Added insulation: Calculate heat savings and payback
How much heat can added insulation save in your home? Here you can calculate an estimate based on the surface you insulate and the difference between the current and new insulating performance of the construction.
Worked example
- U-value after: Added insulation
- Area: 1,076.391 ft²
- U-factor before: 0.07044 Btu/(h·ft²·°F)
- Thickness: 3.937 in
- Thermal conductivity (k-value): 0.2565 Btu·in/(h·ft²·°F)
- Heating degree days: 4,500 °F·days
- Efficiency of the heating system: 100 %
- Price per kWh of purchased energy: 0.15 USD
Reduced heat loss
1,246.7532 kWh per year
New U-value 0.03385 Btu/(h·ft²·°F) · purchased energy 1,246.7532 kWh · savings 187 USD per year
A simplified transmission model. Thermal bridges, moisture and workmanship are not assessed.
Quantity and heat savings are two different calculations
A quantity calculator tells you how much insulation to buy. This calculator looks at the change in heat loss. It therefore needs information about the construction or its U-value and the relevant temperature conditions.
The lower the U-value, the less heat passes through the surface under the same conditions. An extra insulation thickness does not give the same savings in all houses. The starting point, thermal bridges and the heat supply matter.
Guide to a realistic estimate
Describe the existing construction
Use documented information where possible. A thick insulation layer in the drawing is not necessarily built as stated. If the conditions are unknown, calculate with several U-values and compare the results.
Example of changed heat loss
An improvement of the U-value of 0.3 W per m² and degree over 100 m² gives, at 2,500 degree days, about 1,800 kWh less annual transmission loss in the simple model. The economic value depends on how the heat is produced.
Add the price of the project to see a simple payback period. The result does not assess moisture, ventilation or how the construction is built. Use it as a basis for a specific project and a quote where these conditions are also examined. The insulation quantity can be calculated separately once the solution has been chosen.