New flat roof systems and modern materials allow for various ways of utilizing the building’s so-called fifth facade. A flat roof offers far more than only its basic functionality – permanent protection against weather. Increasingly, flat roofs are utilized as an additional green area within the urban environment. They are a place for socializing in the open air as well as an exceptional source of natural light and fresh air for indoor living.

The key challenge with deep or centrally located rooms with no direct source of natural light is how to improve their living quality. This issue applies equally to business premises, schools, kindergartens as well as residential homes. Indeed, well-lit rooms will improve work efficiency. The human biorhythm is boosted by light, meaning that we wake up faster in the morning and remain awake. The work area illumination quality will also affect the working mood. Analyses show that productivity may increase for up to 15 %.

The same holds true for homes. Natural light is a quality and an important factor influencing health and people’s perception of healthy living.

An important factor in lighting – besides its impact on the quality of living – is its contribution to energy saving. High natural light values increase the number of hours in which we do not need to turn the lights on. This effect should be carefully considered in nearly zero-energy buildings. A strong parallel is the quality of living, resulting in increased productivity, better health and associated cost reduction.

Using flat roofs for indoor lighting is strongly advantageous because of the illumination intensity. The zenithal source of light is significantly stronger than light entering the room through facade windows – the latter being nearly double the former. Therefore, using the roof for lighting is an excellent idea. The influence of different sizes of openings should be carefully analyzed and the building’s exterior shaped accordingly. Last but not least, this can also rationalize the building’s construction costs.


An example of a room where glass surface area equals 30% of the floor
area (façade window only).

An example of a space where glass surface area
equals 20% of the floor area.

The advantage with lighting the interior through flat roofs is that the roof opening can be located exactly where necessary – above the office desk, kitchen counter, or in the middle of the corridor. Ideally, the openings positions should be designed integrally along with other openings and installations.

As most heat losses occur through the roof, proper window choice is a major decision. Residential buildings – be it schools, kindergartens, offices, apartments or homes can take advantage of a window especially designed for flat roofs, typically covered with a dome or glass. From inside, then, it looks like a window, and from the outside, the look may be adapted to any aesthetical requirements.

Flat roof windows can also be used for night cooling of the building. Using the controlled opening of windows on the roof and facade, room temperature can be reduced by up to 6 ° C during the summer months.
There are many benefits of using flat roof windows. Follow us in future releases.

Neža Močnik, u.d.i.a.
VELUX Slovenia d.o.o.

document Steps to a durable roof above a cosy home

Quick Guide
Steps to a durable roof above a cosy home

Download document