thin foam polystyrene sheeting behind wallpaper - why?

[Brian Gaff]

Yes its in my house as well, seems to have survived quite well actually. I think the issue was use of a parafin heater.

Brian

[Brian Gaff]

Yes, this house does not have cavity walls and with the paraffin heater it stopped condensation on the walls dead in its tracks. Brian

[JakeD]

Thanks to all for the informative input! Having read all the suggested pros and cons of the said foam sheeting, I'm inclined to scrape it all off, and paint the bare walls with regular emilsion.

It's very true that it makes the walls seem warm to the touch, but I can't really see how 1/8" of anything is going to make any significant difference to the overall thermal insulation of an 18" thick solid stone wall. I could be wrong.

As for the condensation issue, the heating in this house is now coming from radiant/convecting gas fires which I've recently installed. Their moisture-ridden exhaust goes up the chimney, but I wonder if I will still suffer condensation problems if I remove the polystyrene foam sheet from the walls...

As someone rightly said, one of the main problems with the stuff is that a bump or knock to the wall easily creates a nasty scar that's difficult to repair.

Another disadvantage, is that it makes it impossible to remove the wallpaper without damaging the foam. So the previous owners of this house have simply painted over the paper numerous times. This seals in any slight moisture, causing moild to grow underneath.

My guess is that it's probably better to remove the foam and just paint the walls with emulsion.

I was going to say that the stuff must have been largely a con, otherwise it would be more widley in use today. However, perhaps the reason it is not so widely used today, is that almost no-one uses parrafin heaters any more!

Apart from being an anti-condensation measure, I suspect the foam in my house was added to even out what looks like some rather rough plastering. What is the easiest/cheapest way to smooth over iregularities and roughness in plaster? Polyfilla, applied a wide spatula/spreader perhaps? I don't want to go to the trouble and expense of applying plasterboard to the walls. And I don't want to use embossed (or similar) wallpaper. I could skim-coat with plaster, except that the underlying walls have been painted with what looks like vinyl silk or similar.

TIA

Jake

[damduck-egg]

I would have thought it was 20 years earlier than that,parents did some bedrooms around 1964.

Remember actually touching the stuff and getting that effect. Hard to believe now but it was seen as a new wonder material at the time.

Our walls were reasonably smooth .Stone built with no cavity but rendered quite well.

G.Harman

[John Rumm]

It was sold to provide a small amount of insulation and make the wall "feel" warmer to the touch. Quite effective at reducing condensation forming on the walls.

[Ghostrecon]

as a rough estimate treating the 450mm stone wall as dense brick you woud have R as 0.34 (U of 2.9) by itself .... with 5mm of expanded polystyrene r= 0.5 (U u of about 2) .. so would reduce heat loss to about 67% surprisingly effective for such a small addition... but I could be wrong :-)

[stuart noble]

This would appear to make the 22 mm Gyproc Thermaline (12mm of insulation) an attractive proposition for 9" walls. It's the hacking off I can't face.

[Ghostrecon]

using he same figures for the thermal conductivity of the brick wall + 10mm of plaster that gives r =0.19 (u of 5.2) compared to wall+plasterbord

+thermaline r= 0.59 (u of 1.69)so a eduction of heat loss to 33% ish :-)

[stuart noble]

Thanks for doing the sums :-) The way fuel bills are going, the payback time for replastering might make it a sensible plan.

[JakeD]

Ghostrecon wrote in news:995qqn8xxr3y.11pt69rt0lfnx$. [e-mail]:

That's surprising. One still has to consider the disadvantages of the stuff: scuffability, falammabilty etc. It would cost me about £20 to cover the two stone walls in the room (9140mm x 600mm costs £4 at B&Q). I'm thinking that the cost would be better spent on adding loft insulation. The loft above the room only has about 6" of rockwool. I can buy rockwool at £3 for 200mm x 3200 x 1140mm at the moment. Therefore it would cost me £9 to add an extra 6" of loft insulation above the room.

What do you think?

Jake

[dennis]

Don't overestimate the effects of insulation. Putting 6" of Rockwool on a ceiling will reduce the heat loss by a lot. Adding another 6" will only halve the bit of heat that is escaping.

You need to do the sums to see which will save the most and what payback period you will get. In most houses there is a lot more wall so loses tend to be higher through the walls.

[Ghostrecon]

with just a plasterboard ceiling you have a u of 15 ish (r=0.065) adding

150mm of rockwool will reduce it to a u of 0.22 (r=.4.3) adding another 150mm will reduce your u to 0.11 (r=8.4)so you geta big change adding the first insulation (15->0.22) but only a small change when you add the next 150mm (0.22->0.11) so pyback time is longer - dramatically

[Ericp]

Bought some rolls from Wickes last month for condensation problem. Lovely stuff. :)

[Pete Shew]

Would that be Erfurt Wallrock? We have just put some up on a 9" solid brick exterior wall to combat condensation. Not cheap and nor is the (PVA based?) adhesive, but it goes on very easily and with a finish that's ready to paint.

Time will tell whether it works.

Pete

[JakeD]

Hugh - Was Invisible wrote in news:j908q0$340$ [e-mail]:

The other thing I don't like about it is that wallpaper doesn't seem to stick very well to it. The wallpaper is lifting off the polystyrene sheeting in my house, especially around windows. That was what made me inclined to scrape it all off and just paint with emulsion. Having said that, if I do so and find I start getting condensation during Winter, I will probably re-do with new polystyrene sheet or some alternative anti- condensation material.

Jake

[stuart noble]

Sounds like a big improvement over polystyrene from a practical point of view

[Pete Shew]

It is certainly much more structurally durable. SWMBO stepped back and put her heel on the edge of a piece lying on the floor with no noticeable effect. It has a hardish smooth side and a fluffy side. Gob glue on the wall with a roller and stick it on. Butt the edges to leave a smooth finish, but any gaps can be filled with caulk or even the glue which has a filler in it so it will go over rough walls.

No association with the company, but surprised how easy it was to put up (and I've hung a lot of rolls of paper in my life).

Pete

[Dave Liquorice]

I think it would. Solid walls conduct heat out of room very quickly. Bunging a 25mm foam + 12.5mm plasterboard lining(*) in will make a very significant difference to the energy consumption far more than adding 6" of wool on top of an existing 6". Think of the relative areas I suspect you have far more external wall area than you do ceiling.

That few mm of polystrene will be making a difference as well. So if you do remove it expect the rooms to feel colder, might not see much change in energy consumption but comfort is another matter. The walls will be colder and air flow patterns different.

Dot and dab or onto 2x1 battens.

[stuart noble]

I think the Gyproc Thermaline (12mm + 9.5mm) might be more practical, given that it would replace the existing plaster, and skirtings and door frames wouldn't need to be adjusted.

[Alan Braggins]

[...]

Many years ago my father did that to a north-facing solid brick wall (simplified by not havng any windows in it). Made a huge difference to the comfort of the rooms.

(I'm considering doing something similar to timber framed walls that do have insulation in, but the proportional benefit will be less and there are windows. The skeilings where increasing insulation means either doing it in the room or (probably) taking the tiles off the roof to replace fibreglass with Kingspan/Celotex/whatever because the glass is already the full depth of the rafters are a higher priority though.

Unless anyone has suggestions on how to get a long length of board down between the rafters from the loft while keeping it tightly fitting?

Googling for a polystyrene "concertina" board I'd seen shows up Xtratherm Rafterloc as a similar "squeezable" construction in polyisocyanurate, but it is worth paying the price of the better material if you then cut lots of (thin) grooves most of the way though it?

)