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Hot Topic Highlight – Spray Foam Insulation

Building a Better You

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What is this week's blog about?


In this week’s blog, we take a look at spray foam insulation and what you need to know about it as a Residential surveyor.


This is essential reading for all RICS APC and AssocRICS candidates dealing with residential property (or mixed-use property with a residential element), particularly relating to the Building Pathology, Inspection, Loan Security Valuation and Valuation competencies. It is also vitally important knowledge if you are looking to purchase a residential property yourself!


After reading this blog, we recommend reading the related RICS Consumer Guide and  Inspection Protocol, available through the PCA (for building professionals). When reading these, please ensure you read the caveats and scope of each document.


Many thanks go to Tim Hayden-Kenny and Geoff Hunt for their advice and assistance in writing this article.


What is spray foam insulation?


We currently live in a climate of rising energy costs, price inflation and Government 2050 net zero target. This has led to many homeowners considering how to make their homes more energy efficient, creating more comfortable living conditions and reducing energy usage.


Insulation, when specified and installed correctly (e.g. loft insulation using mineral wool rolls), can be an excellent way to achieve these aims. Part L of the Building Regulations, which was updated in 2022, provides the minimum standards for U-values for insulation in new and existing dwellings.


However, some retrofit insulation measures (i.e., used to improve insulation performance of an existing dwelling) can be problematic. Historically, issues have been seen with poorly installed cavity wall insulation (CWI) and urea-formaldehyde foam insulation (common in the 1970s and 1980s).


Currently, there are diverse views about spray polyurethane foam (SPF) insulation, also known as spray foam. It is sprayed using a gun to the underside of roofs, walls and floors.


Where applied, it changes the construction, performance and functionality of the roof – from a cold roof (where the insulation is above the ceiling, retaining warmth in the rooms below) to a hybrid roof (where the insulation is at roof level, retaining warmth in the loft space). We shall call this the warm space type so as not to confuse this with the warm roof deck principles of flat roof construction.


The RICS provide an excellent diagram in their Consumer Guide detailing the differences:

Images of a warm and a cold roof
(RICS, 2023)

Lofts are generally just roof voids (unless they have been converted to usable living space), so they have no requirement to be heated. This means that spray foam insulation is generally not required and better insulating properties (and reduced capital costs) could be achieved by thicker mineral wool loft insulation.


Problems arise in relation to spray foam insulation where it is not specified, designed or installed in accordance with the details in the certified test document or it is applied to a roof that is already in poor condition


What are the key issues relating to spray foam insulation?


There are various issues relating to the use of spray foam insulation installed for insulation purposes.


Firstly, when applied to the underside of a roof it completely obstructs physical and visual inspection of the underside of the roof covering. This can mean that any leaks due to roof defects may not be apparent, which could lead to exacerbated problems with the vulnerable parts of a roof.


As discussed above, the installation of spray foam insulation creates a warm roof space where heat is retained in the roof space.


Professional pre-installation design is necessary to reduce the condensation risk. This will include a clear and detailed understanding of the product specification and installation requirements. Examples of such measured are not applying spray foam insulation directly to the underside of non-permeable membranes or installing sufficient ventilation channels behind the spray foam to reduce the risk of condensation.


The whole energy performance of a roof with ceiling placed insulation needs to be considered. It may be as cost effective to add more layers to existing insulation. However, extra mineral wool insulation will take up more room within the roof. In some designs, the ceiling insulation may also have to be removed.


Seeking specialist advice on energy performance and insulation options from an energy consultant is always be recommended.


Where spray foam insulation cannot be reasonably identified as being correctly installed on visual inspection by a surveyor, its removal is extremely disruptive and costly,


How can a surveyor inspect a property diligently where spray foam insulation is installed?


Surveyors should read the PCA Inspection Protocol stages and apply this in their inspection process. This provides guidance on recording observations, knowledge, assumptions, evidence, opinions and conclusion.  Background reading from manufacturers will be necessary, as well as seeking sufficient installation paperwork and warrantees to draw a reasoned conclusion.


How can spray foam insulation affect the value of a property?


Many mortgage lenders have yet to clarify their position and those who have are asking for very strict paperwork trails. The foam industry is looking to develop industry wide auditable contractors and installation documentation, but so far there is limited availability of this within the industry.  The protocol accepts that surveyors on visual inspections are unlikely to be able to assess compliance an d that a paperwork trail is the only acceptable route to risk assessment on all types of spray foam installations.


Surveyors need to be aware of the  differences between closed cell and open cell spray foam. Open cell spray foam insulation is designed to be more vapour permeable. This helps to control vapour migration and contain condensation risk parameters.  Closed cell is mainly designed to consolidate older roofs with spalling tiles to extend their performance, but could also imply the roof is already at the end of its anticipated design life.


Surveyors undertaking mortgage lending valuations will need to be aware of the joint industry Inspection Protocol, be competent in inspecting properties with spray foam insulation installed, be aware of changes to secured lending guidance and know how to use the protocol to build reasoned conclusions. This may mean that properties with correctly installed spray foam insulation may not be declined or have their value reduced.



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Stay tuned for our next blog post to help build a better you.

N.b. Nothing in this article constitutes legal, professional or financial advice.


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