Insulating two homes for the cost and time of one

// the building envelope

Stephen Smith, Marketing Manager at Knauf Insulation examines why retrofitting party wall insulation can be the most cost effective and time efficient method for improving the thermal performance of our housing stock.

Despite budget cuts, housing associations are under constant pressure to meet the growing demand for new homes.
The National Housing Federation’s survey last year found that housing associations built 40,000 new properties in England during 2015/16 – positive figures, as they play their part in the overall housebuilding industry’s battle to meet its targets.
Despite these promising stats in full, there’s still a large number of existing housing association properties that are in need of retrofit work. This becomes apparent when assessing their thermal performance, as a large proportion of properties don’t have adequate insulation.
It is estimated that there are nearly five million homes across the social and private sector in the UK that currently don’t have party wall insulation, with the majority of these homes having been built post World War Two (1945+). This is not only affecting the environment, but also having a huge impact on household energy bills.
According to research conducted by Building Research Establishment (BRE), if all uninsulated party wall cavities had insulation installed, more than 2.5 million tonnes of carbon dioxide could be saved each year. Equivalent to the emissions generated by one person taking 2.5 million return flights from London to New York, or driving five billion miles in a 4x4 vehicle, this amount of CO2  has a monetary value of £465 million.
How does it affect the property?
Insufficient or no party wall insulation can result in substantial heat loss.
Unlike other thermal elements of a property, improving – or, in some cases, installing – party wall insulation in homes can be a cost and time efficient method of improving their energy efficiency.
Uninsulated party cavity walls can cause a thermal bypass, which is free air movement within the party wall. This creates a chimney effect as the cold air meets the warm air from the adjoining home, which then travels up and escapes through the roof, resulting in heat loss.
What is the solution?
Knauf Insulation’s Supafil Party Wall glass mineral wool blowing insulation has been produced for use in existing homes as well as new builds, to help reduce the heat lost through the party walls. The product provides a full-fill solution which ensures that there are no inadvertent gaps within the insulation that could result in heat loss through thermal bypass.
When retrofitting, upgrading party wall insulation is one of the most cost effective ways of improving the efficiency of housing stock on a large scale.  For semi-detached or terraced houses, it improves the thermal performance of two homes for the cost and time of one, given that party walls are shared.
It is also worth noting that if homes are being insulated as part of the Energy Company Obligation, carbon emission savings for both homes can be claimed, providing further cost savings.
With more pressure than ever before on housing associations, finding alternative routes for retrofitting the existing housing stock is vital. While a party wall is only one section of a house, the overall effect it can have on a building’s heat loss is radical.

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