I recently got a flyer through the letterbox from a company wanting to take advantage of grants to insulate private homes. They say they will insulate my house with mineral wool for £150, and that it is £400 without the grant.
Is it any better than polystyrene? Does mineral wool conduct damp, ie, does mineral wool "bridge" damp proof courses. I know polystyrene does not conduct damp. Also, what would be the cost difference?
Thanks
Bob
Still think this type is best
Is this cavity wall insulation?
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IMO it's the best. No chemicals. No smell. I've had it for about 10 years now without any problems whatsoever. I even had it injected from the inside on the front of the house because I didn't want the very narrow pointing damaged. I can't commment on current costs I'm afraid.
Andy
I agree - I've had mineral wool insulation now for about eight years. No problems at all. Polystyrene insulation, AIR , is injected as small 'balls' together with a binding 'glue' which is supposed to stick them together. I remember reading one or two articles, however, where people who have had this type of insulation have knocked a hole in the cavity wall (eg to put a vent pipe from a tumble-dryer through) and a huge pile of polystyrene balls have just poured out of the hole onto the floor!
Kev
Thermafleece
On a related note, we're trying to scrape together money to cavity insulate our 1930s ex-council semi. Most of the house is brick/cavity/brick/render and there are vent bricks into this cavity (solid ground floor) in several places at the top and bottom of each wall, and the cavity is open to the loft space. Since one of the functions of cavity fill would be to stop airflow through the cavity is this likely to cause us any problems?
Not convinced about the fastness of the exterior skin to penetrating damp either so I'm not too keen on mineral fibre fill, favouring expanding foam at the moment. Does the panel have any opinion on the matter?
Hwyl!
M.
polystyrene can cause damp problems, it saturates with water. Also it contains plsticisers. And when it contacts pvc cables (only in houses where pvc cable is in the cavity) the cable turns to goo.
NT
Other way round. PVC contains plasticisers that cause the polystyrene to turn to goo. This doesn't do anything really bad to the PVC - other than make it inflexible, so it's not a problem in general.
I'm not expert but surely *any* cavity fill will stop air circulation
- that's the whole point, the vital quality is that it doesn't tansmit moisture. As for the air bricks they are removed and the hole lined with wool fibre to create a tube, prior to filling. The open top is not a problem but you might find some fill along the edges of your loft space.
Why should the exterior skin get any wetter than if there was no coating at all ?
Andy
I looked into this,
In a cavity you need "cavity grade" mineral wool, which has been treated to stop moisture transfer, then you can "full fill" the cavity.
Polystyerine sheets are not graded fro "full fill". There is one company in ireland that makes full fill polystyerine.
The puzzle is how do you get either of these into a cavity once the house is built ?
Rick
Why?
So long as it doesn't prevent airflow throught the eaves.
I don't know what the air bricks are for. In my naivety I assumed that perhaps the cavity *needs* to be ventilated for reasons of losing any damp which might have penetrated the outer skin? Now given that we're not likely to be doing anything to the outer skin other than (perhaps) painting it, two potential problems presented themselves:
1: since cavity fill stops the airflow, any damp which *does* penetrate the outer skin will find it more difficult to evaporate. 2: any penetrating damp will find itself next to the insulation. I gather that mineral fibre can be quite good at wicking, and hence wondered about this dampness crossing to the inner skin.I may be worrying for no reason at all, but I know that mum & dad, who had cavity insulation back in the 1980s of the glued polystyrene kind (I think) had very bad penetrating damp problems on one wall for ages afterwards until they had that wall rendered and pebbledashed.
Just came here for opinions, that's all :-)
Hwyl!
M.
Eh? Polystyrene impervious to water.
Rockwool is also, but being fibrous, can soak it up like a sponge.
See my post above. The polystyrene is in the form of 'granules' or little balls - and is injected together with a binding glue to stick it all together.
Kev
Because their purpose is to ventilate the rooms or beneath the floor, which is why there's an air brick in each skin.
True.
I think there were endless problems with early foam. I don't think it can be compared to products with a reasonable proven service life.
If I'm wrong no doubt you'll hear about it soon enough. :-) Personally, I wouldn't hesitate to have it done. I'm convinced it's had an appreciable benefit on my fuel bills, though against the background of a more favourable climate I admit.
Andy
But there aren't. There is no corresponding air brick on the inner skin
*anywhere* in the house, and as I said we're talking about several top and bottom on each external wall. There is no sign that any have been removed / blocked up / whatever either. The lower bricks are at or below the level of the ground floor slab, and the upper bricks are a couple of courses below eaves level.Actually, come to look at it, there aren't top air bricks on every wall, but as I said the cavity is open at the top anyway.
In that case isn't it more likely that they are for ventilating the cavity?
Some houses in the street have had a very thick external render applied (expanding-foam-like substance visible in places) which is presumably an external insulator. These appear to have had the top air bricks rendered over; it's a bit difficult to see the lower ones without wandering into front gardens :-)
[...]Hwyl!
M.
Over the years cavities have been ventilated and unventilated. certainly early ones were. It is also essential that suspended timber floors are ventilated.
Polystyrene foam is expanded, meaning its full of air pockets. Theyre not closed cells, so its porous. If air reaches dew point, condenastion will occur and fill the poly foam. Saturation of foam is a problem in fridges and freezers. There is such thing as marine grade, which is closed cell, but it costs more.
NT
Ther are for underfloor b=ventilation - below damp course usually.
and the upper bricks are a couple of
They may well be to ventilate the roof space. You can do the same job by putting holes in the soffits.
To ventilate the roof...?
Ah. Now I understand why polystyrene foam is used for things like bouys and filling boats. It helps them get waterlogged, and sink.
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