Origin
Developed by Horazio Barra in Italy, the Barra system is a passive solar building technology. This technology involves converting sunlight into a usable energy source, without using any mechanical aid.
What is it?
The primary tool in the Barra system is a collector wall that captures solar heat. It also uses the thermosiphon effect (hot air is lighter than colder air, hence it rises) to distribute the warm air through channels incorporated into the reinforced concrete floors, warming the floors and hence the building. Alternatively, in hot weather, cool nighttime air can be drawn through the floors to cool them, providing a form of air conditioning.
How is the system installed?
The floors are built with reinforced concrete having embedded channels by using hollow concrete blocks. Outdoor air blows through the channels and thermal storage is provided by hot air from the insulated southern-facing collecting wall. The system is open to modification. During the night, a fan blows air through the channels. This stores cold night air inside the ceiling mass. In the day, the cooled ceiling will absorb the heat from the interior space passively.
Despite being lot more comfortable than other passive solar houses, Barras are fairly unknown outside of Europe, probably because of the expenses involved.
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