Sustainable Building Technical Manual - Etn-presco.net

vide an attractive and durable floor surface, are widely available, and readily acceptedby contractors and building occupants. Masonry’s effectiveness can be inhibited ifoccupants place furniture and carpets over the floors. To address this, use masonryfloors only in the areas where direct heat gain and storage is required.– Consider a Trombe wall—a south-facing masonry wall covered with glass spaced afew inches away. Sunlight passes through the glass and is absorbed and stored by thewall. The glass and airspace keep the heat from radiating back to the outside. Heat istransferred by conduction as the masonry surface warms up, and is slowly deliveredto the building some hours later.Trombe walls can provide carefully controlled solar heat to a space without the useof windows and direct sunlight, thus avoiding potential problems from glare andoverheating, if thermal storage is inadequate. The masonry wall is part of the building’sstructural system, effectively lowering costs. The inside, or discharge, surface ofthe Trombe wall can be painted white to enhance lighting efficiency within thespace. However, the outside large dark walls sheathed in glass must be carefullydesigned for both proper performance and aesthetics.– Consider masonry or concrete walls insulated on the outside. Many buildings, especiallylow-rise commercial buildings, are constructed with concrete or masonry wallsthat can provide excellent thermal mass to absorb excess solar heat and stabilizeindoor temperatures. In most climates masonry walls are most energy-efficient whenthey are insulated on the outside of the building, which allows them to absorbexcess heat within the building, without wicking it away to the outside.However, there are barriers to using this technique. It is not common practice forcontractors, and it may seem redundant to cover up an existing excellent weathersurface. Insulated masonry also adds extra width to a wall, making it difficult to finishat the edges of windows, roofs, and doors.Fortunately, new technologies have lowered the cost and increased the options forinsulated masonry. Various foam insulations are available in panels that can beadhered directly to the masonry surface and then protected with a troweled- orsprayed-on weathering skin, and masonry insulated structural panels are also available.Manufacturers are also developing self-insulating masonry materials thatboth increase the thermal capacity of the building and slow the flow of heatthrough the walls.– Consider using double gypsum board throughout the building. Increase the thermalcapacity of a building by simply increasing the thickness of the gypsum board usedon interior wall surfaces of the building or by using thicker gypsum board products.Increasing the thickness of all of the wall surfaces can raise the thermal capacity ofthe building for little additional material cost and practically no labor cost. It has theadded benefits of increasing the fire safety and acoustic privacy of interior spaces. Thisdiffuse thermal mass approach depends on effective convective airflows since roomair is the heat-transfer medium. To really “charge” the walls, temperatures within thespace must be allowed to fluctuate a little more than standard design assumptions,on the order of 5° F above and below the thermostat setting.– Consider water-storage containers for thermal mass. Water has a very high thermalcapacity, about twice that of common masonry materials. Water also has the advantagethat convection currents distribute heat more evenly throughout the medium.Passive solar designers have experimented with a wide variety of water-storage containersbuilt primarily into walls. Creative solutions include enclosing water containersin seating boxes under south windows or using water as an indoor feature such asa large tropical aquarium, pond, or pool.