Insulating a 1967 timber framed bungalow

[SimonD]

14 hours ago, esalglop1945 said:

internal insulation, which would be 4” insulation board applied to all external walls and skimmed.

 

What boards are they proposing?

[CharlieKLP]

1 hour ago, SimonD said:

 

What boards are they proposing?

good question! 4 inches is too thick, insulation board is about half that. 
 

Assuming you don’t live in the Arctic circle 

Edited February 12, 2022 by CharlieKLP

[SteamyTea]

11 minutes ago, CharlieKLP said:

insulation board is about half that. 

Is the word 'board' being used loosely here?.

100mm (4inch) is not a great deal of insulation, even in mild Cornwall.

 

If the property is exposed to the wind, airtightness becomes important.

[CharlieKLP]

There’s already insulation present in the timber frame right?

 

like you say, air tightness is important, I’d be getting new windows.

[PeterW]

7 hours ago, CharlieKLP said:

There’s already insulation present in the timber frame right?

 

like you say, air tightness is important, I’d be getting new windows.

Windows have nothing to do with air tightness - they will contribute 1-2% as they have double seals etc 

[Nickfromwales]

On 12/02/2022 at 14:43, CharlieKLP said:

good question! 4 inches is too thick, insulation board is about half that. 
 

Assuming you don’t live in the Arctic circle 

Insulation is available in varying thicknesses and many different material / performance types

4” EWI is normal, 75mm more popular in terraced. Internally the more the merrier in honesty, but it would be good to remove the internal plasterboard and lose as much in there as possible and then laminate with a thinner continuous internal insulation layer before new plasterboard goes on. 

[esalglop1945]

Received reply from Isothane. They do not recommend filling the 4” gap ‘cos it is likely to deform the plasterboard as it expands. I filled the shop ceiling void where I am now living (1750 townhouse in shopping street) with blown lambswool! But I do not know about using on this project.

Reluctant to tear off plasterboard before examining any alternative suggestions.

[markocosic]

I don't think you should insulate this from the inside if there's a full on plastic air/vapour barrier wrapped around the outside. Not unless you have a *completely* airtight

Is there a crawlspace? (can you access the underside of the floor and the bottom of the wall cavity)

Is there a roof void? (can you access the top of the wall cavity?)

 

 

I think would:

 

- Strip plasterboard from the inside

- Keep the plasterboard in a pile if you have clay soil. People buy gypsum and dig it into the soil to improve it...

 

- Move any internal walls that you want to move for layout reasons

- Swap the windows and doors that you want to swap for insulation / airtightness / aesthetic reasons

 

 

Walls:

- Strip the plumbing and electrics from the walls

- Trash the plastic air / vapour barrier in the cavity. Either by ripping it out from the top / bottom or by drilling some 4" holes through the outer sheathing and pulling the plastic out through the holes

- Full fill 4" mineral wool between the studs (doesn't "droop" like fibreglass, doesn't need professional application like spray foams, isn't a pain to cut around existing structures and seal usefully like PIR boards)

- Air / vapour control layer (airtight, vapour resistant, but not solid plastic)

- Counter batten with 75 mm "battens" every 600 mm (e.g. 36 x 75 mm rough sawn arranged so that )

- Run all new plumbing / electrics in this "service cavity" on the inside of your vapour control layer

- Insulate in this service cavity with more mineral wool

- New plasterboard with sockets etc wherever you want them

 

You've avoided the heavy work of moving bricks / changing structural elements; U-Value of the order 0.23 depending on how much bridging there is. 75 mm loss of space.

 

Bridging can be reduced by using insulated plasterboard instead of the service cavity plus mineral wool...but then you don't have anywhere to run your services. That might be ok if they can sit on internal walls. That might also be ok if you're going to raise the floor and can run your cables under the floor. I don't think it's entirely crazy to use insulated plasterboard with a few "chases down to the floor" where sockets go if you REALLY need a socket in a particular spot but otherwise the outside walls are plain.

 

This isn't the buildup I'm suggesting but it'll give the same U-Value as the buildup described above.

 

 

To do better build a second stud wall "inboard" of your existing wall?

 

- Existing brick and cavity

- Plastic membrane ripped out

- Existing sheathing

- Existing 4" studs

- New full fill 100 mm mineral wool with no bridging (+100)

- New stud wall on 600 centres with full fill mineral wool (+89)

- Vapour control layer

- 25 mm battens horizontally as service void (+25)

- Plasterboard

 

That might give as good as 0.13 for 200 mm loss of internal space.

 

 

Or you could also try to fit PIR boards between the studs, foam them in place then run over the top with insulated plasterboard, again trying to avoid any services in the walls. This will be more of a PITA but allegedly 0.14 for only a 75 mm loss of space.

 

 

 

 

Ceiling easier:

- Air / vapour control layer (airtight, vapour resistant, but not solid plastic)

- Counter batten with 25 mm thick battens every 600 mm (e.g. 25 x 50 mm roofing battens)

- New plasterboard with light etc wherever you want them (lights that don't puncture the vapour control layer)

- Top if off with all the loft insulation that'll fit; paying attention to the eaves to avoid air bypassing under the insulation and to avoid blocking cold roof ventilation

 

After you've put your MVHR in first!

 

 

Floor:

 

Pass. Unclear what room you have underneath this at the moment, if any. If it's block and beam then insulate from underneath?