Cavity Wall Insulation

How Does it Work?

Cavity wall insulation is the process of injecting an insulating type material into the gap between your outer brickwork and the inner masonry skins of the external wall. As up to 33% of the heat produced in your home is lost through un-insulated cavity walls, it makes sense if only from a purely financial point of view to have all your walls insulated.

There is quite a variety of different insulating materials for you to choose from, however, at the end of the day, they all work in the same way. That is, they combine with the still, captive air between the bricks to form an effective barrier to heat loss in the home.

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Having your cavity walls insulated couldn’t be easier. The injected material is normally applied from the outside of the wall through small holes which are drilled between the bricks. As the material is injected through the wall it eventually fills the cavity completely. Once finished the holes are filled in to make as perfect a match as possible to your home colour brickwork.

What to watch out for…

Most modern houses built post war (1945) are constructed with cavity walls, however it is only those houses built post 1990 which were designed and built with cavity wall insulation built in already. If you’re not sure what type of cavity your home has, simply contact a qualified builder… they ay even be able to tell you over the phone.

It is therefore very important when considering having cavity wall insulation fitted to ensure the walls are free of any moisture, and that there is a effective ventilation to allow air movement within your walls. This also means checking the damp proof course (d.p.c.) is intact all around the house to prevent rising damp attacking the newly installed insulation, and the bricks have all been re-pointed if necessary to remove any gaps between the mortar. Take a few minutes to walk around the outside of your home to see if there are any penetrations which water could seep in.

Also ensure all essential ventilation openings, such as those providing combustion air or underfloor ventilation, and all flues and air bricks in the cavity wall are checked. If adequate sleeving or other cavity closures are not present, installation should not proceed until these openings have been sleeved or otherwise modified to prevent blockage by the insulant. Also check for flashings above windows and decks etc.

If the walls are not able to ventilate air properly, the act of insulating the walls can lead to increased levels of moisture within the building which may, over time, result in potential problems with damp. In New Zealand, we have a wet climate, so a ‘moisture free’ home is critical to our health.

Which material?

The materials readily available for cavity wall insulation are Mineral Wool, Urea Formaldehyde (u.f.) Foam, and Expanded Polystyrene Bead. These materials all have the following properties;

- Resistant to water penetration.
- Will not transmit water across the cavity, or via capillary action from below d.p.c.
- Allow moisture to disperse into atmosphere – providing breathable construction materials have been used to ventilate the walls.
- Fire resistant.
- Resistant to rot, fungi and vermin.

These materials all have equivalent thermal insulation properties and are produced under strict quality control to ensure compliance with the building regulations and industry standards.

Mineral Wool
Urea Formaldehyde Foam
Expanded Polystyrene Bead

Other materials are also available which have a much lower embodied energy rating, that is they require much less energy to manufacture and therefore have a much greater positive impact on the environment. Currently though usuage is limited to a small number of installers who work with them.

Organic insulation materials
Natural insulation materials

Can you DIY?

Due to the nature of the products involved in cavity wall insulation, and the technical nature of the installation, it’s not a good idea to do this procedure yourself.

A specialist contractor should install your cavity wall insulation for you, as they will provide all the experience and equipment.

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Client Comments... (All testimonials can be verified as true and correct... updated in 2011)

I enlisted Dean’s services 2 days prior to “D-day” of us purchasing our first NZ home. Dean proved to be an extremely efficient and knowledgeable technician. He has a very good understanding not only of his specific field, but also of general building requirements. He was easily able to spot, and talk me through, existing as well as potential problems, and was very open to answering the myriads of questions I fired his way. Most importantly, he gave me non-biased answers, allowing me to make an objective decision regarding the purchase of a potentially leaky home. Thanks again for excellent service Dean! Simone P - Titirangi

We have lived for some time in an old weather board cottage which we have renovated over a period of years. Recently we discovered a leak, so we googled “find a leak” and found a comprehensive and detailed website of the same name. Next we spoke to Dean and an appointment was made. He was punctual, courteous and his experience was obvious. His thermal imaging equipment is ‘state of the art’ and the source leak was quickly detected.

Dean was able offer practical solutions which we can act on with confidence. As a result of this experience we would recommend the use of his skills before the sale or purchase of any property to be reassured as to the integrity of the property. Dean is personable, a superb communicator and a true professional. Maggie & David M - Waiatarua

Dean was very professional and I would highly recommend anyone that is thinking of buying a property to get thermal testing done. Fortunately it was by pure chance that I even knew these tests were available after speaking to my neighbour and he advising me. The house we were looking at had water leaks and Dean has saved me many thousands of dollars in the long run. David G - West Auckland

Dean is a very professional and friendly guy. He goes step by step through the process which is very valuable. When he finds a potential problem he immediately notified to me and discussed with me in details on what actions could be taken. Anyway no major problems were detected in the property I wanted to purchase. However I greatly advice anyone to obtain Dean's professional service to make sure the property is in a satisfactory condition. Robbie P - Glen Eden

Thank you very much for the great service, very professional and appreciated the time taken to explain the process. Very glad to know that with all the stigma that goes with plaster houses, ours is not a leaky home. The report has helped pin-point some areas for maintenance which we plan to undertake sooner rather than later..Thanks again. Heather M - Maraetai

We were a bit apprehensive about what the leak detection might find, but found Dean’s confident, friendly and very capable approach extremely reassuring. While we were greatly relieved by the findings concerning the exterior of the house, Dean’s thoroughness in looking also for internal issues uncovered a surprise bath leak. Thanks Dean for solving the mysterious odour that’s been bothering us for the last 6 months! We highly recommend Dean to anyone with even the slightest concerns regarding moisture in their homes. Kevin - West Auckland

Thank you Dean for your prompt service. I was given 2 days to have a Building inspection done which found some dampness in the house. It was well worth the money spent as Dean found some other damp issues. He was very thorough and very informative and even though there were issues with the house they were all fixable so I was then able to re negotiate the purchase price. I would recommend anyone buying a house- any type of building structure to have ’Thermo Imaging’ as part of a building inspection. Thank you once again. Maree, Glendowie

We had some concerns about a recently renovation house including a lower basement. Being nosey I popped around to join Dean on his inspection. Apart from enjoying meeting him, Dean was enormously informative, approachable & friendly, I found the technology & information I gleaned fascinating. Fortunately, we identified no significant issues with the property. It gave us great peace of mind & we can enjoy our new home knowing we have bought a dry, water tight property with with hidden surprises. Thank you Dean for your help & reassurance. To my mind it is certainly worth the modest sum versus potential costs you could incur which could also mar one of most expensive purchases of your life.. Diane - Devonport

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