On Mar 30, 10:22*am, Tim Lamb wrote:
In message
, NT
writes
On Mar 29, 10:03*pm, Tim Lamb wrote:
In message , Andrew Gabriel
writes
In article ,
* * * Tim Lamb writes:


Following the prolonged cold Winter, my wife is considering fitting air
extractors to her rented flat. (mould/condensation issues).

The obvious priority placing is in the bathroom with part P
consequences. One possibility is the low voltage offering from Kair
which appears to have provision for humidity stat operation.

The flat was originally heated by warm air ducts from a central off peak
store so there is also an opportunity for a centrally located
extractor/dehumidifier.

Does anyone have insight to the benefits/drawbacks etc?

Nowhere near enough info to diagnose the problem, which is necessary
before any remedy can be suggested.

:-)

First engage your advisor!

What sort of heating is there now?

Conventional full gas CH

Does the place feel warm, or is the heating ineffective?

Depends on how the tenants set the rad. stats but the system is amply
sized.

What moisture sources are there? Cooking, baths/showers, clothes
drying, ...?

Cooking, baths/showers. Hopefully not clothes drying as there is a
condensing washer/drier.

When does the condensation/damp appear?

Particularly after a let this Winter.

Where does the condensation/damp appear?

On upper surfaces of North and shaded exterior walls. Manly bathroom and
bedroom.

Any idea what thermal insulation is installed?

11" cavity wall only. A tentative enquiry to BG bounced as insulation
could only be grant aided if *all* the flats in the block were done.

Are there any extractors, ventilators, etc.

No extractors. Double glazing has trickle vents. Kitchen has double air
brick but buried behind cupboards. Cooker hood is re-circ type.

Has it always been like this? If not, what happened to cause the change?

We thought the CH had solved the problem which had been noticeable with
the old air duct/ storage system. However a long, cold Winter coupled
with a family and children.....

More ventilation and more heat input but you can't stand guard over
tenants.
* We were arranging a simple bathroom extractor (timed on exit if
possible) and realised the added expense of part P. One step further to
a heat recovery, low voltage extractor. But are there any *gotchers*?

Because large parts of the old ducting system are still there, a
centralised system might be possible but issues such as noise, cost of
running a dehumidifier, disposal of condensate, pressure balancing etc..
are a bit mind numbing.

I'm not clear if that means you own the block rather than the one
flat? If the latter, *a plugin dehumidifier is a surer approach than
ventilation, and costs less to run and is trivial to install.

One ground floor flat in a 3 storey block, 60's build. Unfortunately
rather a lot of exterior walls.

Condensate is plumbed to a waste pipe

Yes. The flat has two bedrooms, bathroom, toilet, lounge and kitchen all
arranged around a central access corridor. I doubt the practicality of
fitting a cheap dehumidifier in the bathroom although air could be
extracted through existing ducts to something fitted off the corridor.
All the waste pipes are on exterior walls.

Using flexible 1/4" tube for a dehumidifier makes it relatively easy
to plumb.


I think we should pursue the cavity insulation aspect despite British
Gas. I believe the building is based on a concrete frame so the cavities
might be stopped at each floor.

CWI makes a lot of sense. Grants arent necessary to make it pay. Brush
strips can be used to retain insulation for shared walls. Adhesive on
the insulation can prevent it going anywhere after installation.

Brush strips?

yup, theyre poked into position to stop the insulation passing.

Also, if the cavity is open, the junction is horizontal rather than
vertical.



CWI won't reduce the water load in the air though, either you prevent/
remove it somehow or condensation is inevitable. The usual simple
guidelines like using lids on pans are too often impossible to
implement with tenants, but you can dehumidify. A contract clause can
state that if disabling climate control equipment causes mould, rot
etc they're liable for the damage.

So far it has been superficial mould requiring laborious cleaning.

thats good news, if you put a dehumidifier in the right place it
should clear it up.


Up to 85% recovery is claimed for extractor units or is this overly
optimistic? I think the bathroom is the obvious start point. Material
cost around 200ukp so payback within one months rent.

'upto.' Dehumidifiers give 100% heat recovery all the time. And no
installation cost.

regards


NT