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A U value tells us how much heat is lost from a building through different elements, such as windows, walls and floors.

It is a measurement of heat transference, also known as the “overall heat transfer co-efficient”, meaning the higher the number value, the more heat is being lost, and the less environmentally friendly the building is. A lower value therefore indicates greater insulating properties and is more energy efficient.

Calculating the U Value

The U value of a building element is calculated by working out heat loss for each component of the building. This is determined by the material used, its thickness, and its positioning.

Rooflights are made up of a number of different component materials that each have different properties when it comes to heat transference. Therefore, to find out the U value of this type of element, a number of factors need to be determined.

Firstly, the ability of each component material to conduct heat must be identified. This is shown as a ‘K value’. This value is used along with the thickness of the given material (d) in the following equation to give the resistance of the component material:

R = (1/k) x d

A resistance value (R) must then be found for each component material.

Next, the internal and external faces of the building element must be taken into account. These are known as external and internal resistances and are fixed values. This information is then combined in the following equation to discover the U value (U):

U = 1 / (Rso + Rsi + R1 + R2 …)

Rso is the fixed external resistance and Rsi is the fixed internal resistance, whilst R1, R2… give the sum of the resistances previously worked out for the different building materials in the building element.

Current building regulations in England and Wales allow a maximum U value of 2.2 W/m2K for skylights, covering 20% of the roof surface.

Green Energy Rooflights

 

All rooflights from EOS are energy efficient and feature U values as low as 0.97 W/m2K.

The EOS Eco roof lights, which are triple-glazed and injected with Krypton Gas, have an even lower U value of 0.65 W/m2K and include a centre pane U value of 0.6 W/m2K.

The U values of these skylights are so low that official building standards permit them to make up an additional 10% of the roof area than other, less energy efficient designs – taking total potential coverage to 30%.

So, as well as flooding a building with daylight to naturally enhance the indoor environment, EOS rooflights ensure green energy efficiency by reducing the need for CO2-emitting artificial lighting, whilst guaranteeing that heat isn’t lost unnecessarily.

For green efficient skylights with low U Values, speak to the EOS Rooflights team today.

 

Image Sources

Green house courtesy of Pixabay via CreativeCommons

4.80 Average

136 Reviews

Jake Thomas

We met EOS at the Homebuild Show in Birmingham as we wanted to see the rooflights before we bought them for our extension. We met with Elliot who answered all of our questions and helped out with our plans, as one of the sizes needed amending. The rooflights look beautiful in our kitchen. I would highly recommend EOS to anyone, especially if you this is your first build. Elliot couldn't of been more helpful with answering our queries.

Posted 1 day ago

Anonymous

Excellent product, very stylish and good quality

Posted 6 days ago

Anonymous

Our roof light with rain sensor add so much to our new extension. The window is great. EOS were a great help with waiting for our builders to be ready to install.

Posted 1 week ago

Tim Harris

The EOS rooflight we have installed is fantastic, the light within the room now is beautiful, the rooflight itself is a modern, slick design, it has transformed the space!

Posted 1 week ago

Anonymous

The finish is very good and the rooflight looks lovely. However, my builder has advised to be prepared for it to be a bit fiddly to fit. Now it is up, it looks great and is definitely how I had hoped it would look. Well worth the purchase.

Posted 1 week ago

Gavin Ward

Great product, excellent customer service, very easy process from order to installation. My builder has already recommended this product to other customer and is the best he has fitted!

Posted 2 weeks ago

James Fraser

High quality products

Posted 2 weeks ago

Rob O Carroll

Fantastic. Product really well made. And. Finished to very high standard

Posted 1 month ago

Anonymous

We were very pleased to find a stock rooflight which matched our requirements. The product has only just gone in but so far so good.

Posted 3 months ago

Nick Puxted

I found The sales person very helpful with our bespoke design. The roof light was delivered on time and we are very happy with the product.

Posted 3 months ago

Paul Anderson

from start to finish the service provided was friendly, helpful and professional. we are extremely pleased with the product, looks great and will definitely be using EOS in the future.

Posted 3 months ago

Buba

We ordered a rooflight, the staff were very helpful and giving an appropriate advice. Quick delivery and i’m very happy with the product. Defenitly Recomended

Posted 3 months ago

Sean Barrett

The people we dealt with on the phone were both polite and very helpful with our order, dealing with the whole process very efficently. The rooflights were delivered to site and our customers were very pleased with them once installed and the effect of such extra light into the extension. We would recommend EOS Rooflights as did visit other manufacturers prior to ordering them but found them to be a superior product overall.

Posted 3 months ago

Anonymous

The were very good at keeping you informed as to when the product was to be delivered even down to approx time of the day, very good and would use them again.

Posted 3 months ago

Anonymous

No complaints so far. Rooflights look great and arrived as promised.

Posted 3 months ago

Vassos Costas

I looked at quite a few of the competitors roof windows and none compared to the quality of EOS Rooflights. In situ, they look fantastic. I wanted to construct my own insulated up stands and the sales team at EOS provided plenty of quick technical info to assist. I also need to delay my order and EOS kindly agreed to store a large roof window for a couple of weeks until I had space on the job site. If you are planning to construct your own insulated up stands, beware of the amount of time it will take you or your carpenter and factor this cost against buying the up stands from EOS (you will need an onsite table saw, unless you have a workshop and adequate space for a glue up). Make sure you have a plan on how you are going to get the roof window to its final location prior to purchase-one of mine was 2.8m long and weighed circa 250kg-I had a relatively easy route to the installation point , but I doubt this will always be the case.

Posted 3 months ago

Anonymous

Very nice product, competitive prices and very professional communication. Having researched many similar products, I am very happy to have chosen EOS!

Posted 3 months ago

Peter Kent

From the outset I received excellent service. I enquired about fixed, opening and bespoke roof lights , both Elliot and Chris provided all the information I required. The order was placed and the deliveries were made on time. Following delivery I raised a couple of installation queries and received a speedy response. Very happy with rooflights, and Eos

Posted 3 months ago

Anonymous

Excellent product & service

Posted 3 months ago

Simon Grayson

Great company to use - very helpful with pre-order enquiries, and we’re very accommodating when organising delivery dates and details. I would be happy to recommend EoS.

Posted 5 months ago

Nuno Bernardes

Very easy transaction, great product and delivery service was fantastic. Only constructive feedback I can give is to better highlight the weight of the product and that can/will cause issues with delivery and installation. Luckily we had 6 builders on site who between them managed to move the £140kg roof light but what that meant is that we had to pay extra to re-enforce the roof with different beams

Posted 5 months ago