I was just recently listening to Paul Wheaton's podcast that included some recent temperature numbers for Allerton Abby and I thought that I would share my first winter's experience in our new earth bermed home.
We are located in North Central Idaho. The overall structure is 60 foot long and 24 foot deep. 1440 square feet. The long back wall and 1/2 of one short wall are are made of concrete and buried, annulized thermal inertia style. The floor is also a slab of concrete. The roof was not earth covered. We only had one layer of waterproof material over the thermal mass this winter. And even that was a little problematic as the mass was exposed several times to rain and snow over the winter due to wind blowing the plastic away during storms. The other short side has an attached garage that is not connected to the thermal mass.
We incorporated passive solar heating as well by facing the exposed long side 15 deg east of pure south with an extended overhang that will block the summer sun but allow in the winter sun.
Similar to Allerton Abby we were not able to charge the mass with heat over the course of the summer so we started the winter at a disadvantage.
The first temperature readings that I took were in mid November when the structure was finally dried in. The back wall was reading 45 deg at that time. Daytime temps were around 40 deg, lows were mid 20's.
I began building a rocket mass heater and used a propane heater to keep the internal house temp above freezing during the build. Back wall temps rose to 51 deg, internal air temp varried from night time of 34 deg to daytime of 45 deg.
I completed the rocket mass heater and we moved in on Feb 4th. I was running the RMH for several hours a day during the cobbing of the bench. At the time that we moved in, the bench was still quite wet. Back wall temp was 54 deg, internal lows were 52 deg in the AM, evening internal temp after running the RMH for 3 hours was 63 deg.
Back wall temps continued to climb slowly with a few back slides when the mass got uncovered and chilled by snow or rain. Initially we just had insulation (R38) in the roof but about a month in we finished adding insulation to the non mass walls (R19). Our son says that our lack of insulation is the reason for the mild winter we just experienced. We were heating all of North Central Idaho through our walls.
As of April 30th, back wall is 61 deg in AM, internal low air temp is 58 deg and high temp after 3 hours of running RMH in evening is a balmy 68 deg.