Building Physics
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Transcript of Building Physics
Building PhysicsIntroduction to architectural science
Lecture 3Prepared by:
Dr. Yahia Elbashar
1Dr. Yahia Elbashar
• 12 lectures• 100 marks• 20 HW and attendance• 20 Midterm • 60 final
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Course Contents
• Light: The Luminous Environment• Sound: The Sonic Environment• -----------------• Heat: the thermal environment • Resources: Energy use in buildings
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Light: The Luminous Environment
• Physics of light• Vision• Daylight and sunlight• Design methods• Electric lighting
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Transmission of light
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VISION
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Visual performance• The contrast sensitivity of the eye is very good in good
lighting. • In full daylight a luminance difference between
surfaces as little as 1% can be distinguished, but under poor lighting conditions surfaces with up to 10% luminance difference may be perceived as equal.
• Visual performance is a function of time required to see an object, or of the number of items (e.g. characters) perceived in unit time.
• The time required to perform a certain visual task decreases (i.e. the performance increases) with the increase of illuminance
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Lighting requirements
• The adequacy of lighting is a quantitative requirement, which depends on the visual task: the contrast, the fineness of detail and the speed at which the view changes.
• To set the required lighting level the risk of possible errors must be judged and balanced against the affordability of lighting.
• As visual efficiency of people reduces with age, it is advisable to provide better illuminance for older people.
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suitability of lighting
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DAYLIGHT AND SUNLIGHT• Light outdoors is generally referred to as natural light.
It has two main components: that arriving directly from the sun is referred to as sunlight ( or ‘beam sunlight ’ ).
• Varying fractions of this are diffused by the atmosphere, e.g. by clouds, which is referred to as daylight. (Some authors refer to the latter as ‘ skylight ’, but in general usage, also adopted here, skylight means a roof window.)
• The term daylight, in a loose sense is often used for both, but in technical language (also used here) it means only the diffused light arriving from the sky hemisphere.
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DESIGN METHODS
• Daylight may be introduced into a building using a variety of techniques, side-lighting or top-lighting strategies.
• Integration of daylighting with building design can have a decisive influence on the architectural form.
• In daylighting design, for the positioning and sizing of apertures, there are three main issues to be considered:
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1. to satisfy the visual tasks (provide enough daylight)
2. to create the desired ‘ mood ’ and provide visual focus
3. to integrate daylighting with the architecture.
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References
• Introduction to Architectural Science, Steven V. Szokolay, Routledge, 2008
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