Overheating Risk Analysis - Simplified Method (Building Regulations Part O)

Two Ways to Demonstrate Compliance

The Approved Document Part O introduces two ways to demonstrate compliance:

1. Simplified Method for limiting solar gains and providing a means of removing excess heat through window sizing or window design; or,

2. Dynamic Thermal Modelling or Dynamic Simulation Method which provides a standardised approach for predicting overheating risk for residential buildings based on CIBSE TM59 methodology.

Two Key Compliance Measures for the Simplified Method

Compliance is based on designing and constructing the building to achieve both of the following:

a. Limiting unwanted solar gains in summer; and,

b. Providing an adequate means of removing excess heat from the indoor environment.

Situations where the Simplified Method may not be used

Although designers can choose either the simplified method or dynamic thermal modelling to demonstrate compliance, there are situations where the simplified method cannot be used for overheating risk analysis such as:

i. buildings with more than one residential unit which use a communal heating or hot water system with significant amounts of horizontal heating or hot water distribution pipework;

ii. buildings in locations where external noise is an issue meaning that windows will be closed thereby minimising ventilation;

iii. buildings in locations where pollution is an issue thereby preventing occupants from opening windows.

In such situations, dynamic thermal modelling should be used.

As the dynamic simulation method allows a range of flexibility regarding design options, it is also siutable where the simplified method results in the building failing compliance.

• More about Dynamic Simulation