Presenting the flood-resistant house
David Thorpe | 20 February 2017
As climate change impacts worsen, how we build homes will need to change to protect against hotter temperatures, higher sea levels, and increased storm severity, fire and flood risk. Here we look at a demonstration house with features to protect against floodwater developed in Britain to inspire builders and developers, as well as home buyers, who still persist in building and occupying new homes on land that is vulnerable to flooding despite government advice to the contrary.
The house, built in Watford north of London, includes flood resistant doors and windows, water resilient walls and insulation, a kitchen with moveable units, and floor and wall membranes to channel water towards floor drains.
It also contains an automatic sump pump to stop water rising through the floor, and which also disperses water quickly should it get in.
One-way valves fitted to the toilets and sinks prevent flooding entering from the sewers.
Different types of water resilient insulation have been used including injected cavity wall insulation, thermal board and PUR spray foam, though it is unclear how this would impact upon condensation inside the house if the walls are unable to “breathe”.
There is also guidance on where to place electric sockets and home appliances and how to seal off areas where water could enter the property.
Analysis from the UK Climate Change Risk Assessment indicates the built environment will be increasingly affected by extreme weather events, and that the incidence and severity of flooding will increase.
The house has been developed by housing research group BRE, which says the measures will not only help prevent floodwater entering a building, but will also significantly improve the recovery time after any flooding, thereby reducing the cost and inconvenience caused by the disruption of repairs.
Stephen Garvin, director of the BRE’s Centre for Resilience, said: “It is not yet normal practice in the UK for properties in areas at high flood risk to be made more resilient following a flood. The aim of this project is to show contractors and householders in a tangible way that resilient repair isn’t as challenging or difficult as they may think it is.”
The project has been funded by the BRE Trust and partners AXA Insurance, British Damage Management Association, Cunningham Lindsey, Natural Cement Distribution, Property Care Association and the UK government’s Department for Environment, Food & Rural Affairs (Defra).
Flood resilience training for surveyors
At the same time BRE has also launched a new certification scheme and training courses aimed at property flood resilience surveyors.
It means that certificated surveyors will be able to provide property owners with impartial information about the measures needed to make their homes and businesses more resilient to flooding.
This is a response to a recommendation from Defra’s recent Property Resilience Action Plan.
Supported by training from the BRE Academy and representatives of the insurance industry, surveyors will be trained in collecting and uploading data from the homes to a dedicated Property Flood Resilience Database.
Ultimately the idea is to create a valuable, UK wide data source for “flood resilient” properties that will help vulnerable householders gain insurance and insurance advise householders and businesses in at risk areas.
The threat to British homes
BRE is becoming something of an expert in flood resilience. In 2014 it created a Centre for Resilience with a mission to respond to critical issues such as climate change that affect the built environment.
It has been promoting the uptake of resilience measures. Besides Dr Stephen Garvin, it’s other chief expert is BRE Group CEO Dr Peter Bonfield, who recently led Defra’s development of the Property Flood Resilience Action Plan.
This contains the advice that sometimes floodwater should be let into the property, for example when flood depths reach over 60cm or floods last a long time. At such times attempting to keep the water out can cause serious structural damage because of the unequal water pressures that arise on either side of the walls.
In the UK flooding is the most common and widespread natural source of damage to properties. The Association of British Insurers says that the annual bill for flood damage is around £1.3 billion. However this is misleading because flooding can come from a variety of sources. The most significant source of flooding today (based analysis of the underlying data provided by the lead authorities in each country conducted by the Committee on Climate Change (CCC)) is river flooding, responsible for £560m (40 per cent) of total UK damage, followed by coastal flooding (£320m or 24 per cent), surface water (£260m or 20 per cent) and groundwater (£210m or 16 per cent).
The forecast of flooding in the latest UK Climate Change Risk Assessment from the CCC, which was compiled in 2014 but only published in January this year, says that in the future all of these sources are projected to increase risk but remain in the same proportion.
It says that financial losses from coastal and river flooding in England and Wales could rise by 2080 to between £1.8bn and £2.9bn for global temperature rises of between 2°C and 4°C respectively.
This figure is significantly revised downwards from the CCC’s 2012 report, which put the higher end figure at £6.8 billion by the 2050s.
Even so, 2.5-3.5 million people will be at risk. This places the importance of the demonstration house in perspective.
The minister responsible for reducing and alleviating flooding, Thérèse Coffey, claims that the government is investing “a record £2.5 billion to better protect 300,000 properties from floods by 2021”.
Emma Howard Boyd, chair of the English Environment Agency, said: “There’s no doubt that it’s more cost-effective to make your home or business as resilient as possible rather than pay for the damage afterwards.”
According to BRE, for every £1 spent on these measures £5 is saved that would otherwise be spent on cleaning up the mess.
Should developers be forced to make homes flood resilient?
There are those who say that developers should be forced to implement flood resilience measures, such as those demonstrated in BRE’s house, if they are building in vulnerable areas.
The British Environment, Food and Rural Affairs Committee recommended in January 2017 that the government “impose by the end of 2017 a statutory liability on developers to meet the costs of flooding where their development fails to comply with planning requirements and increases flood risk, whether to a property sited on the new development or further afield”.
Whether the government accepts this recommendation remains to be seen.
David Thorpe is the author of a number of books on energy, buildings and sustainability. See his website here.