Upgrading 1970s timber frame

[Alduma]

Hello all - first poster here, grateful for your collective expertise.

 

I have a 1970s timber frame and timber-clad bungalow, and I’d like to add insulation to the walls (currently none).

 

The wall construction is currently:

 

• Internal plasterboard lining (no vapour barrier but it does have some sort of reflective finish on the back).
• 100mm timber studs with nothing between.
• 20mm boarded timber cladding directly on timber frame (no sheathing).

 

I’m looking at removing the outer cladding in sections and installing Kingspan between the studs. I’ll add battens to provide airflow before refitting the cladding. My questions are:

 

• Should we fit sheathing and breather paper to the outside of the kit before the battens?
• Should we try to address the lack of vapour barrier?

 

Al

 

 

[Russell griffiths]

Pictures and a drawing needed really. 
kingspan or pir would be the last thing I would use, hard to fit well, expensive 

 

i would make the frame deeper and use a rigid rockwool batt of some sort. 
 

are you removing the plasterboard. 

[saveasteading]

Agreed with @Russell griffiths.

I did what you are suggesting, 15 years ago. At the time that seemed like a big deal.

But with experience it's not my suggestion now.

Difficult to cut, and you will have gaps.

The timbers remain a thermal bridge.

 

So I'd use mineral baths. They squeeze in tight. But there remains the cold bridge. Can you fix a layer inside?

Yes, add a breather membrane.

[Redbeard]

13 hours ago, Alduma said:

Internal plasterboard lining (no vapour barrier but it does have some sort of reflective finish on the back).

Sounds like foil-backed plasterboard, the foil being a Vapour Control layer/barrier). On the other hand I have never liked it since, at every joint, there isn't a VCL. Is that picky? Especially nowadays when many use the VCL as the air-tight layer, I don't think so.

 

4 hours ago, Russell griffiths said:

i would make the frame deeper and use a rigid rockwool batt of some sort. 

 

and 

 

3 hours ago, saveasteading said:

The timbers remain a thermal bridge.

 

So if you can afford to lose internal space how about remove the plasterboard, 75 x 50 timbers horizontally at 400-ish ctrs (to suit insulation size), Yes, you still have a full-depth thermal bridge at the cross-overs, but life is not perfect. Either that or go over with some rigid board, such as PIR (I dislike it as much as many), taping all joints and perimeters as you go, and then 25 or 38mm deep battens screwed thro' to the frame and there's your VCL and service void. (and if you take the view that a hole in the VCL for the screw is a hole in the VCL, pre-drill, squirt in silicone and wind the screw through its own 'silicone grommet'.

 

Or can you do EWI? For Best practice you'd still have to address the incomplete VCL but if it is done well it can be a very good thermal overcoat.

 

Out of interest has your frame survived with little rot? 

[Alduma]

[Alduma]

View from the outside (cut a hole in the cladding). You're seeing the rear of the internal lining board, studs, some sort of reinforced building paper, and the cladding.

[Alduma]

All things being equal, I would remove the internal finishes and insulate from the inside, possibly adding a layer of insulated plasterboard across the inside face. But given the outside is accessible (no sheathing) I thought it may cause less disruption and save us moving out. I note what you say Russell, Saveasteading and Redbeard thank you - mineral wool sounds easier to fit. Not looking to achieve current standards, just a marked improvement over what's there.

 

External insulation was my first thought - we have the roof overhang - but hanging weight off the outside rather than sitting insulation within the frame seemed counter-intuitive. External insulation would also mean a change from timber cladding to render - not necessarily an issue but something for me to consider.

 

Al.

[Russell griffiths]

3 hours ago, Alduma said:

All things being equal, I would remove the internal finishes and insulate from the inside, possibly adding a layer of insulated plasterboard across the inside face. But given the outside is accessible (no sheathing) I thought it may cause less disruption and save us moving out. I note what you say Russell, Saveasteading and Redbeard thank you - mineral wool sounds easier to fit. Not looking to achieve current standards, just a marked improvement over what's there.

 

External insulation was my first thought - we have the roof overhang - but hanging weight off the outside rather than sitting insulation within the frame seemed counter-intuitive. External insulation would also mean a change from timber cladding to render - not necessarily an issue but something for me to consider.

 

Al.

Why would you need to change to render. 
insulate between the studs, then over the face of them on the outside with some form of wood fibre insulation, then a batten and then re cladding. 
I’ve obviously missed out lots of steps like membranes, but all different systems have membranes in different locations, so there’s no point going into detail, until you start really looking into what you want to achieve. 

[Alduma]

2 hours ago, Russell griffiths said:

Why would you need to change to render. 
insulate between the studs…

I took EWI to be outside the frame, and insulation, battens and cladding all outside would be chunky.

 

Insulating between the studs but with a thin ‘sheathing’ layer to reduce the cold bridge would work indeed 👍