shed insulation

[pip1954]

hi i have just done my garage i used 3x2 timber kept just of the outside with 100mm loft insulation (b&Q) the roof is pitched so i did the ceiling with 200mm loft (some can be split into two 100mm pieces)
still got a bit to do but seems to work for warmth and noise the garage is precast concrete .that's the way i would go .
all the best pip

 

[fraser]

Pip, my joists are only 2 x 2", I doubt 200mm insulation squishes down that much does it?
Thanks

 

[fraser]

Blister, what is OSB8? Can't find any info anywhere...

Notes and links so far from thread

INSULATION

Glass fibre loft insulation-will compress and easy to cut. Knauff from B&Q may not squish enough (200mm -→ 50mm??) £3

http://www.diy.com/nav/build/insulation ... m-11127503

or

http://www.diy.com/nav/build/insulation ... m-11127504

Celotex-can't find a dealer that sells it and delivers down here so far
Roc slab/mineral wool slab-needs to be right thickness and doesn’t compress
Normal rockwool £3 for 5m2

http://www.diy.com/nav/build/insulation ... n-11797516

http://www.diy.com/nav/build/insulation ... m-11917543

Encapsulated roll (polystyrene, foil and fibreglass) £10 5.5m2
A rockwool slab pack of 12 1200 x 600 £31 plus vat (7.2mx1.2m)
Polystyrene board 2400 x 1200 x 50mm sheet £13
Recticell 1200 x 450 x 50mm £3.82 a sheet

+ vapour barrier??? visqueen…polythene

COVERING BOARD

Soundproof Plasterboard £14 12mm 8 x 4 sheet Cheaper than ply-could be painted white or off white
OSB3-external sterling board-9mm £16??? perhaps looks better than plasterboard but not as good at the job?
OSB8
Birch faced ply-good aesthetics but too expensive

+ possible under and top coat

 

[JakeS]

Blister, what is OSB8? Can't find any info anywhere...

Glass fibre loft insulation-will compress and easy to cut. Knauff from B&Q may not squish enough (200mm -→ 50mm??) £3

OSB is "Oriented Strand Board" - it's that sheet stuff that looks like it's been 'painted' with lots of little shreds of wood - it's 'oriented' because all the shreds are laying in the same plane. Often used for boarding up broken windows and so on. Yes, as I understand it it's the same stuff that also gets called Sterling board. (He didn't mean "OSB 8", he meant "OSB, in 8x4' boards".)

If the Knauf stuff you're looking at is their 'Space Blanket' product, then yes - it will compress to 50mm. It comes at most at that thickness in the roll, if not less than that. But I expect you'll lose half the insulation property with it compressed, as part of the benefit will come from the air gaps in between the fibreglass strands.

 

[fraser]

Hi Jake,
Thanks very much for your reply. I understand about the board thanks, no wonder i couldn't find it.

Regarding the Knauff, are you staying the space blanket comes in at 50mm in the roll? If so then i would
not need to compress it as such as i have a 50mm space to fill. Or are you saying even this is too tight a fit for it to give 100%? Otherwise I'm not sure I see if it's worth getting if i am to loose half of it's properies.

There are other Knauffs i was looking at, one was 200mm and I think some of the Rockwools were similar. I take it this writes them off as they would need to be compressed.

Thanks

 

[JakeS]

Regarding the Knauff, are you staying the space blanket comes in at 50mm in the roll? If so then i would
not need to compress it as such as i have a 50mm space to fill. Or are you saying even this is too tight a fit for it to give 100%? Otherwise I'm not sure I see if it's worth getting if i am to loose half of it's properies.

I used the Knauf 'Space Blanket' rolls to insulate half my loft a few years back; they come rolled up and compressed, and when you first unroll them they stay compressed for a while before slowly expanding to full depth over time. The compressed thickness is probably 30-40mm, from memory - so they could certainly stay in a 50mm gap, to the point that when I first unrolled them I wondered if I'd have to put a second layer down! My joists were - IIRC - 150mm tall, and there was a layer of some kind of foam pebble insulation on them when I started, I'm certain the compressed Knauf stuff didn't come over the half-way point and could definitely have been squished some more if necessary. It expanded over the course of about a day, IIRC, to reach its final height.

