Fitting 70mm celotex between 100mm beams.

[Markymilarky]

Hi Chummmms.
I have walls that are 100mm deep timber uprights with asbestos pannels on the outside. : I,ve taken off the old plasterboard to expose the timbers and the back of the asbestos( . I,ve noticed the asbestos runs with water as the warm air in the room condenses on the freezing cold asbestos.

I have got a load of Celotex quite cheap. I wanted 100mm to fill the cavity but beggars cant be choosers and i have 70mm. I plan to fit it between the joists and tight up against the asbestos so moisture cant condense on it. This will leave a 30mm gap at the front which will be directly behind the plasterboard. Could any of theee in the know tell me if this will be ok please? if not i dont want to buy any more celotex but I have a load of cheap fiberglass insulation, would it be a better idea to fit this directly behind the plasterboard filling the 30mm gap? ch ch ch Cheers Chaps.. mark

 

[noseall]

can you not somehow solid fill the airspece between the uprights?

have a look here

 

[Markymilarky]

Hi Noseall,
Thank's very mucho for the link, cant open it on my machine. but ill try on a friends who has broadband. look froward to reading it. all the best mark

 

[squowse]

Hi Chummmms.
I have walls that are 100mm deep timber uprights with asbestos pannels on the outside. : I,ve taken off the old plasterboard to expose the timbers and the back of the asbestos( . I,ve noticed the asbestos runs with water as the warm air in the room condenses on the freezing cold asbestos.

My first reaction is that the insulation will make the asbestos colder and even more likely to condense the water vapour that's trying to escape the house.

You can still get condensation on the interfaces between the layers of wall / roof construction. It's called interstitial condensation. That said, i can't advise the best way forward off the top of my head. You could try asking here - they are insulation experts.
http://www.greenbuildingforum.co.uk/newforum/

 

[noseall]

by fully filling the void, then sealing with tape, then fixing a vapour barrier and some foil backed boards, this should prevent moist air from getting anywhere near the asbestos.

 

[jkf1000]

If you mount your cellotex leaving a 30mm air space between it and the asbestos outer, you prevent the accumilation of warm air that is causing the condensation, as well as having a air space to allow air flow around the joists. Karl

 

[Markymilarky]

Big thank's Chaps for the replies.

"If you mount your cellotex leaving a 30mm air space between it and the asbestos outer, you prevent the accumilation of warm air that is causing the condensation, as well as having a air space to allow air flow around the joists. Karl"
Cheers Karl,

"by fully filling the void, then sealing with tape, then fixing a vapour barrier and some foil backed boards, this should prevent moist air from getting anywhere near the asbestos." Cheers Noseall.

"My first reaction is that the insulation will make the asbestos colder and even more likely to condense the water vapour that's trying to escape the house.

You can still get condensation on the interfaces between the layers of wall / roof construction. It's called interstitial condensation. That said, i can't advise the best way forward off the top of my head. You could try asking here - they are insulation experts.
http://www.greenbuildingforum.co.uk/newforum/ " cheers squowse.

Ok Chaps, I've taken it all on board. the sole plate isn't sat on any dpc, so ill try and jack the wall up to put some in. dont want to cut anything as i may hit the asbestos which is everywhair. also it seems the asbestos is holding moisture. so im thinking some moisture content will be trapped in the timber and asbstos and may at times condense.
I have a shed load of bitumin tanking I'm thinking of just painting the asbestos and the timbers with it then fitting the celotex, hummmmmm. ill probably knock the place down in a few years but need to keep it going till then. ok Chaps thanks again, im on the fence so going to read all that bumph on the links. thanks again .. mark

 

[noseall]

there isn't the opportunity to vent the void in this instance and there will be no breather membrane either.

i should stick with full fill and vapour barrier.

 

[squowse]

i should stick with full fill and vapour barrier.

seconded

 

[^woody^]

Yes full fill and vapour check is the best way.

But in this case, the timbers are doing to be damp from the existing problem, so you don't want the seal in the damp with a vapour check - which could then lead to rot.

Try and wait until the timber is a lot drier before covering it up, or better still, use a breather membrane (like used on roofs) so that the wall can breath into the room, without moisture from the room getting into the wall

 

[Markymilarky]

Hi Chaps, thanks very mucho.
aaa well i see what your saying about full fill and not locking in the moisture.but my budget wont stretch that far. I could fill the 35mm with glass fiber insulation that i have loads of but me thinks it wont work with the humidity condensation.
ill have a look at polystyrene tomorow it looks a lot cheaper than the polyurathane. i could use that to fill the 30mm left over. Thanks again everyone for all the help. much apreciated. all the best mark

 

[Markymilarky]

Hi Chaps,
new plan. put up a false celing, the studwork is about 3 foot below the original celing. so I'm leaving the walls open above the new celing so they can breath and will fill the wall cavity with celotex against the asbestos ( Im bonding it to the asbestos with bitumin adhesive so no moisture can get inbetween. then 30mm of fiberglass to fill the gap to the back of the plasterboard. Im thinking if there is any moisture left it will be able to vent out the open top of the wall into the roof space. Thanks a lot Chaps for all the help, ive been having a mental block hope this will doo the trick. all the best mark