Garage wall insulation

[Hugo]

I have a detached bungalow with an attached garage.
Now the two rooms that abut the garage are of a single brick purling construction, I found this out when I drilled through into the garage when fitting an electrical socket.
I would like to insulate this wall inside the garage, so the advise I need is, what is the best thing to use and do I need to put some form of vapour barrier in place.  I use the garage as a workshop now so don't put the car in there, in the roof rafters I have in filled with 40mm fibre insulation and the wooden garage doors I have just put 30 mm fibreglass board edged with battens and covered with foil backed bubble wrap.
cheers I await your kindly reply.

[wookey]

Just to be sure I have this right - you want to insulate the wall abuting the house, i.e keeping the garage/workshop itself cold and outside the thermal envelope? You might want to insulate the workshop outside wall to some degree as well to make it more comfortable to use.

What U-value are the walls in the rest of the building? Do you propose to significantly increase those in the future? In general you want this wall to be at least as good as the others, including future improvements, although the spec can be lowered a little if the outside wall of the garage is done too.

I'm just doing my garage/workshop and plan to put 100mm PIR insulation up which gives a U-value of just under 0.2 (with no battens) which I think is an acceptable minimum spec. If you did both walls then something like 70mm on both walls could be OK.

Yes you do want a VCL, on the warm side of the insulation, so that's on the brick side on the internal wall, or inside the insulation on the external wall. The foil backing of insulation can provide this but it's not possible to tape the joints on the back surface so I'd put up a polythene sheet first, sealing the edges with orconF or similar non-setting airtightness adhesive.

As you probably want to put shelves up I'd choose something strong for the internal panelling. Various suggestions are given on this thread about this very subject: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=8111&page=1#Item_7

[Hugo]

Thanks for the reply wookey.
I have no idea what the U values are in the house. The garage used to be the hottest room in our house, heat came into it from the loft.
I only wanted to do the wall that abuts two of our bedrooms, they are a single skin ie one brick construction, but I could do the other side as well as that is of single brick construction as well.
I have had all the other walls in filled with Crown White wool insulation and the roof has 50 mm of granules plus 550 mm of Knauff space blanket laid down, the main room we use  has a total of 800mm laid down.
All windows are double glazed, Two front doors, outer one double glazed, kitchen door is a let down, it is wooden and a stable type door, I insulated in the bottom panel and the over boarded it as well, there was an improvement warmth wise doing this.
18 years ago our gas and electric costs were £1200. WE have been told our next years cost will be £ 740.00 if we use the same amount as last year.
So you can see we have made huge gains in our expenditure by insulating insulating and insulating, all thanks to being on this forum.

[wookey]

By 'crown white wool' I assume you mean crown 'supafil' cavity wall insulation:  http://www.knaufinsulation.co.uk/products/supafil_cavity_wall_insulation.aspx

A standard brick+block cavity wall with that stuff in is U=0.49W/m2K

Your impressive 800mm of knauf space blanket in the loft is U=0.05 - well into passivhaus territory (anything under 0.1).

100mm PIR on the garage wall would be 0.18 which is reasonable (I generally reckon on a target of 0.15 in refurb, but anything under 0.2 is pretty good.

The other thing to really work on is airtightness - which is just as important as decent insulation (because once the insulation is at a reasonable level then most of the heat is lost through ventilation).