Insulating a Bay Window Wall and Ceiling

[chameleon001]

Hi,

My first post here. In process of renovating and trying to do some of the work myself. Found that my bay window is completely uninsulated so want to get this sorted whilst I have all the plaster off.

I have only just found this forum so have already done quite a bit, but want to check I have done it right before I finish the job.

Upstairs in bedroom, I have fitted 100mm of celotex to ceiling section between batons for PB. I then plan to tape between the celotex then fit vapour barrier over this before plasterboarding. I have kept a gap for the soffit vents and enough space for air to flow up into the rafters.

http://www.diy.com/departments/ndc-green-moisture-vapour-barrier/35633_BQ.prd.

For the bedroom bay wall I ended up added a second stud wall so that I could have a windowsill. This has allowed me to get 100mm and 25mm celotex in the wall. I am then going to fit vapour barrier before 25mm batons for service void before PB.

Downstairs in lounge is where I'm more confused. I have extended the celotex from the bedroom down, thickness varies from 50mm to 125mm here. I will try and fit vapour membrane but very undulating/ difficult to do. Feeling I may have been better trying to get one long strip of celotex across here. I could infiltrate the joist sections with thin strips celotex then aluminium tape over the log. I am also unsure whether it is worth putting any celotex above the lounge ceiling and if so whether it needs vapour barrier.

I have foamed a lot of the gaps with expanding foam.

Am I on the right lines or way off course? Any help would be greatly appreciated.

Bedroom Before:

Bedroom roof before:

Lounge now - celotex between timbers total 50 - 125mm thickness

Bedroom now, next stage is vapour membrane then service void batons:

Thanks,

Dan

 

[chameleon001]

Bump, any thoughts?

 

[noseall]

Here is one I did earlier....
We went with two layers of Celotex - 75mm between studs (foamed and taped) and 50mm across the studs also taped.

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[pilsbury]

Sorry to highjack a thread - With a tile fronted bay window in an older house with no insulation and lath and plaster inside, how much difference would insulating like this make to street noise assuming the window is double glazed? Much? Or does the noise come from the glazing?

 

[chameleon001]

I think mine seems less noisy now insulated but quiet road so hard to tell. Got the vapour membrane on, ready for battening

 

[chameleon001]

Mine seems quieter now we have insulated but it's a quiet road so hard to say.

 

[DIYedboy]

Dan,you're doing the job spot on, but don't forget to insulate BENEATH the floorboards or that void will get condensation forming and mildew will grow there (happened to me years ago). The foil layer of the celotex is a vapour barrier, so you only have to tape across the joins between them if you prefer. Your efforts will stop the bay from 'sweating' on the inside due to the single skin wall becoming super cold in the winter.

I have just watche one of my neighbours remove the tiles from his bay, put up black polythene then re batten and fit new tiles, I'm sure he thinks his sweating bay is due to water penetration, which of course it isn't, it's lack of insulation causing a cold bridge!!

 

[chameleon001]

Hi, cheers for that. By insulate beneath the floorboards do you mean just the timber framed wall section below floorboard level or the actual void made between ceiling of lounge bay and bedroom floorboards? As you can see from earlier pics I've got some insulation in the wall bit only atm. I was thinking of getting 100mm of celotex to line the lounge ceiling but that would still leave a smaller gap between celotex and upstairs floorboards, does it have to be completely full?

Thanks for your help.

Dan

 

[DIYedboy]

You must bung the celotex against the outside wall in the void between downstairs ceiling and upstairs floorboards because that hidden area will still get super cold and will then become the only cold area for the warm air to condense on therefore thanks to the new yummy warm surface above it'll get twice the amount of condensation it ever had before!!!