BREEAM HEA01 Daylight calculations
Walker Energy Analysis carries out the daylighting assessment for BREEAM’s HEA01 credit, using dynamic daylight modelling in IES Virtual Environment. Daylighting is worth up to two credits within HEA01, and the criteria have to be checked room by room against a specific average daylight factor and a uniformity requirement, not assessed by eye from the drawings.
How the Daylighting Assessment Works
The core metric is average daylight factor, the average daylight illuminance across a room’s working plane, expressed as a percentage of the outdoor illuminance available at the same time. The minimum required average daylight factor depends on the building type and room use, and typically ranges from around 1.5% to 3%.
Meeting the average daylight factor alone isn’t enough, the room also has to demonstrate reasonably even daylight distribution, not a bright patch near the window and a dark corner beyond it. This is checked through either a uniformity ratio of at least 0.3, or a minimum point daylight factor set at a fraction of the average daylight factor for that room type. Rooms with glazed roofs, such as atria, are held to a stricter uniformity requirement.
We model each relevant space using the building’s actual window design, glazing specification, room geometry and internal surface reflectance, and report against whichever of the two uniformity routes suits the design.
- Average daylight factor calculation, room by room, using the building’s actual glazing and geometry
- Uniformity assessment, using whichever of the two BREEAM routes best fits the design
- Reporting structured for your BREEAM assessor, room by room against the relevant thresholds
- Design-stage feedback where a space falls short, glazing area, room depth, or reflectance changes to bring it into compliance
Where Daylighting Sits Alongside Other Requirements
Daylighting is one part of BREEAM’s wider HEA01 issue, which also covers glare control, view out and lighting controls, assessed separately. It’s also worth checking early against a scheme’s overheating strategy, since glazing decisions made to hit a daylight factor target can work against a TM52 or TM59 assessment, or vice versa, so the two are best considered together rather than in isolation.
Why Work With Us
We’re a specialist energy consultancy. This is the core of what we do, not a sideline. Every assessment runs through IES VE as standard, we turn changes around quickly, and results come back in a format your team and BREEAM assessor can use immediately.
FAQs
Q: What’s the minimum average daylight factor I need to achieve?
A: It depends on the building type and room use, and typically ranges from around 1.5% to 3%. We confirm the specific threshold for your project against the relevant BREEAM table.
Q: What if a room can’t meet the average daylight factor because of its design?
A: We identify what’s driving the shortfall, window size, room depth, or internal reflectance, and feed that back early enough to influence the design, rather than reporting a fail after the layout is fixed.
Q: Does this assessment also cover glare?
A: No, glare control is assessed separately within HEA01. Our service covers the daylighting element specifically.
Q: Can daylighting and overheating be assessed together?
A: We’d recommend it. Glazing decisions affect both, so checking daylight factor and TM52 or TM59 overheating risk together avoids one requirement undermining the other later in the design.
Get Your Daylighting Credit Secured
Talk to Walker Energy Analysis early, while glazing and room layouts are still open to change.
Does your project need something else?