Understanding window and door U-Values

When researching the purchase of new glazing for the home, understanding window and door U-Values helps you make a more informed buying decision. As well as U-Values, Window Energy Ratings is another term you’ll come across. This guide explains window and door U-Values, what they mean and why they’re important.

window and door U-Values for new homes

Why understanding window and door U-Values is important

U-Values is a measure of how any building material insulates your home. U-Values don’t just extend to windows and doors. Walls, cladding, aluminium panels, glass and insulation all have U-Value figures.

The higher the U-Value, the poorer the performance. The lower, the U-Value, the better the insulation properties. The measurement of U-Values is in Wm2K (Watts per metre square Kelvin). Another way of thinking about U-Values is thermal transmittance. In other words how effective they are in heat transfer or energy loss.

What about Window Energy Ratings?

Window Energy Ratings, or WER’s are a little different. These are measured in Ratings of A (being the best) down to G, being the worst. Furthermore, like U-Values WER’s measure the energy loss, but they also measure energy gain. And a WER even measures any air loss through the window frame .

Why do U-Values and WER’s matter?

Both U-Values and WER’s came into force ten years ago and they form part of the current Building Regulations. They’re covered by Part L1A for new build homes and L1B for existing dwelling. Here’s what you need to know on U-Values and WER minimum ratings for your home. Demonstrating how important these ratings are, they also form part of CE Marking. Here are the minimum requirements for doors and windows.

Windows1.6Wm2K or lowerBand C or better
Roof windows or rooflights1.6Wm2K or lowerBand C or better
Doors (more than 60% glass)1.8Wm2K or lowerBand E or better

There are, of course, certain installations such as listed buildings or conservation area properties where it may not be possible to get the required ratings. Exemptions exist to cover these and your local authority or Building Control can provide more information.

What is the ‘centre-pane’ method?

In the early days of U-Values, compliance came by also using the centre pane method. Generally speaking this is a rating for the glass or panel only. In certain exceptions centre-pane method can be used such as listed buildings.

If your window company quotes centre-pane values for your new glazing, this is incorrect. Today, the performance figure you get must be for the entire window and door including the frame.

Do window and door U-Values and WER’s matter?

The good news is, most new doors and windows on the market meet at least the minimum requirement shown in our table. The great news is that many out-perform these figures. The better the U-Value or WER, the better performing your window. For you, this means greater energy efficiency and help in reducing your energy bills. For instance, our Origin OW-80 window fitted with Aerogel meets A++ window energy ratings.

Importantly these figures affect the heat loss from your home. But for balance, they won’t perform as well if your home is losing heat from other areas such as not having loft insulation.

Lower U-Values mean better interior temperatures, less heat loss, fewer draughts and cold spots. Also important is reduced electricity and gas bills and lower carbon emissions.

How we give you great U-values on windows and doors in pvcu, aluminium and timber.

First of all, is the glass. As standard all our PVCu, timber or aluminium products come with double glazed units of at least 24mm or 28mm depending on the product. As standard, you also get a soft-coat low-emissivity coating, warm edge spacer bars and argon gas fill.  This glass specification is toughened safety glass in all doors regardless of location. It’s toughened too in low-level windows and screens.

PVCu frames provide thermal efficiency thanks to their multiple chambers within the frames. Aluminium frames come with a polyamide thermal break. Timber doors and windows need nothing more than the solid wood profile – it’s an excellent insulator.

For aluminium specifically, on it’s own, aluminium conducts heat. The thermal break, aerogel or another insulation type effectively separates the inside and outside profiles. This thermal break also prevents heat loss or transfer of cold.

What about large patio doors?

Our entire range of bifolding doors, comes in aluminium with an advanced, high performance thermal break. These meet and exceed the U-Values required. However, using glass upgrades, triple glazing, integral blinds even laminated glass, it’s possible to get even better thermal performance.

For large glass panels such as those in our slimline or standard sliding patio doors, the same applies. We use high performance toughened glass units, with additional glass options if you want even better performance.

Contact us for more information about energy-efficient doors and windows

At Aluhome our entire product range comes with the best in design, engineering and thermal performance. Whether you choose our aluminium, PVCu or timber windows and any of our aluminium doors. All promise you the latest glass and profile technology and designed for the best energy efficiency and window and door U-Values

Contact us today to find out more or visit our showroom.

Some of the images on our website illustrate how products may look and are indicative. Please contact us for current product details and specifications.

