Published: 8th October 2023

Double glazed or triple glazed – which is better? This question can leave some suppliers and end users mystified. There are pros and cons to both but ultimately the answer can lie in the siting and orientation of your new bespoke rooflight.

One would think that you should always invest in a product with the lowest u-values. This isn’t necessarily true. Triple glazing would be a no-brainer if we lived in a Northern European climate with extremely cold winters. But we live in a temperate climate thus mild winters and warm/hot summers.

Triple glazing without question is more energy efficient in the winter but benefits less than double glazing from solar gain in the remaining nine months of the year. Solar gain is the amount of free heat the sun gives depending on which direction your rooflight faces. This is normally beneficial especially in spring and autumn, as it warms the building’s interior without energy consumption, saving on heating bills. But if your rooflight is in an area of intense sun, you could suffer from too much solar gain in summer and an excess of heat. If this is the case, you can always upgrade to solar controlled glass. This type of glass bounces the suns heat away from the rooflight, thus keeping your interior cooler.

Triple glazing also lets in less light. As there is more glass for the light to penetrate, it can look relatively dark compared to double glazing, an opinion shared by most industry experts. This point is particularly relevant if the rooflight is north-facing or shadowed by tall buildings or trees. Something that can counter this is the use of extra clear low iron glass. Using this type of glass also removes the ‘greeny’ tint sometimes associated with triple glazing.

For the reasons stated above – triple glazing’s lack of solar gain, reduction of interior light and the ‘greeny’ tinge – many UK architects and specifiers tend to opt for double glazed units as they often suit the British climate better. But ultimately the choice is yours.

Both our Double-A and Triple-K Blade skylights comply with Building Regulations heat loss levels, but if you want better insulation levels, then Triple-K skylights will give you centre pane u-values (Ug) as low as an incredible 0.4 w/m2k, while the centre pane u-value of Double-A is 1.0 w/m2k. Please refer to the main website U-values Simplifed section to see what this means and to view overall product u-values as opposed to just the centre pane u-values.

If you need any help deciding which glazing option best suits your installation, please give the Ofset team a call and we will walk you through the available options relevant to your project.