| Metric | Before | After | Reduction | % Saved |
|---|
Why compare loads before and after a retrofit?
The most common HVAC mistake after an energy retrofit is keeping the same equipment. A house that needed a 100,000 BTU/hr furnace before adding R-20 wall insulation, triple-pane windows, and air sealing to 1.5 ACH50 might only need 60,000 BTU/hr afterward. Installing the same size furnace in the tighter envelope creates an oversized, short-cycling system that will underperform for the next 20 years.
Use this tool to right-size replacement equipment
Run your before and after loads through the heat load calculator for both scenarios. Enter both loads here to see the reduction clearly. Then use the after-retrofit load to size the new equipment with the furnace sizing calculator, heat pump sizing calculator, or AC sizing calculator. This workflow is how good HVAC design is done on renovation projects.
Payback calculation
The tool estimates annual energy cost savings from the load reduction using HDD and fuel cost data. Divide the retrofit cost by annual savings for simple payback. Note this is a simplified estimate — actual savings depend on thermostat settings, occupant behaviour, and system efficiency. For a more detailed energy cost analysis, use the home energy audit calculator.
Frequently Asked Questions
A comprehensive deep energy retrofit combining wall insulation from R-12 to R-24, windows from U-0.50 to U-0.28, attic from R-20 to R-60, and air sealing from 5.0 ACH50 to 1.5 ACH50 typically reduces heating load by 40-60% in a Canadian home. The biggest single improvement is usually air sealing combined with HRV installation, which can reduce infiltration load by 60-80% while maintaining good indoor air quality. Wall insulation and window upgrades each contribute 15-25% reductions. Use the load comparison tool to quantify your specific retrofit before selecting replacement equipment.
Yes, this is exactly the right use. Standard sizing practice requires furnace output between 100-140% of design heat loss. If your load comparison shows the post-retrofit heating load is 45,000 BTU/hr, your new furnace output should be 45,000-63,000 BTU/hr. Installing an 80,000 BTU/hr furnace "to be safe" results in short-cycling, poor humidity control, and accelerated equipment wear. Present the load comparison results to your HVAC contractor along with the furnace sizing calculation to specify the correct equipment.