The Building Conservation Directory 2022

PROFESS IONAL SERVI CES 1 41 C AT H E D R A L C O MM U N I C AT I O N S T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 2 2 ASSESSING THERMAL PERFORMANCE TOBY CAMBRAY C LIMATE CHANGE remains the defining issue of our time, but most of the buildings considered to be heritage assets were constructed before carbon emissions had reached the scale we now know to be problematic. Estimates vary but the operation of UK buildings contributes to around 40 per cent of the UK’s domestic carbon emissions, and much of this is due to heating. Older buildings are sometimes branded wholesale as draughty and inefficient, perhaps unfairly. Nonetheless, the operation of these buildings does contribute a significant amount to carbon emissions, and if we are to meet the targets set out in the Climate Change Act 2008 , we must consider what might be done to reduce these emissions. There is enormous variety in what might be considered a historic building: in scale, construction, usage and, of course, age. All of these factors, and many more besides, must be taken into consideration when deciding what interventions, if any, are appropriate to reduce the carbon emissions associated with each building. On the other hand, older buildings have a super-power which has only been brought to mainstream attention in recent years – simply, that they already exist. For many years the issue of up-front emissions (including those caused during the construction of the building and by the manufacture of its components) has been a fringe interest, but the embodied carbon (or energy) of existing buildings is now coming to prominence as an essential issue to consider in construction. This means every existing building has an essential role to play in minimising the effects of climate change. The crisis is upon us, and while the operational energy use over the coming decades is important, the up-front carbon implications are arguably at least as important. In this context it makes no sense to knock down and rebuild, no matter how efficient the replacement. Retaining older buildings is therefore an essential part of our response. If it is possible to improve the operational efficiency without compromising the structure and character of a building, so much the better. The cost of energy is rarely out of the news for long; for as many years as I have been working in the industry it seems that autumn brings headlines about price increases as surely as the leaves fall from the trees. 2021 will also be remembered as the year of the supplier bankruptcies, which some argue is down to a combination of wholesale price hikes and clumsy legislation, in particular retail price caps. The cost of energy puts pressure on heritage buildings in a world where assets are expected to pay their way, so improving their efficiency often has a role in ensuring a building’s ongoing use. For all these reasons and others, carefully considered retrofit to reduce each building’s contribution to climate change should be a priority. The first step in this process is understanding a building’s current performance, which is the subject of this article. MOTIVATION One of the success stories of recent years is the dramatic reduction in the carbon intensity of generating the UK’s electricity, which is now, unit for unit, less carbon intensive than gas, on average. Furthermore, as a heat pump can generate around three units of heat for each unit of electricity, a direct electric heater would result in less carbon emissions than a gas boiler. Does this mean we should swap our heater from gas to electric? While this seems simple from the perspective of each building, unfortunately at a national scale this is problematic: the electricity infrastructure has nowhere near enough capacity and a significant low carbon expansion would be expensive. There 0 50 100 150 200 250 300 350 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 MtCO 2 e Buildings F-Gas Buildings (Domestic) Embodied Carbon Infrastructure Embodied Carbon Infrastructure Operational carbon Buildings (Non Domestic) Operational Carbon Buildings (Domestic) Operational Carbon Buildings (Non Domestic) Embodied Carbon Business as Usual UK Built Environment GHG Emissions 1990-2050 The UK’s commitment to attaining net zero carbon emissions by 2050 under The Climate Change Act 2008 poses substantial challenges for the built environment (Graph: UK Green Building Council 2021)