BREL Reports Explained: What They Are and Why You Need One

If you’re building a new home in England, you’ll need a BREL report before Building Control will sign off your project. A ‘Design SAP’ is needed before building work starts to prove your building can pass Part L targets. You’ll get a predicted BREL at this stage. Once building work is complete, an ‘As-Built SAP’ is required to show the final design still complies. Here you’ll get a BREL that building control need to sign off the building so it can be sold or occupied.

BREL stands for Building Regulations England Part L. It’s the compliance document that proves your new dwelling meets current energy efficiency standards. It’s the document that demonstrates what was designed on paper has actually been built on site.

What is a BREL Report?

A BREL report is the output from your SAP calculation. It shows whether your dwelling passes or fails the three key energy metrics required by Part L of the Building Regulations.

The report was introduced in June 2022 as part of the Part L 2021 update. Before this, SAP calculations produced basic compliance documents, but the new BREL format adds more detail and requires photographic evidence of construction detail.

The whole point is to close the “performance gap” where buildings don’t perform as well as their design predicted. By requiring evidence of how the building was actually constructed, the BREL report helps ensure the finished dwelling matches what was modelled in the SAP calculation.

Wales has an equivalent called a BRWL report (Building Regulations Wales Part L). Scotland uses a different system under Section 6 of Scottish Building Standards with its own compliance documentation.

When Do You Need a BREL Report?

BREL reports are required for all new build dwellings in England. This includes new houses and bungalows, flats and apartments, and any project creating a brand new dwelling from scratch.

You do NOT need a BREL report for conversions (these fall under Part L1B and have different requirements), extensions to existing properties, or refurbishment work on existing buildings.

If you’re converting an existing building into dwellings, you’ll still need SAP calculations and an EPC, but the compliance documentation is different from the BREL format.

The Two Stage Process

Every new dwelling needs two BREL reports: one at design stage and one when construction is complete.

The design stage BREL is produced before building work starts. It shows the target metrics your dwelling must achieve and the expected performance based on the proposed specification. This gets submitted to Building Control with your initial application.

The as-built BREL is produced when construction finishes. It uses the actual specification of products installed on site (not the original design assumptions) to recalculate the dwelling’s performance. This must be supported by photographic evidence showing how key details were constructed.

Both the SAP assessor and the developer must sign the as-built BREL report. The assessor confirms the calculations are accurate and they’ve reviewed the evidence. The developer confirms the dwelling was built according to the specification listed in the report.

What’s in a BREL Report?

The BREL report shows three key metrics, each compared against a target:

DER vs TER (Dwelling Emission Rate vs Target Emission Rate) measures carbon emissions in kg CO2 per square metre per year. Your DER must be equal to or lower than the TER.

DPER vs TPER (Dwelling Primary Energy Rate vs Target Primary Energy Rate) measures total primary energy consumption in kWh per square metre per year. This was added with Part L 2021 and accounts for energy losses in generation and distribution. Your DPER must be equal to or lower than the TPER.

DFEE vs TFEE (Dwelling Fabric Energy Efficiency vs Target Fabric Energy Efficiency) measures the energy demand of the building fabric itself, separate from heating systems or renewables. Your DFEE must be equal to or lower than the TFEE.

All three metrics must pass for the dwelling to be compliant. Failing any one of them means the BREL report shows a fail result and Building Control won’t sign off.

The report also includes a summary of the building specification: U-values for walls, floors and roofs, window performance, heating system details, ventilation strategy, and any renewable technologies.

Photographic Evidence Requirements

This is where the BREL process differs from the old SAP compliance documents. You must provide photographs showing key construction details for each dwelling.

Photos must be digital with geolocation enabled to confirm location, date and time. They need to be clear enough for the assessor to verify the detail being shown.

The required photographs cover:

Foundations and ground floor showing thermal continuity and edge insulation.

External walls for each main wall type, showing insulation quality and installation.

Roof structure for each roof type, showing insulation continuity.

Openings showing window and door positioning relative to the insulation line or cavity closers.

Airtightness details if not visible in other photographs.

Building services showing heating equipment labels with make, model and serial number, plus any mechanical ventilation ductwork.

Each dwelling on a development needs its own unique set of photographs. You can’t use the same images for multiple plots, even if they’re identical house types.

The photos should be taken as each detail is completed, before it gets covered up by subsequent work. This requires coordination between whoever is on site taking photos and the SAP assessor who needs to review them.

BREL vs EPC: What’s the Difference?

Both come from the same SAP calculation, but they serve different purposes.

The BREL report is for Building Control compliance. It proves the dwelling meets Part L energy requirements and is needed for the completion certificate.

The EPC (Energy Performance Certificate) is for sale and rental requirements. It shows the A to G energy rating and estimated running costs. It’s a legal requirement when selling or letting a property.

You need both for a new build. The EPC is produced from the verified data in the as-built BREL report. Without a signed BREL report, you cannot get a valid EPC for a new dwelling.

For existing buildings being sold or let, you only need an EPC (produced using RdSAP, a reduced data version of SAP). BREL reports only apply to new construction.

What Happens Without a BREL Report?

Building Control cannot issue a completion certificate without a valid BREL report. This means you cannot legally occupy or sell the property.

No BREL also means no EPC, which creates additional problems for sale or rental.

If photographic evidence wasn’t captured during construction, producing a retrospective BREL report becomes extremely difficult. You can’t photograph insulation that’s now hidden behind plasterboard. This can lead to expensive remedial work or intrusive investigations to verify what was actually installed.

The sign-off requirement means both the assessor and developer are accountable. If issues emerge later (warranty claims, customer complaints about energy bills), the BREL report provides evidence of what was specified and installed.

Common BREL Problems

Specifications changing during the build is the most frequent issue. If the builder substitutes a different boiler model or insulation product, the as-built BREL must reflect what was actually installed. This might cause a design that passed at design stage to fail at as-built stage.

Missing photographic evidence causes delays. If key details were covered before photos were taken, the assessor cannot verify compliance. Planning the photo schedule alongside the build programme is essential.

Coordination failures between site teams and assessors create problems. The assessor needs to review evidence and may request additional photos if images aren’t clear enough. This works best when there’s ongoing communication throughout the build rather than a last minute rush at completion.

When we complete an As-Built SAP Calculation, we’re with our clients throughout the build. Insulation gets swapped? Window supplier changes? Client wants a big bi-fold? Just let us know and we’ll update the model to see what impact it has. The sooner we know, the better.

Getting Your BREL Report

Your SAP assessor produces both the design stage and as-built BREL reports as part of the SAP calculation service. The reports are generated automatically by the SAP software once all the required data and evidence is in place.

For the design stage BREL, you need architectural drawings and a specification covering construction details, heating systems, ventilation and any renewables.

For the as-built BREL, you need the photographic evidence, any product data sheets for installed items, and confirmation of what was actually built if it differs from the original design.

The assessor reviews everything, runs the final calculations, and signs the report. The developer then counter-signs to confirm the build matches the specification. Both signed reports go to Building Control along with the EPC.