Posted by on June 17, 2024

Cavity Wall Insulation materials

The National Insulation Association represents UK installers and insulation material manufacturers, and its members follow a Code of Professional Practice. You can find a local installer by using their postcode locator. Cavity wall insulation done by NIA members is covered by a CIGA (Cavity Insulation Guarantee Agency) certificate, guaranteeing the work for 25 years. Inspection and certification of insulation products and installers is undertaken by the British Board of Agrément.

The insulating material is injected into the gap between the two skins of brickwork through holes drilled at regular intervals into the mortar joints. Quality control systems ensure that the cavity is filled to the correct density. Cavities can be inspected before or after installation with a borescope if necessary. A thermal imaging camera will show any “cold spots” where insulation may not be present.

The main insulants for cavity wall insulation are as follows. All have similar insulation properties:

Blown mineral wool

Either rock wool or glass wool, is inert and inorganic, and should be free of CFCs and HCFCs. Manufactured to BS3533:1981, it has zero ODP (ozone depleting potential) and zero GWP (global warming potential).  It is blown into the cavity starting at the bottom, and it is important to check that filling is even and to the correct density.

Beads and granules

Expanded polystyrene (EPS) beads are now made using pentane as a blowing agent, therefore are free of CFCs and HCFCs.  They are spherical with diameters varying from 2mm to 8mm. They are very free flowing and therefore require fewer injection holes. They are usually coated with adhesive to limit their potential for escape through holes in the inner leaf of the wall, for example, through service entry points. Granules, either EPS or polyurethane, are irregular in shape and are less free-flowing. There is no fire hazard where the cavity is capped at eaves level.

Urea Formaldehyde foam

UF foam consists of a resin and hardener solution injected with compressed air into the cavity.  After injection, the foam dries and hardens, producing formaldehyde vapour which may enter the dwelling if the inner leaf is not well sealed. Formaldehyde vapour can cause allergic skin reactions and irritation to the eyes or upper respiratory tract. However, once it disperses there is no ongoing problem, and ventilation of the dwelling quickly removes any traces of formaldehyde.

Polyurethane foam

Polyurethane cavity wall foam consists of thin liquids mixed together and injected into the cavity. The mixture expands in the cavity, adhering to both leaves. The foam’s thermal insulation value is very good, but it is more expensive than the other products.

Natural fibres or recycled materials are not generally available for cavity wall insulation.

Cavity Wall insulation and dampness

Cavity wall insulation does not cause dampness. Cavity walls were originally introduced to avoid the dampness problems experienced by older solid walled dwellings. Some people think that filling the cavity (which effectively bridges the gap between the two leaves of the cavity wall) will lead to a greater risk of dampness passing from the ‘wet’ outer leaf to the ‘dry’ inner leaf. In fact, this is not the case. The insulation repels moisture. A government-sponsored independent study carried out in the mid-1990s found that filling the cavity with insulation does not cause a greater incidence of damp problems than occur in cavity walls that have not been filled with insulation.

Damp issues

Filled cavities

Unfilled cavities

Condensation 10% 14%
Damp 3.5% 8%
Rain penetration 0.26% 0.22%
Other issues 2.4%
No problem 84% 78%

However, any house where it is installed must be in good condition and well-maintained, otherwise the insulation may show up areas of penetrating dampness or condensation which may have occurred anyway due to structural problems or the walls not being correctly built. For example problems may occur if any of the following applies:

  • Rubble at the bottom of the cavity or mortar droppings on the wall ties due to careless construction
  • Poor pointing
  • Spalled brickwork
  • Rubber or EPDM materials on roofs can help with installation. More
  • Penetrating dampness for example around badly fitting windows
  • Poor ventilation causing condensation
  • Thermal bridges, for example concrete lintels or floors, or where the cavity is closed at reveals or eaves level provide colder surfaces where condensation may form. Internal insulation at these points should solve the problem.
  • Failed or missing damp proof courses – for example early cavity wall construction did not include damp proof courses at window reveals.

In most cases it is possible to remedy the problem before having cavity wall insulation installed.

Posted in: Insulation
We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.
Cookies settings
Privacy & Cookie policy
Privacy & Cookies policy
Cookie name Active

Privacy Policy

What information do we collect?

We collect information from you when you register on our site or place an order. When ordering or registering on our site, as appropriate, you may be asked to enter your: name, e-mail address or mailing address.

What do we use your information for?

Any of the information we collect from you may be used in one of the following ways: To personalize your experience (your information helps us to better respond to your individual needs) To improve our website (we continually strive to improve our website offerings based on the information and feedback we receive from you) To improve customer service (your information helps us to more effectively respond to your customer service requests and support needs) To process transactions Your information, whether public or private, will not be sold, exchanged, transferred, or given to any other company for any reason whatsoever, without your consent, other than for the express purpose of delivering the purchased product or service requested. To administer a contest, promotion, survey or other site feature To send periodic emails The email address you provide for order processing, will only be used to send you information and updates pertaining to your order.

