Insulating between joists, air brick position, vapour barrier?

[andreas]

On a suspended wooden floor, I have to replace so many floorboards that I have decided to lift them all, insulate between the joists with PIR while they are up and refloor in P5 Caber.

The airbricks are between the joists, same height as the base of the joists. Would chamfering off the end of the insulation to form an air chute be acceptable? I know it wouldn't be perfect from an insulation perspective as it would only leave 30mm thickness at the thinnest part of the chamfer but moving the air bricks is not really viable as they are only one course above outside level - moving them any lower they'll be at ground level (one would actually be below).

Also wondering what the best vapour barrier would be to put between joists / insulation and caber, and anything else I should consider before I start.?

[markocosic]

https://www.fastbuildsupplies.co.uk/53650-150mm-vertical-extension-piece

[markocosic]

Vapour barrier not required there. Glue all the caberdeck joints. Plenty good enough as an air barrier. Your difficult area is the caberdeck<>wall joint. That wants to be airtight. Foam won't cut it. You'll want an airtightness tape there.

[andreas]

10 minutes ago, markocosic said:

Vapour barrier not required there. Glue all the caberdeck joints. Plenty good enough as an air barrier. Your difficult area is the caberdeck<>wall joint. That wants to be airtight. Foam won't cut it. You'll want an airtightness tape there.

Thank you. any recommendations on tape? Is there any *disadvantage* to a vapour barrier other than unnecessary cost?

[markocosic]

1 minute ago, andreas said:

any recommendations on tape?

 

Sorry, no clue.

 

1 minute ago, andreas said:

Is there any *disadvantage* to a vapour barrier other than unnecessary cost

 

An AIR barrier won't hurt you.

 

A VAPOUR barrier will prevent moisture in the caberdeck drying to the outside.

 

Imagine wearing a bin bag on a run. The sweaty sticky mess inside the bag is your caberdeck if you use a vapour barrier.

 

Now wear goretex etc. The vapour goes through but the wind doesn't. This is what you want.

 

Glued caberdeck is enough. The areas to concentrate on are the holes and the edges. No point wearing a coat if the wind is howling through it.

[IGP]

Pro Clima Solido SL tape with the wall sprayed with SPrimer before taping. Not cheap, but excellent stuff. 

[andreas]

On 04/08/2024 at 18:17, IGP said:

Pro Clima Solido SL tape with the wall sprayed with SPrimer before taping. Not cheap, but excellent stuff. 

 

thank you

[Super_Paulie]

i had the same situation in my front room with the OG airbrick, and i did like you say and chamfered the end of the insulation. I sealed between the wall and insulation and then sealed between the wall and caberdeck afterwards. I used Illbruck airtight foam which is a quality product, ive used loads in my place to make the floor draft free as i run UFH as well.

 

Illbruck FM330