Overheating Assessment
Overheating assessments for new residential developments, care homes and student accommodation, helping demonstrate compliance with Part O of the Building Regulations and reduce the risk of excessive internal temperatures.
Overheating Assessments for New Developments
An overheating assessment reviews whether a proposed building is likely to experience unacceptably high internal temperatures during warm weather. The assessment considers solar gains, glazing, orientation, ventilation, occupancy, internal heat gains and the ability of the building to remove excess heat.
Part O of the Building Regulations applies to new residential buildings, including new houses, flats, care homes and student accommodation. Hotels are excluded from the scope of Part O. Requirements can apply to habitable rooms and relevant common areas.
One Stop Consult coordinates overheating assessments and reports through experienced specialists. Depending on the development, compliance may be demonstrated through the simplified method or through dynamic thermal modelling based on the CIBSE TM59 approach.
When Is an Overheating Assessment Required?
Part O is aimed at limiting unwanted solar gains and providing an effective means of removing excess heat from new residential buildings.
New-Build Houses
Newly constructed detached, semi-detached and terraced dwellings may require overheating compliance evidence.
New Apartments
Flats can be particularly sensitive to overheating where there is extensive glazing, limited cross-ventilation or restricted window opening.
Care Homes
New care facilities fall within the scope of Part O and require careful consideration because occupants may be more vulnerable to excessive heat.
Student Accommodation
New student residences may require assessment of bedrooms, studios and relevant shared spaces.
High-Risk Designs
Projects with large glazed areas, single-aspect rooms, limited opening windows or elevated noise constraints often need detailed review.
Building Control Submissions
Building Control may require a report demonstrating the measures used to control solar gains and remove excess heat.
Simplified Method or Dynamic Thermal Modelling?
The appropriate route depends on the building design, location and level of overheating risk.
Simplified Method
The simplified route uses prescriptive limits and design checks to control glazing, solar gain and ventilation. It can be suitable for straightforward schemes that remain within the method's limitations.
Dynamic Thermal Modelling
Detailed modelling simulates room temperatures over time using the building geometry, orientation, weather data, occupancy, ventilation and internal gains.
CIBSE TM59 Approach
TM59 provides a recognised methodology for evaluating overheating risk in homes using dynamic simulation and defined pass or fail criteria.
Design-Led Assessment
Early modelling allows different glazing, shading and ventilation options to be tested before the design is fixed.
What Is Considered in an Overheating Assessment?
Overheating is influenced by the interaction between the building form, glazing, orientation, occupancy and ventilation strategy. A design that performs well in one location may not perform the same way elsewhere.
Accurate architectural and technical information allows the specialist to model the proposed building more reliably and provide meaningful design advice.
Common Causes of Overheating
Modern energy-efficient buildings can retain heat effectively, but this can increase summer overheating risk where solar gains and ventilation are not properly controlled.
Large Glazed Areas
Extensive glazing can allow significant solar heat gains, particularly on south- and west-facing elevations.
Single-Aspect Dwellings
Rooms with openings on only one elevation may have limited opportunities for effective cross-ventilation.
Restricted Window Opening
Safety, security, pollution or acoustic constraints may reduce the opening area available for purge ventilation.
High Internal Gains
Occupants, lighting, appliances and communal systems can add heat to the building throughout the day.
Top-Floor and Roof Spaces
Upper-level rooms can be more exposed to solar gains through roofs, rooflights and unshaded glazing.
Urban Heat and Noise
Dense urban sites may experience warmer night-time conditions while noise can prevent occupants from leaving windows fully open.
How Can Overheating Risk Be Reduced?
The most effective solutions usually combine control of solar gains with a safe and practical means of removing heat.
Reduce Glazing Where Necessary
Review window proportions and large glazed elevations where solar gain is disproportionate to daylight needs.
External Shading
Overhangs, balconies, fins, shutters and other external measures can reduce direct solar gain before it enters the building.
