Changes to Part L of the Building Regulations
The DETR has now issued the draft amendments following consultation in which the effect on historic buildings was a major issue.
1 The Building Regulations 2000: Conservation of fuel and power: Interim DRAFT L Approved Document - DETR March 2001
2 "Climate Change, Draft UK Programme": Product Code 99EP0850 - DETR (for copies telephone 0870 1226 236)
3 Available by email from: chris.wood@english
4 At present the Building Regulations only apply to proposed alteration works if they affect structural safety, means of escape, resistance to fire, access and facilities for the fire service or access and facilities for the disabled
5 Framing Opinions campaign run by English Heritage from 1994-7 which used data from BRESCU to demonstrate that double-glazed PVCu windows were seldom cost effective.
On 9 April the DETR announced its proposed changes to Part L of the Building Regulations' (Conservation of Fuel and Power) which the building conservation community originally feared could have drastic consequences for historic buildings (Context, 68, December 2000). Certainly the first draft that went out to consultation in June 2000 prompted a welter of objections from the heritage sector, leading the DETR to invite English Heritage to attend the drafting sub-committee of its Building Regulations Advisory Committee (BRAC) Working Party. As a consequence the latest proposed amendments published in the April draft break new ground in recognising the special interests of historic buildings and offer the framework for a positive approach to the needs to improve energy efficiency. However there are still some points of concern that will remain a worry.

Part L requires reasonable provision to be made for the conservation of fuel and power by limiting heat loss through the building's fabric and addressing the efficiency of services such as heating, lighting and mechanical ventilation. The operation of these services consumes energy which in turn generates carbon dioxide (CO) emissions amounting to 46% of the national total. The government is committed to the Kyoto Agreement and intends reducing greenhouse gases by 20% of the 1990 levels by 2010.1 The revisions to Part L constitute the Building Regulations' contribution to achieving the government's target.

The DETR's proposed changes, published in June 2000, provoked strong opposition from heritage groups, especially because many key organisations such as the 1H13C, the church authorities and the Joint Amenity Societies had not been consulted. English Heritage submitted a 10-page response detailing its concerns.' While welcoming the initiative to improve energy conservation and many of the improvements in the provision and performance of plant and services, strong objections were raised to the likely effects on existing buildings; particularly on windows, rooflights and internal fabric and fittings.

The most radical proposal was to widen the definition of 'material alteration' so that more maintenance and alterations come under the definition of 'building work' required to comply with the revised regulations.' This would mean that such works would have to comply with the more stringent Uvalues (thermal insulation values to limit heat loss) proposed. The opportunity for tradeoffs (ie by improving the insulation of less problematic construction such as floors and roof lofts and draughtproofing, while leaving sensitive historic fabric such as windows untouched) was vastly reduced. Ultimately this would mean that singleglazed windows would have to be replaced with at least double- (or triple-) glazed units with low-E glass. Such proposals clearly strongly favour PVCu because these frames minimise heat loss. The implications for historic buildings and areas is obvious, something that was recognised by the warning in the draft that 'this could be inappropriate in conservation work and other situations where the existing window design needs to be retained'. It was felt by English Heritage and others that this offered insufficient safeguards against a zealous but intransigent building control officer.

Claims that the proposals were sustainable were questioned, particularly over this issue of encouraging wholesale replacement of existing construction which otherwise would be viable. Total embodied energy losses were not considered at all by the DETR. Direct encouragement was being offered for the removal of perfectly serviceable timber or steel windows to be replaced by an expensive and as the Framing Opinions5 campaign showed, less cost-effective alternatives. The models used by the DETR assume that windows will be replaced every 20 years, an unsustainable concept particularly when allied to the difficulties of disposing of PVC-u.

Raising the standard of air-tightness to reduce unwanted ventilation clearly runs counter to good conservation practice in traditional solid wall buildings with no damp courses. Particular concern was expressed that buildings needed to be considered as a whole, and that unwanted raised dew points and interstitial condensation may occur in other parts of the structure, away from where 'improvements' were being carried out. Insulating walls, floors and parts of the roof might similarly cause unintended problems, as well as being hard to achieve without harming historic fabric.

In light of these and other criticisms, English Heritage was invited to attend the BRAC Working Party dealing with Part L, and a special meeting was organised by the DETR in January with representa~ tives of heritage bodies (including the IHBC). Suggested amendments and inclusions in Part L were drafted and continuously refined over the following two months culminating in a lengthy debate at the BRAC meeting on 5 March 2001.

The Interim Draft Approved Document was issued on the 9 April, though it is not subject to consultation. Changes will only be made if the current review of Part E (sound insulation) raises any conflict or representations are made from the European Commission. Although the proposal to alter the definition of 'material alteration' has been dropped, the definition of "controlled service" is being extended. This means that replacement windows, doors and replacement building service installations deemed to be required to comply with the Building Regulations will need to comply with Part L.

