黑洞社区

You鈥檇 think it would be hard to find anyone who thought improving the energy efficiency of existing buildings was a bad idea. Yet there is one sector of the industry that looks upon it as very much a secondary goal. They鈥檙e the conservationists, and they have greeted the news that historic buildings may no longer be exempt from the increasingly onerous Part L of the 黑洞社区 Regulations with dismay.

Of course, if you know your 黑洞社区 Regulations, you鈥檒l be aware that they already require energy improvements to be made to historic buildings undergoing renovation. However, the 2006 Part L included some last-minute wording copied from the European Directive on the Energy Performance of 黑洞社区s that introduced the exemptions for listed buildings, buildings in conservation areas, ancient monuments and churches.

Now, buried deep in the small print of the government鈥檚 800-page consultation on Part L launched earlier this month, comes a proposal to scrap this exemption, and replace it with 鈥渟pecific guidance in the Approved Documents as to where special considerations apply, and how to arrive at an appropriate balance between heritage and energy conservation鈥�.

The upshot of this is that the type and extent of energy efficiency improvements that take place when a historic building is being refurbished would be decided through negotiations between the local authority鈥檚 conservation officer, building control and the project team. Additional guidance will be given in the Approved Documents to help them arrive at the right balance, but designers won鈥檛 be able to rely on the building simply being exempt.

English Heritage has already said it will almost certainly look for the exemption to be retained. Chris Wood, head of building conservation and research at English Heritage, says a survey of local conservation officers showed unequivocal support for the retention of the exemption, with 88% saying that exemptions had been widely used in their local authority and 87% saying that its removal would make a significant difference to the way historic buildings are dealt with under Part L.

According to Wood, the current use of the exemption in the Approved Documents brings clarity and encourages building control bodies to consult with conservation officers and come up with a sensible solution. 鈥淚t makes it clear that building control officers should take the advice of conservation officers. The danger of replacing this with 鈥檚pecial guidance鈥� means it becomes woolly, and while most building control officers will sit down and come up with a sensible solution, there is the danger that by just relying on special guidance some might push through changes that could be damaging to the building fabric.鈥�

Robert Adam of Robert Adam Architects says the wording of the proposals is both meaningless and capable of creating a legacy of damaged buildings. 鈥淚t becomes a matter of discussion between the planning officers and conversation officers, which is frankly a nightmare,鈥� he says. 鈥淎ny opportunity to have something that isn鈥檛 definite and has to be discussed between officers is likely to cause serious delays and it鈥檚 the clients who suffer.鈥�

English Heritage describes a historic building as one that is listed or in a conservation area, or that is of local architectural or historical interest. There are just over 370,000 listed properties in the UK, most of which are grade II-listed, and about 38% of which are homes. On top of this there are over 9,300 conservation areas in England, encompassing homes, commercial, public and industrial buildings.

Robert Ayton, head of design and conservation at Westminster council, questions whether these figures are significant enough make it worthwhile to lift the exemption, particularly on listed buildings. 鈥淚 tend to think that it鈥檚 getting the whole issue out of proportion because, as a percentage of the total building stock, listed buildings are very small and one could take them out of the equation completely.鈥�

The term 鈥檚pecial guidance鈥� is woolly, and may mean building control officers push through changes that could be damaging to the building fabric

Chris Wood, English Heritage

Ayton says a lot is already done to improve the environmental performance of historic buildings, but suggests that attention should be concentrated on unlisted Victorian terraces, thirties semis and sixties tower blocks. 鈥淚鈥檓 not saying listed buildings shouldn鈥檛 be upgraded but they should only be upgraded without damaging what鈥檚 important to them. Otherwise, what鈥檚 the point?鈥�

One of the things that concerns Ayton is that the single biggest win when it comes to improving the energy efficiency of existing buildings 鈥� the building envelope 鈥� can also be the greatest source of harm. He says: 鈥淲here I do think it might be more difficult is, say, where there is an insistence on putting double-glazed units in listed properties, which can harm the appearance. In a listed building we would say you should stick with the single-glazed windows.鈥�

In an unlisted building this doesn鈥檛 matter so much as long as they look the same as the originals, even if it鈥檚 a conservation area, he says. 鈥淏ut we do have a problem where it is PVCu or aluminium windows in a situation that is inappropriate.鈥�

Insulating roofs and walls can be done with relatively little harm, but walls represent a more tricky challenge. Ayton says that a lot of Westminster鈥檚 grade II-listed buildings have well-preserved interiors that could be seriously affected by any need to put internal insulation on the walls.

John O鈥橞rien, principal consultant of refurbishment and regeneration at BRE, is researching measures that can be put in place to improve older, hard-to-treat buildings. These are defined as those that can鈥檛 accommodate staple or cost-effective fabric energy efficiency measures. There are 9.2 million hard-to-treat dwellings in the UK 鈥� 43% of the total housing stock. The type of building fabrics range from stone-faced and solid brick walls to prefabricated concrete and even cavity walls. O鈥橞rien is trialling exotic products such as aero gels 鈥� a very thin super-insulation product 鈥� vacuum glazing and a host of methods to improve airtightness, measuring the buildings before and after to see how cost-effective the improvements are.

He admits this can be a problem. Old buildings tend to have porous walls and if an insulation material is added that acts as a barrier, it can affect the wall鈥檚 ability to breathe and regulate moisture levels. If moisture becomes trapped in the wall it can lead to damp and structural damage and also affect the wall鈥檚 thermal performance. Insulation materials need to be compatible with the wall materials and allow it to still 鈥渂reathe鈥�.

Instead, O鈥橞rien argues for a compensatory approach. If a wall can鈥檛 be brought up to full 黑洞社区 Regs standards because it has historic features, then measures should be put in place to compensate for it elsewhere. He suggests adding more insulation to the roof or a rear wall beyond the requirements of the regulations, or improving the heating systems by plugging the building into a district heat network, installing a biomass boiler or purchasing 鈥済reen鈥� electricity.

There has always been an allowance for not meeting the 黑洞社区 Regulations because of the historic status of the building, so should people still be able to opt out?

O鈥橞rien says not. 鈥淣ot everyone can afford the bills who live in these Victorian and Georgian properties or grade II-listed buildings, and a lot of local authorities don鈥檛 want to offload them because they have borrowed against them. A large house might be knocking out 13.5 tonnes of carbon dioxide a year, if we halve that, it鈥檚 nowhere near to meeting 黑洞社区 Regulations but it is a huge saving鈥�.