Solar-Control Glazing
Appropriate glazing specifications can reduce solar transmission while maintaining acceptable daylight and appearance.
Improve Natural Ventilation
Increase effective openable area, provide cross-ventilation or improve the arrangement of openings where practical.
Mechanical Ventilation
Mechanical systems may help remove excess heat where natural ventilation is constrained, subject to suitable design and controls.
MVHR Summer Bypass
Where MVHR is proposed, an effective summer-bypass strategy can help avoid unnecessary heat recovery during warmer conditions.
Overheating, Ventilation and External Noise
Opening windows is often a key part of the overheating strategy, but this may not be suitable on sites affected by road, rail, aircraft, commercial or industrial noise.
Where windows cannot reasonably remain open during warm periods, the overheating and acoustic strategies should be coordinated. Alternative ventilation or cooling measures may be needed to provide suitable internal conditions without relying on unrestricted window opening.
How the Overheating Assessment Process Works
Early assessment gives the design team more flexibility to resolve overheating risk before planning, technical design or construction decisions become difficult to change.
Project Review
Confirm the building type, location, orientation, layout and proposed ventilation strategy.
Assessment Route
Establish whether the simplified route or detailed dynamic modelling is appropriate.
Analysis
Assess solar gains, internal gains, ventilation and room temperatures against the relevant criteria.
Mitigation Advice
Recommend glazing, shading or ventilation changes where the initial design does not comply.
Final Report
Issue the completed assessment for the design team and Building Control submission.
Information Required for a Quotation
Provide the full project address, number and type of dwellings, current project stage and the latest architectural drawings.
Please also send available information on glazing, window openings, shading, ventilation, construction build-ups and any acoustic, planning or sustainability requirements affecting the design.
Overheating Assessments for Residential Buildings
Nationwide Overheating Assessment Service
One Stop Consult coordinates Part O and TM59 overheating assessments for projects throughout mainland UK. Support is available for individual dwellings, apartment schemes, care facilities, student residences and larger multi-unit developments.
Other Services Your Project May Require
Important Overheating Assessment Information
The applicable assessment route depends on the project type, Building Regulations transitional arrangements, design and site constraints. Overheating compliance should be considered early because mitigation measures can affect glazing, façades, ventilation, acoustics and room layouts. Final conclusions depend on the accuracy of the information supplied and may require revision where the design changes. One Stop Consult provides consultancy and coordination support through its specialist assessor network.
Overheating Assessment FAQs
What is an overheating assessment?
It assesses whether a proposed building is likely to experience excessive internal temperatures and whether the design provides adequate measures to limit solar gains and remove heat.
Which buildings are covered by Part O?
Part O applies to new residential buildings, including houses, flats, care homes and student accommodation. Hotels are excluded.
Does Part O apply to common areas?
Relevant common areas can fall within the scope of the requirements as well as habitable rooms.
What is the difference between Part O and TM59?
Part O is a Building Regulations requirement. TM59 is a recognised dynamic modelling methodology that can be used to assess overheating in homes.
Can the simplified method be used for every project?
No. Complex or higher-risk designs may require dynamic thermal modelling, particularly where the simplified limits cannot be met.
What happens if the design fails?
The specialist can test changes such as reduced glazing, improved shading, solar-control glass, increased opening area or revised ventilation.
Can noise affect the overheating strategy?
Yes. Where external noise prevents windows being left open, an alternative ventilation or cooling strategy may be required.
When should the assessment be completed?
As early as possible during design, before glazing, façade and ventilation decisions become difficult or expensive to change.
Do you provide overheating assessments nationwide?
Yes. We coordinate suitable specialists for eligible projects throughout mainland UK.
Request Your Free Overheating Assessment Quote
Complete the form below with the project address, number of dwellings and current design stage. Upload the latest plans, elevations, sections, window information and ventilation strategy so our team can review the requirement and coordinate an appropriate quotation.