Cladding and wainscoting of cold internal walls

gutovicky

Good afternoon,
Can you offer me any advice on my next couple of projects?

In two situations, inside my home, I’m thinking of cladding (or part-cladding) external walls (but on the inside) for decorative & insulation purposes, as follows:

Inside one of the bedrooms, I’m interested in completely cladding the external wall without the window.  This wall definitely feels quite chilly and attracts condensation in the colder weather, even when no furniture is standing against it.

Inside the dining-room, I’m interested in putting in wainscoting along the external wall without the window.  This wall generally feels relatively chilly and will get some condensation & mould-growth behind any furniture standing against it.

Please look at these two questions:

1.  In the bedroom, I plan to insulate then clad the cold external wall, in the following sequence: a) screw treated wooden battens to wall; b) fix insulation matting or batts within this timber framework; c) cover all with vapour-barrier sheeting, taped securely to the timber; d) screw (decorative) wooden boards to the timber framework, somehow sealing the holes to prevent moisture entering the insulation.   
Question 1: Is my cladding idea a good way to sort out this cold (damp) wall?

2.  In the dining-room, I feel I need to insulate behind the wainscoting that I’m planning (using a similar method as used in the bedroom) rather than just place the wainscoting directly on the wall.
Question 2: Do you agree that I should insulate behind this wainscoting?

Just so you know, I live in a bungalow with cavity-walls (built 1970).
[I don’t want cavity-wall insulation because of the expense, and because I live in an area that experiences lots of driving rain - so I worry that it would fail].

Thank you for any tips you can offer!
Vicky

FreeBear

gutovicky said: 1.  In the bedroom, I plan to insulate then clad the cold external wall, in the following sequence: a) screw treated wooden battens to wall; b) fix insulation matting or batts within this timber framework; c) cover all with vapour-barrier sheeting, taped securely to the timber; d) screw (decorative) wooden boards to the timber framework, somehow sealing the holes to prevent moisture entering the insulation.   
Question 1: Is my cladding idea a good way to sort out this cold (damp) wall?

Insulated two walls so far here.

The first one, fixed 25x50mm battens to the wall vertically with a strip of DPC material between the battens & brick. Space between the battens were filled with 25mm thick Celotex and any gaps filled with expanding foam. All joints covered with self adhesive aluminium foil tape. A second layer of 25mm thick Celotex then put up with horizontal battens fixed through to the vertical batten behind. Again, gaps sealed with expanding foam and taped. A final layer of 25mm thick Celotex filled the space between the battens, foamed & taped joints. To finish off, plasterboard glued & screwed over the three layers of Celotex.

Second wall - Sheets of 40mm Celotex put up with 25x50mm battens over the top and secured to the brick wall with 120mm frame fixings (foam & taped the joints). The space between the battens, filled with 25mm Celotex, and more foam & tape used on the joints. More plasterboard glued & screwed in place.

The foil facing plus aluminium tape should be more than adequate as a vapour control membrane, and with two/three layers, even more effective. The use of Celotex/Kingspan boards results in a thinner layer of insulation than if fibreglass/mineral wool batts had been used. Yes, the rigid boards are a little more expensive, but this is offset by not needing a VCM and smaller battens. The loss of 75mm of floor space is barely noticeable, where as 150mm (to achieve the same u-value with fibreglass) would be.

An image is worth a thousand words....

Why only 65mm of insulation on this wall ?

This is in a stairwell and there is a step in the wall out of view half way up the stairs. 65mm fills this step nicely and gets me very close to the required u-value of 0.3 W/m²K.

In answer to your second question - It is always worth insulating the external walls. With a cavity construction, you'd get away with just 50mm of Celtex/Kingspan, so could use the same method as pictured above.

gutovicky

Wow, thank you FreeBear for that really comprehensive answer!

Yes, I can see how foil-faced Celotex sheets would do the job (& no extra VCM needed...)

Instead of a final layer of sheet plasterboard, |I'd like to finish off with a timber board - as a decorative, feature wall.
Do you see any problems with that approach, as long as I seal & tape-up behind thoroughly?

Cheers, Vicky

gutovicky

Oh, and FreeBear, is it OK to do all this 'cladding' onto a wall that's still rendered/plastered - not bare brick!
An important point that I forgot to mention at the start....
Vicky

FreeBear

gutovicky said:  Instead of a final layer of sheet plasterboard, |I'd like to finish off with a timber board - as a decorative, feature wall.
Do you see any problems with that approach, as long as I seal & tape-up behind thoroughly?

