Rooflights and Building Excellence
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% and 15% 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.
Archetech - Issue 20 [Page 18]
For any building, there is an optimum target percentage of rooflights
which will deliver the highest level of natural daylight into the building,
making the maximum saving in energy usage and costs. Beyond that
point, solar gain can add to t he 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.
Author: Phil Beswick, Specification Sales Manager for Hambleside
Danelaw.
www.hambleside-danelaw.co.uk
[email protected]