Josh built this very unique passive solar home in Missouri. The
house incorporates the usual south glazing to gather solar heat
and good insulation to reduce heating requirements. But, it also
has a unique heat storage capability using the soil under the main
floor. And, a unique cooling system that makes use of the same
soil heat store.
The south face of Josh's solar home.
Thanks very much to Josh for taking the time to provide the
details on this unique design.
The most unique feature of the house is that it stores excess solar heat
during the daytime in a two foot thick soil bank below the floor slab.
This will allow Josh to reduce the overheating problem that passive solar
homes sometimes have during the daytime, and to store heat in the soil
that can then be used overnight, or even to cover heating needs for some
days with no sun.
The house is well insulated using ICF (Insulated Concrete Forms) for the
main part of the house, rigid polyiso for the roof, and cellulose for
other parts.
The house also has pex piping embedded in the underfloor heat store, and
Josh plans to pipe 62F well water through the piping to cool the heat
storage and provide "coolth" for cooling the house in the summer. A very
nice dual usage of the heat store.
Ducts to distribute solar heat to the below floor heat store.
Pex tubing in floor for radiant heating (and for well water cooling in
summer).
Josh promises an update on the performance of the house once he has
lived in the house for a while.
2024 Update from Josh:
Five year update.
The passive solar house continues to work admirably
well. We were first able to occupy the house on the night of December 23
2018, which is good, because it was getting a bit down in the winter for
RV living. There were plenty of details to be finished up over the next
several years, and of course my progress was much slower than my wife
would have appreciated.
The rough order of projects was:
Upstairs railings so upstairs bedrooms could be used
without small children attempting skydiving from the upstairs loft.
Countertops in the kitchen, no more plywood
Flooring in upstairs rooms
Various exterior work
A garden (Yay!!)
A pump house building at the well head to keep the
water (mostly) from freezing during cold spells. Unfortunately the
occasional water freeze up still occurs, including the cold water to the
kitchen sink due to a poorly planned water line routing near the northwest
band board of the first floor ceiling. I had thought there would be
enough insulation for this to not be a problem, but there is not. The
water line is PEX though, so no harm really, just annoying.
A front porch
A second garden (one that doesn’t flash flood during a
heavy summer thunderstorm)
Exterior siding.
Lots of fence building, pretty much a permanent project
here on the farm.
Addition of a small wood fired stove (cubic mini stove)
which successfully heats the house on about ¼ of a cord of wood per year
Establishment of a cattle herd (thanks COVID for
helping me talk the wife into this becoming a priority) and a chicken
flock.
Re-establishment of chicken flock after various lessons
to children about the importance of closing the coop door at night, and
location of various marauding neighbor dogs.
Various baseboard, door and window trim (this was
somewhat delayed while awaiting material delivery from a family member)
and painting
A “tarp barn” of billboard vinyl over a greenhouse
frame, and consolidation of various building materials under cover of
weather.
Still Left: (hopefully all complete by spring of 2024):
Finish work on stair trim
Various storage area upgrades
Some exterior trim and siding
A greenhouse
Future major projects include a permanent barn, and
finally the “big” house on the bluff that I originally sold my wife on.
Now, on to the technical details!
The house, as mentioned, continues to perform well.
Most years we are into December before there is any need to add any
additional heat to the house. 2023 was a banner year as a cool, and less
humid late spring saw us go almost to July before installing any air
conditioners in windows (we use two 5000BTU units in the upstairs), we are
experimenting with the cooling system, but still I have never installed
ducting to push air through the floor tubes. Circulating cold water
through the floor mass does chill the mass, so this year I plan to work
out the ducting and complete that experiment. In addition, a warm fall
and early winter saw us go into 2024 before the 2023 heating season
actually began. Mostly this year we have just burned lumber scraps left
from trim work, I have not cut any firewood. We have used the radiant
heating loop for a couple weeks during a particularly cold spell. I have
found that during 0F overnights we need no additional heating as long as
there is full sun during the day the house will be about 65F in the
morning. That’s a touch cool for comfort, but many people set their
thermostat to that level or below for energy savings especially in more
northern climates. Also, if the floor mass is all the way warmed up, ~80F
then the house will stay warm for several days straight with temperatures
outside of roughly 40 during the day and 20 at night with no additional
solar gain in that time. This means we have little to fear from even a
protracted power outage. Most importantly, my wife has learned that she
loves radiant heated floors at least as much as anyone else I have ever
heard review the idea. They are very comfortable.
I’m not sure if I mentioned any dollar amounts, but the
build cost about 70K, with maybe 5K more into additional projects since
the main initial build was completed. This includes 12K for framing
labor, 6k for concrete placement labor, 2k for drywall hanging, and 3k for
drywall finishing labor. We also spent roughly 4-5k total on various
earthmoving. If I had had the time, and inclination I could then have
saved maybe 15-20k more on various labor costs. This is for a four
bedroom, 2 bath home that houses a family of 7 with minimal ongoing energy
expenditures.
Someone ought to inform HUD and the DOE that such
performance is possible……
