Too many air bricks?

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Lancashire
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Hi,

We have a 1930s brick semi. At the front, we have a bay (brick). The bay has 4 air bricks in at ground level spaced 58cm, 68cm and 58cm respectively. There is a noticable draft in the front room.

In the side wall where our hall/stairs are there are another 4 air bricks at ground level spaced about 75cm-1m apart. It can get very drafty in there.

Round the rest of the house we only appear to have 2 other air bricks - one is under the kitchen, well below floor level (our back garden is at a much lower level). I find this a little confusing as I am pretty sure that the back half of the kitchen is on concrete as it was extended more recently, so I'm not sure where that vent goes.

The other ground level air brick appears to be ventilation for under the floor in our back room.

My question is whether the air bricks around the front and side seem excessive or whether they are needed eg. for sufficient air flow to the back of the house?

Our neighbour in the other half of the symmetrical semi blocks some of his air bricks with metal plates over the winter (I think about half of them) and removes them in the summer. We've had a new boiler, cavity wall insulation, loft insulation and I've had a look at the hinges and seals on the PVC doors to check for drafts. It seems a shame if we're losing a lot of heat through air bricks if we don't need so many.
 
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Are these vents venting directly into the rooms or just into the underfloor area?
If they are only venting the underfloor area then I would suggest not reducing the underfloor ventilation. Instead you might consider insulating and reducing draughts from under the timber floors.
There are plenty of threads on this topic.

As the kitchen is an extension, the builder may have provided a channel under the concrete floor for the continuation of the under floor ventilation for the rest of the house. Have a look at this link for a better understanding, and scroll down to the photos:
//www.diynot.com/forums/viewtopic.php?t=171482
 
We've got carpet in both rooms which are particularly bad, although I can still feel a draft around the edges of the laminate floor at the skirting boards in other rooms in the house as well.

Is the only way of dealing with this pulling up the carpet and relaying with insulated underlay?
 
Your neighbour is risking damp/rot by blocking airvents in the winter, so don't go down that route. You need to provide a barrier from the cold air beneath the floor. Hardboard over the floor boards before adding the laminate/underlay/carpet.

Ultimately, ripping up the floorboards and insulating between the joists will be the best long term solution, and despite the inconvenience/cost, will save you money on bills and make the room much warmer.

The 'draughts' you are experiencing could simply be convection, air movement within the room itself as opposed to actual cold air coming in from the outside. Even tightly sealed double glazed windows can appear draughty if you hold the back of your hand against them on a cold day.
 
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Ultimately, ripping up the floorboards and insulating between the joists will be the best long term solution, and despite the inconvenience/cost, will save you money on bills and make the room much warmer.

I read about that, but I don't really understand - doesn't that impede the under floor ventilation even more than stopping up half the air bricks would?


The 'draughts' you are experiencing could simply be convection, air movement within the room itself as opposed to actual cold air coming in from the outside. Even tightly sealed double glazed windows can appear draughty if you hold the back of your hand against them on a cold day.

In the hall and on the lower stairs at times I can actually feel a noticeable cold current of air coming upwards through the carpet (if I put my hand on the carpet). I have a thermometer at one end of the hall near the front door and the thermostat at the other end of the hall in the middle of the house (about 3-4m away) and I've seen the thermostat showing 19 degrees celsius while the thermometer is showing 15! (they are both digital and over the summer tend to give very close readings so I doubt that there is a problem with inaccuracy of the readings)
 
I read about that, but I don't really understand - doesn't that impede the under floor ventilation even more than stopping up half the air bricks would?
No beacause your insulation will be imediatly beneath the floor boards between the joists leaving a void between the ground and the underside of the joists. It is this void that needs ventilating. Normally the airbricks are beneath the underside of the existing joists
 
I read about that, but I don't really understand - doesn't that impede the under floor ventilation even more than stopping up half the air bricks would?
No beacause your insulation will be imediatly beneath the floor boards between the joists. Leaving a void between the ground and the underside of the joists. It is this void that needs ventilating.

So how are the floorboards themselves ventilated then?
 
They're not and don't need to be, it is the joists that need ventilating. The boards will be toasty with insulation immediately beneath them and at room temperature above.
 
Hi

As a rough guide you only need airbricks at around 2 metre centres but you do need to maintain cross ventilation, which is shown in the attachments to RedHerring2s' earlier thread.

The laminated floor will be adding to your woes because the cold transmittance from the floor void will be more noticeable with laminated flooring than where you have carpet.

To improve your situation you could use a 'knauf earthwall' flooring grade insulation which would require taking up carpets and laminate, and comes in a thickness of 25mm which would provide some benefit and would be far less intruisive but not half as effective as insulating between the floor joists, just need to consider the benefits of one over the other and make your choice. Obviously you would need to cut 25mm off the bottom of any affected doors.

