In 2017, a couple in Devon took advantage of grant funding to retrofit loft insulation in their 1970 end of terrace property. Spray foam insulation was installed, which the home owners believed would keep the house warmer and lower heating bills. The foam covered every surface of the loft interior including the underside of the roof and its timbers, as well as the internal brick walls. It also covered the air vents set into the tiles which originally provided ventilation within the loft space.
However, in 2014, the couple were approached by a company that told them the insulation had been carried out inappropriately and that it should be removed. Not knowing what to do, they contacted their local independent Chartered Surveyor to ask for proportionate advice with respect to whether, and how, to remove the insulation or take any other action.
We determined that the spray foam had indeed been inappropriately retrofitted – more about that below – but we also discovered that the company that had installed the product had closed down. More importantly, perhaps, a director of the company that approached the home owner had also been a director of the first!
As Chartered Surveyors we are often asked to look at properties where grants have been used to inappropriately retrofit loft insulation. Government energy and insulation grants are there to help support home owners who want to retrofit their properties with the latest ECO technology. However, some of the companies that install the products either lack experience of older properties or simply exploit home owners by misusing government grants.
Here we explain how retrofitting your property can sometimes be a bad idea.
Spray Foam Insulation
Spray foam insulation is put in place as it is a very good insulator that leaves no air gaps. This can prevent there being any ventilation to a roof space and coats most or all of the roof timbers so they cannot be seen or examined.
In any property, the second impermeable membrane (if there is one) can be damaged or leak due to tears or decay. Should the external roof coverings fail, which would allow moisture to reach the second impermeable membrane (if there is one) and there is likely to be some ingress of moisture above the spray foam. Therefore, if there is a leak in the external fabric of the roof, and spray foam has been used, all indicators as to whether that moisture has touched the roof timbers is completely hidden from view.
Air vents in the roof are designed to allow a flow of air through the roof space to prevent the build up of moisture within the space. Once solid foam insulation is introduced, a lack of air circulation and ventilation means that moisture and damp cannot evaporate away, therefore any moisture in timbers will remain damp. The timbers can then decay, causing mould, and then rot while completely hidden from view and ultimately result in an entire roof in need of replacement.
If rot has set into the timber frame supporting the roof, the whole supporting frame may need replacement, significantly increasing costs.
Closed cell spray foam allows no moisture at all through and increases the rigidity of the roof.
Open cell spray foam is softer and allows some moisture through. However, this does not allow the air to circulate around the timbers to enable them to dry out if they become damp.
Mortgage companies, therefore, do not like to lend on properties with spray foam in the roof space. Many strictly do not lend on properties with spray foam in the roof. This can, therefore, significantly compromise a property’s value because it is simply unknown whether a large component of the structure may, or may not, need replacement.
Because some of the installation with spray form prevents there from being any air circulation, it can be that a damp issue can be caused by condensation. The source of the water or moisture might not be from a leak but may be provided by services kept within the roof space.
There will be additional expense, in the case of a property that is not detached, as any roof repairs or renewal may require Party Wall awards for each adjoining property and professional fee costs of supervising said works.
What to do if you have Spray Foam Insulation
The couple from Devon had two options – either to remove the insulation or to leave it in place.
Removal of the Insulation
Removal of insulation is expensive and can typically cost at least several thousand pounds. The removal process can cause damage to the second impermeable underlay which, in turn, can result in the requirement to recover the roof, even if the timbers are found to be in satisfactory condition.
Removing the insulation can expose rot, which may mean all or some of the timbers may also need replacement.
Leaving the Spray Foam Insulation in situ
If there are no external leaks, then there will be thermal benefits from the insulation being in place.
Providing partial ventilation within the roof space will reduce airborne moisture transfer and possible mould growth, but will not allow timbers covered with foam to dry out and will actually negate most of the thermal benefits of the spray foam.