Sunday, October 30, 2011

Passive Solar Heating

Passive solar heating is one of many scientific approaches the Miller home design uses in order to be more energy efficient.

When the leaves have come off the trees, winter sunlight shines on dark tile flooring and helps to warm the room. In the photo, the room is shown in the warmer months, when shade from the foliage and the more overhead angle of the sunlight is preventing the tiles from absorbing the solar heat. This keeps the room at a comfortable ambient temperature for the warm season.

The tiles are laid on top of an extra thick slab for insulation. A radiant heating system is installed in the ceiling. This is different from the more commonly seen radiant floor systems, so that the benefits of the passive solar heating can be realized. If a more common in-floor heating system had been used, the solar benefits would have been wasted, as the tiles can only hold a certain amount of heat (just as a battery is only able to hold a certain capacity of charge).

Low-E (low-emittance) windows are double panes of glass with argon gas occupying the space in between. The gas reduces heat transfer better than air. These are used on north, east and west facing windows. A special coating is added to these on the south facing windows, designed to reduce heat loss while admitting high solar gain. The use of windows has the added benefits of utilizing natural sunlight rather than energy-consuming electric lighting.

Careful attention to provide a well insulated space, as highlighted in the previous post, is essential for retaining the heat gained in the passive solar techniques. Additionally, although there is a small climate control unit, the Miller family notes that the insulation was so effective that the room stayed cool and comfortable during the summer. The cooling unit would only be needed for a group gathering.

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