Sunday, February 24, 2013

How Did January and February Go?

This winter was considerably colder than last, and we burned more wood. But we have enough seasoned black locust and hedge apple to last several years, so why not use it? We have fired the masonry stove an average of about 1.5 times per day, probably burning about 75 pounds of wood per day. The wood is very dry and the fire burns extremely hot and fast. The two-inch iron pipe we added to the masonry stove to allow combustion air under the grate after the fire has burned down works perfectly. As I had hoped, it reduces the burn-time by about an hour or more, allowing me to close the damper sooner and save heat for the house.

The good news is that our house has been considerably more comfortable this year than last, perhaps because I had hooked up the PAHS tubes a while back. But the PAHS tubes have not worked the way one might expect. Outside air has always come in through the lower cold-air tubes, ever since I hooked them up. The average temperature of the incoming air has risen slightly to around 66-68°F, and this is only noticeable when right next to a register. But the thermometer on the thermostat in the hallway doesn't mind. During the day it registers between 71-74°F and at night between 68-71°F. Consecutive sunny days push the reading toward the high end, and consecutive cloudy days push it toward the low end. So our thermal mass is doing an excellent job of smoothing out the 24-hour fluctuations.

Now a bit about the sunroom. It is sandwiched between the north wall of the house and the garage's south wall, and it is on the east side the entry room where the masonry stove is located. It faces about 20° south of east. Its east-facing, sloped roof is entirely of clear, double-layered, honeycombed panels, the same as used in greenhouses. Its east-facing walls are mostly glass. The sunroom has a ceramic tile-covered, concrete slab foor and brick walls on its south and north sides adjacent to the house and garage. This thermal mass stores a tremendous amount of heat when the sun shines in, and slowly releases it otherwise. Several times this winter we have had temperatures near 0°F, and the sunroom temperature hasn't fallen below 40°F with no supplemental heat. We have a number of plants in the sunroom, and they are happy, some even blooming.

Thursday, January 3, 2013

We Have Settled In

December was a month for experimenting.

Over the summer we had used the heat pump just enough to keep the humidity level at 50%, which also kept the indoor temperature around 72-74°F. The PAHS tubes were not hooked up until November, so the surrounding thermal mass probably had not heated up as much as it might have. Then we were away the second half of November, which gave the house a chance to cool a little more.

When we arrived home December first, the average indoor temperature was 68°F. Now the average indoor temperature is 72°F. A month ago the average outdoor temperature was about 20°F warmer than now. Currently the typical indoor air temperature drops to around 71°F at night, and with one exception it rises to 72-73°F in early afternoon. The exception is when the sun shines in brightly through all those windows, and the temperature then peaks out at around 75°F in early afternoon. The thermal mass quickly absorbs this extra heat, and by early evening the temperature is back to around 72-73°F.

Every evening around 5:00 PM we close the insulated drapes, and we open them again just as the sun is beginning to show on the horizon. On cloudy and rainy days we may not open some or all of the drapes during the daylight hours. We still receive considerable light from the upper windows and light tubes, and almost never do we need supplemental light during the daylight hours.

Our current routine with the masonry stove is to fire it up every evening around 6:00 PM and again around 6:00 AM if the day is predicted to be cloudy. Much of the extra heat from the stove and sun is being absorbed into the thermal mass, either through contact with the walls and tile floors, or by warm air flowing out through the tubes and the heat being absorbed into the surrounding soil. The extra heat is slowly increasing the surrounding thermal mass's mean temperature, and we are seeing that in the smaller daily temperature fluctuations around the ideal 72°F value.

What a difference 4°F makes. 72°F still feels a bit cool to me, but it is very tolerable. A 72°F ambient temperature is not nearly as noticeable as a 68°F or 76°F temperature. I look forward to the occasional overshoot to 75°F when the sun is shining. It is enjoyable to soak up the sun's rays, knowing that it is 50°F or more colder just outside that window.

I think that the thermal mass's temperature is slowly being brought into equilibrium with the desired comfort-zone temperature, and we will soon be firing up the masonry stove less. That is too bad, because I have cut so much wood, and I kind of like playing with fire. We may get down to firing the stove once a day by the middle of January, and then once every other day by early February. Last year I think we pretty much stopped firing up the stove in early March. That is about the time to start bringing down the thermal mass's mean temperature in preparation for the cooling season.

Ah, cooling season again and back out to sweating in the garden.