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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

4.83 Average

164 Reviews

Anonymous

All contact with EOS was dealt with efficiently and by friendly staff. The quality of the rooflight is excellent. In a different league to the alternatives I have seen. A couple of points to improve on below, however these do not detract from how the quality of the roof light lifts the whole build..... - Rooflight did not arrive on the advised date, arriving the following morning instead. This required a number of builders to return the following day to lift off the van. - Do not underestimate the weight. Very challenging for my builder just to get off the box van. - The ordering instructions make it clear to provide the size of the hole. That will then equate to clear glass when fitted. However on arrival length and width of clear glass were both 3cm shorter than ordered. This was explained by phone as relating to the rebate for plaster board, however this should be made clearer ahead of ordering as we could have ordered 3cm larger to get the clear glass size originally envisaged.

Posted 1 month ago

Anonymous

Excellent product and faultless service. Fixed rooflight was delivered on time, communication was good throughout the period and staff were always helpful and courteous. Rooflight looks stunning!

Posted 2 months ago

Kevin Dean

Very good product and service from the team. Would recommend

Posted 2 months ago

Sam Phillips

We require 3 windows for 2 projects and they where very well priced and also had them in stock. will be using again.

Posted 2 months ago

James Payne Cook

For all the reasons I have rated them highly

Posted 2 months ago

Sunny Tiwana

Awsome company to deal with, item was out of stock online and thier guys found me what i needed and sorted delivery quickly and efficiently. Will defiantly recommend to others.

Posted 2 months ago

Stuart Herring

Good service and good communications on queries and time scales

Posted 2 months ago

Fiona Whyte

Their customer service was good. I was able to speak with someone quickly and easily by telephone or email to clarify points before I ordered my items. The ordering process was very easy and the items were delivered on time. Upon delivery there was a scratch on one of my rooflights. I contacted EOS immediately and they were happy to send a repair kit to me, free of charge, which arrived in the post within a few days of me speaking with them. I'm very pleased with the service I've received and the product looks great in my new extension!

Posted 2 months ago

Dawn Thomas

Beautiful roof lights - exceeded our expectations

Posted 2 months ago

Piero Realmuto

Good product and service. Have never let me down

Posted 2 months ago

Steve Orr

The roof lights arrived on time, were well protected in transit and all queries were answered to our satisfaction.

Posted 2 months ago

Leanne Wallser

Fantastic service, super helpful getting it all to Jersey and product is perfect for us. Thanks

Posted 3 months ago

Dr J Trinder

Swift. Delivery. Arrived as described. Straight forward payment arrangement. Great advice and support when planning project. Motorised rooflight works remarkably quietly. A little costly however compared to some competition.

Posted 4 months ago

Richard Simmons

They have provided us with a quality product

Posted 4 months ago

Anonymous

Product and delivery as expected.

Posted 4 months ago

Alan Oliver

Good product, delivered on time, and looks great in our new flat roof extension.

Posted 4 months ago

Mike Guirguis

I actually bought my roof lights on the back of EOS’s reviews section, and now my extension is nearing completion, (finally) I wanted to pass on my experience. I couldn’t be happier with my decision, its clearly a very high quality product and they look amazing in our new kitchen. They are heavy so make sure you have lots of strong guys on site. The staff are all very helpful and seem very knowledgable. Highly recommended them.

Posted 4 months ago

Nicole Gray

Excellent customer service. Really took the time to listen to our needs and help us find exactly what we wanted, within the time schedule from our builders. They were also flexible as the schedule shifted and always available for any questions. And beyond that, our roof lights look so amazing! So, I'm a very happy customer.

Posted 4 months ago

Ben Jennings

EOS were very helpful during the sales process, liaising directly with my builder to confirm requirements (when I was way out of my depth). My builder’s feedback post installation is that the windows are heavy duty and top quality, even when compared with more expensive options he’s fitted in the past. He’ll be recommending EOS for future builds.

Posted 5 months ago

Bill Greenaway

Product was just as promised and delivery and information excellent. We are very pleased with it.

Posted 5 months ago

Jason Berry

Really helpful when I called to order my roof lights explaining delivery info, weights, fitting instructions etc.., Really accommodating in facilitating a specific delivery time and date (at relatively short notice); finally the finished product, robust, elegant and fantastic. First class.

Posted 5 months ago