Telescopic air vent issues on self build

[Baz3986]

This is my first post so hopefully it makes sense.
I couldn’t find any information anywhere on this subject so decided to try open a thread and hopefully get some advice.

I’m overseeing my own build and am finding shortcuts & problems every time I look. I have discovered today that the brickies (no longer with me) have put the beam & block underfloor telescopic vents in the wrong place so the tops don’t align with the bottoms as the air bricks don’t match the brick pattern therefore the top half is offset from the bottom. This is obviously now leaving a gap at the side that will just be blowing air into the cavity, although they will still vent the sub floor.

What are the issues with this? As mentioned my sub floor will still get ventilation but my worry is that I’ll now be over ventilating the cavity and potentially causing drafts, cold spots, noise etc. which isn’t ideal as I would obviously like the house to be as energy efficient and air tight as possible.

On one elevation I can use the available extensions as this is rendered, not ideal as I’ll have unsightly vents in the bottom of the render but they’ll be doing their job correctly. This is not possible however on the facing brick section as the air bricks don’t align correctly. I’m thinking of stapling a DPC to the kit and overlaying on the vents / bricks(cavity tray) around the perimeter and this will seal the potential over ventilating at the low level. Any help or ideas are appreciated as this is causing me some stress. The new brickies are starting in 2 days so am keen to get some ideas before it’s too late.

Thanks in advance!

[New Home Expert]

It is NEVER a good idea to get over one bodge, by doing another bodge.
Bite the bullet, cut out brickwork and blockwork and position the air bricks correctly so they match the brick bonding.
Better to start off right.

You are correct, the gaps in the airbricks will ventilate the cavity more and the underfloor less.
Youi will get internal draughts and cold spots from this. No internal blockwork is ever fully filled joints. In addition the softer internal blocks can crack with thermal movement and let in air that way.

I would suggest you use blown fibre cavity insulation (this can be made from shredded recycled plastic bottle), done after the roof is on, but before drylining or plastering.