CPD PROGRAMME | HEATING, COOLING AND VENTILATION working; this will undoubtedly impact the expectations and quality of delivery and operation of services and systems in multiresidential buildings that reach beyond those normally associated with safety. Alongside the new regulations on energy use and lowering carbon, there is also a growing focus on occupant health in buildings, including dwellings. The Future Homes Standard addresses the issues of overheating and indoor air quality (IAQ) as important factors to consider in the design of new homes. To design, build and operate this new wave of homes, and intrinsically the associated building services systems, will set a challenging task across the whole industry supply chain. In Ashley Batesons introduction to a CIBSE Homes for the Future Group event,6 the head of sustainability at Hoare Lea, and chair of the group, identified five key challenges for future homes: Energy efficiency Performance-gap issues Thermal comfort/overheating risk Adaptation to climate change Air quality Health and wellbeing. CIBSE TM60 Good practice in the design of homes provides a useful guide to meeting the challenges, as detailed by Bateson, to design and deliver homes that are safe, fit for purpose, resource efficient, low carbon, comfortable, healthy, and easy to operate and maintain. It notes that, wherever possible, good practice should deliver both lower capital and life-cycle costs. It highlights that potential future needs should be considered when designing homes, as well as meeting the current needs of occupants. Overheating in buildings has a negative impact on occupants, with recent UK government figures indicating that there are around 2,000 heat-related deaths each year in England and Wales, with this number expected to rise to 7,000 per year by 2050.7 London is regarded as a particular risk area because of its geographical location and high building density, which contributes to the urban heat island effect. CIBSE TM59:2017 offers guidance on managing the problem of overheating in homes and emphasises that the health and wellbeing impacts of overheating can be significant for residents, resulting in stress, anxiety, sleep deprivation and even early deaths in heatwaves, especially for vulnerable occupants. Building users have become increasingly aware of indoor air quality (IAQ) in homes,8 particularly with concerns around transmission of infectious diseases. The National Institute for Health and Care Excellence has recently published a guide, Indoor air quality at home9, that is aimed at planners, designers and contractors, and which provides a useful overview of contemporary measures needed to improve home air quality. In terms of building services systems, the key overriding recommendation is to adopt a whole-building approach to heating and ventilation, balancing indoor air quality with standards for energy use, with specific actions to ensure permanent, effective ventilation; minimising exposure to outdoor pollution; and minimising and removing indoor air pollutants from heating, and ensuring that heating and ventilating systems are easily accessible for regular maintenance. The Centre for Cities10 reports that, on a per capita basis, cities have a much lower carbon footprint than the rest of the country. On average, a person living in a city emits around four tonnes of carbon a year, against more than six in the rest of the country. An area of development that has attracted widespread attention is the repurposing of redundant offices in cities. An analysis11 by the Local Government Association found that office-to-residential conversions account for more than one-third of new homes being developed, in particular in urban areas where housing demand is high. In England, 65,000 homes were created from conversions of redundant offices to residential premises between 2013 and 2019,12 and approximately13 23,000 in 2021. Some of the enthusiasm to create such new homes was driven by the limited local authority planning oversight afforded by permitted development right class O. This is likely to be somewhat assuaged by last years introduction14 of class MA that limits such unrestricted developments to 1,500m2. Additionally, there are now specific requirements, including adequate natural light15 and minimum floor areas,16 which will hopefully prevent further conversion developments of the type that have been identified as potential slums of the future.17 The trend for such conversions is likely to continue, including those larger than 1,500m2 that require more extensive planning consents. The recent revision to AD L requires that wet heating systems in new dwellings be sized to allow the space heating system to operate effectively at a maximum flow temperature of 55C or lower. Gas-, oil- and solid fuel-fired systems continue as potential heat sources in AD L for homes, although a fuel factor is no longer applied so that higher carbon emissions are no longer compensated for in establishing the target emissions for a home. Setting a relatively low heating flow temperature eases the application of heat pump technologies, as 55C is readily and efficiently attainable with current vapour compression refrigerationbased systems. (See CPD Module 178, CIBSE Journal, May 2021 for discussion on moving towards the increased adoption of heat pumps for heating and hot water.) The average carbon factor for grid-supplied electricity recently published in table 12 of the UK Governments Standard Assessment Procedure for Energy Rating of Dwellings, SAP 10.218 (which is used to evidence compliance with the requirements of the Building Regulations for homes, starting June 2022) is 1.6kgCO2e.kWh-1 and provides a significant reduction from the previous value of 5.19kgCO2e.kWh-1. The consequences of this are enormous, as it opens up opportunities for heating and hot water systems that Figure 1: Example of a residential water-to-water heat pump employ electricity as the energy source, that includes a 170L integrated tank. The unit can supply which in terms of operating cost hugely both low-temperature hot water (LTHW) and domestic hot water (DHW) up to 60C (Source: Mitsubishi Electric) favours heat pumps. 50 March 2022 www.cibsejournal.com CIBSE March 22 pp49-52 CPD 192.indd 50 25/02/2022 16:59