Energy and overheating software can all contain a three-dimensional building, but that does not make the methods interchangeable. Each has defined inputs, conventions, criteria and approved uses.
Start with what the project must demonstrate. Building use, location, regulatory route, planning policy and the decision required determine the suitable method. Software choice follows that brief.
SAP for dwellings
The Standard Assessment Procedure is the government's methodology for assessing the energy performance of homes. It is used for relevant new-home Part L compliance and domestic EPC outputs through approved implementations.
SAP uses standardised conventions so dwellings can be assessed on a consistent basis. It is not a room-by-room summer-temperature simulation and it does not replace an overheating assessment.
SBEM for many non-domestic buildings
The Simplified Building Energy Model is an implementation of the National Calculation Methodology used for many buildings other than dwellings. It represents zones, activities, fabric, lighting and building services to produce relevant Part L and certification outputs.
"Simplified" does not mean input-light. Poor zoning, generic services assumptions or mismatched schedules can materially weaken the model. The building and M&E information must describe the same design.
Approved dynamic simulation for non-domestic compliance
Some non-domestic buildings or systems are better represented through an approved dynamic simulation model. The applicable National Calculation Methodology and software approval determine whether it can be used for the required regulatory output.
A dynamic model is not automatically more accurate. Its value depends on suitable input data, competent modelling, quality assurance and a clear purpose.
Dynamic overheating analysis
TM59 and other relevant overheating methods examine internal conditions over time using weather data, gains, occupancy, fabric, shading and ventilation assumptions. They can identify when and where overheating occurs and test design responses.
CIBSE published TM59:2026 on 6 July 2026 and recommends it for current industry best practice. Part O in England currently still requires TM59:2017 and the 2016 CIBSE weather files for its dynamic route, together with Approved Document O's additional modelling and mitigation constraints. Planning policy and client briefs may specify different criteria, editions or weather scenarios, so the controlling requirement must be recorded explicitly.
Avoid model drift
Multiple models on one project should share controlled geometry and specifications where the same design input is represented. Differences may be valid because methods use different conventions, but they should be intentional and explained.
Give each model an owner, purpose, version, input date and change route. A beautifully detailed model based on an obsolete façade is not useful evidence.
Define the output
Identify the regulation, planning policy, certification need or design decision.
Confirm the building type
Separate dwellings, non-domestic spaces and mixed-use areas correctly.
Select the approved route
Check methodology, software and assessor requirements for the purpose.
Coordinate shared inputs
Align geometry, fabric, systems and change control across the project evidence.
Frequently asked questions
Is dynamic simulation always better than SBEM?
No. It can represent more detail, but the appropriate method depends on the building, purpose and approved route.
Can SAP assess an office?
No. SAP is a domestic methodology. Relevant non-domestic buildings use the National Calculation Methodology through SBEM or an approved dynamic simulation route.
Can one model prove Part L and overheating compliance?
Separate criteria and approved methods apply. Shared inputs can be coordinated, but the required outputs remain distinct.