Warm loft hybrid

[Just_me]

Hi,
We’ve a very large 4,500 sq ft old farm bungalow that was bodged and very very tired. I’ve shelled it and installed solid floors.

It’s the loft I’m struggling with, in particular insulation. The originals run of the mill insulation was damp and had vermin living in it and dying in it and making nests in it.

That’s obviously easily sorted by reducing the vermin risk. It’s condensation I’m worried about. I’ll ventilate the loft but I’m anxious about using normal fibreglass insulation. I expect it to be in the same way in a few years, it’s a weird roof and loft as it’s been built by semi-skilled rough arse farmer/builders using whatever they could get their hands on.

My plan is to ventilate as much as is reasonably practical.

I’m thinking of just putting solid insulation like chipboard backed kingspan and foaming around the edges and joints. The BCO is happy with this but I’ve never seen this approach before and worried I’m Amy be accidentally inducing condensation between the insulation and ceilings (probably plasterboard but maybe woodwool) in conjunction to whole house dehumidifier system. Tia.

 

[Just_me]

I forgot to add. Any advice appreciated.

 

[a twig]

Hi,
We’ve a very large 4,500 sq ft old farm bungalow that was bodged and very very tired. I’ve shelled it and installed solid floors.

It’s the loft I’m struggling with, in particular insulation. The originals run of the mill insulation was damp and had vermin living in it and dying in it and making nests in it.

That’s obviously easily sorted by reducing the vermin risk. It’s condensation I’m worried about. I’ll ventilate the loft but I’m anxious about using normal fibreglass insulation. I expect it to be in the same way in a few years, it’s a weird roof and loft as it’s been built by semi-skilled rough arse farmer/builders using whatever they could get their hands on.

My plan is to ventilate as much as is reasonably practical.

I’m thinking of just putting solid insulation like chipboard backed kingspan and foaming around the edges and joints. The BCO is happy with this but I’ve never seen this approach before and worried I’m Amy be accidentally inducing condensation between the insulation and ceilings (probably plasterboard but maybe woodwool) in conjunction to whole house dehumidifier system. Tia.

Where are you putting the chipboard backed kingspan? Joists or rafters?

 

[Just_me]

update: I think I’ve sussed out what to do. Wood wool boards backed with insulation and then lime plastered. Job done. Cold loft with ventilation. The good news is that I can use the wood wool insulated boards on the internal walls too. I didn’t think I’d find a breathable insulation option for the walls. Down side…….cost.

 

[Kearn]

update: I think I’ve sussed out what to do. Wood wool boards backed with insulation and then lime plastered. Job done. Cold loft with ventilation. The good news is that I can use the wood wool insulated boards on the internal walls too. I didn’t think I’d find a breathable insulation option for the walls. Down side…….cost.

Yep. Proper sheep’s wool insulation into the rafter voids, the good, treated stuff not thermafleece or similar as they prefer moths! pack out if you need more thermal depth. Woodfibre boards over from the usual suspects and then I’ll be personally going thick with a lime hemp scratch coat, and probably the same for float as well for extra thermal mass.

Make sure the underside of the tiles/ roof covering hasn’t got a non breathable liner or similar though so breathability is good on top as well as below.

 

[Lacan07]

I would definitely go for a cold roof format for the loft if your worried about condensation. The minimum these days as stipulated by BC is 27cm which is way more than our parents had in their lofts and should be effective. You can use sheep's wool and wood fibre board for breathable insulation. I wouldn't be using much PIR board in an old house if you can avoid it. I've used some to install a warm roof detail on a pitched roof but if you go down that road you absolutely have to make sure all joints are sealed, etc, to stop moisture migrating to the cold side.

 

[Lacan07]

Yep. Proper sheep’s wool insulation into the rafter voids, the good, treated stuff not thermafleece or similar as they prefer moths! pack out if you need more thermal depth. Woodfibre boards over from the usual suspects and then I’ll be personally going thick with a lime hemp scratch coat, and probably the same for float as well for extra thermal mass.

Make sure the underside of the tiles/ roof covering hasn’t got a non breathable liner or similar though so breathability is good on top as well as below.

I think it should be pointed out that Thermafleece apparently sorted out the moth issue. The product was relaunched after the original company closed.

 

[Kearn]

I think it should be pointed out that Thermafleece apparently sorted out the moth issue. The product was relaunched after the original company closed.

Time will tell I guess - the jury is still out for many…

 

[Lacan07]

Time will tell I guess - the jury is still out for many…

Has there been reports of a recent incident? I'd be interested to know as I have a couple of bags of the stuff waiting to be laid in the summer.

 

[Just_me]

Where are you putting the chipboard backed kingspan? Joists or rafters?

Hi,
Joists. Most of the bodged half had tarred roofs with oversized joists.