ROOFING SYSTEMS
Benefits for healthcare environments Green roofs have specific advantages for hospitals and other healthcare environments, as a way of creating additional green spaces around the site. Contact with, and proximity to, nature have been shown to reduce stress, improve mental health, and promote healing. Numerous studies over more than 35 years have shown the medical benefits of simply being able to see a natural environment. Research has shown that patients recover faster, require less pain relief, and have fewer medical complications, if they have a view of a landscaped area, as opposed to a view of adjacent buildings. Furthermore, the Centre for Sustainable Healthcare’s ‘NHS Forest Scheme’ was founded on the idea of a connection between health and the environment, recognising that access to green spaces reduces feelings of stress by lowering cortisol levels, and speeds recovery from illness.
Green roofs are an excellent way of maximising the green spaces on healthcare estates by making use of an often largely under-utilised area. For urban hospitals, green roofs may be among the best options for introducing natural spaces if the ground level area around the hospital is limited.
Pathways and safety measures Green roofs can be made accessible with pathways, and the installation of safety measures, to provide a safe exterior space where those patients who are able to can relax and enjoy the natural surroundings. These positive effects also apply to patients’ families and staff. In addition, for long-term care residents, and patients who have to remain in hospital for extended periods, access to green spaces can help make their stay more pleasant and comfortable. Even where the structure or layout of the building does not support the creation of an accessible green roof, boosting the amount of green areas that can be viewed from the building can have a significant impact on health and wellbeing. This can be particularly impactful with biodiverse roofs, which invite wildlife to create habitats. Organisations such as the Wildlife Trust highlight evidence that wildlife-rich environments benefit both physical and mental health.
Furthermore, increasing the quantity of vegetation can also help to improve air quality, something that is vital to protect the health of patients. Plants not only help to filter harmful gases out of the air, but the vegetation also helps to capture particulate pollution, which is then washed into the soil by rain, where it is broken down. Also, a raised rooftop green space will protect patients from street- level pollution, especially if trees or hedges are planted along the roof edge,
86 Health Estate Journal October 2021
towns and cities. This effect occurs when materials such as concrete, masonry, and asphalt, absorb and store heat from the sun. This increases overall temperatures in urban areas, even at night, extending the demand for building cooling. The UHI effect has also been confirmed to contribute to poor local air quality and global warming. Furthermore, a green roof can also be combined with a photovoltaic (PV) installation in what is referred to as a biosolar roof. By combining the green roof and PV systems, the substrate can act as ballast for the PV array frames to make installation easier. Also, PV panels are less efficient when their temperature extends above the ideal operating range, which can occur when installed on a traditional flat roof. The reduced heat storage and evaporative cooling provided by the green roof lowers the temperature of the panels, and prevents them from overheating.
The concept of biodiversity net gain will become a more established part of the design of buildings, including in the healthcare sector.
as this has been proven to provide a barrier to pollution and help disperse it (Trees and Design Action Group: 2019).
Wider benefits for the estate Green roof systems and other sustainable roofing solutions also have other advantages for the operation of healthcare sites. Firstly, green roofs can improve the energy efficiency of the building, by reducing the need for both heating and cooling. The system build-up insulates the building to prevent heat loss, especially in the colder months. In the summer, a green roof helps to reduce the exterior temperature of the building in several ways. It insulates the underlying structure from the sun’s heat, and does not itself absorb and store solar radiation. It also cools the building through evapotranspirative cooling, which occurs when water evaporates from the surface. A study by Nottingham Trent University compared the temperature beneath the roofing membrane of a conventional roof and a green roof in winter and summer. In the summer, the temperature under the standard roof was up to 32˚C, more than 13˚C above the average outdoor temperature, while the green roof showed a temperature of just 17.1˚C. In the winter, the green roof maintained the temperature at 4.7˚C, while the temperature under the standard roof dropped to 0.2˚C (Greater London Authority: 2008).
Reducing the Urban Heat Island effect
In addition to the improved energy performance of the building, the thermal properties of a green roof also help reduce the Urban Heat Island (UHI) effect in
Alleviating the impact of severe weather effects Green roofs can also help control the effects of severe weather events. When heavy rain falls on hard, impermeable surfaces it quickly runs off into drains, which can become overwhelmed, leading to flooding. On a healthcare site, this localised flooding can present many hazards to people, including in terms of accessibility, and, where the flooding is more extensive, it can also damage the building estate. With the occurrence of extreme weather becoming more frequent because of climate change, this issue will become increasingly important in the coming years.
Plants not only help to filter harmful gases out of the air, but the vegetation also helps to capture particulate pollution, which is then washed into the soil by rain, where it is broken down.
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