Overheating Assessments
An overheating assessment checks that a new or converted home won't get dangerously hot, as required by Part O of the Building Regulations. AVA Home Design carries out CIBSE TM59 and TM52 overheating assessments in-house across the whole UK (by the Simplified Method or full Dynamic Thermal Modelling) alongside the design, so your scheme meets Approved Document O without a separate consultant.
Since 15 June 2022, Approved Document O of the Building Regulations requires most new homes to demonstrate that they limit unwanted solar gain and can remove excess heat. For many developers and self-builders this is a new hurdle, and it is often discovered late, after the windows and layout are already fixed.
We assess overheating in-house, at the design stage, as part of the architectural design, not as a separate report bolted on at the end. Because the assessment is a calculation based on your drawings and location, we provide it anywhere in the UK without a site visit. Almost no local design practice offers this combined, which is why developers come to us for it specifically.
Types
- CIBSE TM59 (dynamic)
- The recognised dynamic-modelling method for homes. It simulates the building hour by hour across a design summer against defined comfort criteria for living spaces and bedrooms.
- CIBSE TM52
- The adaptive-comfort criteria used for non-domestic and communal spaces, applied where TM59 is not the right fit.
- Simplified Method
- The quicker Approved Document O route that limits glazing area and sets minimum opening areas for ventilation. More restrictive but faster.
- Dynamic Thermal Modelling
- A full thermal simulation of the building. More work, but usually gives more design freedom on glazing and layout than the Simplified Method.
Frequently asked questions
- When do I need an overheating assessment?
- Since 15 June 2022, Approved Document O requires new residential buildings (new houses and flats, and many conversions and changes of use that create dwellings) to show they limit overheating. You usually need the assessment at the design and planning stage, before construction, because the result can change windows, shading and ventilation.
- What is the difference between the Simplified Method and Dynamic Thermal Modelling?
- Approved Document O offers two routes. The Simplified Method limits glazing area and sets minimum opening areas for ventilation; it is quicker but more restrictive. Dynamic Thermal Modelling, a TM59 assessment, simulates the building hour by hour across a design summer and usually gives more design freedom. We advise which route suits your scheme.
- What is a CIBSE TM59 assessment?
- TM59 is the CIBSE standard methodology for assessing overheating risk in homes using dynamic thermal modelling. It tests the building against defined comfort criteria for living spaces and bedrooms, and is the recognised way to demonstrate compliance with Approved Document O by the dynamic route. We model it in-house from your drawings.
- Do you do overheating assessments outside London?
- Yes. An overheating assessment is a calculation and report based on your drawings and location data, so we provide TM59 and TM52 assessments anywhere in the UK without a site visit. We work from your plans, elevations and specification and return the report with any recommended design changes.