How does Shrunk Punk calculate the heat loss for a property?

Shrunk Punk uses the information from a property’s EPC (or details you enter manually) to build a simple model of the home. It looks at the property type, age, floor area, and the descriptions of walls, roof, floor, and windows. From these, it assigns typical insulation values (known as U‑values) and estimates the size of each surface based on the building form. It then multiplies the surface areas by their U‑values to work out how much heat is lost through each part of the building, and adds them together to give the total heat loss per degree of temperature difference. Finally, this is scaled to the design temperature (for example, 21 °C indoors versus –3 °C outdoors) to give the overall heat loss in kilowatts, along with a breakdown showing how much is lost through walls, roof, floor, and windows.

Important note: Shrunk Punk is designed as a quick, indicative tool to give an early estimate of a property’s heat loss. It does not replace a full room‑by‑room heat loss calculation in line with CIBSE or MCS standards, which is required for system design and installation sign‑off.