Why so many air bricks

[jonnybegood]

I have recently purchased a 1960s semi detached property which has a total of 11 cavity air bricks.
3 at the front (1 below bay window and 2 level with first floor windows), 5 on the side (3 at just above ground level and 2 just above first floor windows) and finally 3 at the rear (1 below ground floor window and 2 at first floor window level).
There is also a through vent in the lounge for the gas fire

I have noticed the neighbors property, same year built, same size and shape has only 3 air bricks, one on each side at ground level.
He has lived there 14 years and suffered no problems from damp or condensation.
Walking around the estate it seems some of the properties have more airbricks than others.

Firstly is there a need for all 11 airbricks?
I have just had cavity wall insulation installed and so was wondering what the point of having 11 air bricks, my neighbors also has CWI.

I notice in the property drafts under the upstairs floor boards and on a cold night the carpets upstairs very cold from the draft underneath.
I covered 2 of the rear air bricks as a trial with duct tape and the under floorboard draft vanished.

I have since removed the tape and the drafts are back, are there air bricks that will not allow draft into the cavity or can I safely block a few of the air bricks? if so which ones the upper or lower?

 

[NickStone]

People sometimes block up airbricks because they can't see the point of them, which might explain why some of your neighbours have fewer than you do. However, if the underside of your wooden floors become mouldy, you run the risk of dry rot so think twice before blocking up the ones that ventilate the floor void. Older gas fires needed a good source of air but the newer balanced-flue ones draw in air from outside and are isolated from the room. You might want to look at this: http://www.diydoctor.org.uk/projects/airbricks.htm

 

[JerryM]

the ground floor vents are essential if you have a wooden floor. i would even go as fare as to drill the holes out to make sure full air flow is getting through. Nickstone's link is spot on. timber soaks up water from in the air like there's no tomorrow. if the moisture (water) in the timber gets to typ 20% and stays that way for any length of time (typ 8wks) wet rot will set in and continue to rot until failure or treatment or replacement.

leave these vents well alone. any vents in roof spaces the same applies (over bay windows, loft space etc).

any upper floor vents in principle can be closed as from their locations i don't believe they were intended to ventilate the 1st floor void (between floor boards and ground floor ceiling). i think these vents were to do with the original open fire and would have had vents on the inside walls at some time to ventilate the rooms.

the only concern is to make sure the 1st floor void has no prospect of getting damp. the fact that there is a draft indicates there is an air path from outside into the void. you ideally need to find the leak and seal it. it's likely to be where the floor board joists sit in the inner brick wall and exterior frame sealant would sort it. suggest take up a section of the 2nd floor board in from the wall as a starting point. it's also 1st perhaps worth having a look into one of the upstairs vents for any clues on the leak and/or if it could be sealed from outside (taking up floorboards is to be avoided where possible (awkward/time consuming job).

the cavity insulation is not relevant as any vents should be closed to the cavity (ie a straight through hole from outside to inside) allowing the insulation to pass on installation around the vent hole.

 

[Thermo]

the cavity insulation is not relevant as any vents should be closed to the cavity (ie a straight through hole from outside to inside) allowing the insulation to pass on installation around the vent hole.

yes they should be but this wasnt done 20-30 years ago. quite often an air brick was put in each skin with no tunnel between.