Insulating Concrete Shed

Sarah 1111

Stoner wrote: »

Would you consider external insulation on the shed? You'd keep the height.

We have already replastered (rendered) the outside - one back wall is hard to get at but we are planning to line that with tin sheets - the place will be watertight - just getting conflicting advice on whether we need a breathable membrane (basically roofing felt) as well... I am not sure how these things work but if its breathable - i.e. allowing any moisture to get out through it - and the concrete block wall behind has been sealed by being rendered - then what's the point?
Would a dehumidifer and ventilation be better?
Proper external insulation is unfortunately beyond the budget I think.

Calahonda52

roofing felt, as generally understood, is not breathable.

You need to distinguish between moisture vapour and moisture: they are not the same.
.
Breathable relates to the vapour passing through it.
Render is not water tight in an absolute sense
You could consider a small MHVR unit which would allow you run the temp high enough to reduce the risk of condensation, or fit a cooling coil to the intake.
It really depends on the economic value of the stuff being stored.
If there is a lot of in and out then maybe a small draught lobby inside the entry door would make sense

Lumen

Calahonda52 wrote: »

You could consider a small MHVR unit which would allow you run the temp high enough to reduce the risk of condensation, or fit a cooling coil to the intake.

That's an interesting idea.

I wonder what the efficiency/effectiveness of MHVR vs dessicant dehumidifier (with no ventilation) is?

I guess it depends on the air tightness. With poor airtightness you're going to be dehumidifying the world.

Calahonda52

Lumen wrote: »

That's an interesting idea.

I wonder what the efficiency/effectiveness of MHVR vs dessicant dehumidifier (with no ventilation) is?

I guess it depends on the air tightness. With poor airtightness you're going to be dehumidifying the world.

vent axis had a small one which I used for two bathrooms in a previous house: it just came on when the showers were in use, I had a 15 minute boost button on it for more odourful tasks:D

MalDoc

Hi,

Sorry to resurrect an old thread.

Also looking to insulate a concrete panel shed.

Will be used mainly as a gym but potentially as an office also down the line.

@68 lost souls it sounds like I've very similar to yourself.

Concrete slabs with a pebble dash on the exterior but a pent style roof instead of an apex.

What I'm thinking is to put up 2" x 1" battens also and then PIR between and also on the roof.

Sheets of ply screwed on to this after.

Reading conflicting advice about a membrane/vapour barrier.

PIR board has foil on both sides and I plan to tape over each joint with aluminium foil also which apparently negates the need for any vapour barrier.....

Sealed the floor already with PVC and will be putting down decent rubber mats.

Don't intend to insulate as even in the recent cold spell it was never that cold to the touch.

What did you decide to after and is there anything you would have done differently now time has passed?

Thanks

10-10-20

If you're going to use it as a gym/office, then you need to think about ventilation in some way - especially if you have foil-backed insulation on the walls all fully taped-up. Questionable in my mind whether you need a VCL there at all, but where would all that moisture end up if it did escape? If it's just going to be sandwiched between the insulation and concrete panels then you'll end up with damp external walls and probable issues with cold spots and maybe mold.

In regard to sealing the floor - do you mean PVA instead of PVC? PVA is a water soluble glue and isn't a sealer. Don't consider it sealed if it's just coated in PVA.

68 lost souls

https://www.boards.ie/discussion/comment/120058964#Comment_120058964

Hey,

I did 50mm thermal board on 3 walls - https://www.goodwins.ie/products/xtratherm-insulated-plasterboard-50mm-8x4-ft.html

On the 4th wall I did 2x2 battens and insulated in between and then plasterboard over so I have wood battens to secure a shelving rack system to.

The roof I put insulation between the rafters and plasterboard over.

The floor I sealed with Chlorinated rubber paint and have some rubber mats on.

Since Covid hit I have ended up working in here most days which had been unexpected and I have a little heater and a dehumidifier in here which is setup to turn on if the humidity gets too high or it gets below 5 degrees.

I think if I had insulated the slab in the first place it would have been a wiser choice given how much time I spend in here now but too late to go back on that. Even just the rubber floor makes a big difference. I didnt worry too much about vapour barriers because I was concerned of in the end trapping moisture and creating mould as s result. It doesnt take long at all to heat up and even if I dont have the heater or dehumudifier on it doesnt get too cold really compared to outside.

Ply would have maybe given me more poitns to anchor too but for my use the plasterboard is fine and looks brighter when I am working in here, was also cheaper. I didn't bother skimming it just taped and skimmed the joints. I siliconed around the bottom where the floor meets the plasterboard.

Ive been tempted to put some of that foil sheet down on the floor under the rubber to see if it makes it even better but the rubber floor tiles did make a big difference cs before I had them down.

MalDoc

https://www.boards.ie/discussion/comment/120059368#Comment_120059368

Hi, sorry I meant PVA. Used a 4:1 water to PVA mix. Sealed might be the wrong word. It was just to keep the dust down more than anything.

Considering I'll be putting rubber tiles on top, do you think there is a need to apply something else also?

I'll be leaving 50-60mm between the roof and back of the insulation boards. The roof itself does have a vapour barrier.

The concrete panels have a cavity on the inside of the shed so would imagine there would be a good bit of airflow even with insulation covering.

It wouldn't be airtight as is either.

Should I be looking to add a vent through the insulation too?

Thanks

MalDoc

https://www.boards.ie/discussion/comment/120059415#Comment_120059415

Thanks for getting back to me so quickly.

I had considered plasterboard alright but thought it might be that bit more difficult to work with.

How did you secure that to the walls without battens?

Would definitely look a lot better than plywood if it's to be used as an office.

Might do plasterboard at either end and ply down the sides.

The pent roof is going to make things awkward so will probably just use 12mm ply there after insulating.

After I started reading up on it I was kicking myself for not considering insulating the slab too but if you got through the last few weeks it sounds more than adequate.

10-10-20

https://www.boards.ie/discussion/comment/120060115#Comment_120060115

Is there a damp proof membrane in the slab at all? With mine I poured a screed over visqueen so that there was no damp coming off the slab directly into the flooring. If you don't have a DPM in the slab then you might need to address that somehow.

MalDoc

https://www.boards.ie/discussion/comment/120060382#Comment_120060382

There is a damp proof membrane in the slab. It's down around 2 months now and dry.

There was a good bit of dust coming off it even when cleaning before I applied the PVA.

10-10-20

ok, good. I'd consider a small vent as it sounds like it could be relatively air-tight (as you can make it with foil insulation and tape. Close it off when you're heating it and open it outside of heating times.

68 lost souls

https://www.boards.ie/discussion/comment/120060219#Comment_120060219

I had an sds drill and used it to drill holes through the plasterboard and into the concrete and used mushroom fittings that hammered in. I believe I also used an expanding adhesive too.

i actually put one batton along the wall with a window that was used also to secure a worktop top.

Here is the before and after

MalDoc

Thanks, looks a decent job!