Part O of the Building Regulations makes overheating risk a compulsory design assessment for every new residential building in England from June 2022. Two compliance routes are available — the Simplified Method and the Dynamic Thermal Modelling method. We deliver both, sized to the risk-profile of the site.
A new residential building must limit unwanted solar gains in summer and provide an adequate means of removing heat from the indoor environment. Every dwelling in scope must demonstrate compliance via one of two routes at building-control submission stage.
A prescriptive test on cross-ventilation potential, glazing area and orientation, useful for straightforward single-aspect dwellings with modest glazing. Fastest and cheapest route, but it fails a large proportion of contemporary apartment schemes.
Hour-by-hour thermal simulation using CIBSE TM59 weather files. Required for most flats, single-aspect dwellings on noise-sensitive or polluted sites, and any scheme the Simplified Method fails. We use approved DSM software with CIBSE-approved weather sets.
At outline design, before window sizes and glazing specifications are frozen. Once RIBA Stage 4 detail is locked, remediation options are limited to added shading, restricted-opening windows or MVHR with cooling — all more expensive than early-stage design changes.
Nationwide desktop service. Simplified Method assessments from £180 per dwelling type. TM59 dynamic thermal models from £450 for a typical apartment; larger and complex schemes individually quoted. Delivered 5–10 working days from receipt of drawings and glazing schedule.
Yes if it is a new residential building submitted for Building Control approval on or after 15 June 2022 in England. That includes new houses, new apartments, and material changes of use creating new dwellings. Retrofits and extensions are excluded unless they create a new self-contained dwelling.
Simplified is fastest and cheapest but fails a large fraction of modern flats — anything single-aspect, or on a site with acoustic or air-quality restrictions on opening windows. TM59 is required for those, and is also the safer route for any scheme where marketing-critical windows drive fixed glazing above the Simplified Method thresholds.
Yes. Both Simplified and TM59 assessments are fully desktop, delivered from your architectural drawings, glazing schedule and location. No site visit required.
The report identifies which factors are driving the failure (usually solar gain from over-large or unshaded glazing, or inadequate cross-ventilation) and models remediation options. Common fixes are external shading, restricted-opening windows plus MVHR, tinted glazing, or geometry changes. Cheapest to fix at design stage, expensive after RIBA Stage 4.
Call 01392 980077 or get a quote online.