1970’s Bungalow Timber Kit Bungalow Renovation - wall insulation

[Steve450]

Hi everyone,

 

I am completely renovating my 70’s bungalow. 

I would love to hear your ideas on is, what insulation spec would you do with my current build up on the external leaf, I am replacing all windows, doors, heating and electrics so I want to get the insulation within a good standard,

 

currently the kit has 70mm stud walls filled with what looks like 50/60mm cotton insulation in brown paper bags with a clear polythene wrap stapled over finished with plasterboard nailed on, studs are 600 centres.  I’m guessing the U value is way above .4 with only basic insulation.

 

my thoughts are

option 1 -

do I leave the walls as they are, they are covered with chipboard wallpaper, I can strap on top of the old plasterboard with say 2x2 into original studs, then add 30/40mm PIR and have a void for airflow and cables. I would lose 65mm off each external wall, I’m guessing the U value would be down to .3 ish with this set up but could there be a chance for condensation? 

Option 2 -

rip off old plasterboard, fill the 70mm void with 70mm PIR, wrap over with foil avcl, stitch a 2x1 batten on top of old studs and have a service void of 25mm, I would only lose 25mm off each external wall
Outcome - Would option 2 with 70mm PIR be more insulated with a 25mm service void and one sheet of plasterboard than option 1 with original 50mm old wool, plasterboard, 40mm PIR and 15mm service void and plasterboard?

I also have the option with option 2 to batten with 2x1.5 battens or 2x2 which would take my 70mm cavity to 108mm or 120mm which would allow a PIR of 80 to 100mm and still have space for a service void to run my cables.

 

I think cost wise the only difference is buying the thicker PIR, I need to buy the plasterboard regardless but option 1 saves a lot of time stripping and getting rid of old plasterboard and insulation and skips etc.

 

I could also just sheet over the plasterboard without doing anything so it’s the original build up but double sheeted, would help noise but not so much insulating the property, this would be cheapest and quickest but I am after a quality set up, 

 

tell me what you would do! And is PIR worth it, only looking at it as it saves spaces over rock wool.
 

If you have got this far thanks you for reading

 

steven

[Squonk]

I had to look at the author to see if I'd written this! I have a 70's bungalow on the west of Scotland, when we bought it last year it was completely uninsulated - not even the loft! We do have double glazing at least, not the latest spec but better than nothing. I now have 300mm of Knaus wool in the attic, and overlay underfloor heating (aka overflow heating) which has stopped some of the draughts from the suspended timber floor. Last year our spare (unheated) bedroom was regularly hitting 7 deg C, now it rarely dips below 13 deg, so I'm making progress.

 

The walls are my next challenge. Behind the plasterboard is an 80mm void, then a bit of block work, and external cosmetic rendering. My thinking is to remove the existing plasterboard, install some Kingspan cavity board and then new plasterboard, either plain or insulated. There seems to be the option of partial cavity fill or full fill, but I'm not sure which way to go. I'm on an island, so options are very limited!

 

Anyway, just wondered if you made any progress?

[Steve450]

Hey, good to here from a fellow 70’s renovator, I have stripped the house now back to the timber floor and walls, I have 70mm extratherm PIR to go in between studs this week, then foil membrane over the top

followed by a 1 inch cavity service void, once the electrical work has been done I will send some photos. Not sure if I’m going with plasterboard or soundbloc but the 70mm PIR will be better than the 50mm fibreglass,

 

Good to hear what you have been up to…was the under heating (overflow heating good to install, where did you buy it? Did you need to PIR between floor joists? I’m not settled on floors yet and I have options to either buy 13 radiators and insulate floors the best I can or buy a water system for joists, I’m not sure what to do

 

 many thanks for any info 

 

 Steve 

[Nickfromwales]

On 22/12/2022 at 00:20, Steve450 said:

Hi everyone,

 

I am completely renovating my 70’s bungalow. 

I would love to hear your ideas on is, what insulation spec would you do with my current build up on the external leaf, I am replacing all windows, doors, heating and electrics so I want to get the insulation within a good standard,

 

currently the kit has 70mm stud walls filled with what looks like 50/60mm cotton insulation in brown paper bags with a clear polythene wrap stapled over finished with plasterboard nailed on, studs are 600 centres.  I’m guessing the U value is way above .4 with only basic insulation.

 

my thoughts are

option 1 -

do I leave the walls as they are, they are covered with chipboard wallpaper, I can strap on top of the old plasterboard with say 2x2 into original studs, then add 30/40mm PIR and have a void for airflow and cables. I would lose 65mm off each external wall, I’m guessing the U value would be down to .3 ish with this set up but could there be a chance for condensation? 

Option 2 -

rip off old plasterboard, fill the 70mm void with 70mm PIR, wrap over with foil avcl, stitch a 2x1 batten on top of old studs and have a service void of 25mm, I would only lose 25mm off each external wall
Outcome - Would option 2 with 70mm PIR be more insulated with a 25mm service void and one sheet of plasterboard than option 1 with original 50mm old wool, plasterboard, 40mm PIR and 15mm service void and plasterboard?

I also have the option with option 2 to batten with 2x1.5 battens or 2x2 which would take my 70mm cavity to 108mm or 120mm which would allow a PIR of 80 to 100mm and still have space for a service void to run my cables.

 

I think cost wise the only difference is buying the thicker PIR, I need to buy the plasterboard regardless but option 1 saves a lot of time stripping and getting rid of old plasterboard and insulation and skips etc.

 

I could also just sheet over the plasterboard without doing anything so it’s the original build up but double sheeted, would help noise but not so much insulating the property, this would be cheapest and quickest but I am after a quality set up, 

 

tell me what you would do! And is PIR worth it, only looking at it as it saves spaces over rock wool.
 

If you have got this far thanks you for reading

 

steven

Hi. Do you not have scope to apply EWI outside the frame? 70mm only in the walls, and in Scotland = cold house and HUGE heating bills.

Are you on gas / oil?

Also, get the ceilings down and cut ( tight fitting ) sections of PIR between the rafters. then go over the top with 200mm of wool. Detail the underside of the ceilings with foil tape, and focuss all your efforts on getting convection heat loss ( drafts ) eradicated.