Most summers in the Eastern Townships include a period, often lasting one to two weeks or more, that is extremely hot and humid. Climate change is likely to result in summers with more frequent or longer (or both) hot spells. Indeed dealing with the heat may become a more pressing comfort issue for households, than winter heating.
Solarhurst has been designed to mitigate unwanted interior heat gain by five means.
Firstly the house is surrounded by tall trees on the south and west sides and their shade will appreciably reduce solar insolation on the house.
Secondly, the substantial insulation and deliberate overhangs (verandah roofs and eaves) over the windows will substantially reduce radiant and conductive heat gain. The house will be painted white, which will further reflect away solar heat.
Thirdly heat that is transferred into the house, will be buffered in part by the large thermal mass represented by the dual stack masonry heater.
Fourthly, all floors, but the upstairs in particular, have been designed for cross-ventilation, and casement windows open in such a fashion so that they are best positioned to direct breezes into the house from prevailing south or west winds.
Finally, the house is equipped with an earthtube. The earthtube works in a very simple fashion. The temperature of the earth a few feet down from the surface remains at a remarkably consistent temperature, changing only slowly with the season. During the summer the in-ground temperature is generally around 13 to 14oC. Moving hot air through an earthtube will simultaneously cool it, and dehumidify it (as cooler air can hold less moisture, the vapor will condense out). In our case the earthtube is an 8” diameter PVC sewer pipe that runs 160 feet in a closed loop, 5 feet below grade, adjacent to the north and west side of the house (taking advantage of the house excavation). The entry and exit port for the earthtube are adjacent to one another on the north wall, and both enter the mechanical room in the basement roughly at basement floor level. The earthtube is then hooked up to the hi-velocity forced air system that serves as back-up heat in the winter. The fan of this unit moves the cool air from the earthtube to select parts of the house (determined by computer adjustable duct dampers and registers), and cools these rooms at a fraction of the energy required for conventional AC or heat pumps. The hot air in the room is drawn back down into the earthtube for further cooling. Testing as the system was installed suggests that an 8oC drop in air temperature for moderate airflow velocities, is easily achievable during a single pass of the air through the earthtube. If the air is recycled through the earthtube, even more substantial cooling can be anticipated.
Closed-loop earthtube prior to burial, running along north (left) and west (right) foundation walls. Additional earthtube furthest away from viewer is an open tube that provides outside air to the HRV unit.