(Internally) Insulating External Walls

GreeBo

Hey all,

I have two bedrooms to redecorate and wanted to improve the insulation while I am at it. (Rooms need to be reskimmed/slabbed anyway)

House is about 18 years old, 9" cavity block with 2x1 battens, plastic vapour barrier and then 12mm plasterboard. There is fibreglass between each batten.

So, I am not adverse to ripping all this off and starting again if its a better job but Im just not sure what will give the best result.

Ive spoken to one "builder" and he said it would be better to take it all off inc battens and stick insulated plasterboard directly to the wall. This would take up less space and also reduce thermal bridging (no battens).

My concerns with this are
a) no battens to fix to
b) have to chase any wiring
c) moisture from blocks

The other option is to remove existing plasterboard, vapour barrier and fbreglass. Add new (better?) insulation and board over with plain plasterboard. Whats the best insulation to use for this, solid or a fibre based one?

Any other options Im missing?

Cheers lads.

RKQ

IMO 25mm thick fibre glass isn't great ( better than nothing)
If you really want the expense of new slabs and skim then consider 50mm kingspan over 25 x 25mm battens to maintan an air cavity from the soild wall.
Use 50mm thick kingspan bonded to plaster slab.

Screw into battens for shelves / curtain pole etc.

northdublin

on my exterior walls i used insulated platerboard fixed directly to the walls using 90mm mushroom fixings. you drill an 8mm hole trough the insulated slab and into the block. you then hammer the fixing trough and it pulls the slab tight to the wall. ive done this on every exterior wall and have had no problems. the insulated slabs are usually foil backed which i think helps with moisture and heat loss.

GreeBo

cheers lads.
I've had a few builders out, each of them with a different idea on the best way to do it.
- kingspan betwwen the existing battens, 12.5 slab over
- 50mm insulated directly onto wall
- 25mm slabbed over existing slabs

clear as mud.:o

RKQ

Its really up to you, as its refurbishment. Cost and speed will be the deciding factor.

50mm to 70mm insulation bonded to slab and fixed to blockwork with plastic mushroom type fixings would give maximum insulation and minimum room area shrinkage. Almost diy job (after electrician is finished). Just keep new slabs plumb.

40mm between batten with 30mm bonded to plasterslab fixed over battens would be similar - reusing existing battens which could also help with future shelve support and good for skirting boards etc.

Finish each with new skim coat of plaster and paint.:)

GreeBo

well some quotes have come back
€1500
€4500
€9400

DIY here I come
I do most of the work here anyway, but was hoping for a bit of a break if the price was right.
I was looking for something about €2500, the €1500 quote was from some polish lads, but I got burnt there before so no dice.

Im going to go with 50mm between the battens and then some sort of insulated plasterboard (no more than 30mm total) as you say, this gives me battens if ever needed and the plasterboard should help eliminate cold spots against the battens. I also guess that I wont need a vapour barrier as it will be on the plasterboard anway?

Whats the best insulation to use? "Kingspan"? Is that cut to size or what?

Cheers!

S.L.F

You could do what I did.

Put battens up onto the wall then put low-e insulation like this directly onto the wall then plasterboard over it then plaster.

The beauty with this stuff is it's equivalent to 8" of fiber glass insulation on your walls

I did this at home and it has made a huge difference to the heat levels in the house.

The first night I had it up we'd had to open the windows we were so hot.

The heating is only on half the time now.

S.L.F

I was trying to edit my post but it was taking forever,

If you put a batten on the wall with the low-e insulation in between them and plaster board over it the distance you lose is the width of the batten and plasterboard which is 37mm plus plaster.

I of course used foil backed plaster board.

GreeBo

To be honest Im not too convinced on these products yet. I can see how they might help with radiant heat, but not much else.
Thanks anyway!

murphaph

If your existing slabs are fairly level etc. then I'd strip any wallpaper and slab directly over them with 29mm Gyproc thermal laminate wallboards using the gyproc 'rf' system (cartridge gun applied blobs of adhesive which are just 3mm deep when board is offered up to wall).

