HVAC Load Calculation Tools

Calculate the total heating load (BTU/hr) for any space using wall, window, ceiling, and infiltration heat loss factors. Essential first step before sizing any heating system.

Determine summer peak cooling loads using outdoor design temperatures, solar gain through glazing, internal loads, and occupancy. Follows ASHRAE fundamentals.

Quick BTU estimate for rooms and whole buildings based on square footage, ceiling height, insulation level, climate zone, and window area. Instant rule-of-thumb sizing.

Industry-standard residential load estimator. Enter construction details, climate data, and orientation to generate a code-conforming heating and cooling load report.

Calculate heating and cooling loads for individual rooms. Accounts for exposed walls, windows, doors, floor/ceiling construction, and room orientation for accurate room-by-room sizing.

Aggregate room-by-room loads into a whole-house heating and cooling summary. Generates a complete load report suitable for equipment selection and permit applications.

ASHRAE block load method for commercial buildings. Handles multi-zone systems, diversity factors, ventilation loads, and internal heat gains from lighting and equipment.

Calculate the overall thermal transmittance (U-value) of walls, roofs, and floors from individual R-value layers. Converts between Imperial and metric thermal resistance values.

Estimate air infiltration heating and cooling loads using blower door test results or construction type. Uses the crack method and ACH method per standard residential guidelines.

Calculate solar heat gain through windows and skylights using SHGC values, window area, orientation, and latitude. Essential for accurate peak cooling load analysis.

Look up ASHRAE 99% winter design temperatures and 1% summer design temperatures for hundreds of Canadian and US cities. Required for all residential load calculations.

Calculate heat loss through exterior walls by entering wall area, construction type, and U-value. Results in BTU/hr and watts with both Imperial and metric output.

Determine heat loss through windows using U-factor, window area, and indoor/outdoor temperature difference. Supports single, double, and triple glazing configurations.

Calculate heat loss through roof and ceiling assemblies. Supports flat roofs, vaulted ceilings, and attic configurations. Inputs include R-value, area, and design temperatures.

Estimate heat loss through floors over unconditioned spaces, crawlspaces, and slabs-on-grade. Uses ASHRAE slab perimeter and below-grade calculation methods.

Calculate below-grade heat loss from basement walls and floors using soil conductivity and depth. Determines insulation needs for conditioned and semi-conditioned basements.

Estimate heat gain from occupants, lighting, appliances, and equipment. Critical for accurate cooling load calculations in offices, restaurants, and commercial spaces.

Calculate the heating and cooling load added by outdoor air ventilation. Accounts for sensible and latent components. Includes link to ventilation rate calculator for CFM input.

Calculate heating degree days (HDD) and cooling degree days (CDD) for energy consumption estimates and equipment sizing. Supports base temperatures of 65°F / 18°C.

Size air-source and ground-source heat pumps based on heating and cooling loads. Accounts for COP degradation at low temperatures and supplemental heat crossover point.

Determine the correct furnace output capacity in BTU/hr or kW based on calculated heat loss. Applies standard 1.4x oversizing limit and AFUE efficiency factor for input capacity.

Size central air conditioning systems in tons or BTU/hr based on cooling load calculations. Outputs recommended equipment capacity with sensible heat ratio check.

Size ductless mini-split systems for individual rooms or zones. Calculates required capacity per indoor unit based on room loads and compares to available models.

Calculate sensible heat load from temperature difference and airflow. The direct-heat component of every room and system load calculation, separate from latent moisture loads.

Determine chiller plant capacity requirements for large commercial and industrial buildings. Calculates total tons of refrigeration, chilled water flow, and peak demand.

Calculate latent cooling loads from moisture sources: occupants, cooking, laundry, and outdoor air. Works alongside the humidity ratio calculator for complete psychrometric analysis.

Calculate the Sensible Heat Ratio (SHR) for a space or system. Used to verify equipment suitability and ensure proper dehumidification alongside cooling capacity.

Calculate heat loss through slab-on-grade floors using F-factor perimeter method. Accounts for slab edge insulation and below-grade depth for accurate foundation loss.

Calculate sensible and latent heat gain from building occupants based on activity level and occupancy count. Uses ASHRAE Handbook of Fundamentals data tables.

Determine heat gain from lighting systems (LED, fluorescent, incandescent). Accounts for ballast heat and return air plenum configurations per ASHRAE methods.

Estimate heat gain from computers, servers, kitchen equipment, medical devices, and other plug loads. Uses diversity factors for realistic peak cooling load assessment.

Calculate heat loss from insulated or bare piping carrying hot or chilled water. Used for boiler room, mechanical room, and distribution piping load estimates.

Compare heating and cooling loads before and after energy retrofits. Quantify the load reduction from added insulation, window upgrades, or air sealing improvements.

Calculate heat loss and gain through ductwork in unconditioned spaces from insulation R-value, surface area, and temperature difference. Feeds directly into total system load.

Generate a formatted, printable HVAC load calculation report from your entered data. Export to PDF for permit applications, contractor quotes, or client presentations.