Internal wall insulation - worth it?

[Cocat2517]

Hi
I own a fairly old house, built around 1900. Solid stone (slate) walls, approx 12"-18" thick.

I want to improve the EPC of the property and was advised internal wall insulation should help keep it warmer, reduce bills & improve EPC. Currently have 300mm in loft.

How effective would this be on an old building with thick solid walls? I was thinking 60-70mm Kingspan k118 (with plasterboard attached). How would I apply this to solid stone walls? Via battens mounted on a breathable membrane?

There's also the issue of breathability. The outside is being repaired & treated with a breathable coating to prevent moisture ingress. Inside I'm fitting a Drimaster Heat in the loft to keep humidity & moisture levels to a minimum & prevent condensation. Is breathability a big deal still?

I'll be DIYing any work due to budget restrictions.

Any help & advice would be appreciated, thanks!

 

[foxhole]

Well worth it, added to around 75% of my property during refurb ( 30s end of terrace) and gas bill is around 30% less in winter months.
Do you not have internal plaster on walls?

 

[Deleted member 174758]

I've worked on a few refurbs of Victorian buildings where the internal PB was mounted onto Gyplyner with an air space between the wall surface and the back of the insulation. The Gyplyner system uses channels located into floor and ceiling tracks and held off the original walls with little folded metal brackets. This shows a close fitted version, but you can space a lot further off the original wall with extra insulation between the channels:

 

[Cocat2517]

Do you not have internal plaster on walls?

Yes, walls are mostly lime plastered, but with modern paint.

 

[foxhole]

Worth a read .
https://assets.publishing.service.g..._Innovation_Final_Report_-_FINAL_Approved.pdf

 

[Cocat2517]

Thanks for input. After reading above article think I'm going to go with a breathable insulation option.

Looking at Steico Therm wood fibre boards (60mm or 80mm), fixed directly to walls (after removing old lime plaster) with these insulation anchors, then plastered with Solo One Coat Lime plaster (3mm deep).

Then some breathable paint, like limewash or claypaint, to finish.

I'll be installing a DriMaster Eco Heat to help keep the house nice and dry too.

 

[endecotp]

After reading above article think I'm going to go with a breathable insulation option.

Looking at Steico Therm wood fibre boards (60mm or 80mm), fixed directly to walls (after removing old lime plaster) with these insulation anchors, then plastered with Solo One Coat Lime plaster (3mm deep).

Then some breathable paint, like limewash or claypaint, to finish.

60-80mm is not a lot of wood fibre. It’s only as good as e.g. polystyrene or mineral wool, about half as good as e.g. kingspan kooltherm. Aim for more like 100mm if you have the space.

I’ve used the low density wood fibre batts (e.g. Steico Flex) between studs with plasterboard over. Easy enough to work with. Can’t really comment on the effectiveness until the project is finished.

I’m not an expert but 3mm of plaster doesn’t sound like a lot over those boards.

I'll be installing a DriMaster Eco Heat to help keep the house nice and dry too.

What sort of heating do you have? Electric heating is expensive to run. Do you have a humidity or condensation problem? Do you have kitchen and bathroom extracotrs?

keep it warmer, reduce bills

One or the other, not both!

 

[Cocat2517]

My main concern is it's an older house, I'm worried about the breathability issue so wanted to avoid something like kingspan and regular plasterboard finishes. Space is a bit of an issue, so didn't want to go for as much as 100mm.

With the wood fibre batts does the wall need to be completely flat? Do they allow air pockets behind them? The walls are fairly uneven, I was hoping to avoid having to fill and flatten it with lime mortar before insulating.

 

[Cocat2517]

How would you insulate this wall? Cost is a big factor, as well as the amount of work/time available to do the work.

 

[endecotp]

My main concern is it's an older house, I'm worried about the breathability issue so wanted to avoid something like kingspan and regular plasterboard finishes.

I believe that a layer of plasterboard is sufficiently breathable.

With the wood fibre batts does the wall need to be completely flat? Do they allow air pockets behind them?

You build studwork off the floor and ceiling so there is a gap and the wall can be uneven.

 

[Cocat2517]

I thought regular plasterboard wasn't breathable? Just been reading about Fermacell plasterboard though.

Going to price up metal stud wall, with Steico batts in-between studs (will fill stud cavities with it too), boarded over with Fernacell.

When you used the Steico Flex batts, did you fit them so they were against the wall? Should there be a vapour barrier between the batts & the wall?

Thanks for your help, feel like I'm getting somewhere now.

 

[endecotp]

I thought regular plasterboard wasn't breathable?

It’s much more breathable than polythene, or celotex, etc.

When you used the Steico Flex batts, did you fit them so they were against the wall?

No; at least 25mm gap.

Should there be a vapour barrier between the batts & the wall?

No. Huh? No point using breathable materials and then a vapour barrier!

 

[StephenStephen]

Here's an interesting approach:
http://www.simonjameslewis.com/bristol-hemp-and-lime/

 

[Cocat2517]

No. Huh? No point using breathable materials and then a vapour barrier!

Do i mean aa breathable membrane then or something? Basically something that'll allow water vapour to pass through, but not damp? Like roofing membrane?

Going for the batts anyway. Metal stud set 25mm from wall, 80mm batts inbetween, Fermacell over the top. All in around £4200 for the whole house. Also (allegedly) no plastering with the Fermacell, which is a bonus.

The cavity in the metal C channels, no reason I can't fill them with insulation is there?

Also, interstitial condensation, is there a risk? How can I negate it?

Here's an interesting approach:
http://www.simonjameslewis.com/bristol-hemp-and-lime/

Thanks, will have a read.

 

[scbk]

If you're bored, have a read through this PDF - https://www.historicenvironment.sco...cationId=179c1909-3679-4486-9583-a59100fa98c1