Insulation for single skin wall - pros/cons

[lordgoata]

After a little advice, I have a single skinned utility room off the back of our kitchen. The roof is twinwall poly sheet, and it looks like its been there a long time (we only moved in just over a year ago).

The room suffered from bad condensation during our first winter (warm air in the kitchen contacting the cold surfaces of the twinwall ceiling - see I have done some research!).

As we can't afford to rebuild it at the moment, I wanted to try and fix it up and make it a little better for this winter.

I have done some reading and seem to have 2 choices:

1. Foam backed plaster board (Gyproc Thermaline Super) D&D onto the brick direct.

2. Foilbacked plasterboard fixed to batterns, with celotex between the batterns.

I believe that was what I concluded anyway (there was a lot of varied advise on here!).

What would be the pros and cons of both methods, or is there another/better way that I have overlooked ?

I realise that warming the room will be futile if the ceiling is still exposed, so was thinking about plasterboarding inside, with some insulation on top of the plasterboard, then an airgap, then the twinwall.

I know I am bound to get shot down in flames and told to just rebuild it, but we honesly can't afford it, where as it looked like I could do the above for £400-600, which is about my budget at the moment.

Oh and I have brought a dehumidifier now too

Any advice welcome.

 

[lordgoata]

Actually ignore this, i just found another post which is almost the same as what I am asking (I have no idea how the hell I missed it before)

//www.diynot.com/forums/viewtopic.php?t=166351

 

[alittlerespect]

Humm! I have read the attachment and as you say, it is almost the same, but not exactly identical.

Your not far off the mark with some of your comments, but I would suggest that you create an air gap between the wall lining material and the external wall, as you are likely to get penetrating damp occurring from time to time with a single skin of brickwork. To resolve the problem stick pads of bitumen impregnated fibreboard (25mm thick) to the external wall (pads say 100mm x 150mm @ 600mm centres horizontally x 1200mm centres vertically) and then stick the British Gypsum Thermaline Super 80 (will do the job) to the pads, you will also need to introduce an air brick or two to the external wall in order that the cavity (even though only 25mm) can breathe and any pentrating rainwater can eventually evaporate. Interstitial condensation should not be a problem as PIR board as well as being a thermal insulator is also vapour resistant. You could also use the same board to clad the underside of the twin wall polycarbonate (assuming that you have a timber frame to fix too- if not you will have to introduce one!)

One comment order of work is reverse - upgrade ceiling then dress the wall cladding to the ceiling.

You will need to provide some heating to the utility room as warm air holds more moisture than cold air - even worse is the moisture laden warm air from the kitchen, to combat this you should introduce an extract fan at high level which has built-in humidistat control.

This work should easily be achieved within the budget that you have in mind and will give many years of satisfactory performance.


Regards

 

[lordgoata]

Thanks for your thoughts and inputs - sounds like the best solution!

I have a couple of questions though (specific to your suggestions, and in general):

1. Any suggestion where I can get the bitumen impregnated fibreboard ? I did a search for it on google and it mainly seems to through up 18mm Hutton Sarket boards.

2. Bit more general this one, never even occoured to me before - how do I run any electrical socket cables ? I assume it shouldn't go in the cavity gap, should it be channeled into the insulation (running through conduit) ? I assume not, as it would reduce the thickness and therefore the effectiveness, but then I am at a loss as to the solution

I do have a timber frame for the roof, so that sounds like an ideal solution - and the humidity controlled extract fan is a great idea, thank you!

Appreciate the help,
Best Regards,
Dave