Building regulations set to get tougher

Legislation to conserve the use of fuel and power along with corporate social responsibility is fast becoming the key driver towards low energy and zero carbon buildings. Long over are the days where buildings can be designed with energy hungry cooling systems and take advantage of cheap energy with little or no thought for the impact on the environment.

Part L in specific Part L2 of the building regulations is perhaps the most relevant to the built environment, covering the refurbishment of and new build non dwellings, which are responsible for around a quarter of all the UK’s total carbon emissions.

Under the last 2010 revisions to Part L, limits were placed on the total solar energy transmission (g-tot) through the glazing including any shading device for the summer period, as solar gain through the windows is the single biggest cause of rising temperatures in most buildings. Whilst this figure, a g-tot of 0.68 (refer to separate article here g-value & g-tot for a detailed explanation of these acrynoms) was not hard to achieve through using a slightly better window system, the building target emission rates (TER) were reduced by 25% against the 2006 Part L. To calculate these new TER figures, a g-value total figure on the glazing of 0.40 was used during the summer period, so, in theory to comply, the windows solar gain properties need to meet this figure.

Whilst this limit can be achieved through much higher performance, solar control glazing, these types of glazing, other than costing considerably more, with a much higher embodied carbon content, have a detrimental effect to the buildings energy use in winter, as they block valuable free solar gain to naturally warm the building, therefore increasing the load on the installed heating system.

Only a dynamic exterior solar protection system can best achieve maximum energy reductions in the use of a buildings installed heating and air conditioning systems. During the summer periods, dynamic external shading provide a physical barrier between the suns energy and glazing, in fact they can lower the g-value total of even the most basic single glazing to only 0.10 (10% total solar energy transmission). In the winter by remaining in a raised position they allow maximum free solar gain to passively heat a building, so for typically installed double glazed low-e windows, 70% of solar heat will transmit through the window to naturally warm a building.

Proposed changes to the building regulations Part L are going through consultation this month. The Department for Communities and Local Government (DCLG) are looking to strengthen new build standards, proposing a 44% reduction in building CO2 target emission rates against the 2006 Part L. They are also looking at increasing the standards of energy efficiency for existing buildings and introducing measures to incentivise improved compliance and as built performance.