By Geoff Wilkinson
Geoff Wilkinson looks at how Part L is affecting Historic Buildings
One of the key changes in last month’s changes to part L was a move to amend the exemptions for Listed Buildings and to encourage Architects to consider upgrades wherever possible.
The Approved Documents 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 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 and significance and its fabric.
In an attempt to reach this balance Part L includes including some specific exemptions and circumstances where special considerations apply for historic buildings and those of traditional construction. In each case the appropriate balance should be discussed early in the design process through dialogue with the Building Control Body (BCB) and the Conservation Officer. As there is a choice between BCBs, Architects working on such schemes would be well advised to check the relevant sector experience of alternate providers before making an application.
It is very important that the selected BCB has an understanding of what constitutes the special interest or significance of a historic building. 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 part L 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 BCB’s to follow when looking at the upgrading of existing traditional buildings.
They can be summarised as follows:
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.
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.
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.
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.
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.
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 exemplary projects on the http://www.rethinkinghousingrefurbishment.co.uk/ website.
(*A free copy can be downloaded from the news page of Geoff’s website http://www.thebuildinginspector.org/)
This article first appeared in the Architects Journal.
13:03, Tuesday 21st December 2010
From my point of view the biggest issue with Part L is that many "property owners" know absolutely nothing about it!
I've had some serious conversations with a number of planning departments and property owners, because reputable companies are losing out to "other" companies who are providing cheaper solutions based on totally ignoring Part L. The sad part is they're getting away with it SO EASY!
This may not be happening so much with imposing manor houses and stately homes, but on a residential and commercial/industrial level it is rife!
The planning departments answer is to sneak around and inform them of the less reputable companies and they'll try and catch them out! (sounds like a great way to waste some time!)
As far as I am concerned, the answer is for planning to inform the general public likely to be affected. It wouldn't be too difficult to send a flyer out with Council Tax reminders.
If they carry out this simple idea, they'll collect MUCH more in planning applications fees and the good companies will win the contracts instead of going bust!