Shading By Alfresco Blinds Co Direct sun can generate the same heat as a single bar radiator over each square metre of a surface, but effective shading can block up to 90% of this heat. By shading a building and its outdoor spaces we can reduce summer temperatures, improve comfort and save energy. A variety of shading techniques can help, from fixed or adjustable shades to trees and vegetation, depending on the building’s orientation as well as climate and latitude. A large pergola with louvres shades wide glass bifold doors that open to a shaded living room. Shading glass reduces unwanted heat gain. Shading glass is the best way to reduce unwanted heat gain, as unprotected glass is often the greatest source of heat entering a home. However, fixed shading that is inappropriately designed can block winter sun, while extensive summer shading can reduce incoming daylight, increasing the use of artificial lighting. Shading uninsulated and dark coloured walls can also reduce the heat load on a building. Radiant heat from the sun passes through glass and is absorbed by building elements and furnishings, which then re-radiate it inside the dwelling. Re-radiated heat has a longer wavelength and cannot pass back out through the glass as easily. In most climates, ‘trapping’ radiant heat is desirable for winter heating but must be avoided in summer. Shading of wall and roof surfaces is therefore important to reduce summer heat gain, particularly if they are dark coloured or heavyweight. Light coloured roofs can reflect up to 70% of summer heat gain. Short wave solar radiation passes through glass windows and is re-radiated as long wave radiation which is trapped inside the house. Solar radiation is re-radiated inside. Shading requirements vary according to climate and house orientation, as shown below. Orientation Suggested shading type North - Fixed or adjustable horizontal shading above window or Alfresco and extending past it each side where possible. East and west - Fixed or adjustable vertical louvres or blades; deep verandas or pergolas with Outdoor Shading Blinds NE and NW - Adjustable shading or pergolas with deciduous vines to allow solar heating or verandas to exclude it SE and SW - Planting: deciduous in cool climates, evergreen in hot climates General guidelines for all climates Use external shading devices over openings, such as wider eaves, window awnings, Ziptrak blinds and or deep verandas or pergolas. Lighter-coloured shading devices reflect more heat, and those with light coloured undersides make better use of daylight than dark coloured. Internal shading does not prevent heat gain unless it is reflective: only shiny surfaces can reflect short wave radiation back through the glass without absorbing it, There are special To reduce unwanted glare and heat gain, use plants to shade the building, particularly windows. Evergreen plants are recommended for hot humid and some hot dry climates. For all other climates use deciduous vines or trees to the north, and deciduous or evergreen trees to the east and west. A deciduous tree near the living area of a house provides shade in summer and allows sunlight to enter during winter. A louvred pergola has the same effect. External shading devices. Within the range of north orientation that allows good passive sun control (20°W and 30°E of solar north) sun can be excluded in summer and admitted in winter using simple horizontal devices, including eaves and awnings. For situations where a good northerly orientation cannot be achieved (e.g. existing house, challenging site) it is still possible to find effective shading solutions. (see Orientation and Passive solar heating) North-facing openings (and south-facing ones above the tropic of Capricorn) receive higher angle sun in summer and therefore require narrower overhead shading devices than east or west-facing openings. Fixed horizontal shading above north-facing glazing is all that is required. Examples include eaves, awnings, and pergolas with louvres set to the correct angle (see ‘Fixed shading’ below). East and west-facing openings require a different approach, as low angle morning and afternoon summer sun from these directions is more difficult to shade. Keep the area of glazing on the east and west orientations to a minimum where possible, still allowing for good cross-ventilation (see Passive cooling), or use appropriate shading devices. Adjustable shading, such as external blinds, is the optimum solution for these elevations.
Posted on: Thu, 23 Oct 2014 09:25:51 +0000
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