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Research shows underfloor insulation can reduce heat loss in older homes by 92%

Adding insulation to suspended timber ground floors commonly found in homes in the UK built before the Second World War can reduce heat loss by up to 92%.

Research from the University of Sheffield and University College London has found that this simple job for the DIY enthusiast has the potential to dramatically reduce heating bills and contribute to the UK’s CO2 emissions reduction targets.

The study undertaken and funded by the EPSRC Centre for Doctoral Training in Energy Demand (Lolo), Dr Sofie Pelsmakers, a lecturer in environmental design at the University of Sheffield and Dr Cliff Elwell of the UCL Energy Institute, tested two different types of insulation in a Victorian house.

In one room, EPS beads were injected into the floor gap, entirely filling it. In another, the floorboards were pulled up and insulation laid between the joists. Results were monitored in 27 locations in the floor.

‘When we analysed the results of the tests, it showed a 65% reduction in heat loss for the wood fibre insulation and a 92% reduction for bead insulation. Our research suggests that there could be massive potential for cost savings in the average property,’ said Pelsmakers.

While modern homes are built with solid concrete floors, homes built before the Second World War typically have suspended wooden timber floors with a small area underneath for air to circulate. Dr Pelsmakers estimates there could be 10 million such houses, which could all potentially benefit from some form of ground floor insulation.

The study, the first of its type conducted in the UK, estimates that installation costs could be as little as £200 per room for the competent DIY home owner. Using the most optimistic models, payback could be achieved within two years, and certainly within five from DIY installation.

‘We’ve already seen how simple steps like improving insulation and reducing draughts can prove economical. In the future, ground floor insulation may provide another effective means to reduce energy consumption,’ Pelsmakers added.

To maximise heat retention, researchers temporarily sealed the properties’ airbricks for the EPS insulation. While no adverse effects were noticed during the research, Pelsmakers and colleagues hope to explore the short and long term effects of sealing air bricks.

But the researchers are urging DIY enthusiasts to be cautious. ‘Our research shows that to gain the maximum benefit from the insulation, it needs to be fitted very well, with no air gaps. However, over time, this could mean that, with the air bricks sealed, there is the potential for moisture to build up in the floor cavity, which could have negative effects. We’re currently investigating solutions to this and hope to test these in the near future,’ Pelsmakers warned.