How do we protect your information?

We implement a variety of security measures to maintain the safety of your personal information when you place an order or enter, submit, or access your personal information. We offer the use of a secure server. All supplied sensitive/credit information is transmitted via Secure Socket Layer (SSL) technology and then encrypted into our Payment gateway providers database only to be accessible by those authorized with special access rights to such systems, and are required to?keep the information confidential. After a transaction, your private information (credit cards, social security numbers, financials, etc.) will not be kept on file for more than 60 days.

Do we use cookies?

Yes (Cookies are small files that a site or its service provider transfers to your computers hard drive through your Web browser (if you allow) that enables the sites or service providers systems to recognize your browser and capture and remember certain information We use cookies to help us remember and process the items in your shopping cart, understand and save your preferences for future visits, keep track of advertisements and compile aggregate data about site traffic and site interaction so that we can offer better site experiences and tools in the future. We may contract with third-party service providers to assist us in better understanding our site visitors. These service providers are not permitted to use the information collected on our behalf except to help us conduct and improve our business. If you prefer, you can choose to have your computer warn you each time a cookie is being sent, or you can choose to turn off all cookies via your browser settings. Like most websites, if you turn your cookies off, some of our services may not function properly. However, you can still place orders by contacting customer service. Google Analytics We use Google Analytics on our sites for anonymous reporting of site usage and for advertising on the site. If you would like to opt-out of Google Analytics monitoring your behaviour on our sites please use this link (

Do we disclose any information to outside parties?

We do not sell, trade, or otherwise transfer to outside parties your personally identifiable information. This does not include trusted third parties who assist us in operating our website, conducting our business, or servicing you, so long as those parties agree to keep this information confidential. We may also release your information when we believe release is appropriate to comply with the law, enforce our site policies, or protect ours or others rights, property, or safety. However, non-personally identifiable visitor information may be provided to other parties for marketing, advertising, or other uses.


The minimum information we need to register you is your name, email address and a password. We will ask you more questions for different services, including sales promotions. Unless we say otherwise, you have to answer all the registration questions. We may also ask some other, voluntary questions during registration for certain services (for example, professional networks) so we can gain a clearer understanding of who you are. This also allows us to personalise services for you. To assist us in our marketing, in addition to the data that you provide to us if you register, we may also obtain data from trusted third parties to help us understand what you might be interested in. This ‘profiling’ information is produced from a variety of sources, including publicly available data (such as the electoral roll) or from sources such as surveys and polls where you have given your permission for your data to be shared. You can choose not to have such data shared with the Guardian from these sources by logging into your account and changing the settings in the privacy section. After you have registered, and with your permission, we may send you emails we think may interest you. Newsletters may be personalised based on what you have been reading on At any time you can decide not to receive these emails and will be able to ‘unsubscribe’. Logging in using social networking credentials If you log-in to our sites using a Facebook log-in, you are granting permission to Facebook to share your user details with us. This will include your name, email address, date of birth and location which will then be used to form a Guardian identity. You can also use your picture from Facebook as part of your profile. This will also allow us and Facebook to share your, networks, user ID and any other information you choose to share according to your Facebook account settings. If you remove the Guardian app from your Facebook settings, we will no longer have access to this information. If you log-in to our sites using a Google log-in, you grant permission to Google to share your user details with us. This will include your name, email address, date of birth, sex and location which we will then use to form a Guardian identity. You may use your picture from Google as part of your profile. This also allows us to share your networks, user ID and any other information you choose to share according to your Google account settings. If you remove the Guardian from your Google settings, we will no longer have access to this information. If you log-in to our sites using a twitter log-in, we receive your avatar (the small picture that appears next to your tweets) and twitter username.

Children’s Online Privacy Protection Act Compliance

We are in compliance with the requirements of COPPA (Childrens Online Privacy Protection Act), we do not collect any information from anyone under 13 years of age. Our website, products and services are all directed to people who are at least 13 years old or older.

Updating your personal information

We offer a ‘My details’ page (also known as Dashboard), where you can update your personal information at any time, and change your marketing preferences. You can get to this page from most pages on the site – simply click on the ‘My details’ link at the top of the screen when you are signed in.

Online Privacy Policy Only

This online privacy policy applies only to information collected through our website and not to information collected offline.

Your Consent

By using our site, you consent to our privacy policy.

Changes to our Privacy Policy

If we decide to change our privacy policy, we will post those changes on this page.
Save settings
Cookies settings