SPAB Magazine summer 2023

One of the perennial intractable problems faced by practitioners is that of the energy performance, upgrading or replacement of traditional windows. Incorrect choices will result in buildings losing much of the character, beauty and historic interest, but doing nothing is no longer an affordable or socially responsible option. In the summer 2023 issue of the SPAB Magazine, Marianne Suhr discusses ways to reduce heat loss and eco-proof listed dwellings without detriment to the heritage value or the climate.

While there can be no excuse for removing an old window with historic significance, the key question Suhr poses is what should be put back when the window to be replaced is genuinely beyond repair? Many historic building professionals remain fixed on the idea of single glazing secured with traditional linseed oil putty as the only option for an old building. Conversely the green lobby, in pursuit of passivhaus standards, has long since moved on to triple glazing in the quest for carbon-neutral buildings.

Suhr notes that many homeowners concerned about energy conservation regard replacement windows as quick wins. Her stance is that there is no one-size-fits-all solution, as each sash or casement window needs to be looked at for its age and significance; its orientation; its condition and crucially, its pattern of use. Only from this level of understanding can a sensible strategy to reduce heat loss be understood.

She rightly identifies the frustration of being unable to find skilled carpenters who can carry out careful in-situ repairs without breaking any old glass, and a decorator to properly remove all the flaky old paint to give the repainted joinery a reasonable chance of longevity. These seem increasingly to be big asks. The article also looks at secondary-glazing issues, and highlights that when upgrading old windows, draft-proofing alone is no longer adequate as this does not address the loss of heat by way of conduction through the glass. The article precedes a conference on the future of historic windows at Warwick University in September, the outcomes of which may be reported later.

Elsewhere Christina Emerson, head of casework at SPAB, gives the society’s view about the controversial proposals for the application to install solar panels on the roof of Kings College Chapel, Cambridge (which John Preston addressed in Context 176, June 2023) and states the conservation principles underpinning the SPAB’s concerns.

As part of its technical role, SPAB recently called for evidence regarding buildings that have received colourless hydrophobic water-repellent treatments, so that researchers could visit the sites to gauge whether this has met with apparent success or where subsequent problems have been identified. The results will be awaited with interest.

This article originally appeared in the Institute of Historic Building Conservation’s (IHBC’s) Context 177, published in September 2023.

--Institute of Historic Building Conservation