Garage conversion internal wall insulation

[tvrulesme]

I'm in the process of planning a detached garage conversion. The wall will need to hold some pretty heavy and important things like:

• Boiler
• Consumer unit
• Wall mounted server cabinet

 

So strength of fixings is going to be important as well as insulation and U/R values.

 

Reading up it looks like fixings for insulated plasterboard are a bit of a pain and don't get great reviews so leaning towards Stud walls with PIR between and plasterboard on top making sure I have extra timber where needed.

 

Given the construction (from planning permission history) is rendered 200mm lightweight block-work. How do I go about calculating the construction for insulation?

 

I seem to be reading conflicting info on whether you need a void depending on whether you have a vapour barrier or not so my initial thoughts from outside-in are:

1. Render
2. 200mm block-work
3. Damp Proof Membrane (any reason why not?)
4. 100mm studs filled with 100mm foil backed PIR
5. Vapour Barrier
6. 12.5mm Plasterboard
7. Skim Layer

 

Is this going to achieve the 0.30 W/m²·K to satisfy Approved Document L - England, Existing Buildings - Refurbishment requirements?

 

Block-work looks like this currently

 

 

[MikeGrahamT21]

Couple of points...

 

Your 100mm studs, should be installed with 75mm foil PIR to give a 25mm air gap to the inside so the foil works.

Don't put a vapour barrier on either side. The Foil will act as the barrier, just tape over the studs with foil tape.

[tvrulesme]

12 minutes ago, MikeGrahamT21 said:

Couple of points...

 

Your 100mm studs, should be installed with 75mm foil PIR to give a 25mm air gap to the inside so the foil works.

Don't put a vapour barrier on either side. The Foil will act as the barrier, just tape over the studs with foil tape.

 

Awesome thank you. So:

 

1. Render
2. 200mm block-work
3. 100mm studs filled with 75mm foil backed PIR
4. Foil tape for joints
5. 12.5mm Plasterboard
6. Skim Layer

 

Any idea where to get the U-values this would generate?

[MikeGrahamT21]

Blocks will be 215mm, look to be aircrete from the photo.

 

u-value will be as follows:

 

[MikeGrahamT21]

36 minutes ago, MikeGrahamT21 said:

Blocks will be 215mm, look to be aircrete from the photo.

 

u-value will be as follows:

 

 

Sorry just realised that didn't even include the u-value! It came out at 0.23U

[tvrulesme]

18 minutes ago, MikeGrahamT21 said:

 

Sorry just realised that didn't even include the u-value! It came out at 0.23U

 

 

Thanks a lot Mike. You missing it off actually prompted me to use www.ubakus.com. What a fantastic site.  

 

Will be using this again and again

Edited November 8, 2021 by tvrulesme

[MikeGrahamT21]

Yeah its a good one, where this came from