SAPs / EPCs

Standard Assessment Procedure / Energy Performance Certificate

An Energy Performance Certificate (EPC) is an official document that provides an assessment of a property’s energy efficiency, expressed as a rating that reflects the potential cost of running the property. This rating is based on the performance of the building fabric (walls, roof, floors, windows) and the energy efficiency of its heating, hot water, ventilation, and lighting systems.

U-value Calculations

A U-Value, also known as thermal transmittance, measures the rate at which heat passes through a building element such as a wall, roof, floor, or window. In simple terms, the lower the U-Value, the better the material or assembly is at insulating and resisting heat flow. U-Values are a critical indicator of thermal performance and are used to assess how energy efficient a building component is.

Thermal Bridging (Psi-Value) Calculations

Psi values represent the rate of heat loss through thermal junctions—the points where two or more building elements meet, such as where an external wall connects to a ground floor or roof. Unlike U-values, which measure heat loss through individual surfaces, Psi-values quantify the heat lost at these junctions.

Due to the complexity and precision required, it’s important that Psi-values are calculated by someone with both technical expertise and experience in modelling construction details accurately.

Part O Overheating Calculations

(Simplified & Dynamic)

Part O of the Building Regulations in the UK focuses on mitigating the risk of overheating in new residential buildings, including dwellings, care homes, student accommodation, and major refurbishments. Introduced to reflect growing concerns around climate change and summer overheating, Part O aims to ensure that homes are designed to reduce solar heat gain and provide sufficient means to remove excess heat without relying solely on mechanical cooling.