insulating above stairs cupboard

[Steve]

Now then, I have a cupboard in the front bedroom above the stairwell, about 1200mm x 1200mm. It used to contain the boiler, an old one so it kept quite toasty in there in winter. The boiler is gone now . . .

It constantly suffers damp in winter - when you open the door, a blast of cold air hits you. The external walls are solid, no insulation, and this cupboard is on the corner of the house so has 2 external walls. I can already see some mould spores growing in there - I washed off all the mould from last year in the spring. It is definitely condensation, the roof was "refurbished" in Feb this year and given a clean bill of health.

The door into the cupboard is basically a pair of old wardrobe doors fixed to a wooden frame and the frame is faced with the wardrobe side panels!

The mould will soon become a concern when our bundle of joy arrives next year.

I want to know if I can - and should - insulate this little cupboard. I want to build a framework against the external walls to accommodate 50mm of insulation between/behind the studs, then face the studs with 18mm ply so I can install shelves galore in there. Would this be enough insulation? Would it work and stop the condensation and make the cupboard a bit warmer? And would I need any ventilation or space behind the insulation?

If money were not a concern I would have external insulation right around the house, but unfortunately it is too expensive and green deal is not for us - we dont plan to stay here longer than 5 more years.

 

[Blagard]

I would get some vertical studding to the external walls (as deep as possible) , positioned to suit future wall fixings. Fill with insulation, then a vapour barrier and finally a board finish of whatever you fancy but 18mm ply seems a bit OTT as you can use the studs for shelf supports. A vent top and bottom at the front would be a good idea and shelves not all the way to the back wall to allow circulation. Don't forget to put loads of loft insulation in the roof over that spot.

Note no space in the insulation but you would need the vapour barrier

 

[Steve]

So the vapour barrier goes on the internal side of the insulation and studs?

What form should the ventilation take? And what will it achieve?

The roof is raked along the front wall of the house, so one wall here has no insulation above it, the other wall being a gable end so will go right up the the ceiling. The loft otherwise has plenty (300-400mm) of insulation (so much that the roofers had to install vent tiles because I'd bunged up the eaves and the felt was old bitumen type felt that cant breathe). The insulation only cost me £4 a roll too, £20 for the whole loft! I think energy firms were subsidising it at the time.

 

[Blagard]

So the vapour barrier goes on the internal side of the insulation and studs?

Yes

What form should the ventilation take? And what will it achieve?

grills to allow your room air to circulate in the cupboard

The roof is raked along the front wall of the house, so one wall here has no insulation above it, the other wall being a gable end so will go right up the ceiling.

I think you may mean you have a small sloping section of ceiling with no insulation in it. - This is really needing attention. On my own I ripped down the old plasterboard, installed plastic vent channels to the underside of the felt to maintain a flow of air. fitted high performance insulation into the rest of the space before reboarding and skimming (Oh yes I installed a vapour barrier there to!)

 

[Steve]

What form should the ventilation take? And what will it achieve?

grills to allow your room air to circulate in the cupboard

OK, I thought you were referring to ventilation within the insulated walls- just to clarify, no ventilation is required within the insulated walls?

The roof is raked along the front wall of the house, so one wall here has no insulation above it, the other wall being a gable end so will go right up the ceiling.

I think you may mean you have a small sloping section of ceiling with no insulation in it. - This is really needing attention. On my own I ripped down the old plasterboard, installed plastic vent channels to the underside of the felt to maintain a flow of air. fitted high performance insulation into the rest of the space before reboarding and skimming (Oh yes I installed a vapour barrier there to!)

I'm not going to be going that far - we have just about got the house looking nice and don't want to get the plasterer back in, at the moment there is no issue with condensation on the raked ceiling except in the bathroom (and I have taken steps recently to improve that including fitting an extractor and opening the window everytime we shower to get good airflow through the room). Also the raked ceiling is artexed with the ceiling - it would be hard to get this right again, and it is lath and plaster overboarded with plasterboard - very, very messy to muck about with.

 

[Steve]

All being well I will start this on friday this week. On my shopping list is

3x2 CLS or similar,
polystyrene or thin fibre insulation,
long fixings for the 3x2 to the wall (I'll countersink halfway through the 3x2),
12-15mm plywood (which will be painted white),
new blade for the FIL's circular saw to cut the above,
caulk/filler for the joins in the plywood,
vapour barrier (hope B&Q sells this),
fixings for the plywood into the 3x2
2 air vents for the doors
jigsaw blade for air vents.
white emulsion!

Worth pointing out that I'm no good with plasterboard, we don't get on! And with the room being purely functional (storage), plywood will suit it just fine - easy to paint, fix to and practical!

Anything else I might need, let me know! Cheers.