Which type and how much insulation

bryanchicken

Active Member
Not specifically home cinema but everyone here has such great knowledge i can't look any further :D

Can you tell me which type, if any, of insulation is preferred on these different wall types and how much is recommended.
Eg, kingspan/rockwool & thickness.

1 - External 2 brick cavity wall which will be battened out and plasterboarded. Insulation/vapour barrier under/over/in between battens? (I don't currently know if the cavity is insulated.

2 - Internal single brick/breeze wall that will be battened out. Insulation in between battens?

3 - Bog standard stud wall. Stuffed with rockwool is what i did previously. Worth it?

I'm mainly concerned with heat, but a certain amount of sound insulation would be beneficial too, but i don't wanna go crazy with sound reduction.


Thanks for the help
 

Geps

Well-known Member
The first two are thermal and it depends on the block/brick type and the method of insulation. You have to achieve certain u values for the room and how you go about doing that is up to you. For example on a barn conversion where you want the brick exposed, you can compensate by putting more in the roof, so you get the same u value as if you had insulated walls and less insulation in the roof.

2) You need to pay serious attention to damp here as it get damp on the inside with only a single skin. Again it depends on brick/block type.

3) Interior walls between living spaces (building regs have the actual definition but I think it's defined as bedrooms, and living rooms) has to have a minimum sound insulation rating. You can achieve this with either insulation (IIRC 50mm minimum) or double board to achieve the same rating. If you download the approved documents they contain examples of accepted practice that any BCO will happily sign off.
 

bryanchicken

Active Member
Did you think number 2 said external? How does damp get onto an internal wall? There are no signs currently.

This isn't a conversion or anything like that, basically renovating an existing place. I've never heard of anyone looking into u values while doing a room up
 

Geps

Well-known Member
Sorry, yes, if it's internal then you don't need to worry about damp.

U values are the underlying principle behind all insulation sizing questions. BCOs often have standard methods for wall types that they know conform to the u values already so you don't need to calculate them on each application. I don't know what your Building Control would be happy to see so can't give you 'Xmm thickness on this wall' etc.
 

bryanchicken

Active Member
Ok, thanks. Considering i'm just renovating an existing room i wasn't gonna bother with BCO, in fact i'm still not. We'll have to involve them every time we paint something soon, its getting silly.
If i went the other route and just skimmed it as it is i wouldn't involve BCO, i don't see why i should have to for this.

I'm gonna assume that a dual red-brick cavity wall is pretty much ok as it is (its only got plaster on it currently). So if i batten out and add _some_ insulation, then plasterboard, then plaster i will at least have made it better than it currently is.
 

Sanders79

Distinguished Member
It's not necessarily a case of having to involve building control, but they are a useful resource to help guide you on stuff like this. They can give you advice about what they would expect to see as a minimum in a new build or extension and you can use that as a guide. They might even have better ideas for how to achieve what you want or how to avoid spending money where you won't benefit.

Many people are wary of building control. In my experience they have only ever been supportive and very useful.
 

bryanchicken

Active Member
I was under the impression you had to pay for BCO to come out? Do they offer free advice over the phone? If its something i would have to pay for, even if its just £50-60, then i don't see it being worth it in this instance.
 

Sanders79

Distinguished Member
It seems to vary from one council to another, Basingstoke council BCOs are great to work with amd always happy to help with questions. However, I have heard tales that others are not as helpful!

As Geps said earlier, they will probably know what they would expect to see as a minimum in your situation, e.g. "x"mm of Celotex boards or similar, plus vapour barrier under "y"mm of plasterboard for insulating the insides of your external walls...
 

bryanchicken

Active Member
ok, thanks all
 

Geps

Well-known Member
Technically you do need building control if you're updating thermal elements of the building. But that said, if you want some guidelines, create an account on the celotex site and you can browse their datasheets and they'll give you some ideas for effectiveness.

