Double the height, double the benefits
The most visible reason for the popularity of double-height appears to lie in the expanse of space it create
During a family trip, while passing by a factory, every kid is excited by the tall towers. When asked about it, how do we answer them? If we take a tour of old European towns, the rooftop chimneys dominate the skyline. Do we really know how do they work? Why are the civic buildings with the tall cloak towers airy inside? What has prompted large hotels and offices to employ central atrium space?
The answer to all the above is a single theme – these tall narrow towers work as hot air chimneys, using technically what we call as stack effect, where hot air rises up along a tapering vertical column. Before the days of mechanical ventilation, people realised they could force air movement using these simple laws of physics! If not for this discovery, the European fire places would not have existed and factories would have billowed smoke all over the place.
Adapting the stack effect
Can all our houses today have a tall, towering chimney? That would be ridiculous! However, it’s possible to adapt the stack effect to a reasonably effective degree by having a common space going high. Then, this room would have the ceiling at the same level as the first floor, at a clear height of 20 ft. instead of the normal 10 ft. Termed today as double-height space or high-ceiling room, most owners prefer it in the living room, dining hall or the family space. In case the final roof is also flat, the clear height would be 20 ft while by designing sloping or curved roof we can reduce the effective height to 15-16 ft. In the last essay we discussed how a high ceiling of 12 or 14 ft. is not needed all over the house unlike in the past. Retaining clear floor height at 10 ft., we can still effect air movement by having one double height space, carefully positioned to draw hot air from all over the house. Only the toilets and bedroom escape from this drag effect, which need their individual modes of displacement ventilation in the form of ceiling-level vents.
Towards multiple advantages
Ideally, the double-height is part of the three-fold design solution including skylights and internal courtyards, which together do wonders to the house micro-climate. While the vertical space distributes light from the sky all over the house, making it bright, and suck the hot air upwards to ventilate, the floor below acts as a passive court or as an active part of the house plan. Double-height spaces chip in more value-added advantages, like the possibility of looking down and talking to people therein.
While the major intention of this idea is green and eco-design, the most visible reason for the popularity of double-height appears to lie in the expanse of space it creates. Even a small house in a 30’x40′ site may look as if it’s in a bigger plot!