Internal Wall Insulation

[Rudie]

I think i'll have to take off the existing plasterboard and replace with insulated option. cant afford to lose internal floor space...

 

[chestercity]

I have just done what you have highlighted because we have bought a bungalow in an amazing position on a hill. As a result of hillside we have a suspended floor on concrete block and this is vented. There are two walls and the cavity has been filled but I read somewhere that this can cause an issue and produce condensation internally.
Even the internal walls of block are very cold so I have just internally rectified a bedroom by using cellotex (25mm), batten (25x40) and jointed. Has worked extremely well and it has become a much warmer room. I also did the same with a corridor that is v wide and leads to another back bedroom which faces north and is freezing. I can assure you this works well. If you need photos I can add here.
I am also going to externally add 100mm insulation and clad or render later on. (Wish to change the exterior look to add value, as well as make it warmer)
I do have an issue with concrete block as unlike brick (not concrete ones), it doesn't retain any heat and cold transmits through it with ease. My view is the suspended floor and cold void under the house affects the internal walls because they extend beneath the floor into the void.
What I have done works really well and I don't notice any shrinkage of the room visually. With p/board and cellotex you are talking about 25+12mm which isn't noticeable.

 

[Rudie]

Thanks for the info. Did you have any airbricks above floorboard level or is it just me?!
As described above i plan to use the dot dab method using either 40mm or 50mm insulation as id rather go high than find out its only slightly warmer.
Pictures would be great too if you can upload.

 

[Gerrydelasel]

You should also consider how much money you want to spend, because it is all too easy to throw good money after bad.
Think about it. You could easily end up spending £300 on stripping, super-insulating, and redecorating the room; but how much heating might that have paid for? My guess is you could have the heating on twice as much during the coldest months (when it matters). So for the same price as all this work, the entire house could in fact be warmer. By the time another winter comes along, you could probably afford it again, right? Not effort required either. Just a thought.

 

[Rudie]

I assume you have only insulated internal outside facing walls? And not internal to internal wall? (if that makes sense)

 

[chestercity]

To answer your earlier question about air bricks-no none in the room itself. All under floor to aid circulation. However I block some in winter. (I am also insulating below floor as cold underneath-tedious job)
I guarantee that 25mm will do the job. I am only paying about £6 a sheet (1200x2.4) from Travis Perkins. 40mm will not give you any discernable difference, whatever documentaion may say. The effect in my room and corridor is astounding.
The comment someone made about just using more heat is nonsense really. The heating fights against the walls which always remain cold and can condensate..
The bedroom was awful before. Now walls are not cold. Effect is dramatic. Buy the 12mm plasterboard with feathered edge so you can joint it and fill. If you haven't done this before I can advise so you get a great finish. No need to plaster whatsoever.

 

[Rudie]

Thanks Chestercity.
Havent considered insulating under the floor yet but that might be the next task.
Can you let me know which items you used as I have a TP close to me. I'll quote it up and try and get it done over summer.

 

[chestercity]

Whoops forgot photos so here they are. Some things to not-sockets and lights have to accounted for. Not hard to sort out so long as you have enough spare wiring to pull through. I just did. I fitted plaster board boxes. The other thing is skirting board will be covered. I am replacing mine anyway-may use some left over sweet chestnut cladding (see image) I strongly advise you not to go to 40mm, just 25mm. I didn't do the window side because I am changing windows (hoping to make my own-if you know anything about routers, let me know!) Even without changing the window external wall side of the room the effect is, as I said before, dramatic. Any questions, just ask. Email via the board if you wish as I am not automatically being updated to the thread.

 

[Gerrydelasel]

The comment someone made about just using more heat is nonsense really. The heating fights against the walls which always remain cold and can condensate..

 

[chestercity]

Thanks Chestercity.
Havent considered insulating under the floor yet but that might be the next task.
Can you let me know which items you used as I have a TP close to me. I'll quote it up and try and get it done over summer.

Its pretty easy. Just measure length of walls and how many sheets of Cellotex you require, together with p/board.
I used a jointing plaster-approx £15 from memory. Scrim tape (self adhesive to run down joints)
Wood-I used treated 25x40mm.
Work from corner out and place verticals (only needed) at 600 mm intervals.
This means the first sheet of plasterboard (1200mm) fixes to second batten
Plasterboard screws
Boxes for switches ( i upgraded mine from singles to doubles)
Use spirit level
If walls aren't square you may need to trim bit of board away but you can fill later. Get first sheet to sit square then next one is easy
If you haven't jointed ask me. (Have now done a few times now and can get it perfect)
4-5 working days should see it done comfortably
Ask if in doubt

 

[Rudie]

I know roughly how many boards I need just need to work out price after deciding on thickness. Any extra I will use in loft. I will dot and dab too and not use timber.

 

[Rudie]

http://www.travisperkins.co.uk/Celotex-Insulation-Board-XR4200-200mm-x-2400mm-x-1200mm/p/778055

Is that the one?

 

[chestercity]

No, that is 20mm. However if you are gluing it directly to wall it could be OK. I believe the glue is pretty costly, but may be wrong. If you stick directly to the wall how do you support it initially and until it goes off? They are large sheets of P/board.
Here is 25mm one:
http://www.travisperkins.co.uk/Celotex-Insulation-Board-25mm-x-1200mm-x-2400mm/p/778035

 

[Rudie]

Good question. I may have to use the odd screw to hold them in place then skim over each hole.
I'll have to get a price on your board as £6 each is a great deal.

 

[chestercity]

Not directly related but in some ways may be relevant to you. I attach a photo showing condensation in room I have done on the windows. The windows although double glazed units are very old and inefficient units. I attach 25mm cellotex on them overnight and all the cold air is locked in, so to speak, between the cellotex and the window. It runs down the window. There is none on the warmer cellotex. I am trying to get advice on the forum re making windows. I can make basic ones OK and can buy sealed units at trade and they are efficient and v cheap. I will literally save thousands if I make them all myself. Know a joiner for advice? Only one thing I need to know...