Cavity vents

[dormermike]

The front bays of my 1930's bungalow have cavity vents - they don't come through to the inside walls. I think they are making the inside walls cold (no insulation) which is causing condensation at the base of the wall at the wall/floor junction.

I am considering blocking them up on the outside - is this likely to cause problems?

Thanks

 

[stuart45]

Cavity vents used to be common in the 30's, but were found to cause cold spots in the wall and are not used now.

 

[dormermike]

OK cool - so sounds like blocking them up might be sensible

Without taking out the vented bricks and replacing with normal bricks, i wonder if a brick fascia could work as a temporary solution until i am satisfied it wont cause problems.. or any other ideas?

 

[karl666]

The front bays of my 1930's bungalow have cavity vents - they don't come through to the inside walls. I think they are making the inside walls cold (no insulation) which is causing condensation at the base of the wall at the wall/floor junction.

I am considering blocking them up on the outside - is this likely to cause problems?

Thanks

I did the same with my house and blocked them off. I cut a piece of clear perspex to size and used clear silicon to hold it in place.

Here is a thermal image from outside showing the cool air circulating in the cavity

Untitled

• karl666
• 10 Nov 2012
• 1

here is the result of the cool air on the inside wall

Untitled

• karl666
• 10 Nov 2012
• 1

 

[dormermike]

Thanks, thats encouraging! Good idea about the perspex too

 

[^woody^]

If you want to block air bricks up, just use clear silicone - which can be removed if you subsequently find out it was a mistake.

Condensation damp at the base of a wall is more likely to be caused by a blocked cavity, and nothing to do with a ventilated cavity

Whilst Stuart is correct, in that ventilated cavities are an old-fashioned concept, it does not mean that you should then just block them up and remove that ventilation

 

[dormermike]

Thanks woodie

To be honest i think the damp is mostly rising and or penetrating. I have had a camera in the cavity and as far as i could tell its not obviously blocked/chocked up.

My main reason for considering blocking the cavity vent is that the internal walls where the cavity vents are are very cold and i think making the rooms colder. Not helping anyway.

Reducing condensation would be benefit. The base of the wall is often around 10-12c.