Which is stiffer Rockwool or dritherm

[mikeey84]

The insulation is fire proof so is the idea behind it to not impede the fireman's progress through the house.

Pretty much, plus the above point about preventing spread

 

[aveatry]

I am learning so much thanks everyone

 

[^woody^]

I have done it before but cant remember what product it was and it was fairly successful but wasnt trying to get it to support itself as it was in aloft which is why I was asking if anyone has had experience with a product.
50mm has to be better than nothing does it not and as the ceiling is already down I am not taking the ceiling down just to fit 50mm

I doubt it.

The effect of 50mm is marginal compared to the cost and effort. By the time you have messed about trying to slim it to 50mm, then tried to juggle fitting the things, and then trying to support them, you may as well just bung the 100mm batts in - which will self-support if you trim them right.

Incidentally there are a lot of threads and posts on this insulation idea, and it appears that it's not actually necessary with little benefit to fitting thermal insulation between rooms. Acoustic yes, but not thermal.

I'd think about fitting acoustic quilt which will additionally give you the same performance as just thermal insulation.

 

[aveatry]

I doubt it.

The effect of 50mm is marginal compared to the cost and effort. By the time you have messed about trying to slim it to 50mm, then tried to juggle fitting the things, and then trying to support them, you may as well just bung the 100mm batts in - which will self-support if you trim them right.

Incidentally there are a lot of threads and posts on this insulation idea, and it appears that it's not actually necessary with little benefit to fitting thermal insulation between rooms. Acoustic yes, but not thermal.

I'd think about fitting acoustic quilt which will additionally give you the same performance as just thermal insulation.

It has since been pointed out to me that I can get 50mm rockwool off the shelf for £53 which would do my whole ceiling so I will not be faffing with halving 100mm.
Quilt - ahhh another part of the equation, I have no experience of quilt, I plan on using the foil backed vapour shield plaster board so if i went for the quilt could I do away with the foil board and just normal. and what about tit properties when crushed between board and joist - wont it allow movemend and so risk cracks in board joints.

 

[aveatry]

Ok based on being advised that 50mm rockwool will not be worth doing I have gone for 75mm dritherm 37 and as its 8 batts I need 2 packs I also decided to go for a 3rd pack which I will use in the roof section to build up to what will then be 300mm at 75mm between joists and the the rest over. In that short 400mm extension roof width they are not really joists as there is noting aboue they are just to support the plasterboard - hence the 75 between joist remark, but I will be adding extra timber supports there too.
I will also have enough batts left over for some other jobs.

 

[JohnD]

Is it heat insulation, draught blocking, or soundproofing, that you want?

 

[aveatry]

Insulation but only to "soften the possible difference between the colder ceiling rafter space which will definitely be colder at the roof end - that's bits no brainer but while the ceiling is down I'm taking the opportunity to but some insulation in the rest, we are big foodies here and can create a lot of heat and steam and am trying to mitigate any possible issues with condensation on what will be a new ceiling.
As explained earlier I previously had a suspended plastic T&G false ceiling which did not have any condensation issues largly I think because of it being suspended but I do not want to be kicking myself that I did not add any insulation up there what I could of - for £30.

 

[aveatry]

Update.
I used the dritherm 75mm in the end, glad for the advise of not going for the 50mm. in the short 500mm extension roof end I filled in between and over the joists with 4 layers giving me 300mm, the rest of the kitchen that has a bathroom above went 75mm.
I found the battens quite floppy and had to add a couple of screws for support in a couple of places. My joist spaces were give or take 400mm so had to slice off a strip from each slab. I did try uncut but it bowed and forced the slab out.
Tip for cutting them is to use an old electric carving knife which worked really well.

 

[robinbanks]

After the fire brings down plasterboard

By that time the place is f***** and no sane person would be going in it anyway

I kid you not. I just fitted it.

And did you then burn it down to check whether you were right?

Having seen what mineral wool is reduced to in a house fire, my take is the reality will differ from your expectations quite considerably

so no requirement for insulation but as the ceiling is down I am going to anyway but just with 50mm

It would be better to take the money and put it to insulating the bathroom ceiling, rather than seeking to make the most moist room in the house colder by taking away a heat source

 

[aveatry]

It would be better to take the money and put it to insulating the bathroom ceiling, rather than seeking to make the most moist room in the house colder by taking away a heat source

The bathroom ceiling is already maxed out with insulation. The kitchen joists also follow through to the living room next door to the kitchen and sticking my head in the kitchen joist space I can see all the way across the living room, so any heat from the kitchen will also be spreading out along to the living room leaving very little to go up into the bathroom.

 

[Wayners]

@robinbanks

I had to add insulation under building regs and get it inspected

 

[robinbanks]

any heat from the kitchen will also be spreading out along to the living room leaving very little to go up into the bathroom.

You spent the earlier posts in the thread fussing about the thermal performance of wool X vs Y, and now claim there isn't any delta T anyway, so you don't actually need any insulation for the proposed location.

Are you just installing stuff for the sake of it without having a clear idea why?

 

[aveatry]

You spent the earlier posts in the thread fussing about the thermal performance of wool X vs Y,

Er - no, I think you are getting confused.