Airbrick into cavity

Looking for a bit of advice, this will probably cover a number of different forums but feel the building forum most appropriate.

We live in a fairly large extended 4 bed semi detached property which has a total of 12 airbricks which go into the cavity and not into the rooms.
Now this time of year with temps -7 degrees and the cold wind breeze it does not matter how much we pump out the GCH there are always cold drafts from under the upstairs floorboards, under the skirting boards, around the waste water pipes etc.
Even in rooms with thick carpet the floor is cold, I lifted the carpet and put my hand through a floorboard and the draft is freezing cold.
Last year we had cavity wall insulation fitted and now wonder why we need the airbricks at all as the cavities are now filled with polystyrene beads.
I have read that downstairs they are often needed for wooden floors to ventilate below, however our downstairs floors are all concrete, although the airbricks at the bottom I would leave alone and only block the higher ones that are just below the guttering.

I did an experiment a couple of weeks ago and covered a small number of the upper airbricks, inside the property stayed warmer longer and the thermostat kept switching the boiler off.

There are other properties along my row of the same design that have no upper airbricks, they were removed when the properties were re rendered.

So are these cavity airbricks still required? Should they have been blocked when the cavity wall insulation was installed? What is the best way to block them, possibly with the option of opening them again should they be required, i.e silicone sealant

Or are there better designed one of the market these days that do not allow drafts in, it just seems like we are throwing £££ out the vent and it defeats the object of cavity wall insulation.

Are the airbricks one course below your dpc? If they are, then they may be vents that are channelled under your ground floor, these are put in to stop a build up of Radon gas and let it out, and I wouldn't advise covering them up

I will leave the lower airbricks, 5 in total (1 at the front, 3 on the side and 1 at the rear) alone, I am more concerned with the 7 upper airbricks (3 at the front, 2 on the side and 2 at the rear of the property) what purpose are these serving except making the upstairs cold, do the upstairs floorboards really need that much ventilation?
Other properties along the row have had their upper airbricks covered with render but the bottom ones remain.
Since having the cavity wall insulation installed I have noticed condensation on the bedroom wall directly behind where the airbrick is located, i assume this is due to the fact that this area of wall is colder than the rest, with cold air coming in through the airbrick, another reason to cover it.

So do you think it ok, a good idea to cover / fill these upper airbricks

Air bricks were sometimes put in to cavity walls at low and high levels to ventilate the cavity. Apart from creating cold spots they could increase the U value to greater than a 9 inch solid wall.
Tawelfryn's point about radon is important, although if the air bricks were put in a long time ago they were probably for cavity ventilation.
As the cavity has been filled the air bricks are probably not really serving any real purpose. There may be some unfilled areas in the cavity.

Thanks for the advice guys, I will start off by closing off 4 of the upper 7 airbricks to see if it makes any difference.
Any ideas as to the best way to close them off without actually replacing with a solid brick.
I was thinking masonry filler or silicone sealant.......

I've only ever replaced redundant air bricks with brickwork, but I would think that a sealant would work.

jonnybegood said:

Since having the cavity wall insulation installed I have noticed condensation on the bedroom wall directly behind where the airbrick is located, i assume this is due to the fact that this area of wall is colder than the rest, with cold air coming in through the airbrick, another reason to cover it.

Click to expand...

So, let me get this straight; the airbrick has always been there and no condensation problems - cavity filled with insulation and suddenly condensation problem.

Says it all really.

As for the high level airbricks, do you have an open cavity into the roof space?(well you did before the cavity fill) If so they're probably venting this so you'll want to leave them alone as well. This should have been sorted by the cavity fill installers before commencing, they should have at least fitted cavity liners to the airbricks.