I doubt that compressing it to 50mm would stop it from insulating at all, but I'm sure it would reduce its effectiveness. It may even be the case that after a certain level of compression you'd be better off using (probably cheaper) expanded polystyrene.

 

[fraser]

Jake, thanks very much for that. I am going to try and head up to b&q tonight to have a look for myself. I doubt if anyone up there has any further knowledge about how compression affects the Knauff but will ask anyway. By expanded polystyrene do you mean the jablite polystyrene boards that you by at b&q? just regular polystyrene boards? This may be cheaper your right, and we did use this at work to insulate a steel shed and it has worked really well.

 

[JakeS]

By expanded polystyrene do you mean the jablite polystyrene boards that you by at b&q? just regular polystyrene boards?

I don't know any brand names, but expanded polystyrene is the one made up of lots of little bobbles formed into a board - similar stuff to the stuff you used to get electrical equipment packaged in. It's dirt cheap and you'll often see large 8x4'/6x4' sheets in DIY shops. Usually breaking around the edges 'cause it's really fragile!

There's also extruded polystyrene, which is a closed-cell foam similar in appearance to the inside layer in the Celotex 'sandwich'. You'll often find smaller boards around 40-50mm thick, often coloured pink or blue - in DIY shops, but it's more expensive than the expanded stuff. I believe it sits somewhere between expanded and fibreglass or Celotex in terms of insulation, but I could well be wrong.

 

[fraser]

Thanks very much for your reply Jake, thats what I thought. Though I did believe the idea of open cell insulation was better than closed...who knows.

I have just been to B&Q to see what they have and speak to someone there. They can order Celotex but it takes 28 days so it looks like that is a nogo.

The options really are as follows.

-They do a Space loft insulation roll that is 100mm thick, so this may solve the problem of compressing the glass fibres too much and loosing its insulation properties. It may loose some by squashing it 50mm, granded, but a much better proposition than the 200mm stuff and could possibly be the way to go. This is £17 for 13.89m2, which is pretty reasonable.

-The encapsulated roll (polystyrene foil and glassfibre) £10 5.5m2 (haven't actually seen this yet-is at another store which I can only get to at weekends)

-Polystyrene board 8 x 4 50mm sheet £13

-Recticell 1200 x 450 x 50mm £3.82 a sheet (haven't seen-same for encapsulated)

Rock wool, apart from the loose lay, comes in 170-200mm thicknesses so I think this probably rules that one out.


-Coverboard wise they have the Soundproof plasterboard-a lovely lilac colour so would need some paint but a good option. Also a 9mm plasterboard with 12mm polystyrene on the back for £16.68. Don't believe the plasterboard on this one is so soundproof though and it also raises the question of do I fill the other inch behind the polystyrene in with something or not. = More money.

Otherwise OSB, MDF etc that looks OK, I guess it does have the plus that it is easier to screw into than the plasterboard but would possibly still have to paint. Doesn't have sound properties of the plaster.


So those are my notes so far, probably leaning to either the Space loft stuff, or just plain polystyrene.

I didn't look for the vapour barrier, would this go between insulation and coverboard?

Also, should I be thinking about doing the same for the floor? Unless it fouls the door obviously. Or something different? I guess the same question also goes for the door, which I guess needs doing.

Thanks for everyones help

 

[galwayworker]

Hi Fraser,

It can be very confusing when looking at insulation products and how effective they are. The three types of insulation products that you are looking at are basically

a) Celotex Insulation; this is a polyisocyanurate (PIR) board product. PIR is considerd to be one of the most thermally efficient insulation boards and as such is one of the most expensive.
b) Polystyrene Insulation; this is the traditional white insulation board. In terms of thermal efficiency it’s pretty good.
c) Fibreglass Quilt / Rockwool; usually laid in attic spaces or timber framed houses, it needs to be fairly thick to achieve the required thermal performance. If you only have 50mm of space for the insulation then squashing 100mm into this space will only achieve the equivallent of 50mm insulation.

A quick basic calculation of u-values for the wall with 22mm board on the outside, 50mm studs, insulation between studs, vapour barrier and 6mm ply on the inside.

PIR insulation; u-value of 0.36 W/m²k
Polystyrene insulation; u-value of 0.53 W/m²k
Fibreglass insulation; u-value of 0.85 W/m²k

So the PIR is the best performaing insulation followed by polystyrene and then fibregalss. I went for polystyrene in my shed (50mm) and it heats up quicky with a small heater and hold the heat well.

