The latest tests on a ‘natural’ house designed by the Prince of Wales’ architecture trust show it is exceeding expectations on energy performance
Prince’s House at the Building Research Establishment (BRE)
The results emerged through a pilot by Building Research Establishment (BRE) of dynamic modelling - a system the organisation says could allow developers in the future to predict more accurately how structures will behave in different locations and under different conditions.
The Prince’s House, developed by the Prince’s Foundation for Building Community at BRE’s Innovation Park in Watford, was built using traditional methods of energy efficiency - as opposed to high-tech solutions - and natural materials to ‘demonstrate that effective low-energy, low-carbon homes need a robust thermal and airtight envelope’.
Taking a ‘fabric first’ approach, the building’s features include an aerated clay block wall construction system, a passive ventilation system, a focus on natural light and a flexible layout.
The house has been subject to tests by BRE since its completion in 2011. The latest testing saw staff at BRE’s Scottish office in East Kilbride collaborate with Strathclyde University to create a dynamic model of the building, which is the only demonstration house on the Innovation Park with permanent planning permission.
The house was then heated up to 30ºC for two days and monitored to see how the temperature dropped off compared to performance predictions available when the house was designed. John O’Brien, associate director at BRE, said this ‘pulse test’ showed the building’s performance matched the original design data in terms of the time taken.
The dynamic modelling also revealed the 80m² house uses 35kW of energy per square metre per year (equating to an annual heating bill of roughly £280), compared to the 40kW/m² predicted ahead of construction.
’There is no performance gap’
Ben Bolgar, senior director at the Prince’s Foundation, said the house is ‘very economical in terms of its footprint’.
‘There is no performance gap,’ he added. ’What we were trying to achieve has been achieved and, in terms of energy projections, better.’
O’Brien said the dynamic modelling being piloted by BRE will allow designers to try something virtually and see the impact on the amount of energy used. For example, it is possible to turn a house through 90 degrees to see the impact of solar gains, what would would happen if it was built in a different location (the modelling takes account of local weather station data) or how it would work in a terrace if you were developing a masterplan for a town. ‘It’s giving people the ability to genuinely predict the environmental use of a development,’ he said.
He added that this was beneficial at a time of rising energy prices and could give developers a ‘commercial advantage’ if they can show they can deliver what is modelled.
Other tests on the Prince’s House have looked at aspects including temperature, airtightness, moisture, air quality and ventilation. The BRE Trust funded an occupancy test of the house, with a couple living there between August 2012 and July 2013, to allow researchers to understand how it performed under real-life conditions.
The Prince’s Foundation has already recreated the natural house in a ‘demonstration village’ at Coed Darcy in Neath Port Talbot, Wales. It is due to sign a contract for ‘four or five’ large houses in Cheltenham later this month.