Our experience with...cavity wall insulation
When my wife and I moved house in January 2008 one of the first things we did was to examine the energy efficiency of the house.
Our house
The house was a pretty standard 1950's brick construction with a cavity. The cavity was not insulated, leading to a significant loss of heat through the walls.
It is well known that cavity wall insulation is a fantastic way to significantly reduce the amount of energy you need to heat your home. The average house could reduce heating costs by 15%. In fact, between 2002 and 2005 around 800,000 households installed cavity wall insulation. It is estimated that these households will collectively be saving nearly 400,000 tonnes of carbon dioxide a year, enough to fill the new Wembley Stadium 46 times...every year!
Now, the government is obliging energy supply companies to subsidise insulation measures, so we contacted our power supplier - Scottish and Southern Energy - who sent a chap round to inspect the house. Apparently the cavity mustn't be too big, or too small, and they also choose a type of filling depending on the nature of the cavity.
How cavity insulation works (graphic from the Energy Savings Trust)
We were concerned about a couple of things: the cost, the appearance of the house afterwards (how would it look with a hole drilled every square metre?!), and the longevity of the product and the risk of damp.
Cost: although the actual process would cost Scotish and Southern Electric about £500, it would cost us less than £180! That seems to make it a no-brainer. Not only would we get a 15% reduction in our gas bill, but Scottish and Southern were effectively giving us another £300 too! And the fuel saving would make it pay for itself in the first year.
Appearance: yes, they drill holes every square metre to inject the material (a kind of polystyrene bead with an additional binder to stop it sagging). But the holes are much smaller than you might imagine, and they patch the holes with a colour-matched resin making it practically invisible. Here's a photo of a part of the wall after - can you see where the holes were? I can't - not even when standing right at it!
Can you see the holes? We can't!
Longevity: The horror stories of the cowboys of the 1970's are long gone. They reckon the insulation will last as long as the house, and give it a 25year guarantee. The old problems of damp bridging were due to inexperience in systems and filling, and no longer occur.
So we booked it, and after a few weeks it was installed in just over half a day. And you could tell immediately! The temperature in the house went up by a couple of degrees straight away. Definitely well worth doing.
Q&A
What product was installed?
InstaBead cavity wall insulation.
Who was the installation contractor?
InstaFoam & Fibre Limited (nominated by Scottish & Southern Electric).
Date and cost
January 2008. £180 (subsidised by Scottish & Southern Electric).
Has it lived up to its energy saving claims?
Since we had not lived in the house before we cannot compare any bills before and after. But we did notice the temperature going up immediately, and for most of the winter/spring we only needed the heating on for a couple of batches of 40 minutes morning and evening.
Have you had problems in service and did the contractor fix them promptly?
The bathroom had an extractor fan which had been fitted as a bit of a bodge job, not in a sleeve, and extracting through an air brick. Thus the contracters didn't spot it and bunged it up with insulation! They promised to come round and rectify it but it was easy enough to do ourselves.
Overall would you recommend your project to others?
Definitely.
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