Insulating a single skin brick room

[TK46]

Hi there, I'm looking to insulate my single skin brick room with 50mm insulation board.

I builder came around recently and told me that I could dot and dab Insulation board to the brick walls. He assured me damp penetration would not be an issue.

Initially I intended to batten out the wall and and then affix the insulation board but he advised against it. According to him, the air pocket between the battens and board would CREATE dampness. He said I would need to fit vents into the insulation board to allow for air circulation.

I'm concerned that if I dot and dab the insulation boards to the walls when it rains damp will travel through the single skin brickwork and bridge across the insulation board.

What do you fine people recommend?

(I'm looking for the cheapest, simplest approach.

 

[AronSearle]

Damp penetration is just that, adding insulation will not create damp penetration, it will just mean less heat loss through the wall which can drive out moisture. 50mm generally doesn't pose a risk, as it still allows some heat to escape, and providing you are not on top of a hill in strong weather conditions, or the brickwork and seals around windows are not poor, you will be fine. Look up English heritage who do a guide on this subject.

Not sure what he is on about with the air pocket creating dampness.

 

[TK46]

Not sure what he is on about with the air pocket creating dampness.

I think he meant the dampness caused by human habitation would pass through the boards and trap between them and the wall resulting in mold and such.

 

[AronSearle]

Yea, but what has that got to do with the airspace.

You should install a VCL on the warm side, or vapour backed plasterboard, otherwise internal moisture could cause condensation.

The 50m airspace doesn't make this worse or better that I can see.

 

[noseall]

What you need to do is separate the outer brick skin from the inner surfaces. This is why we have been building with cavities for decades.

The best solution would be to build a stud or block skin internally complete with an insulated gap or cavity

The problem with single skin structures (as well as insulation) is preventing wind driven rain saturation from causing problems internally.

You also need to get the floor detail right especially the abutment detail and how to account for seepage and cold bridging etc.

 

[freddiemercurystwin]

I've been specifying this set up for garage conversions for yonks, to my knowledge it has not failed (yet ) . Though I did have one inspector who insisted on waterproof fixings into the masonry rather than ordinary plug + screws.

Untitled

• freddiemercurystwin
• 23 May 2012
• 4

If it was an exposed brick wall that had poor pointing I would maybe reconsider.

 

[TK46]

The thing is, the room is already quite small and I don't want to lose too much space.

I have some Tanking Slurry left over from a previous job. How about I paint the interior walls with it then dot and dab my 50mm insulation boards?

There would be no air gap or cavity I know, but where could the moisture go?

 

[jeds]

The simplest solution is to direct fix thermal laminate to the wall. Battens and air spaces are unnecessary and are more likely to create condensation than no cavity at all. Personally I always specify mechanical fixing but you could dot and dab - just make sure you purchase the correct grade. Moisture isn't an issue because phenolic foam is closed cell so nothing can get through it. The boards also include a vapour layer.

 

[TK46]

The simplest solution is to direct fix thermal laminate to the wall. Battens and air spaces are unnecessary and are more likely to create condensation than no cavity at all. Personally I always specify mechanical fixing but you could dot and dab - just make sure you purchase the correct grade. Moisture isn't an issue because phenolic foam is closed cell so nothing can get through it. The boards also include a vapour layer.

Yes, this is what the builder was talking about. He said to fit vents in the insulation board on each internal wall, one bottom left, one top right to prevent condensation between the boards and fixing compound even though its only likely to be about 10-15mm.

 

[AronSearle]

Sigh

As I said, English heritage have a guide on this http://www.english-heritage.org.uk/...g-solid-walls/eehb-insulating-solid-walls.pdf

Has everything you need.

Page 16, chapter 4, insulation solid walls.

No need to re-invent the wheel here.

 

[TK46]

Doesn't insulation board have a vapour control layer included? Doesn't it by its very nature preclude moisture transference?

 

[jeds]

Doesn't insulation board have a vapour control layer included?

The boards also include a vapour layer.

 

[TK46]

Has anyone heard of eco-quilt?

 

[freddiemercurystwin]

Yes,, it would appear that you have a load stuffed in your ears.