Kansas Climate Zone Heat Loss Calculator

Estimate the design heat loss (BTU/hr) for a building in Kansas based on your climate zone, building envelope area, insulation R-values, and design temperatures. Kansas spans IECC Climate Zones 4A (eastern) and 5A (western/northwestern).

ASHRAE 99% heating design dry-bulb. Pre-filled by zone; adjust if needed.

Building Envelope Inputs

IECC 2021 Zone 4A minimum: R-13+5ci; Zone 5A minimum: R-20 or R-13+5ci.
IECC 2021 maximum U-factor: 0.30 for both Zone 4A and 5A.
IECC 2021 minimum: R-49 for both Zone 4A and 5A.
IECC 2021: Zone 4A minimum R-19; Zone 5A minimum R-30.

Infiltration

ASHRAE 62.2 recommends ≤0.35 ACH for tight construction. Kansas avg: 0.35–0.50.

Formulas Used

Conduction Heat Loss (each envelope component):

Qcond = (A / R) × ΔT    [for opaque assemblies]
Qcond = U × A × ΔT     [for windows and doors]

Where: A = area (ft²), R = thermal resistance (hr·ft²·°F/BTU), U = thermal transmittance (BTU/hr·ft²·°F), ΔT = Tindoor − Toutdoor (°F)

Infiltration Heat Loss:

Qinf = 0.018 × ACH × V × ΔT

Where: 0.018 = specific heat of air × air density (0.24 BTU/lb·°F × 0.075 lb/ft³), ACH = air changes per hour, V = conditioned volume (ft³)

Total Design Heat Loss:

Qtotal = Qwalls + Qwindows + Qdoors + Qceiling + Qfloor + Qinfiltration

Unit Conversions: 1 ton = 12,000 BTU/hr  |  1 BTU/hr = 0.000293071 kW

Assumptions & References

  • Kansas Climate Zones: Eastern Kansas (Wichita, Topeka, Kansas City area) is IECC Climate Zone 4A; Western and Northwestern Kansas (Dodge City, Colby, Liberal, Goodland) is Zone 5A, per IECC 2021 / ASHRAE 169-2020.
  • Outdoor Design Temperatures: Zone 4A: 4°F; Zone 5A: −4°F — based on ASHRAE Fundamentals 99% heating design dry-bulb values for representative Kansas cities.
  • IECC 2021 Minimum Insulation Requirements: Zone 4A — Walls R-13+5ci, Ceiling R-49, Floor R-19, Window U-0.30; Zone 5A — Walls R-20 or R-13+5ci, Ceiling R-49, Floor R-30, Window U-0.30.
  • Air Properties: Air density assumed at 0.075 lb/ft³ and specific heat at 0.24 BTU/lb·°F at standard conditions (70°F, sea level), yielding the 0.018 BTU/ft³·°F infiltration constant.
  • Infiltration: Calculated using the air change method per ASHRAE Handbook of Fundamentals. Typical residential values: tight construction 0.25 ACH, average 0.35–0.50 ACH, leaky 0.75–1.0 ACH.
  • Scope: This calculator estimates design (peak) heat loss for equipment sizing. It does not account for internal gains, solar gains, thermal mass, duct losses, or basement/slab-on-grade heat loss.
  • Net Wall Area: Window and door areas are subtracted from gross wall area before calculating opaque wall conduction loss.
  • References: ASHRAE Handbook of Fundamentals (2021), IECC 2021 Table R402.1.2, ASHRAE Standard 169-2020 (Climate Data), ACCA Manual J (8th Ed.) residential load calculation methodology.

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