Air Vent woes

[mike2016]

Hi,

Looking for advice. I'm currently living in a 20 year old semi detached house. The walls are Cavity Block with internal dry lining.

I'm looking at the air vents to make sure they are open and allow air to flow. Two immediate issues found were:

One upstairs bedroom has an air vent visible on the outside but there is a fitted wardrobe right up against where you would expect to see the grill inside!

The living room has two external air vents but only one appears inside. The other has slight discoloration on the wall where you would expect to see the grill.

 

I decided to look behind the air grill in my bedroom and found it partially blocked (See Pics). It has brick lining to either side and the cavity block structure above and below. As I sleep here this is the most important one for me to solve - how should the inside of the air vent be correctly lined as it looks like a bodge job currently? Would any change impact the cavity wall's need to breathe?

I hope to fix my bedroom up properly first, then do the same for any others that are in a similar state before figuring out what to do for the first two I mentioned earlier. 

 

What was the builder trying to do with the bubble wrap anyway?!!

 

Any advice appreciated & Thanks. 

 

[Simplysimon]

two points, cavities shouldn't breathe and nor should they be bridged. our house has ventilators in the walls and a roll of sellotape has stopped a lot of draughts! that said, the house is about 50yrs old and has plenty of ventilation, (draughts) to compensate for the removal of the ones in the walls. 

as for the bubblewrap, a handy repository for waste material and a way to partially insulate the cavity

do you have any other draughts to allow ventilation or trickle vents in windows. being double blockwork, no vapour barrier and not very airtight? so air bricks may be overkill.

[AliG]

Is the house definitely only 20 years old? It seems very odd to have this kind of air brick in such a modern house.

 

The bubble wrap was probably put there by a previous owner trying to stop draughts.

 

Is the cavity sealed all the way round the air bricks, I can see the bricks at the sides, but not the top and bottom? Most air bricks are to ventilate under wooden floors or to ventilate cavities, but these seem to be for room ventilation.

 

If so did the rooms originally have gas or coal fires?They may have been to provide ventilation for the fires.

 

As Simon said they may also have been instead of trickle vents in the windows, but that would seem odd in a 20 year old house. If they are instead of trickle vents they are likely larger than needed by building regs for ventilation.  If windows have trickle vents and there are no fires I am at a loss as to why they are there.

 

I doubt you have to worry about having too little ventilation, assuming you don't have any damp issues. I would be more worried about the heat loss. I would be considering having them closed up but only after ascertaining why they were there and if you have enough ventilation from other sources such as trickle vents.

 

[Simplysimon]

@AliG our house is a wimpey, built early 60's and has these, one in each bedroom, sitting room and dining room. no gas fires nor chimneys other than a coal fire in the sitting room. windows would have been wooden casement originally without trickle vents. the vents were for ventilation though totally unnecessary with the other draughts as opposed to air bricks hence the reason i've taped over them.    would agree with questioning the age of the house though, surprised it's not timber kit if 20yr old

[AliG]

@Simplysimon I can totally see it in your 50 year old house, but not 20.

 

I see you're in Scotland like me, indeed almost everything up here built in the last 30 years is timber frame, but due to issues in the 70s with timber frame houses they fell out of popularity in England. I don't know about Ireland where Mike seems to be.

 

I was thinking the same thing, that a block built house probably has enough draughts that vents aren't needed although building control wouldn't agree. My parents had a Wimpey timber frame house built in the mid 80s and I remember it was a bit prone to condensation. It was single glazed and I don't think it had trickle vents, but my memory is a bit vague. Their subsequent house built in around 1992 had both.

[mike2016]

Thanks all,

The house has gas fired heating and chimney with a gas fire in the living room fireplace (never used). There's no trickle vents in the windows except one at the top of the door in the living room leading to the rear garden. 

I'd say you're right- the bubble wrap is a previous occupants attempt at reducing the noise from a main road outside. Just all seemed a bit rough and ready when I had a look. Wondered if wavin pipe would be worth putting in the vents? Not sure about blocking it up, gets very stuffy (CO2 heads to @2,000 ppm) and with the traffic don't like leaving windows open due to noise. There are a few draughts from one or two windows mostly due to age, original PVC double glazed units. 

At least I didn't get any four legged occupants staring back at me when I cracked it open! 

 

oh - forgot to add - you can see the Cavity Blocks top and bottom and they are open to the vent channel......

Edited April 22, 2017 by mike2016

[AliG]

Ah so it is due to lack of ventilation in the windows. They may have been added to the living room windows due to the fire.

 

Assuming you aren't planning to replace the windows with new ones with trickle vents, which means you could block up the wall vents, I found another discussion about the same issue.

 

You can get cowled vents that reduce noise and draughts through the air bricks. I suspect that these would be a good idea. You could unblock the vents and then put proper vents into them.

 

http://www.airflow-vent.co.uk/product-category/plumbing-ventilation/plumbing-ventilation-through-wall-vents/

 

2000ppm of CO2 is stuffy, although I have never tested what my bedroom gets up to. The easiest solution rather than opening your bedroom to the outside is to open the bedroom door and allow air to circulate around the house. Interesting to see what this guy found here.

 

http://vair-monitor.com/2016/09/29/sleeping-closed-room-indoor-co2-analyze/