Heat Load Calc HVAC

About this app

HVAC Heat Load BTU Calculator helps HVAC technicians, engineers, and contractors calculate accurate cooling and heating loads. Calculate accurate cooling and heating loads using a simplified ACCA Manual J methodology based on room dimensions, insulation levels, window types, and ASHRAE climate zones - the industry standard for professional air conditioning system sizing. LOAD CALCULATION MODES: Cooling Mode - Calculate BTU/h cooling requirement for air conditioning Heating Mode - Calculate BTU/h heating requirement for furnace and heat pump sizing Automatic Tonnage Conversion - Get AC tonnage (0.5 to 5+ tons) from load results CFM Requirement - Airflow from the supply-air temperature difference, around 400 CFM per ton ROOM PARAMETERS: Room Dimensions - Enter length, width, and ceiling height Exterior Walls - Count how many of the room's walls face outdoors Insulation Levels - Poor, Average, Good, or Excellent, mapped to assembly U-factors Window Types - Single Pane, Double Pane, Triple Pane, Low-E, with U-factor and SHGC Window Orientation - North, East, South, West or mixed exposure for solar gain Floor Type - Over conditioned space, over crawlspace/garage, or slab on grade Climate Zones - 5 zones with ASHRAE design temperatures, overridable by hand Duct Location - Add duct gain/loss when the ducts run through unconditioned space Occupant Load - Sensible and latent heat from building occupants COMPONENT BREAKDOWN: Wall conduction load Window conduction and SHGC-based solar gain, shown separately Ceiling and roof heat gain Floor and slab-perimeter load Infiltration load from envelope tightness Occupant sensible and latent heat Duct gain/loss in unconditioned space Sensible and latent totals, tonnage, airflow and BTU/h per sq ft OPTIONAL PRO UPGRADE — $2.99 ONE-TIME IN-APP PURCHASE The following features require a separate one-time in-app purchase. They are not required to use the calculator: • Unlimited saved calculation history • PDF export of results • Dark theme • Ad-free experience WHY HVAC PROS USE THIS CALCULATOR: Faster Manual J estimates than spreadsheets or online calculators Accurate BTU sizing prevents oversized/undersized systems Reduces callbacks from incorrect system selection Quick cooling load checks on service calls ASHRAE-compliant Manual J methodology for commercial work Improves customer confidence with detailed technical reports PERFECT FOR: HVAC design engineers sizing air conditioning systems HVAC field technicians quick-checking load requirements AC contractors preparing accurate equipment bids HVAC apprentices learning Manual J methodology Building maintenance engineers planning replacements Residential and commercial HVAC system sizing Energy auditors estimating cooling needs Based on ACCA Manual J design methodology: assembly U-factors, SHGC-based solar gain, ASHRAE design conditions, and no arbitrary safety padding. Part of HVACTools Suite - the professional HVAC technician app for field calculations, refrigeration diagnostics, and air conditioning system design.

What's new — the load calculation was rebuilt for accuracy: - Assembly U-factors for walls, ceiling and floor replace the single generic coefficient - Solar gain now comes from the window SHGC and its orientation, not from the U-factor - ASHRAE design temperatures per climate zone, with a manual override for your own design conditions - Sensible and latent loads reported separately, plus floor and duct loads - Airflow now follows the supply-air temperature difference (about 400 CFM per ton) - Added inputs: exterior wall count, window orientation, floor type, ducts in unconditioned space - Heating results no longer report tonnage, which is a cooling-only unit Faster cold start: analytics and the ads SDK no longer block the first screen.

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1. First observed Oct 16, 2026 · 4:59 PM $0.99