Energy-Efficient uPVC Windows
Where heat escapes through a window, and what each part of a modern frame does to stop it.
Where the heat goes
An old window loses warmth in three ways: through the glass, through the frame, and through the gaps around the sash and the edge of the opening. A modern replacement tackles all three at once, which is why a good new window often feels warmer to stand beside, not just cheaper to heat.
The glass
Most of a window's area is glass, so the sealed unit does the heavy lifting. We can specify Planibel A, a low-emissivity glass with a very thin coating that reflects heat back into the room while letting daylight through. Paired in a double glazed unit, it cuts the heat that radiates out through the pane on a cold night.
The frame
uPVC profile is built with internal chambers that trap air and slow heat moving through the frame. Unlike metal, the material itself is a poor conductor, so the inside face of the frame stays closer to room temperature and is less prone to condensation.
The seal and the fit
Gaskets around the sash close against the frame when the window locks, and the multi-point locking pulls the sash in evenly along its length. Just as important is the installation: the gap between frame and wall is sealed and finished so that the new window does not simply move the draught to its edges. Our FENSA and CERTASS registered fitters complete the work to Building Regulations and you receive the certificate.
Low maintenance as a bonus
uPVC frames do not need painting or sanding. An occasional wipe of the frames and a drop of oil on the hinges keeps them working and looking right, which is part of why people choose them.
Reading the ratings
Windows are often described with energy ratings and U-values. Our guide to window energy ratings explains what those letters and numbers mean; this page is about the parts of the window that earn them.
Ventilation still matters
An efficient window seals well, so fresh air has to be planned rather than left to draughts. Trickle vents in the head of the frame and the night-vent position on the handle let a room breathe without opening it fully, which helps keep condensation down in bedrooms, kitchens and bathrooms. We discuss where vents are needed at the free survey so the finished windows are warm without being stuffy.
Common questions
- What is Planibel A glass?
- A low-emissivity glass that reflects heat back into the room while letting light through. See our Planibel A page for detail.
- Do energy-efficient windows need special care?
- No. uPVC frames only need occasional cleaning and light lubrication of moving parts.