Simplified Method
Approved Document O details a Simplified method that can be used to provide a different way to assess the likelihood of overheating so that a more complex and expensive TM59 assessment doesn’t have to be done where it is deemed unnecessary. These focus on two areas, limiting solar gains and removing excess heat. The requirements to achieve compliance with these two areas differs depending on the location of the building and whether or not it has cross-ventilation.
The simplified method looks at the area of glazing in proportion to the floor area, and prescribes a minimum free area (the geometric open area of a ventilation opening) that must be achieved. This is called a ‘Simplified Method’ for a reason, and is not an appropriate method of Overheating Risk Assessment in all buildings. Where this method is insufficient, Approved Document O prescribes the use of more complex modelling via the Dynamic Thermal Modelling method.
Simplified calculations can be used for buildings located outside of the postcode areas listed in Appendix C of Part O of the Building Regulations. In these areas, the simplified method is considered sufficient to assess the risk of overheating and ensure compliance with the Building Regulations.
Simplified calculations are a quicker way to assess the risk of overheating in a building. The method is based on the principle that overheating is exacerbated by excess solar radiation and insufficient ventilation.
These calculations use basic assumptions and generalised data to estimate the risk of overheating. While they are not as accurate as dynamic thermal modelling, they can provide a good starting point for understanding the potential for overheating in a building.
Simplified calculations can be used for buildings located outside of the postcode areas listed in Appendix C of Part O of the Building Regulations. In these areas, the simplified method is considered sufficient to assess the risk of overheating and ensure compliance with the Building Regulations.
