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Retro-fit Cavity Insulation
During the 1980’s domestic buildings were starting to be built with cavity wall insulation. During this time period the cavities were a lot smaller than the cavities that new build houses have today. Depending on what materials are being used will depend on what sort of cavity you have. As a general note you will find that modern buildings which are timber framed come with insulation in-between the timbers. Using this method also entails having a vapour barrier. Other sorts of cavity insulation used today in modern builds are generally an outer skin of brick and an inner skin of some sort of thermal breezeblock.
Domestic dwellings before the 1980’s, although having cavities within the Walls generally had no insulation whatsoever, even the size of the cavity varied from location to location and decade to decade. A general note would be that the older the property the smaller the cavity it has. Remembering that cavity walls started being used around the 1930’s, although London properties being the exception to this rule as solid brick buildings were still being built.
The government decided a few years back that homeowners with a property which has cavity walls could apply to have the property retrofitted with cavity insulation. Grants are available for this and the cost in my opinion is quite reasonable.
There are a few different types of retrofit insulation, one of them being polyurethane or UF Foam.
I am of the mindset that whilst sitting in a classroom learning the theory behind certain subjects is all well and good. I like to get my hands dirty and see for myself the practice behind the theory. What I decided to do was to visit a homeowner who had already prearranged a retrofit installation for her cavity walls. I arrived at the property and introduced myself as a domestic energy assessor interested in the procedures and installation of the retrofit cavity wall insulation. The fitters were a couple of great guys and invited me to ask as many questions as I liked.
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The process is this, you contact a company such as Miller Pattison, there are many other companies doing this, I picked this particular one because I have seen their fitters in action and I've also checked out their website and I must say there is a wealth of information to be had there.
The insulation company will instruct a surveyor to visit your property at a convenient date for you to check whether your property or home is appropriate for retrofit cavity insulation. Once you get the green light from the surveyor your details are passed over to a company like Miller Pattison and they organise a convenient date for them to come round and fit cavity wall insulation.
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As I mentioned previously there are a few different sorts of cavity insulation materials used and I was pleased to see that Miller Pattison use white wool or “Supafil plus 40”. This material has been recycled from old glass bottles and has been treated with a fire retardant.
The fitters will start by drilling a 22 mm hole in your wall to check the cavity size. The cavity size can vary from almost nothing to 200 mm and in some circumstances even more. Your cavity must be at least 50 mm for the installation to take place. This is because as the cavity is filled the equipment used to fill the cavity measures the pressure within the wall. Generally the machine is set to accept pressures from a least 50 mm up to 200 mm.
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The pressurised system works in this way so it can auto shut off once the cavity has been fully insulated.
The fitters will also check boiler placement and any open flues as well as gas or electrical fires within a chimney stack. As you will see from the pictures more holes are drilled around doors and window frames and generally a good place to see a property that has been retro fitted with cavity insulation is under a window frame.
Apart from this and depending on what insulation material you use the rule of thumb is 10 bricks up from the floor for your first hole. The ratio after that is 16 bricks up and six bricks across.
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Supafil plus 40 can suffer if it becomes damp from moisture buildup, which is why one of the pictures show the fitters installing a moisture barrier at the corner of the house.
If you are not a detached house than your neighbour's house will have to be checked by the fitters to see if they have been cavity filled as well as a moisture barrier will have to be used between the properties.
One fitter will be drilling the holes and the other fitter will be spraying the cavity insulation into the cavity and making good once this is done with some touchup rendering.
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If you had timber frame floors which require air bricks the fitters will take these out and insert a sleeve and a new air brick. Once your property has been fully insulated you will find that the pressure within the property has changed from when it was originally built. If you have any open fireplaces or electrical or gas fires within a chimney stack they might also have to fit a new cavity air brick of some sort next to the chimney stack.
As far as an energy performance certificate is concerned once your property has been retrofitted with cavity wall insulation it can make a difference of up to 8 points on your energy efficiency rating, so well worth doing.
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I have provided a link to Miller Pattison because of their professionalism, cleanliness and friendliness.
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