Re: Trying to keep cool

[Brian Whatcott <betwys@DIRECTVINTERNET.COM>]

At 02:05 PM 8/20/02, Brian Blais, you wrote:
> Hello,
>
>     As I was experiencing the recent heat wave on the East Coast, I was
>     thinking about the most efficient ways to cool a house.  If you just had
>     fans (no AC), and you wanted to keep your house the coolest, what
>     configuration of fans and open/closed windows would be best?

This is the sort of thing that (some) engineers occupy themselves with.
Let me take a try at it.
It would be helpful to make use of the coolest available air, and use it to
cool something with the greatest possible capacity.
That suggests blowing out warm air, and letting in the coldest air of the
day/night, which can happen around 7 a.m.   Blowing out seems to be
favored if the motor's warm air is thereby extruded too.
Taking the air inlet from the north side seems reasonable, at least in
the northern hemisphere - perhaps a north west face at dawn is better.

I'm sure you have seen the informal thermal reservoirs composed of
concrete masses, water barrels, cans, bottles, stone rubble tanks,
swim pools and so on.    Storing "coolth' long enough to cut the top off
the thermal profile is expensive or bulky however.
A river or cavern is a valuable resource - an ersatz version is provided by
buried pipe.

To add a little more efficiency, for not very much cost or complexity ,
it is quite incredibly easy to arrange a differential temperature sensor
sensing exit air versus incoming air temperature, and drive a solid state relay
powering the fan system.

Enthusiasts will naturally wish to elaborate such a system - and a sparse
water spray for auxiliary inlet air cooling (I am not of course advocating
an evaporative system as commonly applied - too moist and mildew inducing).

It is only the heroic who recall that simple is good - the KISS principle.

>     If you assume that the nighttime temperature dips below the house
>     temperature, but that the house warms up during the day, it would seem
>     that an initial solution is windows open during the night and closed in
>     the day.  If you add fans, is it better to try to blow in the cool night
>     air or blow out the warm house air at night?  Is it better to have some
>     blowing in and some blowing out?  Empirically, it seems that blowing out
>     works better than blowing in, although I am not sure why.
>
>     Any thoughts?
>
>
>             Brian Blais
>
> --
> -----------------
>
>             bblais@bryant.edu
>             web.bryant.edu/~bblais

Brian Whatcott
  Altus OK                      Eureka!