Quick Insulation question

[L Harding]

If im insulating a single brick structure. Plan to batten out the walls to, for sack of argument, 50mm, put insulation in the gaps, either wool/fiber or king span (if this makes a different to the answer please let me know) and then cover in either plaster board or OSB etc.

Should i use something like 30mm of insulation with an air gap? Ive heard this thrown around that you need one. Should it therefore be against the outside wall or the inside boarding? and do you therefore need vents in the wall/boarding top and bottom?


Thanks

Luke

 

[Anonymous]

Luke

Not really my area, however, i am certain if you are battening out 50mm than you will need 50mm insulation to keep it nice and snug.

Cheers

Mark

 

[L Harding]

yea i agree, 50mm wouldn't really be enough, i was more using those measurements for the example to propose if i need a gap or not


Luke

 

[Digit]

Here we move into Mike Garnham's territory, but I have been reading up on this on the subject of sealed systems.
The argument runs thus, the air gap is to permit the removal of condensation, no condensation negates that requirement, as in double glazing and sprayed foam.
From that, if the wall has a vapour proof barrier, and the plaster board is sealed then the gap can be filled with insulation.

 

[Lons]

Here we move into Mike Garnham's territory, but I have been reading up on this on the subject of sealed systems.
The argument runs thus, the air gap is to permit the removal of condensation, no condensation negates that requirement, as in double glazing and sprayed foam.
From that, if the wall has a vapour proof barrier, and the plaster board is sealed then the gap can be filled with insulation.

Spot on but it depends on the use of the building and how much ventilation present as to how much condensation will occur.

if it's likely then instead of a polythene membrane to the brick side, a breathable membrane or building paper should be used.
You could also use foil backed plasterboard which would help.

Bob

 

[johnf]

I would use 50mm celotex or king span 11mm osb put the insulation against the brickwork (no battens)osb against insulation stagger joints fix with 112mm masonry screws there is no cold bridging the foil on the insulation and the osb are more than adequate for a vapour barrier and its easy to do

 

[Lons]

I would use 50mm celotex or king span 11mm osb put the insulation against the brickwork (no battens)osb against insulation stagger joints fix with 112mm
masonry screws there is no cold bridging the foil on the insulation and the osb are more than adequate for a vapour barrier and its easy to do

this does work John but I saw it go wrong on a wall that was facing West and the water which always penetrates the outer brick leaf, tracked along the screws leaving large multiple wet patches.
Luckily the guy had used 12mm WBP ply so damage was minimal and restricted to mould growth.

same could of course be true with battens though :!:

A couple of coats of waterseal on the bricks sorted it and he re-coates every year.

Bob

 

[BigShot]

L Harding
I draw loft conversions and extensions for a living but I can't actually think of a time I've had to specify for a single brick like yours.

My suggestion would be to call your local council building inspector and have a word. You shouldn't need to give an address if you don't want someone coming knocking. The beauty of calling them is you'll get adivce that should apply to the altitude, exposure and location you're in.

I was chatting to the inspector we're partnered with and mentioned an unrelated job and he said something about insulation followed by a story.

A house just near there had problems with a damp patch on the wall when it rained. Thinking it was a problem with ties or something bridging the cavity they had a look and it was not. When it rained again they put a camera into the wall. A tiny crack in the outside wall was letting the wind in and literally spraying rainwater across the cavuty in large enough quantites to soak through the inner leaf and plaster. Fun stuff.

Anyway - have a word with the local inspector - if they are anything like the fella we work with you'll get all the advice you could possibly want.

That or phone the technical department of Kingspan, Celotex or whatever and ask them what they'd suggest.

"I'm insulating a single leaf brick wall and would like to use your insulation. What would you suggest I use and how would it best be installed?"

 

[jeffinfrance]

your house needs to "breathe". almost all damp problems are associated with trying to lock out (which also locks in) all humidity.

check out the centre for alternative technoligies (cat) they have some great books and loads of info on their site.

 

[Qwibble]

I would use 50mm celotex or king span 11mm osb put the insulation against the brickwork (no battens)osb against insulation stagger joints fix with 112mm masonry screws there is no cold bridging the foil on the insulation and the osb are more than adequate for a vapour barrier and its easy to do

I'm about to insulate my single brick garage wall and Johns solution sounds simple and straight forward. First time I've heard of masonry screws that don't need plugs. Good stuff.

 

[BigShot]

JeffinFrance makes a very good point. Don't try to seal everything completely. You do need ventilation.
Call building control or the technical departments of the products you're considering and take their advice. They generally know what they are talking about.

 

[L Harding]

Thanks guys

All seems to make sense, ill need to judge if the walls leak moisture and amount of other ventilation in the new shop when i get there then.

Thanks

Luke

 

[johnf]

I would use 50mm celotex or king span 11mm osb put the insulation against the brickwork (no battens)osb against insulation stagger joints fix with 112mm masonry screws there is no cold bridging the foil on the insulation and the osb are more than adequate for a vapour barrier and its easy to do

I did this on my workshop 5 years ago I have had no problems to date no damp tracking along screws maybe because the masonry screws are fully threaded and the damp cant work along the threads the osb provides a great wall to fix to this is my experience and I would not hesitate to do it again