Passive heating and cooling of a greenhouse

Passive heating and cooling techniques have been used for centuries. They use low-cost techniques that significantly reduce heating and cooling costs while reducing your carbon footprint. Ridge vents work in conjunction with eaves vents and/or windows to either trap heat from the sun during the heating season or create cool airflow during the cooling season. A solar chimney can be used as both a heating and a cooling system, in which air is convectively discharged from a room via a chimney. Incorporating a Trombe wall into a structure captures the sun’s energy during the day and releases it slowly after the sun sets.

During the heating season, all ridge vents, eaves vents and windows are closed. The operation of the vents can be automated to close once the desired temperature is reached. Low-E glass helps harness the sun’s energy, extracting solar heat and heating the space. Opening the doors to an adjacent building allows the excess heat to be transferred to the main room, reducing overall heating costs.

During the cool season, the ridge vents open after sunset, providing an escape for warm air. As the warm air rises, cool, fresh air is drawn from the windows or operable eaves, reducing the cooling costs for that structure. To prevent cool air from escaping the main room, the doors are closed to the attached structure during the day, but can be opened at night or early in the morning to take advantage of the cool, fresh air in the structure.

Solar chimney: heating
A chimney is made of an energy-absorbing material, such as brick or concrete. The south side of the chimney is painted black to optimize the absorption of the sun’s rays, increasing the air temperature in the top of the chimney. The chimney’s outer vent is closed, while the upper, inner vent to the room is open.
The ambient air in the room is drawn into the chimney by convection. As the air rises in the chimney, it is warmed by the heat absorbed by the sun and recirculated in the room.

Solar chimney: cooling
A chimney is made of an energy absorbing material, such as brick or stone. The south side of the chimney is painted black to optimize the absorption of the sun’s rays, increasing the air temperature in the top of the chimney. The outer opening of the chimney is opened to allow air to escape. Cooler outside air is drawn from windows or eaves, which can be controlled automatically when the temperature reaches a certain point. The ambient air in the room is drawn into the chimney by convection.
The warm air escapes from the chimney.

For particularly hot climates, an underground pipe can be installed that draws in warm outside air. Heat is exchanged by the cooler ground as the air passes through the pipe into the room.

Trombe Wall: day and night heating
A Trombe wall is best placed on the south side of a structure and is made of an energy absorbing material such as brick or concrete. It should be painted black to best absorb the heat and contain the top and bottom vents. On the outside, a glass wall should be built just a few inches from the masonry wall, creating a thermal buffer.

To create the most efficient thermal buffer, Low-E glass must be used to let the sun’s energy enter the room, but not let it escape.
For daytime heating, both vents are in the open position. By convection, the ambient air in the room is drawn through the lower vents to the thermal buffer, where it is heated to the upper vent and back into the living space.

For nighttime heating, the vents are closed to prevent warm air from escaping from the living area. The energy collected by the masonry wall during the day is slowly released into the room via radiant heat.

For more information:
Solar innovations
31 Roberts Road
Pine Grove, Pennsylvania 17963
1-800-618-0669
solarinnovations.com

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