Skylights - All you need to know

As the first skylight manufacturer to have its skylights BSI accredited, Sunsquare, offers its advice on what to consider when choosing a skylight.


Will I need planning permission for a skylight?

Since skylights do not tend to overlook other premises and have a minimal visual impact they do not usually require planning permission, although there are some circumstances where they might do.
In England and Wales, you are unlikely to require planning permission for skylights unless:

  • a skylight projects beyond the existing roof plane by more than 150mm (6″ approx.)
  • a proposed skylight installation occupies a large area of your roof beyond what is considered a "reasonable" size
  • you live in a Listed Building or in a designated Conservation Area
  • a so-called "Article 4 Direction" or other planning condition is in place for the area in which you live.

What's involved from a Building Regulations point of view?

There are two sets of building regulations for roofs that could impact the installation of a skylight; work on an existing roof and the construction of a new roof. It's advised to take a look at Parts J and L of Building Regulations. These parts cover energy efficiency, thermal insulations and the protection of building against fire.
Approval under the Building Regulations will generally be needed for the installation of a new rooflight for the following reasons:

  • To install a new rooflight, the roof structure will often need to be altered to create the opening.
  • The roof will have to be able to carry the weight of the new skylight. If the roof is not able to do so it will need to be strengthened prior to installation.
  • In the event a skylight is in close proximity to a boundary, its fire performance must also be taken into consideration.
  • Any rooflight installed must prove it has sufficient insulation against heat loss with effective energy performance.

Is the geographic position of a skylight important?

Positioning of a skylight is not just important from a Building Regulations point of view, there's the UV value to consider too. On average a skylight admits 40% more light than a normal window of comparable size, but with that comes the risk of over exposure to UV. Too many UV rays can quite quickly create a 'greenhouse' effect which can make living spaces too warm in the summer months. There are clever glass specifications now though that remove the UV whilst still allowing for the full amount of light to travel through.

What aspects need to be considered to limit heat loss?

Limiting heat loss during colder months is just as important as avoiding the 'greenhouse' scenario.
By far the majority of skylights have an aluminium frame and by its very nature aluminium transmits heat and cold very efficiently. If the external temperature is allowed to manipulate a skylight frame it can create a significant heat loss issue with resulting condensation.
Look for a skylight that is thermally broken. You should expect to see polyamide sections dividing all materials that sit across the internal to external parts of your building. This is the only effective way of maintaining insulation and, therefore, the climatic control of your building.

How important is it to get the size and access of the skylight right?

Underestimating the size required for a skylight to make the desired impact is a fairly frequent mistake. Of course, you will need to consider the maximum amount of glass allowed within an extension or conversion under Building Regulations though. That said, it is best to have as much natural light as possible but do consider in kitchens that it might be wise to have an opening skylight for ventilation purposes. These can be electronic and have rain sensors built in.

Are upstands just as important as the skylight itself?

It cannot be stressed enough how important it is to have upstands created separately to the skylight. As the frame that a skylight sits on, the upstand plays a vital role in making sure your skylight not only fits well but that it withstands time. Having the upstand created separately enables the roofing membrane to be properly installed prior to the rooflight installation. It also ensures that the correct lean is accounted for to allow water run-off and the right height is achieved to comply with Building Regulations.

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