The greener house effect

Landlords scratching their heads over how to boost their code for sustainable homes rating could do worse than turning to trees and plants.

For a start, horticulture can tick a lot of boxes in category nine of the code for sustainable homes criteria. The category, ‘ecology’, offers nine credits - or 12 per cent - of the total possible points score available within the ‘environmental issues’ section, meaning savvy landlords should be looking to become increasingly green-fingered.

There are also much less cynical, more convincing reasons. The Horticultural Trades Association has just released research showing that planting greenery against brick walls could reduce the average family gas heating bills by up to a £134 a year, meaning plants tackle both fuel poverty and emissions at the same time.

To reach these findings, researchers from the University of Reading experimented by growing hedera, otherwise known as ivy, on an exterior wall which was then exposed to a series of extreme temperatures and compared with another wall without the ivy. It found that as the exterior wall temperatures fluctuated, the greened-up wall was buffered from extreme temperatures. The air temperature on unplanted walls fell to -12˚C in the peak of snowfall and stayed cold longer, while the air temperatures behind the planted walls did not fall below -6˚C.

‘Plants protect walls from detrimental weather effects such as wind, rain, freeze or thaw and solar radiation,’ explains Dr Ross Cameron who conducted the research published at a Building Research Establishment conference last month. ‘As well as helping to soften hard landscapes, plants have an important role to play in terms of insulating buildings.’

The area of planting to insulate buildings is still in its infancy but, according to Dr Ross, research from the United States shows that as well as warming buildings in the winter, trees can cool buildings in summer. The data suggests that a 25 per cent increase in the number of trees can save 30 to 50 per cent of electricity in cooling energy systems such as air-conditioning units. Using computer modelling simulations, Reading University’s research also shows that by using plants as windbreaks, landlords could cut energy requirements for residential heating by 10 to 25 per cent.

Overheating is becoming a growing problem in new build eco developments, (Inside Housing, 24 September 2010). According to landscape architect Peter Wilder, founding partner of the urban environmental land planning practice MacFarlane Wilder, planting trees and shrubbery can offer a natural temperature regulation solution to this problem by creating solar shading and protection from changing wind patterns around the building.

What’s more, there are social benefits for residents. ‘Planting near and within developments, whether social or not, can improve the biodiversity credentials of a building and add a greater sense of well-being to residents’, he adds. ‘This is particularly important in high-rise developments.’

With this in mind, some designers have now begun to involve residents in the creation, and stewardship of surrounding gardens so that they include food production and composting facilities.

‘This not only reduces maintenance costs but increases the value of the garden as a community space that unites residents and becomes self policing,’ says Mr Wilder. ‘While this kind of approach is still the exception, social landlords should be encouraged to invest in green spaces as more than just a banal backdrop to the urban scene.’

Tim Briercliffe, chair of campaign group Greening the UK, agrees. ‘[Housing providers] should be putting landscape at the centre of the development rather than as an afterthought,’ he says. ‘You can then build people into the landscape so they become a part of it.’

Despite its clear merits in increasing both tenant well-being and the code level of properties, use of greenery in developments is still not being widely embraced. Mr Briercliffe says that developers often scrap landscaping, because it usually comes in at the last stage, when they’ve run out of budget. ‘We want to make sure that what is implemented at planning stage is actually implemented at delivery stage. We’re just not seeing that. Landscaping is an easy hit.’

Horticulture may be easily pruned back from development budgets, but it is also an easy ecological win. When it comes to sustainability - even if it
is just to get a higher code rating - landlords will only reap what they sow.