doors and Windows

Select the Direction that the windows face that best describes your situation. Enter the temperature difference in the Difference field. This is usually the same value that appears in Step 2 (Summer Outside Temperature less Inside Temperature).

Enter the total area of the window in the Area field by multiplying the height and width of the window.

The last step is to select the appropriate window frame type. You may have multiple window types. If you have more than one of the same window types, add the total area of these window and enter this total into one field.

Step 7: Calculate and View Report

Click the Show Report button to calculate the work sheet and generate the report. You may print the report and even save it to your hard drive.

To print the report, Click File and select Print on your browser.

To save the report, click File and select Save As.

More Information

We have our own fantastic heat gain and loss program that is inexpensive (for now) but contains all of the features most of us need. Check out Easy Load Calc here.

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