Our house is built and insulated for cold weather here in Colorado. That’s why these below zero temperature spells are so rewarding.
I have a pair of MCCREO WiFi temperature meters on the Trombe wall. One is outside under the glass and the other inside in a convenient hole drilled into the wall. Although on our coldest day when it did not get above zero, the outside only reached 50, the inside radiated 64.
For more common cold weather, on a sunny day the temperature against the outside wall rises several degrees higher than the inside wall. Then the inside wall maintains a warm temperature through the night.
The 14th was mostly sunny so our passive solar took over in the afternoon hours.
A sunny day uses fewer hours of heat from the boiler. The family room is on the north side of the house benefits less from the passive solar. These are our Nest thermostat use displays. I have the 13th showing the total for the day and the 14th showing the time of day use.
The rear bedrooms have an Ecobee thermostat and a zone sensor because at the time the Nest did not have extra sensors. We now have a Nest sensor in our primary bathroom connected to the primary bedroom thermostat so that zone’s temperature is determined by either. The ecobee sensor is in the second rear bedroom and either controls the thermostat. The rear bedrooms also have less solar exposure and have the old radiators instead of under floor heat. So the duration of the call for heat is longer. Even so, the by afternoon it was warm enough and didn’t resume until after sunset.
The next day the high temperatures were higher and the lows lower and it snowed most of the day so no sun.
The effect on the room temperatures are obvious. The sun is not adding as much heat to the rooms. But the high mass of the house also loses heat slowly. The North rooms are affected the most. Notice the family room run time.
It was a perfect day to supplement the gas boiler with wood boiler heat. For this I turned up the heat in the dining room to distribute some heat to that floor. Most of the time the rear bedrooms were calling for heat too. Although there are some short stretches of adequate set temperatures in these bedrooms.
The wood boiler puts out about 30,000 btu’s of warmed water that circulates in the radiant system. The red zone is the family room, the blue is the dining room, green is the living room, gold and purple are on the same zone, primary bedroom and bath. the rear bedrooms do not have in floor radiant.
The fire lends a lovely ambient glow to the room.
While most homes need to run the furnace/boiler all day and night our system runs far less even on the coldest days. The cover to the boiler is off because the aging fan needs observation but the zone controller shows only green and no red dots showing call for heat.
The manual J design used 0° as a low design temperature. But the systems (solar, boiler, wood boiler) together work very well in extreme cold spells.