Part L of the Building Regulations 2000 - Conservation of Fuel and Power

Part L - Solar Shading Holds The Key

Part L of the Building Regulations 2000 - Conservation of Fuel and Power - came into force on April 1, 2002 and it has had a major impact on raising awareness and changing the way new buildings have been designed and built in the UK since then.

An integral aspect of the new regulations is concerned with new buildings and the reduction of carbon dioxide emissions from them, to bring them in line with the Government’s proposed targets of a 20% reduction on 1990 emissions levels by 2010, and a further 60% reduction by 2050.

buildings account for 50% of the UK's CO2 emissions

Buildings are the biggest culprits when it comes to carbon dioxide emissions - accounting for around 50% of the UK’s total. However, with electricity consumption in the commercial sector having doubled between 1973 and 2000, largely due to the increase in computers, it is difficult to see how the Government’s proposed 20% reduction will be achieved, let alone the intended 60% reduction required.

It is recognised that one of the largest energy users and, by implication, creators of carbon dioxide emissions in the UK, is air conditioning. Recent studies have shown that a significant reduction in the need for A/C can be achieved simply by limiting solar heat gain in buildings.

To this end, a further requirement of the new regulations limits exposure to solar heat gain in buildings, (including all new non-domestic buildings, extensions and some changes to existing buildings such as façade replacement) and is paving the way to significant reductions in line with the Government’s targets.

need to limit exposure to solar heat gain

The need to limit exposure to solar heat gain applies to naturally ventilated buildings as well as those that have mechanical ventilation, thus avoiding the retrofitting of non-environmentally friendly mechanical cooling systems, such as air conditioning, in naturally ventilated buildings that suffer from solar heat gain.

The new regulations only apply to certain areas of the building - basically those that are occupied most of the time. For example, atriums and circulation areas that are only occupied on a temporary basis i.e. with people moving from one area to another, are not classed as occupied. Atriums or breakout areas that contain receptions or cafes areas where people would be situated for substantial parts of the day are included as ‘occupied areas’.

The regulations suggest that there are three design strategies to avoid solar heat gain within these aspects of buildings. These are:

Appropriate glazing design
Use of exposed thermal mass with night ventilation
Use of solar shading

Glass remains an important design material

Appropriate glazing design all too often means limiting glazing area. However, glass is one of the most important and widely used building materials and specifiers are very unlikely to want to move away from creating vast expanses of glazing in their buildings.

Guidelines have been published which provide figures as to the percentage of glass that can be used, compared to floor space, when designing a building with glazing to one side only.

For a north facing façade 50% of the area can be glazed. For a south, northeast or northwest facing façade, this figure reduces to 40%, whilst on an east, southeast or southwest facing façade, the figure drops to 32%.

These guidelines basically limit the possibility of creating overly large glass facades, which are becoming increasingly popular on modern buildings. So does this really offer specifiers a feasible route to achieving Part L?

Thermal mass does offer a method of reducing or even eliminating the need for air conditioning in buildings, but trying to design systems to be integrated into buildings with hidden slabs and night ventilation strategies are complex and often costly. Also, on its own, thermal mass cooling will do very little to help reduce solar heat gain as unless heat into the building is reduced and managed, then the cooling system will constantly be fighting against warm air.

solar shading - a barrier between sun and glazing

That leaves solar shading. Solar shading is a proven method of significantly reducing, and in many cases, eliminating solar heat gain. It effectively forms a barrier between the sun and the glass without reducing light into the building and vision out of the building for the occupants. By forming this barrier, the sun does not reach the glass and in turn create solar heat gain within.

Solar shading is not a new concept. It has been around for centuries starting with fabric awnings, more commonly seen on villa style buildings in Europe.

Today there are literally dozens of options, from modern interpretations of external fabric roller blinds to intelligent fin style louvre systems that, thanks to their own built in control system, follow the sun to achieve optimum protection whilst allowing maximum visibility.

Most common are fixed aerofoil fins and matrix style louvres which are now commonplace on buildings ranging from apartment blocks to schools, offices to hospitals, leisure facilities to commercial institutions.

As designers create more complex buildings with large curves and dramatic angles, so solar shading solutions have had to evolve. Large spans can now be created, walk on systems are available and ingenious systems that ensure that solar shading systems appear to seamlessly form an integral part of the building, are just a few examples.

a wide choice of materials

These systems can be created in a wide choice of materials to ensure they blend with and enhance the exterior appearance of buildings and also to provide specifiers with the ability to create something that fits in with the ethos of their building. Aluminium, which can be powder coated to virtually any colour, timber, glass and even fabric solutions are all available.

To meet the requirement of Part L, reducing solar heat gain and helping to reduce carbon dioxide emissions, solar shading therefore really does offer the most viable option. It also offers specifiers the ideal solution in terms of design license, letting them continue to use large expanses of glass without limiting their design.