Sustainable Building Technical Manual - Etn-presco.net

Thermal mass and energy storage are key characteristics of passive solar design. 1 They canprovide a mechanism for handling excess warmth, therefore reducing the cooling load,while storing heat that can be slowly released back to the building when needed. Thethermal mass can also be cooled during the evening hours by venting the building,reducing the need for cooling in the morning.. ☛ SUGGESTED PRACTICES AND CHECKLISTIPassive Solar Heating❑ Analyze building thermal-load patterns.An important concept of passive solar design is to match the time when the sun can providedaylighting and heat to a building with those when the building needs heat. Thiswill determine which passive solar design strategies are most effective. Commercial buildingshave complicated demands for heating, cooling, and lighting;; therefore their designstrategies require computer analysis by an architect or engineer.❑ Integrate passive solar heating with daylighting design.A passive solar building that makes use of sunlight as a heating source should also bedesigned to take advantage of sunlight as a lighting source (see Chapter 9, “Daylighting”).However, each use has different design requirements that need to be addressed. In general,passive solar heating benefits from beam sunlight directly striking dark-coloredsurfaces. Daylighting, on the other hand, benefits from the gentle diffusion of sunlightover large areas of light-colored surfaces. Integrating the two approaches requires anunderstanding and coordination of daylighting, passive design, electric lighting, andmechanical heating systems and controls.❑ Design the building’s floor plan to optimize passive solar heating.Orient the solar collection surfaces, for example appropriate glazings in windows anddoors, within 15 degrees of true south, if possible. Because of the solar path, the optimumorientation for passive solar buildings is due south. South-facing surfaces do nothave to be all along the same wall. For example, clerestory windows can project southsun deep into the back of the building. Both the efficiency of the system and the abilityto control shading and summer overheating decline dramatically as the surfaceshifts away from due south.❑ Identify appropriate locations for exposure to beam sunlight.Overheating and glare can occur whenever sunlight penetrates directly into a buildingand must be addressed through proper design. A “direct-gain” space can overheat in fullsunlight and is many times brighter than normal indoor lighting, causing intense glare.Generally, rooms and spaces where people stay in one place for more than a few minutesare inappropriate for direct gain systems. Lobbies, atria, or lounges can be located alongthe south wall where direct sun penetrates. Choose glazings that optimize the desiredheat gain, daylighting, and cooling load avoidance. (see Chapter 9, “Daylighting”).❑ Avoid glare from low sun angles.In late morning and early afternoon, the sun enters through south-facing windows.The low angle allows the sunbeam to penetrate deep into the building beyond the normaldirect-gain area. If the building and occupied spaces are not designed to controlthe impact of the sun’s penetration, the occupants will experience discomfort fromglare. Careful sun-angle analysis and design strategies will ensure that these low sunangles are understood and addressed. For example, light shelves can intercept the sunand diffuse the daylight. Workstations can be oriented north-south so that walls orhigh partitions intercept and diffuse the sun.❑ Locate thermal mass so that it will be illuminated by low winter sun angles.Building design should incorporate a sufficient amount of correctly located thermalmass to effectively contribute to the heating requirements and provide cooling benefitsin the summer.