Thermal Engineering Services 

Sydenhams Timber Engineering are unique with the ability to offer full thermal engineering services from inception to completion of a domestic project. We offer the following services in addition to Timber frame, Trusses and Joists.

  • Standard and Advanced Overheating Calculations
  • Pre SAP assessments
  • Full SAP assessments
  • Independently assessed Psi Value Thermally Modelled Junctions
  • In House air testing

Combining the above services with our design capabilities we can value engineer your project and save money in insulation costs and still achieve High A rating buildings. We have 2 fully trained in-house Energy Assessors and a Level 2 airtightness testing technician. We can help ensure you reach the requirements of Part-L and Part-O in a one stop shop.


The updates to building regulations in June 2022 Included a new Part, Part O.

It is now part of the building regulations that all designers perform an overheating risk analysis of all new domestic buildings. We offer this service in house, Architects and designers can contact us for prices on doing full overheating calcs on their projects. We use the latest software which asses sun paths on the hottest days of the year to ensure overheating risk is minimised.

 For more information, please refer to the approved documents.

Standard Assessment Procedure 

SAP calculations have been a requirement of building regulations since 2010 it is a way to produce an EPC (Energy Performance Certificate) rating for your house based on the energy costs scored from 1 – 100. It takes into account materials used during its construction, the heating and hot water systems you use, the internal lighting and any renewable technologies used within the build.


The ‘Pre’ SAP element should be conducted during the initial conception phase with the Architect, we offer a wide range of wall, floor and roof constructions which can help get a better rating. We also offer high discounts if the Timber frame projects come to us for the design and build (subject to contract specific requirements). Using the elemental U-Values, Openings, Ventilation, heating systems. The software we use will determine if the building will comply to Part L of the building regulations. The assessor will then inform the client of any short falls, and potential ways to resolve any issues. This may include more renewable technologies or a more efficient heating system.  Once Agreements have been reached then we can issue a BREL As designed Certificate for the building.

‘Full’ Sap Assessment

Once the building is completed we will have to complete an ‘As Built’ Sap assessment. As with anything in construction, it is likely some elements may not be as originally designed so it is likely that these changes will have to be taken into account. Thermal junctions may also require assessment and be thermally modelled. Photographic evidence of the junctions which are a requirement of the building regulations will need to be apprised. All lighting elements, heating systems and penetrations which also need photographic evidence supplied need to be taken into account. We will the perform an ‘Air Test’ on the building which will give us the amount of air changes per hour for the building to input into the SAP assessment software. From this we can then issue a full BREL As Built Certificate of compliance.

For more information, please refer to Part L of the building regulations.

PSI – Value Modelling

As part of our thermal analysis we may need to thermally model junctions to get a better EPC rating for your building. This involves using the design detailing for penetrating elements of the building, and perform a thermal calculation to assess the difference between the heat loss through a junction when compared to the adjoining elements. Each Wall/Floor/Roof type will give a different result so it may be unique to your building. The detailing should be discussed with your designer and SAP engineer prior to completion of the works to ensure you are following the correct procedure.

Photographic evidence of your junction will be required as part of Part L of the building regulations.

Air testing

We have an in house Level 2 air testing technician who can perform an air test on the building as part of your SAP assessment. This is done by installing a large fan in the door opening and filling the building with air to a pre-set pressure. It will then measure the time it takes for the pressure to change. This will then be fed into a calculation and give us the air changes per hour for the building. This information will then be inputted to the SAP calculation.