On Sun, 02 Jul 2006 22:50:09 +0100, David Hansen
wrote:

On Sun, 02 Jul 2006 21:45:19 +0100 someone who may be Peter Parry
wrote this:-

One could, it makes very little difference however.

That depends on how well the house is designed for natural
ventilation.

It is quite possible to design houses for natural ventilation, there
are quite a few in the Middle East. However, to work effectively
natural ventilation needs a sufficiently high building and high
rooms. IT also requires space. Without adequate height the natural
draw is minimal. Current planning rules force low ceilings and high
density occupation. These are not conducive to either efficient nor
pleasant living.

I know of houses, including my own, where the
appropriate use of windows and vents allows a nice even temperature
to be maintained in hot weather, day and night, including the
southward facing public rooms.

Some can. It helps if you have someone with nothing else to do with
their time than go around all day opening and closing windows and
curtains. Most however can't.

Depending on the
orientation and design of the house it should be possible to provide
gentle ventilation that will keep the house cool via the windows and
other ventilators.

Not it won't,

I disagree, having seen all sorts of naturally ventilated buildings.

I've seen hundreds of various ages in very hot countries. The best
that can be said is that they work a bit.

Ventilation serves two primary purposes. Firstly it prevents
condensation and rot. Very little air flow is required to achieve
this and a house which becomes unbearably hot may still have quite
sufficient ventilation to prevent either.

Secondly an air flow through the house creates wind chill so people
feel cooler. The air is still at a high temperature - ventilation
cannot cool a house to below ambient.

It is possible to have passive cooling to below ambient but only by
utilising a passing lake or deep buried ventilation chambers.
Neither are very practical for 33b Acacia Avenue.

the upstairs is going to be too hot in summer.

Cross.

The upstairs may be too hot in summer, but only if the house is
badly designed.

Absolute rubbish. Houses are often unoccupied during the day, that
means windows and doors are closed (or you have no insurance).
Amazingly not many people consider steel grills on all their doors
and windows to allow them to be left open to be "good design".

Most people also don't consider heat generating devices such as
refrigerators and freezers to be "bad design". Modern building
regulations go overboard on keeping heat in but totally ignore
cooling. The net result is an increasing number of houses which are
uncomfortably hot in the summer and the inevitable consequence that
people fit air conditioning to remain comfortable.

Near here are a collection of up-market "apartments" each supplied
with an electric Aga (I agree, an entirely idiotic device). These
are less than two year old yet I'd guess about a quarter are now
sprouting air conditioners.

Secondly, some houses are used for work. This involves heat
producing devices such as computers and lights. Home offices are
often in a spare bedroom so the heat contribution makes the second
floor (which is always going to be warmer than the ground floor) even
more uncomfortable.

However, you do have a point - many houses are not adequately
designed. However they exist and peoples lives are tied up with
them. What do you propose should be done with all these badly
designed houses?

There are numerous greeny house is Milton Keynes and Oxford which are
abandoned in summer because they are unbearable.

Not places I frequent. Were they designed for passive solar
ventilation?

Of course, I am amazed you have never heard of them as they regularly
appear in greeny propaganda leaflets.

Suitable and adequate loft ventilation to prevent rot will have
almost zero effect upon temperature in the loft.

That depends on how it is designed and operated.

It won't make any difference whatsoever. To prevent rot requires
nothing more than trickle ventilation. Your claim that if the loft
is hot there is a risk of rot is fatuous.


--
Peter Parry.
http://www.wpp.ltd.uk/