HeatFlow — Residential HVAC Load Calculator

01 Project Info

Project NameCity / State Indoor Heating DB °FIndoor Cooling DB °F Outdoor Heating DB °FOutdoor Cooling DB °F Outdoor Moisture gr/lbSupply Air Temp °F

02 Walls

OrientHeightLengthPresetU

03 Ceiling / Roof

Area ft²TypeU-Factor

04 Floor

Area ft²TypeExposed Perimeter ftF-FactorU-Factor

05 Windows

OrientAreaPresetUSHGCShade

06 Doors

OrientAreaPresetU

07 Infiltration

MethodACH50CFM50N-FactorBuilding Volume ft³Avg Ceiling Height ft

08 Internal Loads

OccupantsLighting WattsAppliances BTUHOther Sensible BTUH

09 Ducts

Duct Location

Whole-House Block Load Estimate

Heating Load—

Total Cooling—

Cooling Sensible—

Cooling Latent—

Recommended Cooling—

Heating Output—

Required Airflow—

Step-by-Step Breakdown

Component	Area	U / Factor	ΔT / CLTD	Heating	Cool Sens	Cool Lat

Heating transmission uses U × A × ΔT plus infiltration sensible load.
Cooling uses CLTD for opaque surfaces and simplified SGF for window solar gain.
Duct multipliers are applied before equipment safety factors. Manual S still gets the final word, because HVAC likes paperwork.