|
|
re: looking suggestions dream house design
24 may 1996
david grizzle wrote:
>i live in n.e. oklahoma( 45 mi n.e. of tulsa)...
let's see... watova? chelsea? big cabin? adair?
>where we have hot, humid summers and moderately cold winters.
nrel says tulsa has a min/avg/max of 73/83/94 f and 0.015 #w/#da or 64%
relative humidity and a 9.5 mph average wind in july (do you have much
wind at your site?), and 1210 btu/ft^2/day on a south wall in december,
with an avg/max avg temp of 35/45 f and record low of -8 f in january.
>the house that i'm proposing to build is a 2 story post & beam with
>strawbale infill( 18" thk walls), 26'x26' external wall dimensions...
>the ceiling will contain 2 layers of r19 insulation.
good walls :-) r30? you want to add up the wall area, divide by 30 (?),
and add that to the ceiling area and divide that by 38, and add up the
window area and divide by their r-value, then add in the cfm coming from
air infiltration (0.5achx11kft^3/60 = 90?) to find the approximate thermal
conductance of this house in btu/hr-f. say that's 200.
>the current plans call for a lot of south facing glazing for solar gain,
>5- 3x8 downstairs windows and 4- 3x5 upstairs windows.
i suppose these windows would be between the heated living space and the
outdoors? is there any way to insulate them at night, or during a week
without sun? if they were in a room with a door, and you could close the
door at night and let the room get cold, that might be a good idea...
that's 180 ft^2 of r2 (?) windows, that might admit 174k btu/day, and
a 200 btu/hr-f house would need 24(65-35)200 = 144k btu/day to stay warm
on an average jan day, and 70k of that might come from the electricity
that you use inside the house (and more from the sheep in the basement,
perhaps), so it looks like you would get enough average sun to heat a
house like that in january. what do you do during a cloudy week? how will
you make hot water?
>my original idea
>was to use wood heat with propane backup, neither of which am i fond of.
me neither.
>after seeing all the posts concerning solar rooms and closets i'm now
>wondering if i could get by without backup heat and maybe even eliminate
>the propane water heater.
hey! probably...
>i still haven't fully grasp the solar closet concept however.
you are not alone...
>what keeps the heat from leaking out of the thermal mass on cloudy days
>and at night?
a solar closet is an box with insulation on _every_ side, containing some
sealed containers of water to store heat. the sun never shines on the
containers of water. it has an air heater attached to the side facing the
sun, ie on that side, the insulation has a dark color, and there is a layer
of glazing over that, with an airgap between the insulation and the glazing.
during the day, the sun shines in through the outer sunspace glazing and
on through the inner solar closet glazing, and heats up the dark-colored
insulation, which in turn heats some air which flows through some kind of
one way damper, near the top of the dark insulation, eg through a motorized
damper or a plastic film backdraft damper, perhaps with a small, low-power
fan, and that warm air flows past the sealed containers in the closet and
heats the water inside through the container walls. this is sort of like
a rock bin, but the airflow resistance is a lot less, so it can use a low-
power fan or natural convection instead of a high power blower to get the
heat into the thermal mass, and if you use water, you only need 1/3 as much
volume for the thermal storage to store the same heat as in a rock bin.
then that air flows down through the closet and back out into the airgap
between the glazing and the dark-colored insulation, through a hole in the
insulation wall, and it gets heated and flows back into the closet again.
the solar closet air is warmer than the 80 f sunspace air. the two never mix.
at night, the damper closes and no air flows, and the heat stays inside
the insulated box.
>also what about radiant floor heat? could it be connected to these
>solar closet water vessels to supply heat?
the easiest way to do all this, it seems to me, is to put the solar closet
in the basement, and insulate the ceiling, and open a damper or two in the
floor, under a grate, to let some warm air out of the closet into the living
space in the room above when you when you want it. if you really want a
"radiant floor," you might insulate the basement ceiling around the edge
but not in the middle, and put some insulation above the closet and open
a damper in the basement, near the ceiling, to let some warm air float up
and pool at the basement ceiling, where it will conduct heat through the
floor above. a few holes here and there in the floor would help...
piping heat out of the closet as water and pumping it around thru pipes
in the floor can be inefficient and costly, by comparison. if what you
want is warm air in the living room, it's best to let some warm air rise
up directly from the closet into the living room, next best perhaps to
heat the floor from below and let the floor heat the room, and most
difficult to convert the hot air in the closet to hot water first.
storing 144k btu of heat x 5 days in 55 gallon drums takes about 29 drums,
at (130f-80f) 500 lb = 25k btu/drum.
>i would also like to avoid the expense of air conditioning. one idea that
>i keep kicking around is to bury an old gasoline storage tank or such next
>to the house and pipe cool air into the house in the summer...
where would the coolth come from? do you have a high water table or moving
water near the surface to make good heat conduction in the ground? if not,
i'd try something like a shallow roof pond, flooded at night, to evaporate
water and cool it if the air is cooler, and to radiate heat to the sky on
a clear summer night.
nick
|
|
