Shed insulation?

[rkid84]

I'm building a large shed and I'd like some advice.

I have a concrete base which is enclosed in a damp proof membrane.

The shed is wooden and has no windows.

I will use it to store garden equipment but also my exercise bike. I use this regularly. The conditions during exercise are naturally humid.

I am planning to install high and low vents as well as an extractor fan that will periodically kick in to help air flow.

I'll be boarding up the inside of the shed so I can mount/hang things.

My question is whether I should insulate it too? Im thinking yes so I can regulate the temperature better during the year.

My next question is whether I need some kind of vapour barrier or a dpm?

This is all to prevent mould and mildew build up.

Any advice is welcome.

Thanks

 

[morqthana]

Yes, I'd insulate it. Floor & roof too. Yes to a vapour barrier - easiest way is to use foil-backed rigid foam - Kingspan/Celotex type.

So on the outside of the structural frame inwards:

a breathable membrane under the cladding (which you'll have given a few coats of anti-fungal preservative on both sides even if pressure treated, and don't forget end-grain treatment, especially on cuts).

If there's a sheet layer under the membrane on the outside of the frame, treat both sides of that too.

You'll need an air gap, 25mm-ish, between the insulation and the outside face of the shed, so fix battens to the rear of the frame or to the outer sheet.

Insulation boards into the gaps (what's your frame depth & spacing?). Tape the joins.

Interior panelling.

Install any electrical cabling in the air gap (check if the insulation affects the size?) or just surface mount in conduit or trunking.

Roof similar.

Floor - insulation goes between the joists.


HOWEVER....

I'm building a large shed

If you've not started, and not bought the materials yet, have you considered using SIPS as an alternative to all the above faff? The can

The conditions during exercise are naturally humid.

Which is why you'll need a preservative treatment on the inside as well.

I am planning to install high and low vents as well as an extractor fan that will periodically kick in to help air flow.

I'd look into installing an integral (i.e. non-split) through-the-wall AC as well. It will get hot in the summer. Most ACs will also provide heating for the winter.

I'll be boarding up the inside of the shed so I can mount/hang things.

If you'll have expensive garden machinery/exercise gear you could fix a metal grid under the interior cladding to make it difficult for anyone to break/cut through the walls.

Keep track of where the frame members are in case you ever need substantial fittings.

 

[rkid84]

@morqthana

Thank you for your very detailed reply. I have started to look into your suggestions. Can I also ask whether I should still for permanent ventilation to the shed eg high and low vents? I'm conflicted about why I would insulate the shed but then keep open vents.

 

[big-all]

ventilation is essential
best to have far too much say 4 to 6 and on all walls with hit and miss vents or insulation foam plugs to fill unused holes
what sort off heating are you planning as gas or parafin generate masses off moisture

 

[rkid84]

No heating at all. It is a shed doubled up as an exercise room.

 

[big-all]

ok insulation will do no more than slow down heat movement if the average temperature is say plus5 degrees day and night out side it will hover around that lever in the shed and indeed iff it averages say minus 5 day and night it will hover around that level so without heating insulation has reduced value

 

[morqthana]

No heating at all.

You might come to regret that.

As big-all says, insulation keeps heat in (or out), it doesn't create any heat to warm the space. You do it to make it cheaper to heat - reduce the amount wasted. But if you aren't going to heat it, why insulate?

 

[rkid84]

You might come to regret that.

As big-all says, insulation keeps heat in (or out), it doesn't create any heat to warm the space. You do it to make it cheaper to heat - reduce the amount wasted. But if you aren't going to heat it, why insulate?

Well I guess that's why I've come on to this forum to get some advice on. I don't know if I need to insulate it or not.

 

[morqthana]

Well, I'd say you do, because you'll almost certainly end up wanting to heat it.

 

[big-all]

Well, I'd say you do, because you'll almost certainly end up wanting to heat it.

yes i fully agree people in general have little concern for tools welfare
the fact off wanting to insulate suggests use on a weekly or daily basis as time permits

 

[robinbanks]

While I'd use that or a similar wall buildup for a house, I'd do away with the outer membrane and preservatives for a shed and downgrade the insulation if it was for occasional use. From outer to inner I'd have:

Cladding
Battens
Sheathing (OSB)
Studwork with mineral wool insulation
Visqueen
Battens
Plasterboard

Cabling, if any can go in the void formed by the battens behind the plasterboard

Ceiling buildup from outer to inner:

EPDM membrane
OSB
Joists with wool between
Visqueen
Battens
Plasterboard

If there is a possibility you'll end up using it as a garden room or office consider adding a layer of sheet insulation (50mm kingspan) between battens and Visqueen. If you're willing to tape the joints in the kingspan you can do away with the Visqueen

For ventilation a single heat recovering extract fan will be enough for the claimed use. If you need to heat it because it becomes unbearably cold to exercise in a fan heater would be sufficient - one has to remember that most humans would be OK with cycling outside even on a cold winter's day because they generate their own heat. You'll do no different on your exercise bike and will feel warmer sooner as you're not being exposed to the same level of windchill as a moving person would so you likely will get away with no heating. The debate over whether to insulate it at all really comes down to what you'll end up using it for. If spending hours in there hiding from the wife, doing something relatively inactive like fixing the lawnmower then you'll want something that means that hearing the space is actually effective

I don't know if I'd bother to insulate the floor unless I was putting underfloor heating in and planning on it becoming a regularly used space

 

[rkid84]

Thank you for all the responses.

I'm not bothered about the cold. I initially thought to insulate it to help reduce the risk of condensation during the winter months. I don't know if that is right or not. I thought the insulation would reduce the heat transfer to the 'cold' cladding. The extractor fans would then vent the moisture and the hot air outside.

 

[robinbanks]

If the cold doesn't bother you, you can just build the shed like every other shed and have an air-leaky vapour permeable single skin

 

[rkid84]

I also want to board the inside of the shed so I can mount plugs, a TV etc etc. Would that membrane go in between the cladding and the boarding?

 

[robinbanks]

I don't personally think that outer membrane (between cladding and boarding) is necessary on a shed if there is an inner vapur impermeable membrane, though I'd use one on a house. If you do use one, use a breathable one; hit up ebay for part rolls of roofing felt - I think the cheapest at the moment is Cromar's Vent range. If you're only installing one membrane for draft reduction, make it the outer one. Cables etc would go in the void formed by the battens on the inside of the wall in my proposed buildup but if you aren't having any insulation or inner membrane then you can dispense with the batttens too and drill the studs with a spade drill for routing the cables through. If you later decide to insulate between studs, be aware that wrapping wires in insulation reduces the ability of the wires to carry current, so size your cable or circuit breaker according to the current carrying capacity of the cable as installed