What's a 'window'?

10 Dec 2017
Reaction score
United Kingdom
...seems like a daft question. But Regs designate a window to the outside a 'controlled fitting' so its kind of important. I have a floor to ceiling (almost) aperture which has a window in the top half and a cosmetic panel in the bottom half. The panel is hardwood. Is my 'window' just the top half or does the bottom half also amount to a 'window'. I definitely can't see through the bottom half! If its not a 'window' I guess it must be a 'wall'.
On reading Part 'L' (well some of it) such a design would no longer be permitted as the bottom half is more or less a heat sink. I'm a bit surprised it would have been permitted seven years ago when the building conversion was done. Anyway I plan to box out the interior and add insulation and window board to (vastly) improve insulation but in the absence of an external brick member even then the insulation will be less than desirable.
Sponsored Links
Sponsored Links
You can have a window in a door, you can have a window that is a door, you can have a door in a window. You can have an arrow slit in a castle that is neither a door nor a window.
Before I converted it, our kitchen was the old dairy, and it didn't have any glazed windows, just holes with wooden shutters that opened for light and ventilation. It was meant to be cold, and was!
Thanks all for your observations. Without leading them, and providing a photo, Building Control treated the lower panel as a wall - a 'thermal element' - but due to its size in proportion to the whole wall, it is outside part 'L' requirements for a 'thermal renovation' and Building Control application.
Regardless, it will be much, much warmer once I have added a couple of layers of insulation behind the panel.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local