Stud Wall Insulation

[Dallypro]

Hi All

I am in the process of converting an out building into a summer room. The construction is single skin block on flat, some of which is below ground level.

I have built an internal timber stud wall (38 x 63), which is lined externally with a roof membrane to prevent any damp that gets into the wall hitting the insulation.

I will be applying a vapour barrier over the top before plaster boarding.

The question is regarding the insulation that goes in the middle. I see that I have 3 options:

1. Celotex - I know this is what i should do, but it costs, so i thought i would ask the question about other options and get shot down.

2. 50mm Acoustic insulation - not sure about the thermal benefit which is probably more important than the level of sound insulation.

3. 100mm loft insulation that is wedged in - not even sure it would fit without bulging.

Any thoughts other than use celotex?

Cheers in advance

 

[^woody^]

What standards or regulations are you expecting to meet?

 

[oldbutnotdead]

Presumably your project is small enough for building regs not to apply?
Any insulation will be better than none. Your acoustic stuff should have an R value of some sort, compare it with the R value for loft insulation (and the cost per cubic metre)
Stuffing 100mm into a 63mm gap isn't clever, compressing the loft insulation reduces its efficiency. Cost-wise loft stuff is the way to go if you have the room- to achieve the same U value as 100mm thickness of celotex takes about 200mm of loft stuff- last time i looked loft insulation per cubic metre was about a 6th of the price of celotex per cube.

 

[dontbelieveawordofit]

25mm recticel isn’t dear enough to justify not using it.

 

[Dallypro]

Hi All

Thanks for the replies

Its a small project started during lockdown, and continuing every time we have to isolate (this is number 3 now - toddler at nursery ends up with a cough every 2 minutes!) so really just about getting the best result I can for the minimum cost. No real desire to hit specific regulations - just to do a job that wont leak/go mouldy/be completely freezing cold in winter.

I understand the point with regards to recitel, but for 25mm it would be at least double the price of 50mm acoustic, and nearly 3 times the price of 100mm loft insulation.

I've looked into R values, and from what I can work out:

25mm Board: 1.1
50mm Acoustic: 1.562
100mm Loft (however it would be compressed to 63mm so I have used 0.063 as the depth): 1.431

Never looked at R values before, so my maths may be wrong.

Based on this, I will go with the acoustic to avoid having to jam loft insulation into the gap.

Cheers

 

[oldbutnotdead]

One other bonus with the softer insulation is it is much easier to get a full fill & avoid draughts. Have fun

 

[JohnD]

jam loft insulation into the gap.

Mineral wool loft insulation is made almost entirely of air. Get hold of a piece and see how much effort it takes to press it from 100mm to 50mm. It easily squashes into corners and irregular shapes to block draughts. You can fluff it up again with a fork. I recommend the brown stuff treated with Ecose to prevent it shedding loose fibres and irritant dust. I would never use the yellow glassfibre again.

 

[Dallypro]

Mineral wool loft insulation is made almost entirely of air. Get hold of a piece and see how much effort it takes to press it from 100mm to 50mm. It easily squashes into corners and irregular shapes to block draughts. You can fluff it up again with a fork. I recommend the brown stuff treated with Ecose to prevent it shedding loose fibres and irritant dust. I would never use the yellow glassfibre again.

View attachment 205082

That works for me! Thank you for the input. Not ordered yet so will go for loft insulation option. Cheers!!!

 

[dontbelieveawordofit]

plasters back in the shops, jus sayin.