Confused over cavity wall insulation

[cbarn]

Hello

I wonder if someone could offer some words of wisdom. A couple of years ago I qualified for free loft/cavity wall insulation under the Warm Front scheme and they sent a surveyor round to look at my property. He told me that my property (built around 1990) already had a layer of insulation compressed against one wall of the cavity (I assume the inside wall) and that there was still a cavity. He advised against filling the available cavity as it may cause damp problems in the future and went away.

Our local council is currently offerring free cavity wall insulation and I am now finding that my neighbours are all having it done - our houses were contructed at the same time so should have identical cavity walls. They have all had "surveyors" visit and apparently there are no potential problems. I no longer qualify under the Warm Front scheme so this offer is tempting as it ends in a few months.

However, I can't see why Warm Front told me that they couldn't do cavity wall insulation and everyone else has been told that it's ok. I am really reluctant to go with the crowd in case I set myself up for future problems - the surveyor from Warm Front seemed to know what he was doing so I still have some trust in his judgement.

Can anyone advise?

[Someone-Else]

My opinion is:

Walls have a cavity to insulate the house, apparently it was "invented" if you will, so keep houses by the sea, warm, since it would insulate against driving rain. (The rain can't get into the inner layer of bricks)

If you put something in the cavity you are then making a bridge from outside to inside. A bridge can be crossed by water, all be it slowly. The other point to watch for is uneven insulation, suppose there is for what ever reason a less dense or missing patch in the insulation. The house internal walls will be less warm where this patch is, if something is less warm there is the possibility that warm moist air could condense on this cooler area.

There should also never be any electric cables in the cavity, but if there are and you have polystyrene put in the cavity, oh dear. A very big oh dear. (Like wise if any overflow into the loft) Modern PVC cables do not get along with polystyrene, (I don't know why, they just don't) The polystyrene "melts" and in this process it severely damages the cable sheath. (its not instant, it does take a while)

Also if at a later date you have any building work done and a brick or more is removed, or window frame changed the insulation will fall out.

There is also the old thing about it settling after some time. (It may be some time, but unless it has support, surely it must settle)

[jackspratt]

Hi it sounds like your property has the modern way of insulation which is to place insulation boards ( king span ) against the block work of your house leaving a cavity before it reaches the brickwork . I dont agree with filling the cavity with full fill insulation and have seen alot of problems with it causing damp . The cavity is there to stop water from reaching the iner skin and filling this can cause problems

[aeromech3]

Don't know if Polystyrene is used so much now-days but there is a version which is treated fire retardant; rockwool is popular, check what they are using and yes if you have exposure to driving rain and damp then take heed but I have, as many millions, have gone with cavity wall insulation and felt immediate benefits; air is still the insulator but the medium stops excessive airflow in the cavity and hence temperature drop; works the same as a continental quilt IMHO, phew hot in here init .

[Pooneil]

There is nothing inherently wrong with cavity wall insulation, simply saying 'I don't agree with it' or listing faults with electrical installation or poor bricklaying is scaremongering. If your property is suitable and it is installed correctly you will save on your heating bills with absolutely no risk to your house... like the vast majority who've already had it done.

If you already have damp, are particularly exposed, or your cavity is already bridged by mortar snots – all problems independent of having your cavities filled – then you may make matters worse. That will be what the surveyor will be looking for. It could be that your previous survey was for a different product or set of circumstances.

I your case I would want to ask the council what kind of heat saving benefits you can expect (considering it sounds like you already have part fill insulation), how thorough the survey is (raising the issues mentioned) and what kind of guarantee you get. Then you can make an informed decision.

[Perry525]

Building regulations advise against fitting cavity wall insulation in areas in the west of the UK, or anywhere where the home is in an exposed position.
Your home has been built the way it is with good reason.
The brick layers are always mean with their mortar and they leave thousands of holes in every wall.
The wind driven rain blows through the wall and runs down the inside of the cavity, thats what the cavity is for. Removing cavity wall insulation after it gets wet is a pain and expensive.
Water is 4000 times better at conducting heat from a home than dry air, a damp wall will put your heating costs up.

[cbarn]

Thanks for your advice everyone.

I have decided to wait. It means that I will miss out on free cavity wall insulation this time round but my local council (in the East Midlands by the way) may offer this free again in the future. In the meantime I can see what happens with my neighbours' properties and whether they have any problems. Even if I have to spend a good few hundred pounds paying for it myself it could end up cheaper (and less messy) in the long run than having it removed! Time will tell whether I have made the right or wrong decision.

Plus, my combined gas/elec bills are £60 a month so it's not like I already pay through the roof (no pun intended ). Maybe the insulation I already have is doing a good enough job afterall.

[Perry525]

That is a good decision.
I don't know how large your home is but, I wish my heating bill was as low as yours.
The average seems to be around £1,200 per year.

[cbarn]

I'm always surprised at how low my bills are. I have a three bed semi with new loft insulation and double glazing. Part of the savings is probably due to the fact that I have sinus problems so I hate having a hot house as it gives me headaches and ear pain all through the winter (despite little pots of water on each radiator). Because of this I don't heat the house above 19 degrees and wear a few more layers to keep nice and warm. I have just had a combi boiler installed for the first time so hopefully that will offset any price hikes in the near future!