Building envelope and energy calculators
The building shell: effective R-values, blower-door results and seasonal heating energy from degree days — and what insulation and air sealing save.
Wall Assembly R-Value Calculator (Framing Effect)
Find the effective R-value of a framed wall, ceiling or floor, where heat bypasses the insulation through the studs or joists (parallel-path method).
Answers: What is the real R-value of my wall once the studs are counted?
Heating Degree Day Energy Calculator
Estimate a season’s heating energy and cost from a home’s heat-loss rate and heating degree days, and the savings from insulation or air sealing.
Answers: How much heating energy does my house use in a year, and what would insulation save?
Blower Door ACH50 Calculator
Convert a blower-door result (CFM50) to air changes per hour at 50 Pa, and estimate average natural air changes with an N-factor.
Answers: How do I convert CFM50 to ACH50 and natural air changes?
The shell decides the load
Insulation, framing and air leakage set how much heat a building loses. These tools find the real R-value of a framed assembly, turn a blower-door result into air changes per hour, and estimate a season’s heating energy — and what insulation or air sealing would save — from heating degree days. Material R-values come from product labels and manufacturers; no material tables are reproduced.