Sustainable Building Technical Manual - Etn-presco.net

Building Shape and Orientation❑ Choose the most compact building footprint and shape that work with requirementsfor daylighting, solar heating and cooling, and function.The greater the amount of building skin in relation to the volume of space enclosed,the more the building is influenced by heat exchanges at the skin. Excluding considerationof window openings and glazing choices, if two building designs under considerationenclose the same volume, the one with the more compact plan will have greaterthermal efficiency. A square floor plan is more thermally efficient than a rectangularone because it contains less surface area over which to lose or gain heat. However, thismay not be the most efficient or desirable form when other considerations such as daylighting,passive solar heating and cooling, need for temperature variation, and occupantuse patterns are included (see also Chapter 9, “Daylighting” and Chapter 11,“Renewable Energy”).❑ Site and orient the building so as to minimize the effects of winter wind turbulenceupon the envelope.The shape and orientation of the building shell has an impact upon wind turbulenceand opportunities for infiltration through the envelope. However, an orientation thatminimizes winter wind may also limit opportunities to make use of cooling breezes insummer. An understanding of the site-specific microclimate is needed. Coniferous treesmay be used for windbreaks (see also Chapter 5, “Sustainable Site Design.”)Doors, Windows, and Openings❑ Size and position doors, windows, and vents in the envelope based on careful considerationof daylighting, heating, and ventilating strategies.The form, size, and location of openings may vary depending on how they affect thebuilding envelope. A window that provides a view need not open, yet a window intendedfor ventilation must do so. High windows for daylighting are preferable because, ifproperly designed, they bring light deeper into the interior and eliminate glare.Vestibules at building entrances should be designed to avoid the loss of cooled or heatedair to the exterior. The negative impact of door openings upon heating or coolingloads can be reduced with airlocks. Members of the design team should coordinate theirefforts to integrate optimal design features. For passive solar design, this includes theprofessionals responsible for the interactive disciplines of building envelope, daylighting,orientation, architectural design, massing, HVAC, and electrical systems.❑ Shade openings in the envelope during hot weather to reduce the penetration ofdirect sunlight to the interior of the building.Use overhangs or deciduous plant materials on southern orientations to shade exteriorwalls during warmer seasons. Be aware, however, that deciduous plants can cut solargains in the winter by 20 percent. Shade window openings or use light shelves at workareas at any time of year to minimize thermal discomfort from direct radiation andvisual discomfort from glare.❑ In all but the mildest climates, select double- or triple-paned windows with ashigh an “R” value as possible and proper shading coefficients within the project’sfinancial guidelines.The “R” value is a measure of the resistance to heat flow across a wall or windowassembly (with higher values representing a lower energy loss). Shading coefficient is aratio used to simplify comparisons among different types of heat reducing glass. Theshading coefficient of clear double-strength glass is 1.0. Glass with a shading coefficientof 0.5 transmits one-half of the solar energy that would be transmitted by cleardouble-strength glass. One with a shading coefficient of 0.75 transmits three-quarters.