# Draughts from Wall Air Vents - advice please



## Henno (16 Oct 2012)

House is a always cold - and even With the CH on - there are differences in temperature within each room.  One room was registering 20 degrees C at waist level and at floor level it was registering 13 Degrees C.  There are draughts coming in at the top of skirting boards on the ground floor (solid concrete floor) and also the upstairs skirting boards ( suspended timber floor).  Also draughts from behind wall light fittings (upstairs).

Construction details: house constructed in the 1990's. Terraced. Front has cavity wall (not filled). Rear is cavity block externally rendered.  Internal walls front and rear are clad in insulated backed plasterboard.

Have tracked down what I believe the problem to be.  There are wall Air Vents located in each room.  I removed the interior plastic wall grill - which revealed that there is no conduit between the exterior grill and the interior grill.  Also there is a gap between the internal side of the external wall and the plasterboard. So essentially air is coming in through the vent from the outside and flowing In-between the interior side of the external wall and the plasterboard. - and then out the skirting boards and wall light fittings. Also the internal hole for the vent is a circular punched hole in the plasterboard - which you can just about get your hand in to.

My question is - what is the correct procedure (compliant with building regulations) to address the gap between the internal face of the exterior wall and the insulated backed plasterboard.  Is it permissible to simply fill this gap with expanding foam - or will this cause other issues?

Also should the internal hole in the plasterboard for the vent - be of a certain min. diameter ?


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## Sue Ellen (16 Oct 2012)

Can't give you a knowledgeable answer but IMHO the hole is there to allow a flow of air to prevent carbon monoxide poisoning so filling the holes with expandable foam is a definite no no.  You will most likely also land up with condensation problems.

Others here should be able to give you advice on resolving the problem in other ways.


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## Henno (16 Oct 2012)

I am not suggesting filling over the vents - Just the gap between the interior side of the external wall and the plasterboard - leaving the vents to vent - but to stop air travelling in between the interior face of the external wall and the plasterboard - and out the skirting boards.


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## Shane007 (16 Oct 2012)

Google Hamilton Gas Products. They do a wall vent that has baffles inside it that stops wind howling through but still allows the required air flow. They are telescopic so will suit most wall thicknesses.


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## Henno (16 Oct 2012)

Thanks Shane007 - so just to answer my query - is it permissable to use expanding foam around the edge to seal up the gap between the internal face of the exterior wall and the internal plasterboard - while still leaving the vent unobstructed? Or would this cause some other issues?


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## Shane007 (16 Oct 2012)

Very hard to control expandable foam. Better with sand/cement or bonding if it is deep and finish with coat of filler.


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## Henno (16 Oct 2012)

Ok thanks - so technically no issue using expanding foam - ie. there is no issue with contact between wall and plasterboard that would cause any damp issues - as it would just be sealing up the edge of the gap ?


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## Shane007 (17 Oct 2012)

There is no technical issue, I just am not a fan of it. Very messy and I once came across a gas boiler that foam had been used around the plastic flue and it can compressed the side wall of the air intake of the flue.
I find a bag of bonding cheaper and easier to use and gives a better finish as you can leave it just shy of the wall finish leaving room for a skin coat of filler. You cannot control the finishing point of the foam.


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## Leo (17 Oct 2012)

I'd agree with Shane007, be careful with the expanding foam. It can cause a lot of damage if it's ability to expand is restricted.


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## Henno (17 Oct 2012)

Thanks for taking the time to respond guys - much appreciated.


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## Sue Ellen (20 Oct 2012)

Another thing about expanding foam is the dreadful colour that it adopts over time.  Disgusting dirty yellowy foam, whatever about use outside it looks dreadful inside a home.


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