Glass and Energy, What is glass and energy
Glass and energy speaks to what is glass and energy, why glass and energy.
The fact is that glass is a two way pipeline for the flow of both conducted and radiated heat. Glass when doubled or tripled conducts heat rapidly into or out of a building. It can also collect and trap large amounts of solar heat inside a building.
In residential buildings, the conduction of heat through glass should be minimized in the extremely hot or cold seasons of the year. Double glazing, low-e coatings, low conductivity gas fills and snug curtains or shutters are desirable features for residential windows.
Warming sunlight is welcome in winter but highly undesirable in summer. This leads the conscientious designer of residences to orient major windows toward the south, with overhangs or sunshades above to protect them against the high summer sun. Large east or west windows can cause severe overheating in summer and should be avoided unless they are shaded by nearby trees.
In non residential buildings heat generated within the building by lights, people and machinery is often sufficient to maintain comfort throughout much of the winter. In warmer weather, this, heat along with any solar heat that has entered the windows must be removed from the building by a cooling system. In this situation, north facing windows contribute least to the problem of cooling the building and south facing windows with horizontal sunshades above allow the entry of solar heat only in the winter.
East and west windows are problematic, as they contribute strongly to summertime overheating and are very difficult to shade. Shades or blinds inside the glass are helpful in eliminating the glare from such windows but they do little to keep out the heat because once sunlight strikes them, its heat is already inside the building and little of it will escape.
Tinted and reflective glasses are of obvious value in controlling the entry of solar heat into buildings, to the point that they might be perceived as encouraging the designer to pay little attention to the window size and orientation. A growing number of larger scale buildings are characterized by different glazing schemes for the different sides of the building, each designed to create an optimal flow of heat for the building for that orientation with each making creative use of the available type of glass for this purpose.
The results as measured in occupant comfort and energy savings, are generally impressive and he aesthetic possibilities are intriguing. This last statement could apply equally well to the role of glass in admitting light to a building. Electric light is often the major consumer of energy in a building, especially when the heat generated by the lights must be removed from the building by a cooling system.
Daylight shining through windows and skylights, distributed throughout a space by deflecting and diffusing surfaces, can reduce or eliminate the need for electric lights under many circumstances and is often more pleasant than artificial illumination. Low cost computer models make it easy to predict the levels of daylighting that can be achieved with alternative designs which enable more architects and engineers to become expert in this field.
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