"Peter Parry" wrote in message
...
On 16 Mar 2004 04:18:43 -0800, (Neil Deinhardt)
wrote:


The unit is fitted with a number (5 or 6) filters for the
incoming air, which I was told reduces airborne dust (consequently
having beneficial impact for asthma suffers).

This is often touted as a "benefit" in fact there is no evidence it
makes any difference at all. The amount of dust in a house is
primarily affected by the type of furnishings and floor covering and
people (shedding skin particles). If anything forced air systems
stir up the air more therefore slightly increasing exposure to dust
particles rather than decreasing it.

With electrostatic air filters this is not the case at all.

I'd really like to find out (a) general opinions on this sort of
system relative to conventional radiators

To achieve equivalent comfort levels you need to operate the house a
degree or two warmer than you would with radiators as there is no
radiant heat.

Totally untrue. The heat emitted from radiators is 90% convection.

In well insulated houses the upstairs rooms tend to
become warmer than the downstairs ones which some people don't like
(most prefer bedrooms to be slightly cooler for the best quality
sleep).

One again untrue. This appears a well designed and installed system. The
upstairs, or any room, can be balanced to reduce air flow.

Some people find the temperature stratification in rooms to
be uncomfortable.

(b) experiences from any owners, past or present

My experience has been several years with the older, truly awful,
variety and over the last year or so observing a colleague of mine
who has (with the aid of the manufacturers and lots of qualified
engineers) tried without success to get a brand new installation
provide him with a comfortable house. He finally ripped it all out
and replaced it with underfloor heating (at vast expense). That
installation was quite complex as the house is large but he found the
hot head/cold feet characteristic of air heating to be unacceptable.

This was obviously a bad design/poor installation, etc. certainly not
typical for a two duct good design job.

Having lived with the older systems and experienced the more modern
system I would not consider buying a house with forced air heating.

Because you have only lived in houses with very poor, cheao and nasty
systems.

(c) how easy they are to control, ie. can you
easily turn up the temp in individual rooms by adjusting the flow to
that room, and do they respond generally quicker or slower than
radiators?

Over the whole house they are very easy to control, individual room
control isn't quite so easy and depends to some extent upon how the
original airflows were calculated (or, more likely, not calculated at
all - there are many poor installations).

Individual room control is possible by having modulated registers and
variable flow fans

(d) how do they compare to conventional systems in terms
of cost of ownership.

Running costs tend to be slightly higher as you need higher room
temperatures.

Total nonsense. Running costs are slightly lower than rad systems.

Repairs and servicing can be expensive as there is
only one manufacturer,

Most gas forced air units are on the British Gas list. Most burner controls
are comonn with boilers.

not to many installers will work on them

What installers are you on about? Cowboy plumbers putting in rad systems?

and those that do have little competition and tend to inflate their
prices.

Any proof of this? B Gas charge the same for forced air and boilers.