Energising Historic Homes in the UK
England has 21.6million homes, amongst the oldest in Europe. Around 45% are over 50 years old compared to 39% in France, 30% in Germany and just 24% in the USA. Over one quarter were built before 1914 and half before 1945.
The poor quality of the building fabric across the whole stock means that space heating accounts for roughly 60% of total delivered residential energy demand. Some 2 million homes in England are rated with a SAP score of below 30, representing a very low efficiency standard. In contrast, a handful of pioneering housing developments have been designed and built to a SAP rating of 100 achieving zero space heating demand.
Improvements through a range of cost effective energy efficiency measures are currently promoted in a variety of Government programmes, and heat loss standards for new homes have become progressively tighter in the regular cycle of revisions to the Building Regulations. Despite this the net effect on the UK housing stock has been negligible with just a 1% annual drop in fabric heat loss from UK homes between 1970 and 2001
One of the key changes in last month’s changes to UK Building regulations was a move to amend the exemptions for Listed Buildings and to encourage Architects to consider upgrades wherever possible. Most buildings built before 1840 in England are listed and a large number built between 1840 and 1914 are also listed. There are limited buildings post 1914 that are listed typically those of definite quality and character, including the principal works of the principal architects.
The new regulations now make it clear that it is no longer acceptable to create a blanket exemption for listed buildings and that a reasonable attempt to meet energy efficiency targets must always be made. At the same time it is acknowledged that there is a fine balance that needs to be achieved between building conservation and measures to improve energy efficiency if lasting damage is to be avoided both to the building’s character, significance and fabric.
In an attempt to reach this balance the regulations retain some specific exemptions and circumstances where ‘special considerations’ apply for historic buildings and those of traditional construction. Very often technical, philosophical and aesthetic conflicts will need to be resolved and on occasion highly creative solutions to problems will be necessary.
To aid those working in this field English Heritage have this month (Nov 2010) revised its ‘Guide to the application of the Building Regulations to Historic and traditionally constructed buildings*’. The new 2010 version of the guide sets out a methodical process for designers and Building Inspectors to follow when looking at the upgrading of existing traditional buildings.
They can be summarised as follows:
Step 1. Firstly consider repairing the building using compatible materials and techniques to reinstate its optimum original performance. This should extend to removing any damaging alterations and additions which compromise the building’s permeability.
Step 2. Secondly look at benign enhancement through improving heating strategies, controls and equipment. For example, condensing boilers are highly efficient and combined with effective controls and programming can make substantial reductions in energy use with negligible impact on the character of the building.
Step 3 The next step is to control draught/air infiltration throughout the building. Large amounts of energy can be lost through gaps in construction, and as a result will reduce the effectiveness of any upgrading work which might have been carried out elsewhere on a building. For instance, start by repairing any cracks and holes in the construction, and incorporate draught proofing and/or secondary glazing.
Step 4 Once these steps have been completed you can then incorporate insulation options, starting with those which utilise existing voids and reversible techniques. For example insulation can be installed either at ceiling level, between the rafters or between the floor joists, though careful detailing of ventilation is required to control any condensation. Again the use of secondary glazing and is cited in Part L as an effective way of meeting the target U value and can be both discreet and reversible.
Step 5 Before undertaking more intrusive insulation options, such as re-cladding of the external envelope, a detailed assessment should be carried out. It is acknowledged in the guide that these techniques can be highly effective and in some cases match the performance of new construction. However, such techniques will have obvious effects on the character and appeal of older buildings and are less likely to be acceptable.
Step 6 Lastly don’t forget carbon neutral energy supply from micro-generation where practically possible. The most common options such as Solar panels and wind turbines are unlikely to provide a visually acceptable solution. However, small-scale hydro-power schemes and combined heat and power systems can be highly viable options. Another option is to incorporate a ground or air source heat pumps which provide constant low-level heating, which is particularly beneficial in traditional buildings, as they typically have a high thermal mass which allows heat to be constantly “topped-up” to the benefit of both the building and its occupants.
Whenever any of these insulation techniques are being considered they should be supported by Dew point calculations undertaken to ensure that the proposals do not create conditions that will lead to condensation forming within the structure, which could lead to its long term degradation.
For those wanting to know more about best practice in this field there are a number of exemplar projects on the www.rethinkinghousingrefurbishment.co.uk website.
Sustainable Cities Collective