Shelter, the charity for homelessness, goes even further, saying in October 2016 that four in ten existing homes are not meeting the ‘Living Home Standard’, a measure devised by them to determine what makes an acceptable home.
Many of these homes may be classed as hard-to-treat and cannot be insulated in the normal way. The walls are generally responsible for the largest area of heat loss. 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.
The use of injected polyurethane foam can provide the best solution for these properties. 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 an additional barrier against water ingress through the walls.
Which material is suitable?
Where the primary purpose is energy efficiency, then the closed cell option is normally preferable. Closed cell foams offer superior energy performance and are resistant to driving rain meaning that the material stays dry with no loss of thermal properties. The insulant can help act as a barrier to prevent flood waters from entering the building through the walls. The British Board of Agrément certification approves this insulant for cavity walls in all exposure zones. Closed cell foams which achieve a Class 1 fire rating when tested to BS476 Part 7 are available. Or, where non-Class 1 materials are used on internal applications these must be covered by plasterboard, or a similar thermal barrier.
A closed cell sprayed polyurethane can also be used to insulate roofs to superior insulation standards – it has one of the highest insulation values commercially available. It also helps to achieve excellent structural stability for a building, adhering to the building substrate and setting quickly to form a rigid layer.
Conversely, open cell polyurethane foams do not have the high insulation properties associated with the closed cell materials. They do not have the same fire performance as closed cell, so they should never be left exposed; they have no structural strength to stabilise roofs or walls. However, they are better suited for their enhanced sound attenuation properties. Open cell foam is also useful in situations which require more air and vapour into a building’s interior.
The British Urethane Foam Contractors Association represents professional installers of sprayed and injected polyurethane foam systems. A BUFCA twenty-five year insurance warranty is available for cavity wall insulation projects.
When choosing a BUFCA registered installer, customers can be assured of the highest standards of quality and service. Installers are required to abide by the Association’s Code of Professional Practice which aims to further good technical and professional conduct and promotes sound relationships between members and their customers. A survey is carried out before installation to check that the building fabric is sound, with any necessary rectification works carried out.