John wrote:

"Clive Long,UK" wrote in message
om...
Hi,

Does anyone have experience of extraction fans that use the heat
from the outgoing air to warm the in-coming air? I read about this
approach to reduce the possibility of condensation in houses where
they were insulated and glazed tight as a drum but the lack of air
circulation with the outside was causing damp / condensation problems.

I have found a suitable unit a CES in Whetstone London, and I only
have a one bedroom flat - but I just want to know if anyone has use
done successfully in any domestic situation?

yes fitted one a few years ago in a domestic bedroom, seems to have done the
trick with the condensation and mould on the walls.

Drilling a 6in hole through the double brick wall was tiring tho (even with
a diamond core bit)

My thinking behind fitting such a device, rather than a
conventional extractor is that any incming air would probably be
colder than the expelled air and the classic argument is the
condensation occurs at lower levels of "water saturation" when the
temperature of the air drops. Hence I want the in-coming replacement
air to be heated , if possible

Prob works as well as an extractor - but if warm are is sucked out it has to
be replaced somehow (i.e with cold air from outside) this would increase
heating costs. The heat exchange system goes some way to reduce these heat
losses. Your point is theorecticall valid tho.

Commonly used here, for the last 10 to 15 years, in a climate
slightly colder and with a much longer winter than the UK; they
are in fact mandatory in any house constructed to meet R2000
standard; which means heavily insulated tightly sealed.
Both my daughters houses have them. They run continuously
(probably 15 watts or so?) blowing air in and out through a core
with many square centimetres/inches of surface area. Water
condenses from the moister/warmer outgoing stale air and runs
down a small tube to a drain or container.
Typical cost is IIRC about the equivalent of 500 to 600 quid for
the basic unit for, say a three bedroom 1500 to 2000 sq. foot
house. Then installation is needed with in ceiling ducting to and
from various discreet ceiling outlets in most rooms. Probably
cost about 1000 pounds total for a typical installation in new
home construction. More difficult to add later; also difficult to
retrofit insulation and vapour barriers to meet anything close to
R2000 after home has been built. Our 1970s home is not so
equipped; we know it is somewhat more leaky than an R2000 and
therefore more expensive to heat but we but have no problems with
stale air, mould etc. during a long heating season.
In all/most homes including R2000s there are also specific
'exhaust' fans, not connected to the 'Air exchanger' which are
run for shorter periods in bathrooms, toilets and kitchen/cooking
areas at discretion of residents.
Air exchangers appear to work well; however one son in law has
found his unit caused drafts and so has a) slowed the fan and b)
partially screened some of the vents. Neither of the homes has
had any dampness, mould or mildew problems and it does seem to
take care of smoke from perfumed candles. (Never could see the
point of burning several pounds/kilograms of hydrocarbons inside
a house except during an emergency/power failure!).
The 'Air exchangers' also referred to as heat exchangers are
claimed to be 80% efficient in reclaiming heat that would
otherwise be lost outside. I personally doubt that high a
percentage, over the range of temperatures we encounter. Units
require cleaning at least twice a year depending on how dusty is
your house, pets etc.
I would say that they are absolutely essential in a well sealed
home; despite the heat loss they may engender. If I was ever
building again I would definitely include an Air Exchanger and
probably other technology for health and conservation of energy.
Whether they are necessary in a one bedroom flat? I guess we
don't sleep with the window open these days? Might be an
unnecessarily expensive solution though, if all that is required
is a bit of ventilation to change the room air every few hours
and avoid condensation?
Terry.