YBS Insulation solid wall insulation

WWF Green Game-Changers Innovation Award

What is the most effective way to improve the energy efficiency of a home?

It is a testament to the immense challenges presented by the energy efficiency dilemma that there is no agreed answer to this critical question.

Insulation is commonly touted as the most effective means of improving the energy efficiency of a building, but installing it is often challenging and while good insulation will curb energy use it rarely delivers the deep savings that will be necessary if the UK is to meet its carbon targets. You can, of course, cut energy use to almost zero if you knock your house down and replace it with one built to Passivhaus principles, but this is neither practical, cost effective, nor particularly green given the embedded carbon associated with the construction.

With domestic properties accounting for around 27 per cent of the UK’s greenhouse gas emissions and current approaches to improving energy efficiency delivering incremental improvements it is increasingly apparent that a “game-changing" solution is required – which is exactly why Knowsley Housing Trust walked away with the inaugural WWF Green Game-Changers Innovation Award at this year’s BusinessGreen Leaders Awards.

The Merseyside-based not-for-profit housing association secured the award for its highly innovative work turning three 1950s terrace houses into an exemplar of energy efficient housing – and all without requiring people to leave their home or invest in costly high-tech renewable energy or smart building technologies.

The Lordens Road project – which brought together Knowsley Housing Trust with insulation specialist YBS, architects BYA, heating provider The Electric Heating Co, consultancy Solarcrest, and contractor BAAS – took the innovative approach of eschewing yet more in-house or cavity wall insulation in favour of deploying a “Multifoil insulation" shell around the entire exterior of the properties.

The net result was a slashing in the level of heat loss from the buildings, confirmed by thermal imaging cameras and air pressure monitoring equipment, and a reduction in the number of air changes per hour experienced by the building to just four air changes per hour – a huge reduction on the 13 air changes per hour that were occuring before the work was undertaken.

The savings are delivered through the relatively simple feat of sealing the building behind a continuous barrier and then installing a mechanical ventilation heat recovery unit that stops the building from becoming unbearably stuffy, while recovering 90 per cent of the heat from controlled air changes.

“We have done insulation and cavity wall insulation, but we still have cold buildings and high fuel bills for tenants," says Anthony Jarvis, energy efficiency officer for Knowsley Housing Trust. “Improvements have not been done holistically and a lot of improved buildings still have problems. The basic problem is that it is the junctions where you lose the heat. If you do not have a proper seal for the building it is going to be cold."

The multifoil sealing solves this problem, and even limits heat loss through the ground by extending the insulation down alongside the buildings foundations. “Heat does not transfer through the ground below a depth of 600mm," explains Jarvis. “So if you can stop the heat going sideways through the ground it has nowhere to go."

Perhaps most of important of all, the Housing Trust found that this relatively low tech solution is equally simple to deploy. “The governing principle behind the project was how can we implement this on the ground, not simply whether or not we could technically do it," explains Jarvis. “You can do incredible things with energy efficiency now, but only without anyone being in the home and a budget of £100,000 plus. That is simply not feasible with the vast majority of properties."

In contrast, the Lordens Road project was completed with tenants remaining in their home – a feat that was made easier by a remarkably courteous approach from contractors that Jarvis says he “cannot praise enough" – and a total budget of £80,000, or £26,700 per property.

Jarvis is confident that if deployed on a larger scale the approach could get costs down to around £15,000 per building. This is still higher than the £10,000 that is likely to be made available to households through the Green Deal, but Knowsley Housing Trust is still confident it can access the loan scheme to fund a wider rollout of its home improvement programme.

“The next stage is we are going to Ofgem to present plans to replicate the project on a larger scale," explains Jarvis. “We want to get this funded by the Green Deal, then we can go and do whole street makeovers… There may be cost issues, but we are confident we can get the costs down, and Knowsley is the fifth most deprived area in the country, so we will be looking for access to the ECO."