Gooches Court,
Opening Hours
Monday 9:00 am – 5:00 pm
Tuesday 9:00 am – 5:00 pm
Wednesday 9:00 am – 5:00 pm
Thursday 9:00 am – 5:00 pm
Friday 9:00 am – 5:00 pm
Saturday 10:00 am – 4:00 pm
Sunday Closed

Based on 27 reviews
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Charles Twort
Charles Twort
17:28 15 Oct 21
What a fantastic company! I had been searching for a specific configuration of interior and exterior doors and windows... and was struggling to find them. Then, by accident I came across Tim's company. From the moment we started to communicated I knew who I wanted to work with. Tim's techncial advice from choosing the right solutions, through to how to manage the site build requirements was second to none. The professionalism of his surveying and installers teams, didn't let me down in any department. Always professional, courteous, and tidy, while at the same time a pleasure to work with.read more
Carl Amess
Carl Amess
14:05 07 Oct 21
Exceptional company to purchase from, small enough to care but large enough to supply the sliding doors in a... configuration we couldn't find anywhere else. Frame rebate was one of the smallest we could find with 3 extremely large doors that did not need to be fixed in any specific position when open. We can know look out on our back garden and barely notice the doors. Tim and Anita are both Amazing and so are the guys that fit the Doors. Very happy to recommend!!read more
09:03 06 Oct 21
A completely: professional, knowledgeable, courteous team at Aluhome that we would wholeheartedly recommend.Customer... service from start to finish has been exemplary.We would strongly recommend anyone who is in the market for new bi-folds to visit the showroom. As with other reviewers, it would have saved us an enormous amount of time.We would emphasis the whole team, as from start to finish we have had a seamless experience.Our install was not without it’s technical challenges. Solutions offered up by other suppliers did not match our desires. Tim listened and took the time to understand what we ultimately were looking for. Combined with Aaron, they have provided a superb solution that matches our brief perfectly.Manufacturing timescales were explained and the forecasted install date was achieved as smooth as could be wished for.The install was also seamless. Aaron and the install team were again: professional, polite and took great pride in their work.We are now the proud owners of two sets of high-end, beautiful bi-folds, provided at a competitive price. We have worked with a truly professional company and are thankful we placed our trust in Aluhome as it has been completely repaid.Mike and Debbieread more
Anthony Holmes
Anthony Holmes
22:18 19 Aug 21
Thanks to ‘Aluhome’ for first class (well Informed) advice with regard to the suitability of replacing our existing ... French doors with a Less obtrusive Aluminium framed Sliding Door system.What a difference! - the views into our garden now they are clear of window frame obstructions is delightful. This coupled with more natural light to the interior, is another bonus.The installation was carried out by fitters who clearly knew their trade and with the minimum of inconvenience to us.We are happy to report that the finished job from appearance, practicality and quality, exceeded our expectations.read more
Beth Loder
Beth Loder
08:39 28 Jul 21
Tim and his amazing team have been a godsend during our extension project. His advice and friendly chats together with... his highly experienced team of surveyors and fitters made the whole experience simple and hassle free. What he doesn’t know about his products isn’t worth knowing and we came away from the showroom feeling knowledgeable and that we’d made a great informed product choice. A big thank you to the whole team, and I promise once the garden's done and the kitchen's in we will update our photos which currently I’m almost embarrassed to upload as they don’t do the bifolds justice at all! We love them, the light is amazing, thanks again Tim & Team!read more
rick davies
rick davies
13:07 24 Jul 21
Based on our recent experiences, we are happy to recommend aluhome. During a visit to their office and display room Tim... was able to give a comprehensive description and assessment of all aspects of the door and windows we were thinking of installing (replacing 25 year old wood framed patio doors and windows). The timing of delivery and installation was as predicted. The cost was more competitive than similar offers. The installation team were on time, friendly, competent and efficient. And they left the patio area as clean as it was beforehand. And we are now very pleased with our new patio door&window. Best wishes, Rick and Moread more
Lorna Kavanagh
Lorna Kavanagh
18:25 23 Jul 21
A quick and professional job, from an experienced team who care. Tim took the time to understand the project and... budget, you just can't beat face to face customer service. Aaron and Terry were reassuring and informative at every step and the install went very smooth. I always felt like I was in good hands and nothing would be a problem. Thank you guys, I'll raise a glass as I enjoy my new view!read more
Emma Price
Emma Price
11:27 19 Jul 21
