Rooflights and building excellence

Correct rooflight design at the outset of the building concept can have dramatic, positive effects on all aspects of the building from the owners potential asset value to the wellbeing and productivity of the final occupants. Phil Beswick, specification sales manager for Hambleside Danelaw discusses

Rooflights play a vital role in the modern building but far too often they are overlooked or used as an afterthought. Rooflights are the common link to many aspects of building design and can help the designer, the building owner and the occupier to achieve a truly sustainable, energy efficient and enjoyable place to work and live in. Correct rooflight design at the outset of the building concept can have dramatic, positive effects on all aspects of the building from the owners potential asset value to the wellbeing and productivity of the final occupants.

Rooflights are generally regarded as the most simple and cost effective means of introducing natural daylighting into the building envelope. Positioned within the roofscape, they are orientated upwards to conduct the maximum amount of light into the interior and can provide up to three times as much light as conventional windows located in walls, helping the building to more readily comply with the Building Regulations and improving the internal environment for the occupants.

Rooflights also deliver a more even and useable distribution of natural light into a building, particularly in large structures where light is required deep into the building or in enclosed areas that cannot be lit through an external wall. The light that enters a building can be direct light such as that which passes through clear or transparent materials, or diffused light that is created by surface textures designed to create diffusion by surface refraction, or by materials that are translucent and naturally diffusing.

It is now no longer acceptable to think purely in terms of a simple rooflight area percentage to ensure that the building achieves the right amount of daylight. Frequently it is simply assumed that all that has to be specified is a rooflight area of between 10 per cent and 15 per cent and the building will be well day-lit. However, with buildings now requiring Energy Modelling and Energy Performance Certificates, and the tools for designing daylight requirements are becoming even more sophisticated.

For any building, there is an optimum target percentage of rooflights which will deliver the optimum level of natural daylight into the building, making the optimum saving in energy usage and costs. Beyond that point, solar gain can add to the energy consumption if powered cooling systems become necessary.

It is therefore vital that rooflights are specified correctly right at the outset; the correct balance of light, thermal and solar transmission properties should be taken into account and optimised for any building design. For example, it is no longer satisfactory just to state daylight factors for a room, as climate based daylight modelling should be used to assess the correct daylight requirement. This type of modelling takes into account the dynamic meteorological data that is now available. Indeed the Government, as recently as December 2014, published a benchmark document on the requirements for new schools to be modelled using a Climatic Based Daylight Model System. This will continue to spread to all types of building in the near future. With many Local Authorities insisting on a BREEAM assessment before they will give planning permission, it is vital to obtain the correct rooflight design, distribution and product type. Using low carbon rooflights is a good example of correct product choice because of the low embodied carbon that can have a significant effect on the BREEAM assessment.

We know that achieving a BREEAM rating of ‘Excellent’ as opposed to ‘Very Good’ can make a huge difference to the developer who is trying to let an industrial warehouse to a prospective client. We know that having a building that is well day lit will improve the efficiency productivity and reduce the absenteeism of the occupants that have to work in these buildings. We know that in the current age of building design, with good air-tightness and low U-values, lowering the use of artificial lighting is the best way the building owner can reduce energy costs.

So, when considering the design of a modern building it is vital that rooflights, rather than being an afterthought, are treated as an essential design consideration right at the start.