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About Us > Sustainable Systems > Passive Solar Design

Passive solar design and cooling systems are simple in design and use. These systems are different from active solar systems in that they have few moving parts. To take advantage of the sun's energy directly, the buildings must be oriented correctly on the site and the spaces in the buildings must be able to collect the energy.

The Convento is a very active, public part of the monastery. It required a location at the front of the property and a strong connection to the chapel, while maintaining a subordinate face to the chapel, the monastery's main focus. The design criteria established that:

  • The major functions could be arranged in a linear configuration.
  • Aligning the 140 feet of structure along an east-west axis would result in maximum southern exposure.
  • The smaller face of the rectangular structure is appropriately scaled for the neighboring chapel.

Given these factors, the Convento was a perfect candidate for passive solar design. passive solar design requires clear direct access to solar south. Siting the structure parallel to the northern edge of an arroyo guaranteed the convento's unobstructed access. Because the spaces are utilized throughout the day (and during cloudy weather) the heating system required a component to store heat when the sun is out and then release the heat in the evening when the sun has gone down. The solution was a trombé wall that runs the length of the southern wall.

A trombé wall consists of a large area of vertical glazing in front of a wall of dense, heat absorbing material. The heat of the sun is trapped between the glass and the wall and is slowly absorbed into the dense material. The heat radiates through the material to the interior of the building. Ideally it should take about 12 hours for the heat to reach the inner surface where it warms the air through conduction (two mediums in contact with each other). This means that heat stored in the afternoon would be released twelve hours later during the coldest part of the night. A trombé wall is most efficient when the mass wall meets the ceiling. At the monastery, the trombé wall stops short of the ceiling to allow the inclusion of operable windows. The windows provide natural lighting, ventilation and a view to the landscape. An overhang shades the trombé wall and windows from the summer sun to protect the spaces from overheating.

The Cloister (monks' quarters) is a very private area of the monastery, located away from the public areas of the monastery. Also, it was desirable to locate the cloister near the refectory and existing monks' cells at the north end of the property. (The existing cells and the cloister could eventually be incorporated.)

The monks desired a traditional cloister plan-cells opening around a central courtyard. This scheme meant that, if sited correctly, at best only half of the cells could benefit from passive solar design. Connecting the cloister to the refectory would eliminate another side to passive heating, but would be more efficient in terms of circulation and construction. Instead of combining heating systems, the design team decided to use a more active solar heating system for this structure. The heating system circulates hot water through tubes in the floors of the cells. As in the convento, there is a need for heat storage. The heat from the hot water is transferred through conduction to the floor material, brick on a sand bed. A layer of insulation beneath the sand inhibits the flow of heat into the earth below and directs the heat upward. Solar collectors located on the roof of the cloister heat the water circulating through the floor. Water pumped through the collectors is exposed to solar south, then circulated through storage tanks. Here the heat is transferred through conduction to the water that runs through the floor tubes. The collector system also heats the domestic water used in the bathrooms of the cloister.

 

The corridor

The corridor

The corridor connects the new Cloister, the Refectory, the Abbey Church and new Convento. The Computer Room is located along the path. The position of the corridor was determined in large part by its relationship to the chapel. As a result of the desirable connection to the back (east) of the chapel, most of the corridor's exterior walls face east. This is not a good orientation for passive solar design. There was, however, one opportunity for direct solar access. The corridor was enlarged and the computer room is located here to the north of the circulation space. The southern wall of the corridor is glazed. The sun shines directly into the space and warms the air in the corridor in a direct gain heating method. The northern wall of the corridor (the wall that separates the corridor from the Computer Room) is adobe brick with an adobe banco (bench). The adobe wall and banco act as heat storage, as in the convento and cloister. The adobe mass also helps to moderate the temperature of the corridor by absorbing some of the heat from the air during the hottest part of the day. This is especially important in small solar heated spaces. The moderating temperature creates a comfortably warm space to take a break from the day's work. An overhang eliminates direct sunlight into the corridor during the warm seasons, reducing the amount of solar heat.

The computer room takes advantage of its position to the north of the corridor in two ways. Computer equipment emits heat, which could lead to high ambient temperatures, especially during the summer. Cooler air drawn from the northern, shaded side of the structure will be beneficial. During the colder seasons, the computer room may supplement its heat from the corridor. Vents placed at the floor and ceiling of the adobe wall will allow warmer air to move into the computer room through the high vents while cooler air moves into the corridor through the lower vents. This is Passive solar design by convection.