Unlagged pipes in suspended timber 1st floor.

[Mike Halmarack]

To lag these pipes properly would mean pulling up a lot of floorboards. Does there really need to be quite so many air bricks allowing such a cold draught in a floor of this type, at this level?

[Ian Stirling]

It's a fine balance. You really, really don't want to get rotted floors, due to condensation.

Water comes out of the ground as vapour - if the underfloor is not properly sealed, and from the top, though the floor. If it then condenses, when it hits the cold underfloor void, bad things happen. I wonder how much power heat recovering vent bricks would save...

[Mike Halmarack]

It's a well insulated and warm house, with pleasantly low power bills, though things seem set to change. It was just a shock when I pulled up a floorboard to realise what a cold wind was blowing through there. The CH pipes are bare and the DHW flow and return from boiler to storage cylinder only have a thin layer of that old brown sacking type of insulation. Reducing the air circulation would be a lot easier than lagging the pipes but I wouldn't want to be the cause of someone falling through a rotted floor at some later date.

[<me9]

He's talking abou a first floor, which will have a ceiling below. These are rarely ventilated.

[Mike Halmarack]

This one has 2 louvered vents in the east facing wall at 1st floor level. the other 3 walls have none. This may be enough to provide the stiff breeze passing through but it could also be coming from elsewhere, like up the cavity. But with this kind of timber framed construction with a brick skin outside I think there's continuous boarding between the frame and the cavity.

[Mark]

Yes, unless you want to kill your house and yourself Google "blocked air bricks" and "health risk damp spores"

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[Mike Halmarack]

Thanks for the cautionary tips. Maybe there's a moderated air flow achievable the will have the required anti-damp damp effect, without carrying away quite so much heat. Perhaps an adjustable louvered vent in place of the fixed louvres.

[Tournifreak]

I don't get it. Very few houses have airbricks at first floor level. But a few do around this area. So why is it necessary for some houses and not for others? Was it just a short-lived idea sometime in the early 20th century? I'm sure someone on here knows...

Jon.

[The Natural Philosopher]

What do you mean by 'first floor level

In US terms thats ground floor level

If you are talking in terms of between lower and upper storeys, i.e. well above ground, there is no point in ventilating at that level unless there is some specific unique damp problem.

Cavity walls need some venting allegedly, but that need not extend inside the floor structure.

chances are the joist are laid into the inner wall leaf and simply have random gaps around them. Plug the gaps, or stuff the floor with rockwool.

[Mike Halmarack]

I must check, it'll give me an excuse to get out more. :-)

I can currently only guess at the structure of this 1984 built house and I'm not going to take it apart to any great extent to check. Other than membranes etc. it seems to be a box with plywood sides surrounded by a cavity, then a single skin of bricks. Just below the ground floor, on two sides of the house there are 6 air vents which are ducted through the cavity and an inner skin of blocks. These ventilate the under floor space including the exposed floor joists of the ground floor. By doing this, they don't seem to be ventilating the cavity.

The 2 air vents at 1st floor level may not be ducted, so they might only be ventilating the cavity directly.

The first floor is a multi-compartment box, with floorboards above and plasterboard below the compartments are formed by the floor joists which aren't likely to be weakened much by cut out vents. The joist ends finish at a timber wall plate of the same size to complete the box effect. So where the stiff breeze comes from I still don't know for sure.

I don't know if the

[Mike Halmarack]

I was hoping that in the UK it would mean the floor above the ground floor.

There isn't one of those.

That's what I thought

There may be gaps somewhere but where I can see them the joist ends are close jointed to a timber wall plate, which, if countinuous, would pretty much air seal them.

If I was happy to pull up the tongue and groove flooring to do that I'd have no real problem there. i realise that I wouldn't have to pull it all up but I'd like to keep damage to the structure to a minimum.

I've pulled up some boards for plumbing purposes though and modified the method of cutting the tongues that I read on this NG, so maybe I'll mention it in another thread.