Regards
 
As a rough guide you only need airbricks at around 2 metre centres but you do need to maintain cross ventilation, which is shown in the attachments to RedHerring2s' earlier thread.

That's interesting, because even if I average them out across the width and depth of the part of the house with floorboards, I think that they are around 1m apart centre to centre round the front and side of the house. The back seems to only have 2 though, which seems too few.

Is it possible that the air is blowing in at the front and side and the majority of it isn't blowing out of the back because of the lack of air bricks there, so it is blowing up into the house and creating drafts?


The laminated floor will be adding to your woes because the cold transmittance from the floor void will be more noticeable with laminated flooring than where you have carpet.

Ironically, the cold is far more noticable in rooms with carpet (although I'm not in the habit of walking around barefoot so much), so I'm inclined to think that the laminate is blocking some of the draft. On the other hand, the rooms with carpet are over the air bricks and have a larger surface area of windows as well, so it probably isn't a fair test.

A quick peek under the edge of the carpet in the bay reveals that there is a draft coming up at the very edge around where an air brick is on the outside. I'm not sure if this is coming under the skirting board or through the gaps in the floorboards where there is no underlay beyond the carpet grippers. The skirting board is noticably cold despite being directly under a hot radiator. I'm wondering whether to just peel back the edges of the carpet and silicone the gaps where I can feel a draft or put something down over the floorboards?

I'm beginning to suspect that there may be much larger areas in the hall which have gaps in the underlay which is why I can feel so much of a draft.

To improve your situation you could use a 'knauf earthwall' flooring grade insulation which would require taking up carpets and laminate, and comes in a thickness of 25mm which would provide some benefit and would be far less intruisive but not half as effective as insulating between the floor joists, just need to consider the benefits of one over the other and make your choice. Obviously you would need to cut 25mm off the bottom of any affected doors.

Thanks. I'll have a think about this. For the moment, I've just turned up the thermostat from 19.5 degrees celsius to 20.5 and I'm going round adjusting the thermostatic radiator valves in the rooms that feel too hot, but this does seem like a bit of a waste of gas. I think I'll monitor my gas usage for a few days and see if it looks like we're using a lot more before I decide what it is worth doing. As much as it seems wasteful and I am mindful of the environmental impact, I can't really justify the cost of doing anything significant at the moment if it isn't going to pay for itself in a couple of years.
 
The back seems to only have 2 though, which seems too few.

We don't know how many there were before the extension.

We have four airbricks across a frontage of about 9 metres at the front, and four across the back which has only about 5 metres of vented solum 'cos the other rear quarter is solid floor, and none at the side. There is a danger of dead airspace with this type of arrangement, but there's little I can do about it now.

In the past, I've blocked up the space between floorboard and skirting, and the gaps at the ends of the floorboards, with decorators caulk, or even expanding foam for larger gaps.
 
We don't know how many there were before the extension.

That's true, and the extension has probably been there over 40 years, which is a little worrying!

In the past, I've blocked up the space between floorboard and skirting, and the gaps at the ends of the floorboards, with decorators caulk, or even expanding foam for larger gaps.

Did you find that it made a noticeable difference?
 
Did you find that it made a noticeable difference?

Yes, very much so. You do need to be aware of the need for ventilation as well, but hopefully, preferably controllable ventilation.

So, be aware, if you have any other form of heating in your property, and/or if you suffer from any condensation/damp issues.

Incidentally, I still have the habit of laying newspaper on the floor underneath the underlay. It used to be a method of preventing the rubber underlay sticking to the floorboards.I think you can buy the proper paper underlay for this.
 
You do need to be aware of the need for ventilation as well, but hopefully, preferably controllable ventilation.

Hmm. I'm not actually aware of any other ventilation.

So, be aware, if you have any other form of heating in your property, and/or if you suffer from any condensation/damp issues.

We have 2 gas fires in open chimneys which I think we've briefly used about three times in the 4 years we've been living here.

Our bathroom suffers from quite a bit of condensation and our bedroom windows sometimes have some condensation. These rooms are upstairs though, so shouldn't there be separate ventilation upstairs? (I should probably pop around the house and have a look for upstairs air bricks)


Incidentally, I still have the habit of laying newspaper on the floor underneath the underlay. It used to be a method of preventing the rubber underlay sticking to the floorboards.

Does that help to reduce the drafts as well?
 
Your neighbour is risking damp/rot by blocking airvents in the winter, so don't go down that route. You need to provide a barrier from the cold air beneath the floor. Hardboard over the floor boards before adding the laminate/underlay/carpet.

You don't need to go as far as hardboard. A layer of paper, available as rolls at the sheds will do the trick nicely, avoids the need to trim doors and stops the underlay sticking to the floor boards as well. Just staple down.
 

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