I hope this hasn’t confused the issue further

 

[foxhunter]

If you have a Champions Timber depot near you take a look at their Sheet Materials book. It is very useful and gives the various properties of insulating etc materials.

 

[fraser]

Foxhunter, I don't but thanks very much anyway. We don't have much choice on the isle of wight.

Galaway, thanks very much for taking the time to do that for me. I think looking at the maths you have done, and considering just the four walls for now, polystyrene is only £30 more expensive than the loft insulation and probably represents better value for money. Plus the ease of fit. I will probably also use this on the floor and roof though for this weekend, that will keep me busy. The celotex/recticell is just too expensive for me at the moment.

I think I will be covering it with 9 or 12mm shuttering ply, probably 9, then paint.

I do have concerns about a vapor barrier, just as perhaps polythene, which I can get through work. If I use this between the exterior shed walls and the polystyrene, will the polythene not gather moisture, thus making the insulation wet? A couple of people have said to use it but I'm not too sure how it works?

 

[fraser]

As I understand, this is the order in which this should be done

Cladding
Breathable membrane stapled to the cladding and inside edges of the joists
2" polystyrene or 100mm loft insulation
Polythene stapled to face of joist over insulation as vapour barrier
9mm shuttering ply

Is this correct? I am a bit concerned that the membrane and vapor barriers will be sat against the insulation and interior and exterior walls. If they get wet which i guess they will if they are acting as a barrier, surely everything else will get wet?

 

[Dee J]

With a fairly impermeable insulation like polystyrene a vapour barrier is less of an issue. But if you fit a vapour barrier (aka polythene) make sure it's on the warm side of the insulation. In this situation, breather membrane is a bit OTT.

Dee

 

[galwayworker]

I agree with Dee on the vapour barrier.

If it was a domestic setting where you are trying to maintain a constant level of heating (say 16 degrees) then the risk of condensation would require a vapour barrier. In a shed that is only going to be heated for two or three hours every few days then I don't think the risk of condensation is very high. Polystyrene is waterproof and I don’t think it's thermal performance is affected if it gets wet. The problem of installing a vapour barrier is that it needs to be airtight when you are finished. All the joints and where it has been stapled to the studs have to be taped up to ensure this airtight finish (including where it meets the floor and ceiling). In a timber frame house it’s a right PITA to do it… so in a shed I don't think the barrier will stay airtight very long (fixing shelves etc to the wall).

I would keep it simple, 50mm polystyrene and your ply.

 

[MickCheese]

As I understand it and how I have done it in the past.

Starting from the outside - Shiplap, (the last two sheds had a sort of tar paper, don't know what it is called) then the insulation, vapour barrier, plasterboard / ply or whatever.

Mick

 

[decas]

If you are still interested in panel insulation then you might add these guys to your list. I have had Kingspan seconds from them in the past and they gave good prices and service. They will give advice if you ring them up. Good delivery service. Look under the special offers on the website - what is available changes all the time depending on what they get from suppliers.

This is my first post so it won't let me post you a link so put secondsandco into Google.

Dave

 

[fraser]

Hi guys
Having put the insulation in and paneled over it a few weeks back, I have finally managed to get back in the shed to give it a lick of paint. I thought I would be nosey and see if there was any condensation between the shed and the visqueen vapour barrier on the ceiling so took a panel down to have a look. It is wet...it hasn't got through to the insulation but there must be water getting in (through the felt?) somewhere and stopping on the visqueen, creating some small puddles. The joists and roof are therefore wet.
What can I do about this? I thought it was pretty water tight but clearly not, or could this be water in the air and something I really cannot do anything about? I havent looked at the walls yet, not sure if I can bring myself to do it!
Any help would be really great
John

 

[fraser]

Just to add, I have only actually insulated half the ceiling so far and the joists on the half without the insulation, are dry.
Could it be that the visqueen is inviting the water from the air to sit there. It is not condensation from my breath as I have not been in the shed since I did this, which was a few weeks back, and it is the wrong side of the visqueen for that anyway.

 

[foxhunter]

Just a thought from someone who knows nothing about anything!

I remember on a thread some time ago from a guy who has now left the forum it was mentioned that it is important that the vapour barrier is fixed on the inside of the insulation - OR IS IT THE OUTSIDE!