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Seeking opinions on best material:

Discussion in 'Lighting' started by Jeff Engel, Dec 3, 2004.

  1. Jeff Engel

    Jeff Engel Guest

    The premise:
    When sunlight enters the space through a window or skylight, it brings
    not only light energy but also heat energy. Except in cold climates,
    this solar heat gain from daylight can be a burden on the building
    cooling system, and sunlight must be carefully controlled to avoid this.

    But with good design, the daylight is not only a good source of light
    but the most efficient. The number of lumens per watt (efficacy) of
    daylight is twice that of a fluorescent lamp and ten times that of an
    incandescent lamp. Properly designed daylighting strategies can both
    reduce electric energy demand for lighting and minimize loads on the
    cooling equipment.
    Our subject: What material or method will pass or reflect most light
    and reflect or absorb most heat? Anything more practical to be done
    with the waste heat? Are those efficacy claims above valid? Is this
    more interesting than LED holiday lights?
  2. TKM

    TKM Guest

    No doubt about it; daylighting is a good thing especially when the new
    research about light and hluman health is factored in. Boiled down, it
    leads to the conclusion that humans need bright days and dark nights.
    Electric lighting can't easily meet the "bright days" criterion -- too much
    energy use, cost and heat result if the high lighting levels required are
    put into work spaces. But daylighting is a good solution for most climates.

    The last time I checked, sunlight came in at 120 lumens/watt and "low E"
    glass was a great way to handle the radiant heat; but I'm not an expert.

    Terry McGowan
  3. David Lee

    David Lee Guest

    TKM wrote...
    I was very impressed at the daytime-lighting installed in the kitchen area
    of the Worcestershire Wildlife Trust headquarters (UK). The kitchen was
    built onto the back of an existing barn and has a turf roof running down to
    ground level and so has no natural light. Prisms on the roof collect
    sunlight and pipe it down to light fittings in the ceiling. It's extremely
    bright and of course zero cost in energy to run.

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