Heat Loss Calculation Application: Excellent when determining heat loss of a building as a whole.
This calculation will help determine a boiler size for a home.
This is to be used as an estimation. A detailed heat loss should be provided before a new boiler is installed.
Heating multipliers (H.M.) BTU/Hr based on 60 degrees F Temperature Difference (T.D.)
Procedure
 Measure the total length of all outside walls for the house. Calculate gross wall area by multiplying total length by height of the walls.
 Measure the window and door area. Select proper H.M.
 Record Net Wall Area=(gross wall area minus door and window area) select proper H.M.
 Measure the ceiling area and select H.M.
 Measure floor area and select H.M. ( H.M. of 4 used over unheated basement )
 Multiply Floor area by ceiling height to obtain volume of home and select proper air change factor: 1.61 for Loose House – 1.07 for Average House – .81 for Tight House.
Windows/Doors  H.M.  Wall  H.M.  Ceiling  H.M.  Floor  H.M.  Infiltration  H.M. 

Single  67  No Insulation  15  3 Inches  5  No Insulation  4  1 ½ Air Change  1.61 
Single Insulated  41  2 Inches  6  6 Inches  4  Overhang 3”  5  1 Air Change  1.07 
Storm  34  4 Inches  5  9 Inches  3  Overhang 6”  5  ¾ Air Change  0.81 
Double Insulated  30  6 Inches  4  10 Inches  2  Overhang 9”  2 
Windows/Doors  H.M. 

Single  67 
Single Insulated  41 
Storm  34 
Double Insulated  30 
Wall  H.M. 
No Insulation  15 
2 Inches  6 
4 Inches  5 
6 Inches  4 
Ceiling  H.M. 
3 Inches  5 
6 Inches  4 
9 Inches  3 
10 Inches  2 
Floor  H.M. 
No Insulation  4 
Overhang 3”  5 
Overhang 6”  5 
Overhang 9”  2 
Infiltration  H.M. 
1 ½ Air Change  1.61 
1 Air Change  1.07 
¾ Air Change  0.81 
Total Room/Building  

Length  =  
Width  =  
Height  =  
Windows/Doors  
Total Area (ft^{2})  =  

Total Room/Building  Area (feet^{2})  H.M. (BTU/Hr.)  

1. Windows & Doors  X  
2. Net Walls  X  
3. Ceiling  X  
4. Floor  X  
5. Infiltration  X  

Based On  Area (feet^{2})  H.M. (BTU/Hr.)  Heat Loss  

1. Windows & Doors  X  =  
2. Net Walls  X  =  
3. Ceiling  X  =  
4. Floor  X  =  
5. Infiltration  X  =  
Total Heat Loss for 60° F Temp. Diff.  =  
Total Heat Loss for 70° F Temp. Diff.  =  
Total Heat Loss for 80° F Temp. Diff.  =  
Total Heat Loss for 90° F Temp. Diff.  =  
Total Heat Loss for 100° F Temp. Diff.  =  