Press release: ‘No need to neglect hard-to-treat cavity walls – insulate with polyurethane’

There is no need to neglect the insulation of hard-to-treat, or non-standard cavity walled housing. Around 1.3 million properties have non-standard, unfilled cavity walls according to research published by the Department for Business, Energy & Industrial Strategy on 9 November 2017. Insulating these properties is trickier because standard cavity insulants are generally not advised – however injected polyurethane foam could be the solution for many.


The research ‘Quantification of non-standard cavity walls and lofts in Great Britain’ was prepared by the Energy Saving Trust to understand the number of dwellings with unfilled non-standard cavity walls and lofts. The report suggests that there are a further 2.2 to 2.4 million dwellings which have standard cavities with defects which may require remedial works before insulation can take place.


Standard forms of cavity wall insulation may not be possible for a number of reasons. These properties may have irregular or narrow cavities which restricts the use of injected insulation methods, or have defective/corroded wall ties, or be unsuitable for external wall insulation due to planning restrictions. Other reasons could be where internal wall insulation may disrupt tenants, or those located in high or severe wind driven rain exposure conditions, or where properties are at risk of flooding.


The use of injected polyurethane foam can provide the best solution for hard-to-treat properties. The process can easily be used for walls or sprayed in as roof insulation to effectively insulate most housing. Closed cell polyurethane foam has been around for over 30 years. The polyurethane insulant is a two-component liquid system which produces a highly-efficient blanket of insulation with an exceptional thermal conductivity figure. Systems can be applied to various depths and have K-values in the range of 0.025 to 0.028W/mK.


For cavity wall insulation, injected polyurethane foam provides a superior performing insulant which also helps to bond the inner and outer leaves providing strength to the building. Air leakage through the cavity can be reduced to zero. Because of the greater thermal performance and the reduced air leakage polyurethane foam outperforms all other forms of cavity fill. Injected polyurethane cavity wall insulation can be used in flood-plain areas to provide a flood resilient form of cavity wall insulation.


Often occupiers living in hard-to-treat properties may be classed as living in fuel poverty, whereby a large proportion of their income is required for heating their homes. They may be elderly or vulnerable and would particularly benefit from well insulated homes. In fact, it is often these people who end up in hospital with cold-related illnesses. If all homes were brought up to a decent standard of energy efficiency this could certainly relieve some of the pressure on hospitals both in terms of admissions and the resultant cost savings.


Polyurethane foam is often the most cost effective solution for uninsulated cavity walled properties. The British Urethane Foam Contractors Association represents installers of sprayed and injected polyurethane foam systems. A BUFCA insurance warranty is available for cavity wall insulation projects.




Department for Business, Energy & Industrial Strategy, 9th November, 2017: Research and analysis: ‘Quantification of non-standard cavity walls and lofts in Great Britain’