Michael said:
Do you really think that you can keep pulling air out, without
sucking hot outdoor air into the house?
Certainly not, but the air outside is usually cooler than the air in a room
with three computers (let's say 1kW). Actually pulling in air from outside
can solve heat problems. This is all under the condition that there's no
aircon in the building.
The negative pressure will pull
air in form anywhere it can, including a crawl space, and areas that
have been sprayed with pesticides.
Don't spray pesticides near your house if you don't want it inside, too. At
least not when your house has a "crawl space", i.e. is one of those cheap
(but overpriced) US buildings, which have no proper isolation, and are very
far from being airtight.
The outdoor air is humid, and could
lead to black mold problems, which can make you sick, or even kill you.
Black mold is mostly a problem when the dew point of the air *inside* is
above the wall temperature - i.e. in winter, with unaired rooms (high
humidity) and unisolated walls (cold). With the computers heating up air
inside (but not adding more humidity to it, like sweating humans would),
it's a non-issue. You can have summer black mold in tropical countries
where the bottom 2m in summer usually are so damp that it's fog everywhere.
Solution: Build house on stilts (then you don't have to crawl in your crawl
space), make sure you use tropical wood which resists the mushrooms.
Actually, controlled air-flow similar in spirit to this idea in server rooms
solves quite some problems, and reduce energy consumption (and is actually
state of the art). You cool down outside air with an aircon (say from 30°
to 20°, and reduce humidity), feed it through the fresh air channels
(that's also where the crew works), heat it up inside the servers to 50°C,
and then take it out through the backside channels. That way the aircon
removes only 1/3 of the thermal waste of the servers, whereas a closed
circuit airflow would require to cool the 50°C down to 20°C, and the normal
way things operate (with unordered racks and no air flow control), you even
need strong airflow at lower temperatures to achieve an intake temperature
of 20°C, since the thermal output dilutes the air in the whole server room.
In most circumstances, you can use ground water for the cooling, since most
non-tropical regions have average temperatures below 20°C, so all you need
are some water pumps. In winter, you can heat up entire office buildings
with your servers.
Scaling down that idea to three random computers in a room (e.g. one tower
under the desk, a laptop on the desk, and a HTPC in a rack full of other
equipment, which also dissipates heat) is far from trivial ;-).
