Internal Wall insulation

[adrianpettitt]

Hi, I am renovating our 1930s semi, making the existing ground floor kitchen, dining room and lounge, into an open plan space. The walls are solid (Pebble dashed outside), so I'm going to insulate internally.  Can PIR be fitted to the wall, then 25mm battens to hold it in place and allow services, then 12.5mm Platerboard?

 

Is phenolic insulation better than PIR? And can it be installed the same way? Space is at a premium, so whatever is the thinnest option is prefered.

 

Thanks.

[Timedout]

I am surprised no one has responded to this. 
your walls - at 1930 it is unlikely to be solid. There will probably be a small gap between the inner and out leaf of bricks. We owned a 1929 house, rendered like yours and the walls were as I have described. I did internally insulate a 1901 house (not mine but one still lived in by a relative) using the very method you describe. The walls on that one also features that small gap between the bricks. This was done in 2015 and the design was accepted by building control and subsequently signed off. They were very keen to see that we sealed all the joints in the boards and to all the edges. Between the first floor joists was a bit testing. Because we had the floors out we made sure the wall and floor insulation was contiguous. That house had no physical DPC so we had also (laboriously) raked outed in sections and inserted a modern DPC. I believe all other types of damp proof treatments to be tosh.

Things have moved on and I guess the BCO may want to see something like butyl tape under those battens to be sure of reducing the scope for humid internal air getting to the masonry. There is good range of fixings now rather than the frame fixer types we used then. When you set out the battens you need to be sure all the forces bear on the floor. If you rely on the longish fixings through the batten and insulation layer, over time there may be movement leading to joint cracks in the plasterboard particularly where it meets the ceiling. Common sense.

 

If you are spooked by the idea of highly inflammable insulation in the house, there is a system I saw a while back in France. It uses Gypliner type tracks and adjustable plastic stand-offs. The void is filled with mineral wool batts and then a layer of smart membrane, then final vertical track with plasterboard over. Never seen it in the U.K. but forum members may have. I am fairly certain the useful bit, the adjustable plastic stand-off, was a Siniat product. Gypliner type stuff and its perimeter track is commonly available. If I was doing a project like that again I would seriously consider it myself.

[Mike]

4 hours ago, Timedout said:

there is a system I saw a while back in France. It uses Gypliner type tracks and adjustable plastic stand-offs. I am fairly certain the useful bit, the adjustable plastic stand-off, was a Siniat product.

I've been installing exactly that in France today, using Knauf's Easy Click (various ways of fixing it, here's one). There are multiple companies that produce the plastic stand-offs in Europe, including Siniat, but I've not seen them in the UK.

[Iceverge]

On 17/08/2023 at 20:18, adrianpettitt said:

Can PIR be fitted to the wall, then 25mm battens to hold it in place and allow services, then 12.5mm Platerboard?

 

Yes, that'd work. Care will be needed to ensure a straight wall however. Maybe shims behind the battens. I would use 22*70mm battens too as they're a little meatier and less lightly to split. 

 

Most people I know just use insulated plasterboard, hard to get good airtightness though compared to boards that are foil taped and properly foamed and sealed to the wall and ceiling. 

 

I suspect you do have a cavity too. Have you investigated?