I'm going to be renovating an early 80's 9" cavity block built bungalow (no insulation apart from cavity in blocks!) and it's brass monkeys and it will be for letting out so a BER cert is required from January. Thankfully it's well skimmed with few irregularities so I'll be using the above system to bond 38mm insulated board to the inside of the exterior walls directly. Using this measured cartridge gun technique (1 squeeze of the trigger per blob) seems much easier to me than trowel applying bonding compound and leveling each board to the next and so on.

When one reads the proper way of applying such dry lining boards and then one's brother (tradesman) tells one "nobody does it like that on site" one realises why irish houses are such utter draughty rubbish.

RKQ

GreeBo wrote: »

Whats the best insulation to use? "Kingspan"? Is that cut to size or what?

Kingspan , Xtrathemp etc all are very similar. Check u-value on the board as you compare prices.

Thickness is very important when it comes to high density foil backed insulation - as it has an IAB Certificate it'll do exactly what its says on the tin - great stuff that really works.

Boards can be bought in standard widths for drylining or (cheaper) buy 2400 x 1200mm sheets then cut to size with circular saw - very fast with perfect edge!

GreeBo

murphaph wrote: »

If your existing slabs are fairly level etc. then I'd strip any wallpaper and slab directly over them with 29mm Gyproc thermal laminate wallboards using the gyproc 'rf' system (cartridge gun applied blobs of adhesive which are just 3mm deep when board is offered up to wall).

The walls were papered directly onto bare slabs so trying to remove the paper takes longer than just reslabbing!

murphaph wrote: »

When one reads the proper way of applying such dry lining boards and then one's brother (tradesman) tells one "nobody does it like that on site" one realises why irish houses are such utter draughty rubbish.

I have found that a lot of the "builders" you get now dont have a clue about the more technological areas of building. i.e. you cant just fire up the board and then its job done, lost of these things, especially insulation, dont perform even nearly properly if they are not installed exactly as per the design. But unless you are actually watching them put it in you will never know. Maybe this new push to get all work signed off and certified will make a difference...maybe.

GreeBo

RKQ wrote: »

Kingspan , Xtrathemp etc all are very similar. Check u-value on the board as you compare prices.

Thickness is very important when it comes to high density foil backed insulation - as it has an IAB Certificate it'll do exactly what its says on the tin - great stuff that really works.

Boards can be bought in standard widths for drylining or (cheaper) buy 2400 x 1200mm sheets then cut to size with circular saw - very fast with perfect edge!

Cheers, question though, I cant seem to find "standalone" insulation on either kingspan or extrathem websites. Its all either already bonded to the plasterboard or seems to be designed for between cavities... Can you point me in the right direction please?
/edit or is the cavity stuff the same stuff I can/should use?

Also, any recommendations offhand for a supplier in Dublin?

thenightrider

Hi im just wondering if you stick up the insulated kingspan plaster boards do you have to put a skim of plaster over them or can you just paint them and leave them as is just put a skim of plaster were two boards join ?

GreeBo

You basically treat them the same way as standalone plasterboard. I Would always skim (or rather get someone to skim!) as you get a better finish in the long run I believe.

murphaph

GreeBo wrote: »

The walls were papered directly onto bare slabs so trying to remove the paper takes longer than just reslabbing!

If it isn't textured/embossed wallpaper I'd say you'd be alright just stripping the bits where you need to apply adhesive to slab over. I'd be reluctant to rip it back to the battens/wall as you have a nice level base to start from in your existing slabs.

GreeBo

murphaph wrote: »

If it isn't textured/embossed wallpaper I'd say you'd be alright just stripping the bits where you need to apply adhesive to slab over. I'd be reluctant to rip it back to the battens/wall as you have a nice level base to start from in your existing slabs.

