Insulating bay

[Clint]

Looking for advice on thermal insulation, needs to be fairly non
messy.

I've a 1930's semi detached house that's got bay windows, the
downstairs is fine, cavity wall under the window and the cavity is
filled with insulation but upstairs it seems to be a plaster lath
construction with the outside being roof tiles nailed to some kind of
frame over a waterproof membrame.

Given the horrific rise in energy costs I'm trying to insulate and
draught proof as much as possible and wondered if anyone could give
some advice on how to insulate this sort of mess?

Preferably without resorting to ripping it all out and starting again
if possible so some kind of internal fixing insulation. The interior
of the bay isn't really seen but I'd like to be able to decorate over
it.

I'm thinking some sort of polystyrene or expanded foam sheet?

[Andy Cap]

Could you drill holes on the inside and have it filled with blown fibre ?
You may be able to locate the vertical studs with a detector to get the holes in
the right places. That how I had my tile hung walls done, from the inside, but
they are ordinary cavity, not lathes.

Andy C

[Tim Watts]

Hi,

The best answer is celotex (which is a brand name, but the actual material
is manufactured by many others: Celotex, BallyTherm, Kingspan).

Twice the efficiency of glass wool depth for depth, easy to work with.

I did my bays, but I ripped the ceilings off and installed between the
rafters. Even 2" thick of the stuff prevents snow melting on the lead above.

If you don't want to tak ethe ceilings out, you could put 1", 2" or 3"
thickness onto the existing bay ceiling depending how much height you re
happy to lose.

Then put a sheet of plasterboard over that and repaint.

You can fix the celotext into the existing rafters with screws and large
spreader washers (sold for the job, usually plastic, sometimes metal, about
3cm diameter.

Then screw the plasterboard with suitably long plasterboard screws through
the whole lot again into the rafters.

You can also fix with PU foam adhesive but in this case you will have to
suppport everything for 30-60 minutes while it sets.

As another option, you can buy a premade plasterboard/celotext composite
(Kingspan I think).

Wickes sell celotex in small quantites and half sheets.

HTH

Tim

--
Tim Watts

[AlanD]

I assume you wish to insulate the bay wall under the window, not the
ceiling above?
I have a similar 1930's semi, with the same arrangement.
Upstairs the wall was the same thickness as the uPVC window, no sill on
the inside.
I created a wooden frame by screwing 50mmx50mm timber to the inside of
the bay, 6 straight sections make up the bay shape, then filled with
rockwool insulation, and fitted plasterboard over the top.
(I also fitted an MDF window sill screwed to the frame, plasterboard
between underside of sill and floor).
Skimmed over the joints and decorated.

End result much warmer. If doing the job again I'd use Celotex or
similar for it's superior insulating properties over rockwool.

[fred]

In article <76bf8$4ea55368$5213010d$17...@usenext.news-service.com>,
AlanD <alz_...@ajdeane.co.uk> writes

>
>I assume you wish to insulate the bay wall under the window, not the
>ceiling above?
>I have a similar 1930's semi, with the same arrangement.
>Upstairs the wall was the same thickness as the uPVC window, no sill on
>the inside.
>I created a wooden frame by screwing 50mmx50mm timber to the inside of
>the bay, 6 straight sections make up the bay shape, then filled with
>rockwool insulation, and fitted plasterboard over the top.
>(I also fitted an MDF window sill screwed to the frame, plasterboard
>between underside of sill and floor).
>Skimmed over the joints and decorated.
>
>End result much warmer. If doing the job again I'd use Celotex or
>similar for it's superior insulating properties over rockwool.
>

These days I'd be inclined to glue an inch of celotex inside and then
face that with some 6mm MDF, again fixing with glue[1]. Some light caulk
type filling should give a good finish in short order and seal any gaps
against draughts.

[1] Using one of the 'sticks like' variants
--
fred
FIVE TV's superbright logo - not the DOG's, it's bollocks

[NT]

I'd avoid polystyrene foam, in a fire its a killer. PIR foam is much
safer, insulates better, and of course costs more.


NT

[harry]

> Tim Watts- Hide quoted text -
>
> - Show quoted text -

To fit rigid board insulation between rafters, cut 20mm undersize and
fill the gap with canned foam. Virtually impossible to cut to an
exact fit but it's important there are no gaps at all.

Seconds of these boards can be bought around half price with minor
damages, easily fixed with the canned foam.
http://uk.ask.com/web?q=insulation+boards+seconds&dm=ctry&qsrc=19&o=0&l=dir

[AlanD]

Agreed, for this application glued on foam would be sufficient, and not
leave insulation bridges.

[CJ]

On Oct 24, 10:22 am, Andy Cap <wlhch...@trashmail.net> wrote:

> Could you drill holes on the inside and have it filled with blown fibre ?

I don't think there's a cavity to fill, I think it's just a single
skin and not even of brick, rather a thin wooden construction with
tiles hung on the outside and plastered on the inside :(

[CJ]

On Oct 24, 3:31 pm, NT <meow2...@care2.com> wrote:

> I'd avoid polystyrene foam, in a fire its a killer. PIR foam is much
> safer, insulates better, and of course costs more.

Good point, I mentioned polystyrene as I didn't really know how else
to describe what I wanted but thanks, yes, definitely a bad choice
>
> NT

[NT]

What you want is polyisocyanurate


NT

[The Natural Philosopher]

I assumed that was what he meant by PIR


cost that means in my DIY book 'passive infra red' as applied to
automatic light switches.

>
> NT