For the most part, English Heritage's suggested drafting for historic building clauses were accepted by the DETR and are included. Several references are now made to historic buildings including within the important introductory Section 0 at the beginning of the document (see below).

Clearly the statements now included in the revised Part L and set out below provide flexibility, so the requirements of Part L should not result in unacceptable change being carried out to historic buildings. No doubt there will be conflicts and if these are to be avoided a sensible working relationship will be needed between building control and conservation officers. The definition of historic buildings will include buildings which have limited architectural and historic interest and may be capable of achieving substantial improvements in terms of energy efficiency without detriment to their character and appearance. However, for the majority it will not be possible to upgrade to meet fully the requirements of Part L. Guidance on illustrating how benign improvements can be made are now needed, for example by showing the U-values of traditional materials or other benign works such as the use of shutters or insulated curtains. This will be important, particularly for commercial buildings which, if they fail to meet a specific standard for energy efficiency, could suffer a loss in value and become tomorrow's 'buildings at risk'. English Heritage is discussing with the DETR a proposal to produce two guidance notes:

  1. A best practice note for local authorities, detailing procedures between planning and building control departments
  2. A note illustrating ways of improving energy efficiency without harming the character of the historic building.

No programme or budget has been set for these yet. Urgency is required as the government intends to publish the Approved Document L in August in two parts: L 1 covering dwellings and L2 other types of buildings. The changes are expected to come into effect in February 2002.

The very stringent U-values required for replacement and new windows could have a drastic effect on the steel window industry. While the repair/upgrading/facsimile replacement of windows in historic buildings (as defined above) should remain unaffected, replacements or new windows on other buildings will have to meet U-values which can only be achieved with double-glazing, highquality low-E glass, and argon gas between the panes. This may well prove uneconomic to specifiers and clients, certainly in competition with other materials. Although the steel window industry is confident of being able to 'improve' its product range, the costs and length of time needed to develop and market new products is likely to be at least two years. The problem for the conservation world is that this could lead to the loss of these specialised companies who provide the expertise to repair and upgrade existing steel windows.

The revised Part L does offer an alternative method of calculating U-values which offers marginal help. However, across Europe there are different methods for carrying out these calculations and it appears that until a common European standard is in place, continental competitors may well have a distinct advantage. Interestingly the U-value requirements for walls was reduced during the consultation period. The same benefit would do much for those producing windows using traditional materials and designs.

Selections from the Interim Draft
0.28 Advice on the factors determining the character of historic buildings is set out in PPG 15. Specific guidance on meeting the requirements of Part L when undertaking work in historic buildings is given in sections 1 and 5 of this Approved Document.

Section 1. Dwellings: Work on existing dwellings 1.64 Reasonable provision where undertaking replacement work on controlled services or fittings (where replacing with new but identical equipment or with different equipment depends on the circumstances in the particular case and would also need to take account of historic value (see para 1.70 et seq) ... The section then includes the minimum Uvalues for replacement windows, doors and rooflights).

Historic buildings
1.70 Historic buildings include:

  1. listed buildings,
  2. buildings situated in conservation areas,
  3. buildings of local architectural or historical interest and which are referred to as a material consideration in a local authority's development plan,
  4. buildings within national parks, areas of outstanding natural beauty, and world heritage sites.

1.71 The need to conserve the special characteristics of such historic buildings needs to be recognised (a footnote here reads..BS 7913 The Principles of the conservation of historic buildings provides guidance on the principles that should be applied when proposing works on historic buildings). In such work, the aim should be to improve energy efficiency where and to the extent that it is practically possible, always provided that the work does not prejudice the character of the historic building, or increase the risk of long-term deterioration to the building fabric or fittings. In arriving at an appropriate balance between historic building conservation and energy conservation, it would be appropriate to take into account the advice of the local planning authority's conservation officer.

1.72 Particular issues relating to historic buildings that warrants sympathetic treatment and where advice from others could therefore be benefical include:

  1. restoring the historic character of a building that had been subject to previous inappropriate alteration, eg replacement windows, door and rooflights;
  2. rebuilding a former historic building (e.g. following a fire or filling a gap site in a terrace);
  3. making provisions enabling the fabric of historic buildings to 'breathe' to control moisture and potential long term decay problems (see The need for old buildings to breathe, SPAB Information Sheet 4, 1986).

Section 5. Work on existing buildings
5.3 same as 1.64 above. 5.10-5.12 same as 1.70-1.72.

Material alterations
7.7 Reasonable provision where undertaking material alterations depends on the circumstances in the particular case and would need to take account of historic value (see para 5. 10 et seq) ... Possible ways of satisfying the requirements are given and include roof, wall, floor insulation, sealing measures and controlled services and fittings.

Material changes of use
7.8 The same provisions are given in 5.7

Chris Wood is in the Building Conservalion & Resear ch Team at English Heritage and is a member of the IHBC's Technical Advisory Pane
CONTEXT 70 : JUNE 2001