Cold lounge/subfloor ventilation questions

Our home is a 1930s detached house, brick-built with cavity walls and suspended timber floors at ground level. There are airbricks to two sides of the house, with varying degrees of clarity, whilst a modern extension and a conservatory - both solid-floored - are now appended to the rear and one side of the original house.
In a recent underfloor excursion I noticed a massive difference in the dampness of the subfloor between our lounge - which is on one of the open sides of the house - and study, which is effectively in the centre of the house with minimal ventilation. In fact the study was cinder-dry and just covered me in dust, whilst the subfloor in the lounge was earthy and clammy. On a previous visit both rooms were equally dry.
As well as seeming a bit damp underfloor, the lounge has always been extremely cold. There are two sizeable radiators, but also an open fireplace which must remove a lot of warm air. In fact, sometimes the carpet feels a bit wet on the surface,as if condensation is forming.
Is it generally advisable to insulate the underside of the wooden floor? There is nothing at present. Will this have a detrimental effect on the already-poor ventilation, which is presumably the root of the dampness?
I also noticed that two airbricks at the rear are actually placed level with the floorboards, i.e. only the bottom half of the brick is below floor level. Not surprisingly, my coathanger doesn't get very far in the top half. Even in the bottom half I would say only 10-20% or so of the airbrick is clear.
Any advice is welcome, both on the potential damp situation and on warming the room up as autumn draws in.
Thanks, Gareth
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"no_heat" wrote:

It should be bone dry under the lounge floor. If you have 4 airbricks, 2 being partially blocked, this may not be giving adequate under-floor ventilation. My 1900 semi has suspended floors for the lounge and dining room, with a total of 5 airbricks, 2 at the front, two at the side and 1 at the rear. I don't know anything about the effectiveness of insulation between the joists, it doesn't seem to get mentioned in advice on energy saving and insulation. I went for draught-proofing the floors and cavity wall installation; this has made a big difference, especially to the previously cold and draughty north-facing lounge.
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Thanks Phil.
Where is the best source of objective professional advice on the damp situation? Chartered surveyor, builder?
Phil Anthropist wrote:

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"no_heat" wrote:

An independent building surveyor or structural engineer.
http://www.localsurveyorsdirect.co.uk/
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On Thu, 31 Aug 2006 15:46:15 +0100, "Phil Anthropist"
|"no_heat" wrote: |> Thanks Phil. |> |> Where is the best source of objective professional advice on the damp |> situation? Chartered surveyor, builder? | |An independent building surveyor or structural engineer. | |http://www.localsurveyorsdirect.co.uk/
Test to see if this appears on Google Groups
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method of accessing usenet. GG subscribers would be well advised get a
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Dave Fawthrop wrote:

I can't see it from here.
MBQ
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On 3 Oct 2006 08:35:22 -0700, snipped-for-privacy@hotmail.com wrote:
| |Dave Fawthrop wrote: |> On Thu, 31 Aug 2006 15:46:15 +0100, "Phil Anthropist"
|> |> |"no_heat" wrote: |> |> Thanks Phil. |> |> |> |> Where is the best source of objective professional advice on the damp |> |> situation? Chartered surveyor, builder? |> | |> |An independent building surveyor or structural engineer. |> | |> |http://www.localsurveyorsdirect.co.uk / |> |> Test to see if this appears on Google Groups | |I can't see it from here.
GG and the rest of the usenet propagation system is a bit slow. I will check after tea.
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Dave Fawthrop <dave hyphenologist co uk> Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
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Dave Fawthrop wrote:

I was replying from GG ;-) Never mind.
MBQ
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Dave Fawthrop wrote:

It's virtually instantaneous if you post via GG ;-)
MBQ
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On 4 Oct 2006 06:02:26 -0700, snipped-for-privacy@hotmail.com wrote:
| |Dave Fawthrop wrote:
|> |> | |> |Dave Fawthrop wrote: |> |> On Thu, 31 Aug 2006 15:46:15 +0100, "Phil Anthropist"
|> |> |> |> |"no_heat" wrote: |> |> |> Thanks Phil. |> |> |> |> |> |> Where is the best source of objective professional advice on the damp |> |> |> situation? Chartered surveyor, builder? |> |> | |> |> |An independent building surveyor or structural engineer. |> |> | |> |> |http://www.localsurveyorsdirect.co.uk / |> |> |> |> Test to see if this appears on Google Groups |> | |> |I can't see it from here. |> |> GG and the rest of the usenet propagation system is a bit slow. | |It's virtually instantaneous if you post via GG ;-)
I was testing from News,individual.net.
The joy of usenet is that you can receive it from many newsservers and with many sorts of software.
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Dave Fawthrop <dave hyphenologist co uk> Google Groups is IME the *worst*
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Dave Fawthrop wrote:

But not through some firewalls. no matter what software you use.
The joy of GG is that you can access it with just a browser available virtually anywhere there's a PC.
MBQ
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snipped-for-privacy@hotmail.com wrote:

Replying from Google Groups, new posts from uisenet seem to reactivate a thread
Dave Fawthrop
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snipped-for-privacy@hyphenologist.co.uk wrote:

You really need to get out more...
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==================================A bit more information would help. Were any air bricks covered up or removed when the extensions were added? Is there any possibility of underground water (from a water leak or natural drainage) causing the damp under the lounge? Did the damp arrive as a result of the extensions?
As far as the partly blocked air bricks is concerned it's possible that they're not actually blocked. They may be attached to 'periscope' air ducts which deliver air from a higher outside level to a lower inside level. You should be able to see these if you do another crawl. If they are really blocked then they should be cleared and possibly lowered and if any vents were blocked up or removed by the extensions new air bricks should be fitted and arranged so that no 'dead' areas are left. Ideally everything should be cross vented.
I would suggest that you cure the damp problem before you consider adding any insulation. This is standard advice - cure the problem at source rather than try to cover up the symptoms.
Cic.
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Cicero wrote:

It is possible that some airbricks on the opposite side of the house were blocked/removed during the extension work. Strange that the room that is now in the centre of the house, i.e. with the damp lounge on one side and the new extension on the other, is seemingly dry.

I wondered about the periscope ducts. Certainly when poking around from outside with a coathanger wire I can't detect any opening in the base of the airbricks.

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=============================I think it's possible that you're getting a 'rain-fall' effect produced by the possible loss of cross ventilation. It's possible that warm moist air is being driven in through the air bricks adjacent to the lounge where it meets a wall of still cold air. Unable to travel further it just dumps the moisture and leaves the inner area (study) untouched. Just a theory.
It would be worth finding out the true situation about the possibly removed / blocked air bricks on the two walls where the extensions have been built. My guess is that that is the source of the problem.
Cic.
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