Remember insulation is a case diminishing returns, so don't always be tempted to pack in as much as you can.
 

stevos

Distinguished Member
I am interested by option 3.

Most new builds have double layer of plasterboard between rooms, with a small gap between the boards.

I would be curious to know how effective filling in that gap with some form of insulation would be at reducing noise transfer and how difficult it would be do achieve for an existing wall.
 

bryanchicken

Active Member
for anyone else that happens across this thread (and me when i have to look it up again) i found this quite useful:
http://www.greenspec.co.uk/internal-insulation.php

The "insulation fitted between battens" method is what i was interested in. I note that 50mm of Polyurethane / Phenolic foam / Polyisocyanurate insulation is enough to achieve a U value of 0.3 (which i believe is the value required for new builds?) on a single skinned brick wall. As my wall is an unfilled cavity wall i would be beating that U value by doing that.
Can anyone tell me what that parge coat/breather membrane is for? Is that because its a single skin?

This was my idea before hand and i think it will suffice based on that link:

External brick : empty cavity : internal brick : 50mm studs and insulation : vapour barrier : studs (50mm?) to create a cavity for services : plasterboard : skim
 

Geps

Well-known Member
for anyone else that happens across this thread (and me when i have to look it up again) i found this quite useful:
http://www.greenspec.co.uk/internal-insulation.php

The "insulation fitted between battens" method is what i was interested in. I note that 50mm of Polyurethane / Phenolic foam / Polyisocyanurate insulation is enough to achieve a U value of 0.3 (which i believe is the value required for new builds?) on a single skinned brick wall.

It's not I'm afraid - it states:
"Values assuming construction: 215mm existing solid brickwork with plaster finish" which is a double skinned wall.

Can anyone tell me what that parge coat/breather membrane is for? Is that because its a single skin?
The vapour barrier is to stop the warm moist air permeating the insulation and condensing on the cold side and causing water buildup.

This was my idea before hand and i think it will suffice based on that link:

External brick : empty cavity : internal brick : 50mm studs and insulation : vapour barrier : studs (50mm?) to create a cavity for services : plasterboard : skim
I've done what you're suggesting in my house, albeit with a solid wall as opposed to cavity, including the 50mm studs. If you switch to a foil backed insulation board like GA4000 from celotex, then you don't need to bother about putting up a complete membrane, you can just tape the joints with aluminium tape for a vapour proof seal.

HTH
 

Geps

Well-known Member
I am interested by option 3.

Most new builds have double layer of plasterboard between rooms, with a small gap between the boards.

I would be curious to know how effective filling in that gap with some form of insulation would be at reducing noise transfer and how difficult it would be do achieve for an existing wall.

Realistically the only way you'd be able to do it on an existing wall (without stripping the plaster off) is to blow the insulation in like they do for cavity walls.

This however still wouldn't be a trivial matter as the studs would prevent the entire wall filling up in one go, meaning multiple holes would need to be drilled.
 

stevos

Distinguished Member
Yep, but if it walls absorbed noticeably more sound, it would be worth it.
 

bryanchicken

Active Member
It's not I'm afraid - it states:
"Values assuming construction: 215mm existing solid brickwork with plaster finish" which is a double skinned wall.


Ok, i might be confusing the terminology as i'm not a builder. When i said single skinned i meant it doesn't have 2 separated (by cavity) brick "skins". 215mm is the length of a standard brick, so those U values are for a non-cavity wall.
My wall is a cavity wall, so my wall does trump that for u-value.

The vapour barrier is to stop the warm moist air permeating the insulation and condensing on the cold side and causing water buildup.

I know what the vapour barrier is for, i was asking about the parge coat. On the diagram i am referrring to they are 2 different things
 

Sanders79

Distinguished Member
I believe a parge coat is basically a thin coat of plaster or sand & cement to make the surface flatish and seal up any big air gaps. If the wall is already plastered and the plaster is sound then that would do the same job.
 

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