Timber would be fine, just not MDF or hardboard please.

One more bit of advice - Over the top of the windows, use a strip of 12mm plywood, say 150mm wide, and extending ~150mm either side of the window. This will give you a solid surface to attach curtain rails/poles to.

And once you have insulated the external walls, radiators can be hung on internal walls. If you want to stick with the traditional location of under a window, put some extra battens in for the radiator brackets to attach to.

gutovicky

No worries, no MDF or hardboard!!!

I hear what you say about the Window-Wall - in the bedroom in particular, but actually I was not going to include that wall (at this stage anyhow).
I was just aiming to internally-clad the non-window external wall in that bedroom.
I realise that's not a complete job and therefore not ideal, but would it actually create a big problem?

FreeBear

It would be better if you could insulate all external walls in the bedroom if possible (and don't forget to do the reveal). It saves having to make mess twice, and if you are paying a plasterer to skim, you only need him/her in the one time.

Is this the same room you are having a new window fitted and the opening made smaller ?

gutovicky

Agreed FreeBear!  I know, in my heart(!), that it would make more sense to internally-clad/insulate BOTH external walls....
I'm assuming that by insulating JUST the windowless external wall, I will find that the 'window-wall' gets MORE condensation - is this the problem that you see ahead?
(I was hoping that increased condensation on the window-wall could be 'controlled' by the ventilation that opening the windows can provide).

It's down to cost I'm afraid...
I feel I can insulate the windowless wall MYSELF (DIY) - in the way we've explored in this conversation.
That would give me a whole wall against which I could put furniture or shelving - something I can't do now.
To try to insulate the window-wall is a step-too-far for me, because I'd have to reposition a big radiator.
To get a tradesperson in to do the work may be too costly for me (though I have not researched this....).
One of the reasons that I was aiming to finish off my insulated bedroom wall WITH TIMBER SHEETING, was to avoid the expense of having a plasterer in.

No FreeBear, this was not one of my window openings I'm hoping to make smaller in the near future.  This bedroom window is already double-glazed.  Though, as an aside, I think it's a silly-big window on a north-facing wall!!

So, do you think insulating the one, windowless wall is worth the effort - if that's all I can take on that at this stage in my life's journey?

Cheers, Vicky

FreeBear

gutovicky said: I feel I can insulate the windowless wall MYSELF (DIY) - in the way we've explored in this conversation.
That would give me a whole wall against which I could put furniture or shelving - something I can't do now.
To try to insulate the window-wall is a step-too-far for me, because I'd have to reposition a big radiator.
To get a tradesperson in to do the work may be too costly for me (though I have not researched this....).
One of the reasons that I was aiming to finish off my insulated bedroom wall WITH TIMBER SHEETING, was to avoid the expense of having a plasterer in.

OK. Having a radiator under the window does complicate things - The (small) bedroom I insulated had a ruddy great radiator running under the window. It was a real old one from the 1970s, and gave me great delight in ripping it out. It was replaced by a tiny little Type 21 on an internal wall and keeps the room nice & warm. Plumbing isn't something that everyone can do, and if you have a modern pressurised system, that complicated matters. It might be worth asking a plumber (or heating engineer) to give you a quote for relocating the radiator.

Insulating just one wall will cut the overall heat loss in the room, so yes, do that wall if you can. Using wood paneling means you can come back at a later date to do the other wall and only need to remove a single strip of timber in the corner.

gutovicky

FreeBear, thank you for taking the time to pass on your knowledge and experience - really useful & reassuring..

I'm interested in your comments about moving a rad and replacing with a much smaller, efficient version - if/when I ever go down the 'insulating both external walls' route....   
No, my CH system isn't a pressurised system [It's open-vented with a hot-water tank and 2x water tanks in the loft].  So I've taken on board your suggestion that moving the rad would be quite straightforward (at least for a plumber!).

In the meantime, you've reassured me that I WON'T BE DOING SOMETHING COMPLETELY BONKERS by insulating that one windowless wall...   
and I'll have the option to bite-the-bullet and extend insulation round the corner & across the window-wall at a later date.

So thank you FreeBear  

FreeBear

gutovicky said: and I'll have the option to bite-the-bullet and extend insulation round the corner & across the window-wall at a later date.

When (if) you do the remaining wall, also worth insulating the reveals..

Work in progress... New window (80mm profile), 50mm Celotex under the sill, 25mm up the sides. Once the sill & wood trim is fitted, about 25mm of the frame will be exposed. Wall will get a similar treatment to post #2.