Insulated plasterboard, how much difference will it make to solid brick walls?

[MisterBoy]

My house is ~1860 with solid walls. My home office has two external walls and in colder months, I get a cold draft washing down the walls which leads to very cold feet
I wondered about interior cladding with PIR-backed plasterboard, it's 25mm insulation on 12mm plasterboard.

Maths or more anecdotal answers welcome, I don't need the room to be super efficient just to avoid icy-cold walls which also risk condensation/mould problems. Would this make a significant improvement to my solid brick?

Ta.

 

[Mr Chibs]

Can't speak for 25mm, but 50mm will make a world of difference, I've lived in old property no insulation and current old house has 50mm internal insulation and it's fantastic.
Do the floor too if you can, with rockwool to save some lolly.

It's cheaper to buy the insulation and plasterboard as separates if required, plus you get double sided foil barrier when done this way.

 

[MisterBoy]

Done the floor already - there is a cellar under so we put PIR between the beams when re-doing the ceiling down there. 100mm from memory.

 

[Mr Chibs]

Good, you're good to go then... my whole house has been done, it's very warm and even in the last couple of weeks, won't go below 16/17° overnight, once the heating has gone off at around 10pm (heating set to 19°)

 

[JohnD]

Would this make a significant improvement to my solid brick?

Yes.

 

[JohnD]

Measure the exterior wall area in square metres. For ease, assume a 20C difference between indoor and outdoor temperatures.

Look up U- values

https://www.greenspec.co.uk/building-design/u-value-introduction/#:~:text=The technical name for which,the inside and the outside.

Also
https://www.gov.uk/government/publi...at-losses-and-the-potential-for-energy-saving

There might be a simpler webpage somewhere.

There are bound to be variations and inaccuracies but it will give you a pretty good idea.

You can knock off the old plaster first if you want.

A wooden frame is not necessary.

 

[howbut82]

Personal experience... using the 38mm board from wicked, within a corner box room, wall surface temperature increased from 14 to 19 degC on a cold day (external 5C).
Hugh difference from the radiation heat transfer perspective. Best £150 I spent to be honest.

 

[MisterBoy]

Personal experience... using the 38mm board from wicked, within a corner box room, wall surface temperature increased from 14 to 19 degC on a cold day (external 5C).
Hugh difference from the radiation heat transfer perspective. Best £150 I spent to be honest.

Very helpful, cheers for that.

 

[howbut82]

Very helpful, cheers for that.

To achieve Building Regulations 0.30 U-Value, you will need to use the 62.5mm board (Kingspan K118 or similar).
Once you hit that high U-Value, make sure all gaps are sealed with tape to maintain the vapour seal, otherwise, there is a risk of condensation (and mould) form between the insulation and internal brick face.

The K118 technical datasheet gives quite good instruction regarding detailing.

 

[JohnD]

Personal experience... using the 38mm board from wicked, within a corner box room, wall surface temperature increased from 14 to 19 degC on a cold day (external 5C).
Hugh difference from the radiation heat transfer perspective. Best £150 I spent to be honest.

The first inch of insulation saves a lot more energy than the second inch.

 

[Captain Nemesis]

Uses a lot more too.

 

[Rad1o]

We moved into a house - 1930ies with solid walls - with an extension - 1970ies with cavity wall insulation. The house had always been cold while the extension felt a lot warmer. I have insulate all the rooms in the house with 50 to 60mm dry wall insulation from Kingspan or Celotex depending on price at the time. The house is very different now. Take pictures when you do it for future energy certificate purposes.
I have also changed windows and the outside doors to frame insulated and triple glazed parts. Another big difference.