The luxury of high roofs
Room volume as a way of cooling is definitely a valid method, largely discovered by the British
FOR A BALANCE: Ceiling height decides functional and aesthetic aspects
For all of us, visiting the grand old home of a distant aunt is an unforgettable experience. Stepping into the living room, we notice the large volume, with high ceiling, often with light pouring in from the roof. In summer, the cool inside cannot go unnoticed, more so if we walk in just in time for lunch!
Where is the magic? Commonly it’s attributed to high roof, which is rather unfair to all other aspects of passive cooling. Anyway, room volume as a method of cooling is definitely a valid method, largely discovered by the British. They would insert a horizontal window in the roof called as clear storey which had openings in the sides. Sometimes, there would be louvers at the top of walls or window shutters fixed in their centre to be operated by long ropes or steel rods.
Impressed by all of this, when we plan for a new home now, we insist that the rooms be at least 12 ft. high. This decision could be useful or a waste of money – so, let us try to understand this phenomenon first.
Old time solution
High ceiling does not reduce the heat gain at roof level, but decreases its effect during floor-based activities. However, room air also gets heated up, hence the high level openings which are provided are to let hot air escape. The British tried up to 15 or even 16 ft. high rooms, and ensured these rooms were proportionately spacious in plan. The resultant volume of the room would create different aesthetics, but more importantly, create a sense of coolness.
It is not worth blindly copying these designs today; we need to realise our project contexts to apply these principles. If the building has a first floor, high ceiling on ground floor has no climatic effect, though it may create spacious looks. Height without displacement ventilation could be detrimental to the cause, since the air and heat trap zone above the lintel level increases! Added height would increase the run of the staircase, volume of wall and length of service lines, all adding to the construction cost. With the present set of electrical gadgets adorning the roof, higher the roof, lesser the effect of fan and light, besides the problems of replacement.
We cannot stop atmospheric heat, but can reduce its ingress and let it escape again. Passive cooling ideas offer many options, where indoor temperatures can be reduced, compared to normal construction systems. In case of minimal indoor air movement discouraging ventilation, thermal currents can be created by letting heat inside through skylights, resulting in displacement ventilation. As such, today there are simpler and more economical solutions, without taking the roof to great heights.