Climatic design in homes
Houses in The Bahamas must respond to a hot sun, cool breezes and hurricanes. In the “old days” they were designed using elements that made living in them easier than it is today. They were cooler inside, and therefore more comfortable, and they could be prepared to respond to an oncoming hurricane quickly and easily, unlike today’s “modern” Bahamian houses. Is there a reason houses must be less accommodating today? Why are the houses designed today so much hotter and less comfortable?
The answer, of course, is that we have forgotten how to “read” the climate. For most new homeowners, the design process does not even include a discussion about climate. Questions about shade, orientation and hurricane protection are more often left to the addition of accessories, rather than the basic design. This article is to address the basic requirements of climatic design.
What, then, is the purpose of climatic design?
Climate has a major effect on building performance and energy consumption. The process of identifying, understanding and controlling climatic influences at the building site is perhaps the most critical part of building design. The key objectives of climatic design include:
• To reduce energy cost of a building;
• To use “natural energy” instead of mechanical system and power;
• To provide comfortable and healthy environment for people.
(From Climatic Design of Buildings – Hong Kong University Paper)
Energy in buildings is used to create creature comfort, which requires maintaining the temperature between roughly 70 and 80 degrees, with a reasonably low humidity. If the temperature is higher, cooling is needed, for which there are several solutions, including fans and air conditioning. Energy is also used to give light and to heat water.
The way designers use the design process to reduce the need for energy is to first reduce the heating up of the interior by avoiding insolation, then by encouraging evaporation of moisture from the skin (thereby creating cooling) using air movement (breezes). They also reduce the need for artificial light by bringing sunlight inside without its heat. Finally, they use the sun, a plentiful resource in The Bahamas, to heat water and even create an alternate source of power.
To do this, they must know both the elements of climate in the general area as well as the climate on the site. They must know where the sun rises and sets, which direction the breezes come from and when, what happens when it rains a lot, and what elements are affected by a hurricane. They must know what materials do well in humid conditions, which ones are good near the sea. They must know which trees have a canopy and which ones shed their leaves during winter.
Examples of the features of traditional buildings that respond to our particular climate are:
• The high pitch of the roof, which removes the water generated by rainstorms quickly;
• The porch, which keeps the direct sun away from the openings that expose the interior of the house;
• Push-out shutters, that keep the sun away from windows as well as provide easily operated hurricane protection;
• Cross ventilation, providing air movement for human cooling as well as removing stale air, improving air quality;
• Raised floors cooled by breezes below;
• Trellises and screens that create shade wherever needed;
• Short overhang to avoid uplift by hurricanes;
• Heavy planting on the west side of the house, usually with fruit trees;
• Wood shingles that “breath”, making attics cooler;
• Dormers and vents to habitable attics;
• Gable vents to inhabitable attics that removed warm air and left ceilings below cooler.
These are the types of concerns that climatic designers use to create buildings that are more comfortable and less expensive to use. We believe the average Bahamian building uses at least 40 percent too much energy. The return to climatic design is an important tool in the war against energy cost.
• Patrick Rahming & Associates is a full service design firm providing architectural, planning and design services throughout The Bahamas and the northern Caribbean. Visit its website at www.pradesigns.com and like its Facebook page. The firm’s mission is to help its clients turn their design problems into completed projects through a process of guided decision-making, responsible environmental advice and expert project administration.