The heritage lobby will be delighted with a new Guidance Note to Part L, which will exempt many historic buildings from the new thermal performance requirements. But it won't please building control officers trying to impose the tough new standards.
Buckingham Palace didn't have to replace its traditional windows with uPVC frames after all. When changes to Part L of the Building Regulations were first mooted it was thought that the Royal residence would be among those historic buildings that would have to replace its windows to comply with the new energy standards.

The approved Part L documents published on April 1 let the Palace off the hook, recognising the need to preserve the special characteristics of historic buildings. It stated that improvements in energy efficiency could be carried out but only if work did not prejudice a building's character.

Now a new Guidance Note on Part L written by English Nature and supported by the DTLR, is set to make more historic buildings exempt or partially exempt from Part L.

The definition of historic buildings laid out in Part L is widened in the Guidance Note. It calls for "sensitive considerations" to be made for historic buildings even if they fall outside the definition of a historic building in Part L.

The four categories of historical building listed in Part L are: buildings in conservation areas; Listed buildings; buildings within National Parks and Areas of Outstanding Natural Beauty and World Heritage Sites; and buildings of historic or architectural interest in a local authority's development plan.

The Guidance Note also adds buildings in historic parks and gardens, and buildings near Scheduled Ancient Monuments to the list

If there is any doubt over the historical or architectural importance of a buliding the Guidance states that a conservation officer should be contacted.

This will cause conflict with those building control officers eager to impose the new Part L thermal standards. It means that conservation officers in local authorities will have a much stronger hand with which to make historic buildings exempt from Part L.

In the Guidance Note English Heritage has identified a number of areas where improvements in thermal performance may compromise the character of the building.

English Heritage draws particular attention to windows stating that "Part L must not become the agent for the thoughtless destruction of historic windows". Windows should generally not be altered in their proportions or details, states the Guidance Note, and where old glass survives it must be retained.

The Guidance Note, due out at the end of this month, is intended to provide interim guidance until an-depth document is published in 2003. This will give detailed advice on how energy efficiency can be improved without harming the character of historic buildings. Technical information on traditional materials and illustrated details and case studies will be included.