Energy efficiency
How aluminium windows and doors meet Approved Document L: whole-unit U-values, thermally broken frames and glazing make-up, confirmed at quote.
Whole-unit U-values, not just centre-pane figures, so the number on the datasheet matches what is actually fitted.
Whole-unit U-valuesFrame and glass quoted together, not centre-pane alone.
Thermally broken aluminiumLow-conductivity break between inner and outer profiles.
Approved Document LSpecified to meet the conservation-of-fuel baseline for the project.
Energy performance is quoted as a whole-unit U-value, frame and glass together, not the centre-pane figure on its own. Confirm the achievable U-value for the chosen product route, size and opening style before using it for compliance.
Aluminium uses a thermal break, a low-conductivity barrier between the inner and outer profiles, to cut heat loss through the frame. The break depth, the profile and the glazing combine to set the result.
Double or triple glazing, low-E coatings, warm-edge spacers and gas fill all move the U-value. The glass is specified with the frame so the target is realistic for the size, weight and exposure.
For dwellings in England, Approved Document L sets the conservation-of-fuel-and-power baseline, including the U-values new and replacement windows and doors are expected to meet. Aluminium reaches these through thermally broken profiles, the right glazing make-up and correct installation, so the figure on the drawing is the figure that gets fitted.
Low-U routes are project assessed. Send sizes, opening style, glass target and drawings, and VitrineAlu confirms the achievable whole-unit U-value for the product route before a quote is issued. Bigger glass, slim sightlines and exposure all affect what is realistic, so the specification is set against the project rather than a brochure figure.
Most relevant on windows and tilt-and-turn routes: aluminium casement windows, aluminium tilt and turn windows, and the trade note on low-U routes for trade estimates.
Related guides
For the detail behind the numbers, see the guide to aluminium U-values and how an aluminium thermal break works. For the wider spec, see weather ratings, acoustic performance and maximum sizes. To weigh the frame material itself, read aluminium vs uPVC windows and doors or aluminium vs timber. On glass, finish and style, see glazing explained, finishes and colours and window styles.
The whole-unit U-value (Uw) covers the complete window: frame, glass and edge seals together. The centre-pane figure only measures the middle of the glass, so it always reads lower. Compare units on Uw, never centre-pane. We confirm the whole-unit Uw at quote on our energy-efficiency page.
A thermal break is an insulating barrier between the inside and outside faces of the aluminium frame. It stops heat passing straight through the metal, so it cuts heat loss and reduces condensation on the inner frame. Every window and door we make uses thermally broken frames. We confirm the whole-unit Uw at quote.
Glazing make-up drives most of the thermal result. Double or triple glazing, low-emissivity coatings, the cavity gap and warm-edge spacers all cut heat loss, and an argon-filled cavity improves it further. We spec the frame and glass together to hit your target, then confirm the whole-unit Uw at quote on our energy page.
Approved Document L sets the building regulations baseline for windows and doors in England. The required figure depends on the project and whether it is a replacement or new build. We spec glazing and frames to meet or better that baseline, and confirm the whole-unit Uw at quote for your job.
We confirm the whole-unit Uw at quote, calculated for your exact frame, glazing make-up and sizes, not a generic catalogue figure. That gives a like-for-like number you can put against Approved Document L. Send your sizes and target performance through quote and we will spec the unit to suit.
Proof, not promises
Paul Fradley, Director and Technical Lead, has worked almost every role in windows and doors across more than twenty years: surveyed, fabricated on the floor, fitted on site, then ran the technical and operations side. He leads the spec on every project, so what we quote is what we fabricate.
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Send sizes, drawings or a quick project brief. VitrineAlu will confirm the right product specification for the project at quote.