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control humidity inside buildings. Materials that remove moisture from the air are known <br />as desiccants. Desiccant technologiessre evolving and can be integrated into evaporative <br />systems for use in all climates. <br />;w: _ ..:...~... <br />~ ~ a <br />~. <br />.. ...~5,... ..,..~. <br />CourtesyofpOE/NRELandthe Sustainable BUiltlings lndusWes C°undl <br /> <br />Local development <br />controls should <br />encourage <br />subdivision layouts <br />that provide for <br />maximum east- <br />west orientation <br />for. residential <br />and smaller <br />nonresidential uses <br />Geothermalheatpumps.Thegroundmaintainsarelativelyconstant[emperatureof <br />5o to 6b°F (io to i6°C). Thus, the ground temperature is warmer than the ai r temperature <br />in winter and cooler i n the warm months. Geothermal (orground-source) heat pumps take <br />advantage ofthe earth's constant temperature to heatandcool buildings. Because the sys- <br />tem is outside the building, geothermal requires more land area than the othertechniques <br />discussed above. <br />IMPLICATION FOR LAND-USE CONTROLS <br />Currently, relatively few communities in- <br />cludeprovisions intheir local development <br />controls that ensure tfia[ environmental <br />resources can be used to heat, cool, day- <br />light, and electrify buildings.The discus- <br />sion that follows outlines a number of <br />considerations for subdivision and zoning <br />standards that would help private develop- <br />ersbuild and remodel buildings that are <br />better able to~take advantage of access to <br />solar energy. <br />Subdivision design <br />Local development controls should encour- <br />agesubdivision layouts that provide for <br />maximum east-west orientation for residen- <br />tial and smaflernonresidential uses. In the <br />northern hemisphere, major living, work, <br />and study areas should face south (north <br />in the southern hemisphere) to the extent <br />possible.ltis easiesito protectsolarac- <br />cess insubdivisions having streets that run <br />east-west or z5degrees ofeast-west. Where <br />streets run north-south, cul-de-sacs or loop <br />streets help provide forsolar access. For <br />dense development, creative site design is <br />essential. <br />Develbpment standards <br />Yard and height requirements ofzoning <br />ordinances can be used to ensure solar <br />access. In an ideal situation, south-facing <br />glazing should receive four hours ofsun <br />on December zi. That generally means <br />that there should be no obstruction within <br />an arc of 6o degrees on either side oftrue <br />south. Relatively good solar access will still <br />occur ifthe glazing is unshadedwithin an <br />arc of45 degrees. Whatthe horizontal clear <br />distance needs to be islocation-specific <br />and depends on the height of the sub- <br />jectbuilding ofinterest and the adjacent <br />structures. Boulder, Colorado, for example, <br />includes shadow lengths by height of <br />building forio:oo a.m., noon, and z:oo <br />p.m. on December zt in its development <br />code. Properly sized overhangs will shade <br />the glazing in the summerwhen the sun is <br />higher in the sky. <br />Since not all lots are large enough to <br />accommodate optimum solar access, it <br />is important [o assess shading patterns <br />in establishing compromises on yard re- <br />quirements.One possible compromise is <br />a flexible approach to building orientation <br />and yard requirements wheastreets run <br />north-south. With appropriate side yard <br />ZONINGPRACTICE q.ap <br />AMERICAN PLANNING AGSOCIAmONIp°g¢5 ~l r1 <br />