Historic Churches 2022

8 BCD SPECIAL REPORT ON HISTORIC CHURCHES 29TH ANNUAL EDITION Cushions in pews to provide a thermal break between the person and the cold surfaces of the pew seat can be helpful. Having breathable carpet runners on the floor in front of any seat avoids people having to place their feet on hard cold surfaces. Focusing on providing comfort, as opposed to achieving a certain temperature set point, is key. DAILY CHURCHES At the other end of the spectrum of usage are those, usually large, and frequently urban, churches that are in very regular use every day. Typically these have a permanent, paid staff team and run outreach and missional events throughout the week supplemented by lettings to other community groups, and by hosting services such as foodbanks, counselling and others. Due to the usage that this type of church has, the preferred strategy for achieving thermal stability within the fabric is to provide a constant level of background heating (say around 12 to 14 degrees) and then to raise this up during the day or at the time the building is used. The insulation of the fabric therefore becomes much more critical to both the effectiveness and the economics of the heating system. Every opportunity should be taken to reduce the thermal loss and adding in appropriate insulation to roof and floor voids is typically the best place to start. This needs to be done with expert advice. Any thick, solid walls are likely to be relatively reasonable if well maintained in terms of not letting them become damp from poor roof coverings or failing rainwater goods. It is the windows and the doors that are then likely to be the biggest thermal weakness and careful consideration should be made to any appropriate treatment of those depending on the space. Small, plain rectangular windows in the likes of vestry and office space may be suitable for a consideration of high-quality secondary glazing that would be inappropriate on fine large and complex stained-glass windows. The net zero carbon heating solution within these types of churches is likely to be based on a heat pump. These come in many different forms with their own pros and cons. Air-source heat-pumps include air-to-air, air-to-water and high temperature air-to-water, while those that extract heat from other sources include ground source and even water source heat pumps. These are all viable options that can work in different circumstances. A ground source heat pump frequently has many challenges in historical settings given the archaeology in the churchyard, because it involves laying many metres of pipes in the ground. A water source heat pump requires a large body of water such as a lake, river or canal in very close proximity which obviously limits its applicability. Therefore, air source heat pumps (both air-to-water in their low and high temperature forms, and air-to-air) are often the most viable types of heat pump to consider. Air-to-water systems can be the more obvious choice where there is underfloor heating already installed which remains on all the time, and where the building has a good level of insulation and draught proofing. Some heat pump solutions may need ‘topping up’ with another solution such as direct electrical heating on the coldest winter days or for events with higher comfort requirements. One of the key findings from the CofE Wayfinders programme was the relevance of an air-to-air heat pump solution within churches which are used daily. Most will be more familiar with this form of air source heat pump when it operates in its cooling mode as an air conditioning unit. In its heating mode it can send warm air into a space relatively quickly and with higher efficiencies than an air-to-water heat pump which has to transfer its heat into water circulating around a heating system. It does have the disadvantage of requiring a fan (both inside and out), and while both fan units are now supplied with extremely quiet noise ratings (when installed correctly), there is no escaping the fact that there is a fan. As most readers will have had a good night’s sleep in hotel rooms with AC units, we know that the fan noise need not be unbearable. The heat pump market is now producing internal units that move away from the classic lumps of white plastic often seen at high level on a wall in an office meeting room and there are units which can be located on the floor and are hard to distinguish from a fan convector heater. For those churches that are used often and currently have fan convector units, this solution is an easy substitute and one that other churches that are used daily should consider. The use of refrigerant gases within these systems needs to be a consideration. These gases have a highly potent ‘global warming potential’ but only if they escape into the atmosphere, so the key is to make sure that they don’t escape. Having short pipe runs with few joints is helpful in this. The reality is that well installed short lengths of refrigerant pipework in static buildings are at much lower risk of leaking than the AC system in cars. ADJUSTING TO THE ‘NEW NORMAL’ In summary, the route to decarbonisation can often be found with direct electric heating in little used churches and heat pumps (most likely in the form of air-to-air units) in daily used churches. The challenges come with churches that have a usage between these two ends of the spectrum, or are little used but have removed all of their pews. These circumstances certainly require some expert advice on their individual circumstances. We all have to rapidly move to a new normal where gas, oil and LPG are assigned to history. Where gas mains and oil tanks are replaced for higher levels of incoming electrical capacity and where comfort is as important as flexibility. We can achieve the NZC target with today’s solutions and in a way that makes our historic buildings more comfortable, more relevant and better able to continue their future on a more stable planet. MATT FULFORD is Director of Inspired Efficiency (www.inspiredefficiency.co.uk) , a company which has advised churches, historic buildings and other organisation on how to save energy and reduce their carbon emissions for the past nine years. The heat-exchanger of an air-source heat pump on a chancel wall 1 Any proposal to go from some background heating in a historic building to none must only be implemented with professional advice and supervision giving due regard to the specific individual nature of the building, a review of any special features such as wall paintings and consideration of internal artefacts including fabrics and instruments.