When it comes to keeping buildings energy efficient, windows certainly pose a challenge. It was with this quandary in mind that a British scientist has created a new type of window – one that’s filled with water.

There are two main problems with conventional windows. For one thing, most of them allow heat to escape during cold weather, causing the building’s furnace to run more frequently. For another, they allow sunlight to stream in during hot weather, creating heat that causes the air conditioning to kick in.

Dr. Matyas Gutai, a lecturer in architecture at Loughborough University, believes that his “water-filled glass” (WFG) windows may address these limitations.

Each window contains a vertical sheet of water, sealed between two sheets of glass. As sunlight passes through the glass, it heats the water, thus keeping the room itself from getting as hot as it would otherwise.

Once it reaches a high enough temperature, that sun-warmed water is pumped out of the window, travelling through pipes in the wall to a storage tank elsewhere in the building. Cooler water is simultaneously pumped into the WFG, to replace that which was pumped out.

When the outdoor temperature drops later on, the stored warm water is pumped back out of the tank and into the pipes, warming the room by radiating heat through the walls. Alternatively, that warm water can also be used in the building’s taps, reducing the need to run the water heater.

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