Chartered Surveyor

Energy Efficiency I

English Heritage

“Historic and traditional buildings make up about 25% of the housing stock. While they are not exempt from EPCs (Energy Performance Certificates), they do require more careful consideration since they are built very differently from modern housing and because listed buildings and buildings in conservation areas are subject to statutory protection. The software that generates EPCs, if not controlled by the Domestic Energy Assessor, could generate ratings and recommendations that are inaccurate, misleading, inappropriate and possibly illegal to carry out. This could lead to unnecessary expense for homeowners, harmful alterations to precious buildings, and possibly claims against the Domestic Energy Assessor. ………….Standard measures to improve energy efficiency which are appropriate for modern buildings, are often expensive, ineffective and potentially harmful when applied to traditional buildings.

David Rawlins Ltd can advise the most appropriate improvements to period & listed buildings as an aid to energy efficiency, which should not adversely impact on the original building.

Windows

Many original vertical sliding sash windows incorporate original crown glass, which is much lighter than modern glass, but offers light refraction: any such glass can be expensive to replace: Whilst care will be necessary with young children, it must be remembered that it is very rare for such glass to be broken. I was recently asked to inspect the windows of a school constructed in 1860. The Headmaster was concerned that, for reasons of Health & Safety and the presence of significant condensation, the windows should be replaced with double glazing or toughened glass. This was despite the fact that no child had ever been in danger of being hurt by broken glass. A scheme was worked out to enable the original windows to be retained whilst offering improved safety, but with further advice with regard to the likely causes of the condensation and the action necessary to reduce the excess moisture in the building.

Of course, the windows are a particular feature of the Property and should be retained where at all possible. Many argue from a perspective or historic point of view. However, it should be remembered that the original windows were constructed of timber which was of much better quality than is commonly found today. The timber invariably originated from trees which had been growing for in excess of 100 - 150 years. Under the circumstances, the growth rings were relatively close together, providing significant strength and resistance to decay (Heartwood). Most decay &infestation tends to occur in timber taken from the outer part of the tree (sapwood). Most modern timber is now made up of sapwood rather than heartwood due to the rapid growth of the “modern” trees. Hence, any replacement joinery is likely to have a much shorter life span than the original, unless action is taken to find timber of similar quality to the original. The type of paint used can also contribute to decay if moisture in the timber is not allowed to evaporate.

Consideration should also be given to the fact that when decay is found in window, on most occasions, it affects the sill and bottom part of the window only. Why replace the full window if the only the rot affected areas require replacement?

I hear the argument to replace the original windows with plastic incorporating double glazing. The double glazing contractors are very ready to argue the energy efficiency advantages of their windows and the significant reduction in the requirement for maintenance. However, little seems to be said with regard to the “costs in use” of such windows, or the likely impact on the building itself. How many purchasers read the small print of the contractor’s guarantee? Whilst there are clearly improvements being undertaken all the time, there is no question that some guarantees specifically exclude the matters that go wrong, invariably just after the guarantee period has finished! For instance, how many guarantees in the market offer a 1 year warranty on the hinges &handles, 5 years on the sealed double glazing units, (*Seals to double glazed units are known to fail after 6 – 15 years and sometimes less.) but also specify that their guarantee will be invalid if the windows, including the PVC, glass &gaskets around are not cleaned every three months, and the hinges &handles greased? Basically, all windows, whether of plastic or timber, require regular maintenance.

Consideration must also be given to the fact that, at present, plastic is inclined to degrade over time and therefore tends to have only a limited life, particularly when subject to ultra-voilet suns rays. Whilst they been developed &improved over the last 25 to 30 years, the current anticipated life span of a UPVC double glazed window is clearly open to question. We are increasingly coming across house owners who wish to replace the “defective plastic double glazing”. If one considers the costs of manufacture, the costs of transporting the windows into this country or to the area of installation, plus the other costs to the environment when the windows come to be taken out or disposed of; plus the number of times such windows need to be replaced to compare with the proven life span of the original traditional windows, the argument for replacement of the original windows must surely be questionable.

When one considers the question of heat loss, the BRE (Building Research Establishment) accept that the replacement of the original sash windows in uPVC would not be justified on insulation grounds alone: Double glazing to windows and doors reduces heat loss through their openings by about half but they represent only a small proportion of the external surface area of the building and the "payback" is long in terms of energy savings (100 years?). As an alternative, a good case can be made for well-designed and carefully installed draught-proofing or secondary glazing.