Cavity

[petra robbie]

Hi all, I wonder if anyone can advise.
We bought a 1930s property and decided to sleeve off/bridge the airbricks that were already there to ventilate the underfloor.

I heard that the cavities need ventilation too? Will bridging the airbricks afect the cavities?

We are planning on installing cavity insulation and that’s why we are bridging the airbricks so the EPS beads do not fall out.

I keep reading negatives about the insulation however we live in the southwest with properties either side of our external walls.
My assumption is also that if the is no moisture penetrating the external walls(let’s say they are suitable rendered) then the cavity does not need to whisk away any dampness/water away from the internal wall and so can be filled?

any discussion on the above would be greatly appreciated

Petra

 

[KenGMac]

petra robbie, good evening.

OK the information on the web is / can be confusing and contradictory, if not presented correctly.

In old property such as yours [1930 s] cavities were indeed blocked off, air flow was minimised / non-existent, the concept was that air flow in a cavity would [tend] to draw heat from the house, a sealed cavity would not do that and, air is a good insulator if it does not move.

Modern buildings, when the property is being constructed Insulation is built in, this Insulation must have the cavity vented, this to prevent condensation and internal dampness. such issues did not generally occur in the older properties.

Yes you should block of the air vents for the U/Floor area, if you do not the vent may block with the retro-filled insulation and the insulation will cascade into the under building.

Ken

 

[petra robbie]

That’s very reassuring, many thanks Ken for taking time to replay