The Building Conservation Directory 2023

54 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 3 | C E L E B R AT I N G 3 0 Y E A R S C AT H E D R A L C O M M U N I C AT I O N S carbon of its materials and construction. Attitudes have changed dramatically since Covid. The Architects’ Journal has launched a campaign called Retro First, promoting the view that the reuse of old buildings should be prioritised. Planning applications are beginning to demand an explanation why the existing building cannot reasonably be reused, and what are the carbon consequences. In 2022 SAVE successfully persuaded Michael Gove to call in the proposed demolition of the Marks and Spencer building on London’s Oxford Street and its replacement by a new office building. The developer argues that it was formed from three existing buildings and cannot efficiently be converted; SAVE points to the loss of 40,000 tonnes of embodied CO 2 if the building is demolished. It promises to be a test case with major significance for future redevelopments. If successful, buildings will increasingly come to be seen as capital assets rather than as purely revenue assets with a life of 25 years, and will be built to last. Serban Cantucuzino coined the phrase ‘ long life, loose fit’ as long ago as the 1970s. It remains relevant today as the approach that should be taken in designing new buildings, and converting old ones, for a sustainable future. Those buildings which are today considered to be ‘heritage assets’ (whether listed, in a conservation area or of local significance) have survived over the years because of their ability to respond flexibly to conservation and reuse. Georgian terrace houses have proved particularly adaptable owing to the simplicity of their plan form – front room, back room and staircase – as have 19th century warehouse buildings with their robust structure and open plans. It is also the case that traditional materials and structures are inherently sustainable because they were made to last, because of their capacity to be maintained and repaired, and because their materials were readily recycled. These traditional technologies and the use of locally sourced materials offer lessons to the designers of new buildings. REDUCING THE CARBON FOOTPRINT OF OLD BUILDINGS Of course it is necessary to adapt old buildings to reduce their carbon footprint in use, and to increase their contribution to mitigating global warming and climate change. However, this should be considered in the context of holistic sustainability goals, including their contribution to social, economic and environmental sustainability. Part L of the Building Regulations is not intended for rigid application where heritage assets are concerned, and the different performance of traditional buildings must be understood in order to avoid aggravating their contribution to global warming through misplaced interventions. These include ill-considered retrofits that cause problems of poor air quality, condensation and decay, and in some cases may even cause heat loss to increase as the walls grow damp. Other technologies simply waste resources and energy because their embodied (capital) carbon is out of kilter with the amount of carbon they save in use (revenue). Having said that, there is a lot that can be done to upgrade the thermal performance of old buildings safely. The Society for the Protection of Ancient Buildings (SPAB) took the lead in raising public awareness of measures that can be safely undertaken without risk to the fabric and significance of historic buildings, and their example has been taken forward by the Sustainable Traditional Buildings Alliance. STBA carries out research into the performance of traditional buildings and has published its latest guidance in Planning responsible retrofit of traditional buildings. STBA stresses the importance of a holistic ‘ whole house approach’ that is appropriate when upgrading traditional buildings without affecting their significance as historic buildings. The essence of its advice is the need for balance and reasonableness in dealing with potentially conflicting aspects of environmental protection. The advice covers ways to reduce fabric and ventilation heat losses without loss of historic significance. UPGRADING VENTILATION It is sensible to consider interventions in order of their impact and cost. In many buildings the highest priority is reducing the ventilation heat losses, and there are now myriad varieties of draftstrip to seal windows and doors. The basic principle is that foam or rubber draftstrip should be compressed between the moving parts of doors and windows and their frames, while brush seals may work best on surfaces where the seals would be dragged off by the friction. In the case of sash windows, thin strips can be built up to fill the gap between the sashes and the frame, and between the meeting rails. In the case of hinged casement windows and doors the draft strip should be fixed to the face of the reveal of the frame that faces the opening casement. In new buildings the aim is to make the entire envelope as highly sealed as possible, and substitute ventilation by mean as of MVHR (mechanical ventilation and heat recovery) units that use heat in the outgoing air to pre-heat the incoming air. However, these systems need to checked regularly as failure of MVHR units will lead to the risk of condensation and unhealthy conditions. Traditional buildings rely for ventilation on air leakage through the fabric or through the windows and doors, and this may prove a less intrusive approach to the provision of ventilation where the concomitant heat requirement can be provided by electricity from non-carbon sources. CARBON EMISSIONS OVER 60 YEARS 151 tCO 2 e 59 tCO 2 e 59 tCO 2 e 28% from construction 2% from retrofit 4% from demolition of existing house 68% from operational emissions 98% from operational emissions 100% from operational emissions UNALTERED HOUSE (BASE CASE) REFURBISHED AND WELL INSULATED NEW-BUILD EQUIVALENT Research carried out by Carrig Conservation for Historic England showed that when embodied energy is taken into consideration, a suitably retrofitted terraced house competes well with an energy-efficient modern home over 60 years, and outperforms it in the period to 2050, the date by which the UK has committed to reaching net zero.