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Heat Loss Calculator

Room Dimensions

Enter lineal ft dimensions in appropriate shaded area and enter number of exposed (cold) walls of that length or width in appropriate shaded area.

NOTE: walls adjoining heated area's have no heat loss through that wall

Wall & Ceiling Insulation Values

Wall Insulation Level
Ceiling Insulation Level

If room is situated below a heated area there is no ceiling heat loss.

Note: Fiberglass batt insulation has an R value of approx. 3 per inch.

Door and Window Values

Type of Doors
Size of Doors (sq. ft)
Type of Windows
Size of Windows (sq. ft)

Floor Type & Insulation Value

Concrete Slab (on grade)
Basement Slab (below grade)
Frame Floor

Infiltration Values & Calculation

Infiltration losses include both losses through structure construction (e.g. cracks, leaks, etc.) as well as losses due to the normal air changes such as opening of outside doors etc.

Note: Calculations are based on average residential values only, adjustments should be made for non-standard situations such as high traffic entrances etc. or for alternate building construction materials and methods. Values listed are for sheltered or partially sheltered to wind exposure. Use next lower value for exposed locations and second story rooms.

Infiltration Category
  • Loose construction with no attempt to air sealing
  • Pre-1970 style of construction c/w air/vapour barriers, no attempt to seal joints within vapour barriers
  • As above but with specific attempts to tape and seal air/vapour barriers, floor and joist headers sealed.
  • R-2000 style of construction

Alternate Design Temperature Difference (D.T.D)

The above calculated values are based on a design temperature difference of 72 degrees F (based on an outside temperature of 0 degrees F and a required inside temperature of 72 degrees F). There may be situations where this value should be adjusted accordingly.

These include:

  1. Rooms that are currently partially heated
  2. Geographical locations that are either warmer or colder than a 75 degree temp difference
  3. Situations where an inside temperature of 72 degrees is not required

Required D.T.D. = Degrees F

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