About
HeatLoss Pro is a heat loss calculator and heat pump sizing tool that runs in your browser. You draw the walls of a house, or trace them over a floor plan, and it works out the heat loss room by room and the heat pump size the house needs.
It is made for installers, engineers and homeowners who want a sound figure without a week of spreadsheets or an expensive CAD package. Drawing is free; a calculation costs from €1.
How it works
Each room loses heat through its walls, windows, floor and ceiling, and through the air that leaks or is ventilated out. The tool follows the room-by-room method of EN 12831: it multiplies each surface by its U-value and the difference between the room and the coldest outdoor temperature, and adds the ventilation loss. The heat pump is then sized on the whole house at that design temperature, from the unit's own datasheet figures.
If you draw the heating as well (radiators, underfloor heating, pipes), it checks pipe sizes, flow and pump head, and balances the circuits.
An estimate, not a survey
The results are only as good as the drawing and the values in it. Have an installer or an engineer check anything you intend to buy or build from. See the terms.