I should have said that 2 of the 3 external walls are already part stripped due to a leak around two windows so its not too much of a biggie.
Also the battens are 50mm so I dont want to waste that space by slabbing over, I want to fill that and then slab with a thinly insulated board.
I just dont know exactly what I need to insulate between the battens

GreeBo

Ok, Ive stripped back the plasterboard and vapour barrier and insulation on one of the external walls. The insulation (fibreglass) is filthy and looks as if there is a breeze blowing around in there.
Can/should I seal these blocks with something before I start insulating/reslabbing them?
Do they need to be parged or is there something that I can paint on to seal them? I know you can get concrete sealant but I thought thats usually for external use and Im somewhat worried about causing damp issues in the cavity.

cheers!

murphaph

I am sure there are many suitable rigid materials you can use for between the battens but I personally wouldn't paint/seal the bare blockwork with anything. I presume there's no damp and the blocks are dry?

GreeBo

I'll be using a rigid insulation between the battens but the block wall itself is very drafty, obviously missing pointing somewhere along the way. The existing fibreglass is literally black in places from this air leak. I want to plug this up before I install the new battens/fibreglass/board.

I guess a half inch or so parge is the way to go. Will there be any issues with fixing the battens to this? I was hoping to use a no more nails type of fixing rather than nail/screw each batten (have about 12m to do)

bigstar

just repoint with sand/cement. dont use no more nail to fix battens, thats just asking for trouble

RKQ

GreeBo wrote: »

I guess a half inch or so parge is the way to go. Will there be any issues with fixing the battens to this? I was hoping to use a no more nails type of fixing rather than nail/screw each batten (have about 12m to do)

What do you mean by parge?
I wouldn't use anything on the walls other than sand / cement mortar to point up holes. A vapour over the insulation will stop all draughts entering the room.
I won't depend on any glue to hold a wall in place. Screws are quick, easy and strong.

GreeBo

RKQ wrote: »

What do you mean by parge?
I wouldn't use anything on the walls other than sand / cement mortar to point up holes. A vapour over the insulation will stop all draughts entering the room.
I won't depend on any glue to hold a wall in place. Screws are quick, easy and strong.

Parge as in sand/cement mix (or just plaster) spread out over the wall to seal up and gaps. I guess its the same effect as individually pointing holes, but the walls are so bad I think It might be quicker to just do the whole thing, also adds thermal mass

Well I was debating on relying on the vapour barrier on the back of the plasterboard rather than add a separate one, but I think surely its better to not have a breeze blowing around the insulation? Wont that somewhat defeat its purpose?

RE: No More Nails
I was hoping you wouldnt say that as I didnt really think it would be good enough, but the suppliers do.
I'd rather screw than nail, but thats just me and nailing.

RKQ

GreeBo wrote: »

Parge as in sand/cement mix (or just plaster) spread out over the wall to seal up and gaps. I guess its the same effect as individually pointing holes, but the walls are so bad I think It might be quicker to just do the whole thing, also adds thermal mass

I learned something new today -cheers - never heard it called Parge before. Using it on your walls sounds like a good idea.
I prefer a good screw myself!

GreeBo

RKQ wrote: »

I learned something new today -cheers - never heard it called Parge before. Using it on your walls sounds like a good idea.
I prefer a good screw myself!

Its supposed to be very good on party walls for acoustic insulation as it blocks up all the little gaps in the blockwork that help the sound to travel through. Gypsum make a plaster specifically for this.

Im gonna give it a go, the pointing on the walls is so bad that even if I make an arse of it, the wall will still be flatter than it is now so it wont affect the battens

I also discovered that two of the purlins(?) coming down from the joists in the attic are just hanging freely against the wall. Another quality construction :rolleyes:

neilthefunkeone

murphaph wrote: »

If your existing slabs are fairly level etc. then I'd strip any wallpaper and slab directly over them with 29mm Gyproc thermal laminate wallboards using the gyproc 'rf' system (cartridge gun applied blobs of adhesive which are just 3mm deep when board is offered up to wall).

Brilliant this is the answer to the question i didnt need to ask..

Girlfriend just got a new house.. needs some insulation.. Stripped the wallpaper and its all skimmed nicely so was hoping to just put new insulating boards straight onto this!! 25mm prob.. Exterior walls only.. Skim it and paint it..

Anyone other opinions on this.. YAY or NAY??