We used AluHome to design and fit steel-look replacement french doors and windows at the back of our house in central... Stamford. Tim and the team at AluHome have been outstanding all the way through the process. They took time to understand our requirements and communication has been exceptional throughout. There were no delays, the doors look wonderful and the installation team were prompt, knowledgeable and paid a high level of attention of detail. There is no need to look elsewhere, we strongly recommend Tim and the team.read more
Claire Gaunt
Claire Gaunt
21:27 12 Jun 21
Highly recommend.After searching the internet high and low for information about sliding doors, Aluhome were able to... provide all the information I needed. From my first phone call I felt confident that they were the company I wanted to use.From start to finish the service has been second to none.read more
Mike Farrah
Mike Farrah
17:10 29 May 21
Great experience from start to finish. Tim was extremely helpful in assisting us with the initial enquiry for French... doors and windows that needed a specific “U” grade for building regs. He invited us to the the showroom and gave us a thorough walk through of the products. The quality of the product is second to none. Aaron - in charge of fitting- worked closely with our builder in terms of planning and measuring as well as giving some on site advice and recommendations.The provision and installation was on time with no issues and very professional.The French Doors now form the focal point of our kitchen extension and have really made the project.We highly recommend Tim and Aluhome!read more
michael dunford
michael dunford
09:13 22 May 21
We are delighted with our new front door from Aluhome. Tim and his team were a pleasure to deal with throughout.
Kevin Riley
Kevin Riley
19:56 10 May 21
A big thank you to Aluhome and all their team. Fantastic service from the moment we contacted on a Sunday. From the... solving of an issue we had (large opening and our wish to have 3 leaf), with doors new to the market and the overall quality of service and product. The 2 x bifolds and back door are excellent and we are delighted. The attention to detail throughout is amazing. Thank you!read more
Jill Dent
Jill Dent
08:51 04 May 21
We visited Auhome to help choose doors for our new extension. We met Tim who was very helpful and extremely... knowledgeable and offered useful information to help me decide between sliders or bi folds. The showroom has a good choice of doors which again helped with our decision. I am delighted with the Sunflex sliders we chose, they completely make our room, great quality and fitted expertly by the team. Thank you Tim and all at Aluhome in Stamford. I would thoroughly recommend you.read more
Carrie Armitage
Carrie Armitage
09:54 21 Apr 21
Extraordinarily good looking aluminium windows; excellent service; fantastic fitters who were punctual, tidy and did a... great job. Highly recommended and a great personal service from Tim.read more
Stuart Bailey
Stuart Bailey
10:49 10 Apr 21
We had decided to replace our old UPVC french doors with aluminium doors and had already researched different brands.... Having decided that Origin was the right product for our house, we approached Aluhome for a quotation. From that point onwards the whole process was quick and efficient. We met Tim at the showroom in Stamford who gave us excellent advice on options for glazing bars, handles etc.etc.We were happy with the price and delivery was much quicker than we had expected with good communication throughout.Fitters Aaron and Terry were a pleasure to deal with where nothing was too much trouble. They were careful and tidy at each stage and had all of the right tools and equipment to do a good job.Any issues during the installation were dealt with professionally and quickly to our satisfaction.Overall a really good experience and well pleased with the product.read more
Simone Lynch
Simone Lynch
13:56 25 Mar 21
A warm welcome at the showroom in Stamford which has a range of products on show. We were shown the options available... to us as we were looking to buy bifold doors. We were advised on what would suit us best and the various options available as regards colour, handle options etc. They were fitted very quickly and although we had a couple of issues they were dealt with quickly and efficiently by Tim. Very pleased with our doors and the service from Tim and his fitters. Would recommend.read more
Joy Bates
Joy Bates
10:08 23 Mar 21
AluHome fitted all new windows, including two sliding doors to our unusual 1960's house.Response to our initial... contact was very prompt and we decided to visit their fabulous showroom in Stamford where we were made very welcome and received excellent technical advice, helping us to make our final decision.Communication has been brilliant throughout with Tim the owner. The fitters Aaron and Terry were a pleasure to deal with - nothing was too much trouble. We had some issues due to the quirky nature of our house but these were dealt with efficiently and without fuss.We are very happy with our windows - the transformation is amazing.Thank you team AluHome!read more
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Published on November 13, 2020