Adapting buildings for a warmer climate
Research and recommendations on how to respond to increasingly hot summers are contained in a new guide from CIBSE.
With the higher temperatures associated with climate change, the traditional approach of using outside air for cooling buildings cannot be relied on. DR JALE HAKER and PROF MICHAEL HOLMES consider how buildings can be adapted.New research commissioned by the Department of Trade & Industry provides a template for how UK buildings can be adapted to cope with increasingly hot summers — one of the main effects of climate change. The research and recommendations carried out by Arup are published by CIBSE and RIBA in a new 52-page publication.* Unreliable
Historically, most buildings in the UK have relied on outside air for cooling in summer. This approach is becoming increasingly unreliable for several reasons. Firstly, summer temperatures have increased, particularly since the late 1980s. Secondly, building usage in offices has changed with increased occupancy levels, longer working hours, use of desktop computers, photocopiers and laser printers and deeper floor plans —all leading to greater internal heat loads. Using the latest UKCIP Climate Change Scenarios (web site below) for the United Kingdom (UKCIP02), the research, using quantitative computer modelling, studied 13 different types of building, including houses, apartments, offices and schools, to determine how well they will cope with higher outside air temperatures. The research went on to outline ways in which those buildings can be adapted to improve comfort levels for people who have to work or live in them. Although both residential and non-residential buildings are affected, the adaptation methods will be particular to each type of building. Even within similar types of building the solutions will differ according to factors such as how the building is used and the preferences of the owners/occupiers. Overall, buildings with the ability to limit unnecessary heat gains (e.g. from the Sun, lighting and electrical equipment) and control ventilation rates will be fare the best. Buildings with high thermal mass will also be less affected and easier to adapt than lightweight structures without the use of mechanical cooling. Key concern
A key concern with respect to the internal environment of buildings is the potential for significant increases in building energy use due to mechanical comfort-cooling systems. This increased use of mechanical systems will hamper efforts to reduce greenhouse-gas emissions and limit climate change. The quantitative dynamic thermal modelling focused on London and made use of the present-day CIBSE Design Summer Year (1989) and synthetic future DSYs under the UKCIP02 medium–high climate-change scenario. The results for this location and climate change scenario indicate the following. 1. For schools, the high internal heat gain from classroom occupants together with the high fresh-air ventilation rates required to maintain good air quality mean that as the external air temperature increases it becomes increasingly difficult to achieve comfort standards through use of passive systems alone. Even in very well designed passive school buildings, the results suggest that a move to a mixed-mode approach, in which mechanical systems are available at times of peak cooling need, may be warranted. 2) For offices, a range of buildings have been considered. HVAC systems for the offices include both passive and mechanical ventilation, passive and mechanically assisted thermal-mass cooling, low-energy mechanical cooling and full air conditioning. As for school buildings, the modelling suggests it would be difficult as the climate warms to meet present-day comfort expectations in offices adopting a purely passive approach — again suggesting that the mixed mode approach may provide the most practical way forward. 3. The effects of climate change are projected to be largest in South East England, and effects will be less severe in other parts of the country. However, significant climate impacts are expected in other regions as well, and some adaptation is likely to be needed. The research also included modelling for buildings in Manchester and Edinburgh. 4. In all the case studies, the warmer climate conditions point to the need to limit summertime heat gains to spaces as far as possible as the first and most energy-efficient measure to reduce the need for mechanical comfort cooling. This means employing solar shading, reducing the density or power output of lights, machines and, possibly, the density of occupants, and providing the ability to reduce ventilation to minimum levels during hot periods of the day. For buildings with exposed thermal mass it also means making it possible to purge spaces with cool air at night and during periods of cooler weather to maximise the capacity for passive heat absorption by the building fabric. Dr Jake Hacker and Prof. Michael Holmes are with Arup.
*TM 36 ‘Climate change and the indoor environment: impacts and adaptation’ is available from CIBSE Publication Sales on 020 8772 3618 or online at the CIBSE website below. It costs £56 (plus postage and packing), with discounts for members of CIBSE and RIBA. More information on UKCI The impact of climate change on modern building services was discussed by Jacqui Harman of UKCIP in the September 2004 issue of Modern Building Services
. You can reach it using the link below