The house size is just under 600 sq. ft. One story. The sandbed is two feet
deep and extends under the full house.
The solar thermal collectors total 160 sq ft., and are conventional
panels manufactured by
Solar Skies here in MN.
The walls are straw bale, attic insulation is 18' inches of blown in
cellulose.
The Sandbed
The highest temp we have ever seen at the sensor down in the sand at the
depth of the tubes is 97 F, lowest 50 F. Our slab temp (the actual floor we
walk on) has gone as low as 49 during an extended absence in January, and as
high as 90 F. (90 F is unusual for the slab.) Slab temp between 68 F and 75 F
for probably 90 percent of the year.
The guys at Artha
designed the system, sized of panels relative to floor, chose the length and
diameter of PEX, length and diameter of shunt, size and make of pump, size of
PV panel, etc. That was probably the best money we spent on any consultants
during our building project, great value. They were super about answering
questions. It's great t be able to rely on knowledgeable people.
Performance
We just finished our third winter in the house which uses a Ramlow sandbed
storage heat system.
We are located in Northern Minnesota, slightly inland from Grand Marais.
I would say our system supplies all the heat we need during the shoulder
seasons (when you wouldn't expect to be heating all through the day but would
probably have a fire in the evening, the morning or some point during the day.)
During December, Jan and Feb we burn a small fire most of the time we are awake,
but let it go out at night and whenever we leave. We burn about a cord per
year.
We start storing heat in the sandbed in mid August. I think that being able to
start in August makes a big difference, because solar energy is not really
bountiful at this northern latitude in November, December and January.
Not having fires at all during the shoulder seasons really saves wood.
The wood burning season is APPROX December through mid-March. In our previous
house we sometimes had a fire in June, (Average date of last frost here May 31)
and always had fires at night starting sometime in September . We burn something
less than a cord per year to heat our 600 sq ft house.
Even more than the economy I am blown away by the comfort. Even on the coldest
night in January, the fire goes out at about 9 or 10 o' clock, and when we wake
up the temp in the house is 65.
This is a great way to heat - I can't imagine any reason not to include a system
in new construction.
