Low Energy Windows & Doors FAQ

Please ring us on 01484 463336 for advice on the best range for your project. See our summary and overview of the ranges.
Please complete our online quote form
Yes, we do! Our fitting service operates throughout the UK.
Yes, we have a showroom in Huddersfield and a permanent exhibition at National Self Build & Renovation Centre, Swindon. Find out more about visiting our showrooms.
We do exhibit at a number of events throughout the year covering a wide geographical area, making it easier for customers to see our high performance triple glazed timber windows first hand.
Our ranges can be inward or outward opening.
21°’s windows and doors are triple glazed as standard.
21° windows & doors are all made from timber. Our ranges are made from FSC® certified Redwood or Oak. Modern timber finishes are now so durable that, for most applications, we recommend them over aluminium cladding or UPVC.
In addition to our triple glazed timber windows and doors, 21° offers a wide range of products and services, including advanced MVHR heat recovery ventilation, specialist airtightness & insulation products, and consultancy.
We provide up to 10 years warranty on our range of timber window and doors. Speak to our team to find out more.
Green Building Store was set up in 1995, under the name Environmental Construction Products. We changed our name to 21° in 2024.

21°s windows and doors are available in the RAL classic range and we also have a selection of natural wood stains to choose from.
Yes, please specify this when requesting a quote.
21° windows and doors can be made Part Q compliant, please specify this when requesting a quote and our estimators can use your elevations and floor plans to ensure we comply with Part Q.
21° windows have an option to be SBD compliant, please specify this when requesting a quote.
Yes, our Lift & Slide Doors have Class 4 airtightness with optional SBD/ Part Q security.
Yes, we can include cat-flaps in fully glazed doors. Please note that the cat flap would be at least 300mm from floor level. Our doors all achieve the highest level of airtightness at Class 4, but adding a cat flap would obviously affect this. Cat flaps are not advised for Passivhaus builds unless you use a specialist Passivhaus-suitable cat-flap, which we can advise on.

You can download these on our technical pages.
Or find out more with our technical resources
U-Values measure how well heat is transferred by the entire window/ door – the frame, sash and glass – either into or out of the building. The lower the U-Value number, the better the window or door will keep heat inside a building on a cold day.
Yes, we supply PHPP data on our windows and doors for those needing the information for Passivhaus projects. You can download our PHPP10 file on our technical page.
Quadruple glazing is not energy or cost optimal in the UK climate zone. Although the thermal transmission is reduced, so is the solar gain. So on balance, this gives worse performance for the building at a significantly increased cost. Triple glazing is at the ‘sweet spot’ of optimal energy balance while satisfying our need for warm inner surfaces to meet Passivhaus comfort criteria. In colder climates, quadruple glazing is required for optimal energy balance and warm inner surfaces.

Yes, we have a dedicated Aftersales team with office and on the road staff.
Yes, these are sent out with each order.
Yes, please contact the team.
Yes, please see our Installation & aftercare page for windows and here for doors.
Yes, we use 3 star Brisant ULTION cylinders and our hardware is all multi point locking.

Windows & doors FAQs