Home Insulation R-Value Calculator — NH Climate Zone Heat Loss Estimator
Calculate heat loss through your building envelope and get recommended R-values based on New Hampshire's climate zones (Zone 5 and Zone 6). Uses ASHRAE 99% design temperatures and IRC 2021 insulation requirements.
Formulas Used
Thermal Conductance (UA):
UA = (1/R) × Area [BTU/hr·°F] for opaque assemblies
UA = U-factor × Area [BTU/hr·°F] for windows and doors
Peak Heat Loss:
Qpeak = UAtotal × ΔT [BTU/hr]
where ΔT = Tindoor − Toutdoor,design
Annual Heat Loss:
Qannual = UAtotal × HDD65 × 24 [BTU/yr]
Annual Heating Cost:
Cost = (Qannual [MMBtu] / η) × $/MMBtu
Assumptions & References
- ASHRAE Handbook of Fundamentals 99% design outdoor temperatures: Concord NH −3°F (Zone 5), Berlin NH −16°F (Zone 6).
- Heating Degree Days (base 65°F): Concord NH ≈ 7,383 HDD; Berlin NH ≈ 9,100 HDD (NOAA 30-year normals).
- Recommended R-values per IRC 2021 Table N1102.1.3 for Climate Zones 5 and 6.
- Window U-factor ≤ 0.30 per ENERGY STAR Northern Climate specification.
- Calculation covers conductive heat loss only; infiltration/ventilation losses are not included.
- Wall R-value should include cavity insulation plus any continuous exterior insulation.
- Energy costs: Natural gas ≈ $10/MMBtu, heating oil ≈ $22/MMBtu, electric resistance ≈ $34/MMBtu (2024 NH averages).
- NH falls entirely within IECC Climate Zones 5 (southern counties) and 6 (northern counties).