Internally insulating external wall

[hammerhorror]

Hey all,

This seems to have been covered a lot, but I seem to be reading myself in circles with different ideas as to how to do the same thing

I am looking to renovate some single brick outbuildings to fit a downstairs WC and laundry room. They are attached to the house, which is otherwise all insulated cavity wall. I am at the point of insulating and was planning on battening, insulating and boarding, but have a few questions if anyone would be kind enough to offer some advice!

First, should I have a vapour barrier between the external bricks and the internal stud battening? What would be recommended as the best insulation to use? (cost is an issue, so am thinking polystyrene - does it require an airgap?) Should there be a further breathable barrier between the timber battening and the plasterboard? Does anyone have any specific product recommendations? It seems the Kingspan Kooltherm plaster and dab boards always get a good rating, but have already purchased all the battening, and can't ideally afford it

Any help appreciated!

 

[vbpupil]

I have just finished battening and boarding out my down stairs spare bedroom approx 3m X 2m. I bought my batten from wickes came in bundles of 8 and was real cheap, I then filled the gaps with polystyrene and covered this with a plastic membrane and then boarded over the top. I cant comment on how good the insulation is as its just too hot at the moment to tell.

The room itself has a portion of it which is single skin and had a history of damp, hence my reason for the polystyrene and membrane.

When choosing a batten make sure you get some which is just a little thicker than the board you will be using (ie kingspan thermal boards or polystyrene), i read a guide and they suggested getting the same thickness as the board and my plasterboard would not screw to the wall (polystyrene sheets are not forgiving at all), and you have to allow for your walls to be a little uneven.

I used:
Polystyrene - £4 per sheet (2400mm x 600mm x 25mm)
Batten - £10.75 per pack (Pack of 8 - 25mm x 38mm x 2.4m)
Membrane - £27.99 (4m x 12.5m)

hope it helps.

 

[noseall]

for a single skin building i would be thinking about building an internal frame or stud wall away from the brickwork and insulating the gap as well as between the studs.

any improvements you make will be of some benefit, it is just that you may not notice them unless you beef it up properly.

for instance, in periods of extremely cold weather you may still get condensation forming with mildew as a by-product. particularly secluded areas behind cupboards or wardrobes for instance.

it will depend upon how much you value your space over comfort.

 

[kitessurfer]

From a diyer;
build stud wall internally away from brick and insulate (I'm not sure if you would stuff insulation in the whole gap or perhaps better just in the depth ofthe new stud wall?).Search the web, I think kingspan are good for insulation, and insulation backed plasterboard, there's some good stuff on the market.
ks