How will climate change impact buildings?
Buildings face major risk of damage from projected climate change impacts. This section will outline some of these risks but also provide some examples of how these can be overcome through building design.
The National Planning Policy Framework (NPPF) sets out a requirement for Local Planning Authorities (LPAs) to “adopt proactive strategies to mitigate and adapt to climate change, taking full account of flood risk, coastal change and water supply and demand considerations.” Therefore local councils have a key role to play in adapting our homes and buildings to climate change.
Some of the ways in which climate change is and is expected to impact buildings are:
Warmer summers mean that we will require a greater need for cooling. The summer 2018 heatwave for example is Britain’s longest spell of hot weather in 42 years.
This report shows that some types of property are more prone to overheating than others – top floor flats and new-build detached houses, as well as housing in dense cities and towns rather than in rural areas. This is due to the Urban Heat Island effect*. There is also currently no standard definition of excess heat in the building regulations, meaning that discrepancies can occur in building processes, impacting residents in different ways.
Successive updates to the building regulations have encouraged designers to increase insulation levels. The NBS also says that increased air-tightness and insulation requirements have not been matched by cooling and/ or ventilation requirements, to prevent or expel excess heat build-up.
Use vegetation (deciduous is effective) to provide shading to buildings, whilst at the same time providing more greenery for both health benefits and to absorb carbon dioxide.
Passive Solar design: Passive solar design refers to the use of the sun’s energy for the heating and cooling of living spaces. If designed correctly they require minimum maintenance.
How does it work?
Solar radiation is trapped by the greenhouse action of correctly oriented (north-facing) glass areas exposed to full sun. Trapped heat is absorbed and stored by materials with high thermal mass** inside the house. It is re-released at night when it is needed to offset heat losses to lower outdoor temperatures. Passive solar heating is used in conjunction with passive shading, which allows maximum winter solar gain and prevents summer overheating (Your Home).
Some features necessary for passive solar buildings:
- Roof Overhangs: in the summer months, these provide shading and limit the heat absorbed.
- **Construction from materials with high thermal mass. This building design has largely been overlooked in the UK to date, mainly because of the typical cool climate of the UK. 'Thermal mass' describes a material's capacity to absorb, store and release heat. For example water and concrete have a high capacity to store heat and are referred to as 'high thermal mass' materials (Green spec).
We can think of thermal mass as a sort of battery. When the air is hot, the battery (or walls of a building) becomes charged up. When the air becomes cooler, the heat starts to flow out. By alternately storing and releasing heat, high thermal mass effectively diminishes the extremes in temperatures. In warm climates where there is significant temperature variation between day and night heat is absorbed during the day and then released in the evening when it gets cooler.
The NBS say that ‘shading and insulation measures need to be considered in tandem with energy efficiency, and care needs to be taken to avoid providing summer cooling at the expense of increasing winter heating costs.’
*Urban Heat Island: on average, the temperatures in towns and cities are higher than in rural areas. This is because the dark materials such as paving, tarmac and bricks absorb heat during the day, then re-emit the heat at night, leaving no time for the buildings to cool down.
The UK Climate Risk Assessment (2017) places the health threat from flooding resulting from climate change, as one of the highest priority areas for adaptation, along with health risk from higher temperatures. Flooding is the direct result of a warmer atmosphere holding higher amounts of water vapour. Therefore the UK is predicted to have:
- Increased winter rainfall (especially in the north and west)
- Intense and highly localised summer rainfall (especially in the south and east).
In all, around 5.2 million properties in England, or one in six properties, are at risk of flooding (Environment Agency). Present day expected annual flood damages for the whole of the UK are estimated to be £1.1 billion (UK Climate Risk Assessment).
Floodwater is invariably contaminated in some form and these contaminants can cause further damage to buildings and services, besides posing a threat to public health.
The Government currently has a flood risk investment programme, which will drive down the overall risk of flooding and coastal erosion to better protect over 300,000 homes from flooding by 2021.
In April 2016 this not-for-profit scheme came into effect in the UK, which has been designed to ensure that flood insurance remains relatively affordable and available until 2039. It includes:
- A cap on flood insurance premiums
- An industry-backed levy: all UK household insurers have to contribute to this levy, creating a fund which can be used to pay claims for homes at risk of flooding.
- Savings of around 30-40% on overall policies for people in high flood risk areas
Be smart about where we build
In 2016, 1 in 10 homes in England were built on floodplains. It is very important that building on floodplains is discouraged and certainly not incentivised. Houses built post 2009 are therefore excluded from the Flood Re scheme.
Sustainable Drainage Systems (SuDS)
SuDS have an important role to play in managing surface water flooding. 2.8 million properties in England are susceptible to surface water flooding alone (Environment Agency). In prolonged, heavy downpours, the ground becomes saturates and the drains and sewers which carry away surface water cannot cope, leading to surface water flooding.
SuDS mimic nature and always have a ‘green’ element. Because of this they also benefit water quality and biodiversity. There are 3 types of SuDS:
- Source Control: these allow water to infiltrate into the ground as soon as they hit the surface. They may include green roofs and permeable paving.
- Conveyance: transport surface water from one area to another. They may include swales and channels.
- Attenuation: store water and safely release to watercourses. These type of SuDS include ponds, wetlands and rain gardens.
More innovative approaches to the unpredictability of flooding include the concept of ‘floating’ structures which, while tethered or anchored in position, are able to rise and fall in response to water levels.
Ground movements can be caused by excessive wet and dry weather periods. Excessive dry periods can cause shrinkage of the ground, and prolonged rainfall can swell soils. In some cases, this can impact buildings.
The UK Environmental Change Network makes the following predictions in relation to drought by 2080:
- Summers are likely to be drier, with decreases in rainfall of up to 40% in South West England
- Summer temperatures are predicted to increase by 2.5ºC in Northern Scotland and 4ºC in the South of England.
Current average water consumption in the UK is around 145 litres per day. Falling ground water table levels not only lead to soil shrinkage and subsidence, as discussed above, but also reduce the supply of drinkable water. As households become more affluent, and as population levels increase, so to the demand on the country’s water resources rises.
BREEAM and the Code for Sustainable Homesoffer credits for the implementation of water-saving measures in new buildings.
Rainwater collection systems:
An average of 85,000 litres of rain falls on building roofs in the UK every year and the use of rainwater harvesting systems provides many benefits (Gutter Mate):
- The water can be used for laundry and toilet flushing, car washing, swimming pools and watering plants
- Significantly reduce mains water usage of a typical home by 70%
- Savings on household utility bills
Monitor water use through water meters:
This can act as an incentive to reduce water consumption and can help householders make significant savings on their annual water bill.
Grey water recycling systems:
These systems collect wastewater from showers, baths and wash basins and recycle for use in WCs and/ or washing machines.
Click here to read about the government policy regarding buildings, climate change and energy efficiency.
Date of Publication: 28.07.2018