Part L
Energy and SAP calculations
Design-stage and as-built SAP calculations for new and converted homes, with the EPC lodged at completion.
Energy calculationsView service
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Energy & performance calculations
Overheating assessments
We show how a new residential building limits overheating in summer, using the Approved Document O simplified method or dynamic thermal modelling to CIBSE TM59, and give you the report and checklist building control asks for.
When you need it
Part O applies to new residential buildings: dwellings, care homes and similar premises where people sleep, and student accommodation. It does not apply to extensions, conservatories added later, or buildings undergoing a change of use. There are two routes: the simplified method, which limits glazing and sets minimum openable areas, and dynamic thermal modelling to CIBSE TM59.
The simplified method has tighter limits in parts of London classed as high risk, and is not suitable for every building, for example where noise means windows will stay shut at night or where communal heating has long horizontal pipe runs. Checking the route early avoids redesigning windows late.
What is included
Included
- Review of the site, layout and which route suits the building
- Simplified method assessment, or a TM59 dynamic thermal model
- Advice on shading, glazing and ventilation where results fall short
- Report and Approved Document O compliance checklist for building control
Priced separately
- Noise surveys or acoustic assessment
- Mechanical cooling or ventilation design
- Remodelling after major design changes
- Energy statement or planning overheating reports beyond the agreed scope
Your written quotation confirms the exact scope, what is included and any limits for your building.
What you receive
An overheating report showing the building meets Part O by the chosen method, with the Approved Document O compliance checklist to pass to building control.
Sent as a PDF. We can send it to your building control body or agent on request.
Our reports and testing support the compliance process. Approval and completion decisions remain with your building control body: the local authority, a registered building control approver, or the Building Safety Regulator for higher-risk buildings.
How to prepare
- Site address and the surroundings, including noise sources
- Plans, sections and elevations with window sizes
- Window and door types and opening arrangements
- Ventilation and heating systems, including any communal heating
- Any planning condition on overheating
Send what you have. Missing details will not stop an enquiry; we will tell you anything still needed.
How it works
Tell usChoose the service or describe the job.
Written quotationScope, deliverables and price, confirmed in writing.
We manage the workArranged and coordinated by RegulaBuild. Technical work is carried out by appropriately qualified professionals.
Your reportThe output named in your quotation, with any follow-up.
Questions
Does Part O apply to my extension or conversion?
No. Government guidance confirms Part O applies only to new residential buildings, not to extensions or changes of use.
Which method is better, simplified or TM59?
The simplified method is quicker where the design fits its limits. TM59 modelling gives more design freedom and is needed where the simplified method does not suit the building.
Can the planning authority ask for overheating analysis too?
Yes. In London, for example, the Mayor’s energy assessment guidance asks for TM59 modelling for residential schemes referred to the Mayor. We can coordinate the planning and Building Regulations work.
Often booked with
Combine them in one quote request
Part F
Ventilation design
Ventilation strategies and system design to meet Part F before work starts.
Design and approvalsView service
Planning
Energy statements
Energy and carbon statements for planning applications, written to the local plan policy that applies.
Energy calculationsView service
Where we work
Overheating assessments across England
Request a quote
Discuss overheating assessments
Start with this service and add anything else you need. If you are unsure, say so and we will advise.