Are rooflights an energy efficient option for specifiers?

Rooflights deliver twice as much light as verical glazing, reducing the need for daytime artificial lighting.

Building design and building fabric specification, including the inclusion of rooflights, remains one of the best tools for keeping energy bills as low as possible.

What makes a rooflight energy efficient?

Like the roofs they are installed in, rooflights have U-values to demonstrate the heat loss through them. This is true of opening or fixed rooflights or whether a rooflight is for a pitched roof or flat roof.

One of the simplest ways to reduce heat loss through the building fabric is to choose a rooflight with a lower U-value, such as one that is triple glazed rather than double glazed.

Getting installation right for better rooflight energy efficiency

Like any area of the building fabric, a rooflight will only perform if the standard of installation is right. The key to achieving the energy efficiency requirements in building regulations like Part L is well insulated and reasonably airtight building fabric, with thermal bridging kept to a minimum.

Careful detailing of where the rooflight sits within the roof build-up, especially in relation to the roof insulation, is essential to avoid a break in the thermal envelope and reduce the risk of significant thermal bridging.

Letting in more daylight through rooflights to improve energy efficiency

Rooflights deliver at least twice as much natural daylight as vertical glazing (based on windows of the same size). They can therefore provide higher illuminance levels and a better distribution of daylight using a smaller total area of glazing and reduce the use of artificial lighting.

Balancing daylighting, solar gains and overheating for overall energy efficiency

The climate is making overheating in buildings an increasingly pressing issue. Since warm air rises, opening rooflights are the most effective way of losing excess heat in conjunction with opening windows to allow fresh air into the building.

Glazing Vision bespoke sliding-over-roof skylight with glass fins for instant cooling and ventilation.
Cutting energy use: openable rooflights help reduce overheating in buildings and the need for mechanical cooling.