19-23 February 2018








Concept of the Week: Climate and Architecture

Humans have been constructing houses and other buildings for thousands of years not only to protect themselves from the weather and other environmental factors, but also to create a comfortable indoor environment that would exhibit energy efficiency, especially in harsh climates. For centuries, natural or primitive housing reflected an adaptation to the climate of the locale and the availability of local building materials.

In order to maintain a tolerable level of comfort within a building, attention must be paid to thermal effects, ventilation, illumination and atmospheric humidity.

The indoor thermal state ultimately depends upon the building's energy budget involving incoming and outgoing radiation, latent and sensible heat loss and by interior heat sources or sinks. The indoor thermal level is mainly associated with the external energy load on the building. The external energy load on the building depends upon the latitude of the building, season of the year and time of day.

In tropical latitudes and during midday hours in summer, the sun's path across the local sky increases the solar radiation incident upon the roof and walls of the building. In polar latitudes, or during the winter or the amount of available sunlight is significantly lower, with the loss of infrared radiation causing a net cooling from the building. Changes in the color of the roof and the outer walls can affect the amount of incoming sunlight absorbed. Building orientation and the effective use of overhangs can also affect the amount of sunlight absorbed. Furthermore, the amount of insulation, often related to the thickness of the walls, reduces the conduction of heat into or out of the building. Thick adobe walls have been used effectively in the Southwest to moderate indoor temperature. These walls reduce the heat flow into the building during the daytime and in summer and out from the building at night or during winter.

The size and placement of windows also affects the energy balance. Large windows on the side of the building facing the sun's path tend to permit large amounts of sunlight to penetrate into the building. However, large windows on the side facing away from the sun can cause for heat loss due to conduction, as many types of windowpanes are not energy efficient.

Effective landscaping can reduce energy demands upon a dwelling: Deciduous trees planted on the south and west sides of the home provide cooling shade during the summer, keeping sunlight from entering the windows. These trees will lose their foliage in fall and allow the sun to shine through in winter, and warm south facing rooms. Evergreen trees or dense shrubbery on the north side can serve as a windbreak, which reduce the cold northerly winds from striking the house in winter.

Energy losses from buildings during the upcoming winter in northern latitudes can be seen readily by how quickly snow melts from roofs and by how big the icicles form. Heat losses from buildings occur with larger negative energy budgets, which are reflected also in higher heating bills during the winter season. However, the heating bills also depend upon the severity of the winter season that can be ascertained from the number of accumulated heating degree-day units. Check last week's Supplemental Information...In Greater Depth for how you can monitor the number of heating degree-day units to date in your state for this coming heating season.

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Prepared by Edward J. Hopkins, Ph.D., email hopkins@aos.wisc.edu
© Copyright, 2018, The American Meteorological Society.