Air tightness and first floor joists

[Rob55]

Hi

 

Can anyone give me advice on how to airtight first floor joists which penetrate the inner leaf blockwork into cavity walls?  I am wondering should I use plasterable tape, and wrap it around each joist where it punches through the wall.  And then plaster all blockwork between the joists?

 

I am currently renovating a 1980's house which I intend to go with full air tightness measures.  All plasterboard is down so I have a chance to remedy all weaknesses, and the first floor joists are top of my hit list!!

 

Thanks

Edited November 1, 2020 by Rob55

[Nickfromwales]

8 minutes ago, Rob55 said:

Hi

 

Can anyone give me advice on how to airtight first floor joists which penetrate the inner leaf clockwork into cavity walls?  I am wondering should I use plasterable tape, and wrap it around each joist where it punches through the wall.  And then plaster all blockwork between the joists?

 

I am currently renovating a 1980's house which I intend to go with full air tightness measures.  All plasterboard is down so I have a chance to remedy all weaknesses, and the first floor joists are top of my hit list!!

 

Thanks

What is the construction type? Block and brick? You'll need to parge-coat all of the internal walls and not go for dot n dab. You could just use a membrane to go from 50mm below to 50mm above the joist detail, and AT tape the hell out fo everything before covering the tape with wet plaster ( parge-coat ). This will be a bugger to detail over a whole house, but remeber that you will need MVHR or at least MV to pass building regs in an AT house. 

[Onoff]

This any good?

 

https://www.everbuild.co.uk/product/thermofoam/

 

Says "Certified air permeability: a<0,1 m³ to EN 12114:2000"

[tonyshouse]

https://readinguk.org/draughtbusters/going-further/first-floor-void/

[Onoff]

35 minutes ago, tonyshouse said:

https://readinguk.org/draughtbusters/going-further/first-floor-void/

 

Interesting. No sign of air tightness tape being used in the fixes, just board and gun foam. Unless I missed it they don't say what brand foam.

 

I think the right foam is good, look at Icynene!

Edited November 2, 2020 by Onoff

[Russell griffiths]

You can buy air sealing liquid in a 5kg bucket, it is like a thick paint with fibres, 2 inch paintbrush and off you go slap it on everywhere. 

Easy peasy. 

[tonyshouse]

My guy used insulated plasterboard and gun fire foam i think 

[Rob55]

On 01/11/2020 at 23:34, Nickfromwales said:

What is the construction type? Block and brick? You'll need to parge-coat all of the internal walls and not go for dot n dab. You could just use a membrane to go from 50mm below to 50mm above the joist detail, and AT tape the hell out fo everything before covering the tape with wet plaster ( parge-coat ). This will be a bugger to detail over a whole house, but remeber that you will need MVHR or at least MV to pass building regs in an AT house. 

 

Construction is dense blockwork cavity walls.  The house is already plastered so the only exposed clockwork that really needs parged is the ceiling void with the first floor joists.

 

MVHR is already agreed upon.  The last house is built was tested at 0.8ACH and I'm optimistic I can get close on this retrofit!