Friday18 August 2017

Green notebook: Part L is just the beginning

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The Code for Sustainable Homes could mean even tougher rules

Code for Sustainable Homes

With all the excitement over the new Part L, it is easy to forget that the government originally announced that the Code for Sustainable Homes would also be effective from this month. But a recent announcement suggests that following the consultation period on the code (which closed last month), the government intends to produce a clear set of minimum standards of energy efficiency for each of the five levels of the code - including a base level that will be tougher than Part L. We assume these will be announced later this year.

Since the government also made it clear that the code would form the basis for future building regulations, it's reasonable to assume it will use the carbonmetric system introduced by Part L - which uses CO2 emissions as a measuring stick for energy efficienc. In other words, it is conceivable that on certain residential projects, architects will be expected to design to a carbonmetric standard well beyond Part L in the very near future.

It's also interesting to consider that embodied energy in construction could figure in the equation before too long - this was certainly flagged up in the futures paper on the ODPM website during last year's Part L review. The lower the operational energy of a building, the higher the relative impact of the initial energy expended in manufacturing, transport, construction and ongoing maintenance.

The problem for architects is that product manufacturers have been shy to voluntarily declare their energy and other environmental impacts. While the full BRE Environmental Profile is the Rolls Royce of declarations for products and materials, there seems to be scope for a lesser declaration, whereby manufacturers could declare their products' environmental attributes and satisfy the growing market for products with "green" attributes including low embodied energy.

Heat reclaim through smart window design

When we were working on our low-energy proposals for the Vauxhall Tower, we developed a high performance triple glazing system. Exhaust ventilation air is introduced into the cavity between the outer double glazing and inner glazing to reheat the glass envelope and reduce conduction heat exchange.

Last week, I attended a seminar run by Product Innovation in Architecture, an RIBA-sponsored group which brings together architects and designers with an interest in working with manufacturers. It included a presentation on an innovative whole-house ventilation system using a similar principle, but at the more affordable end of the product spectrum.

The Dwell-Vent system uses supply air as a preheating device, drawing in intake air through vents at the bottom of the windows' outer frames. The air is drawn up into the gap between the panes, and in so doing is warmed by heat escaping from the room or, at certain orientations, by solar gain. This free heat gain can be a substantial benefit. The system relies on passive stack ventilation from kitchens and bathrooms, with the pressure differential drawing air gently through the house towards the stack. The windows have a non-return valve at the room outlet, and the glass has a low-E coating on the inner pane's outside face.

Overall, the system claims to reduce space heating costs by 15-20%. If that's correct, the system could be a promising example of affordable, low-tech innovation. Demonstration pilot projects are underway, and computer simulations will determine when site characteristics, building layout and orientation are appropriate to achieving such an impressive level of energy savings compared with a small additional cost for the windows.

Planning for sustainability

The government has been under pressure to streamline and simplify the planning approvals process to minimise alleged barriers to housing supply, with initiatives such as design codes and affordable housing quotas. While the Merton Rule on renewables expectations and the London Plan's Energy Strategy were seen by some as potential barriers to streamlining, it is clear that by setting the bar high, they have in fact had a major impact on the uptake of renewable energy and on projects' sustainability.

Indeed, although the government stated that it did not intend to make the Code for Sustainable Homes a condition of planning consent, the ODPM recently announced it would be analysing further ways to increase takeup of the code, such as incentives in the planning system.

Those of us who feel the planning approval process is the ideal time to persuade developers to commit to sustainability strategies welcomed David Miliband's recent announcement (News April 7) that a new planning policy statement will set out how the planning process can achieve further carbon savings.


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