FIGURE 15. Passive Strategies Generally Suitable for the Seven
Climatic Regions of Texas.
Building climatology refers to the study of climate as it affects human comfort and to strategies that use the climate as a resource to lower the energy demands of buildings. These strategies, which are mostly passive in nature, all involve working with the climate rather than against it to minimize space conditioning and lighting loads. Some of the strategies, like shading windows to minimize solar heat gain, will be familiar to any Texan, while others are not so intuitive. They can be summarized as follows:
Shade- providing external shading of windows and structures
during hot, sunny periods.
Solar gain- using sunshine incident on vertical, south-facing
surfaces to warm structures when temperatures drop below comfort
levels.
Ventilation- employing natural or fan-forced air flow to
maintain comfort during hot, humid conditions.
Mass- constructing building envelopes of massive,
heat-retaining materials (like adobe structures) to moderate the high
diurnal temperature swings of arid climates.
Night ventilation- flushing building structures with cool,
nighttime air to minimize the next day's cooling load; works best in
conjunction with massive envelopes.
Evaporative cooling- evaporating water directly into hot, dry
airstreams to produce cooling; limited to arid climates.
Daylighting- substituting sunlight for artificial lighting
through skylights and windows.
From a building climatology perspective, Texas has a fundamentally temperate climate in that all parts of the state have both heating and cooling loads. Within this framework, however, there exists considerable variation, ranging from the humid Gulf Coast to the arid Trans-Pecos, and from comfort needs dominated by cooling loads in the Rio Grande valley to heating-dominated conditions in the panhandle. As a result, different passive design strategies will be appropriate in different parts of the state. Figure 15 identifies seven climatic regions and the various options appropriate for each. The comments and suggested tactics are geared toward residential structures-buildings whose energy needs are driven by climatic loads rather than internal load-dominated structures such as offices.
The strategies above can often be incorporated to reduce energy demands and to improve comfort in buildings. Of course, actual recommendation are specific to the characteristics of the building site.
An additional resource not mentioned in the figure that has potential across the entire state is daylighting. Daylighting is particularly pertinent for commercial buildings. About 25% of a typical office building's total electricity consumption is in lighting. Lighting also contributes substantial heat that must be removed during the cooling season.
Passive strategies can improve any building's energy demand, but will only reach their full potential when incorporated into design and construction. Certain techniques simply cannot be retrofitted. Decisions about siting, orientation, and mass can have an enormous impact on a building's energy consumption and are permanent. For example, simple decisions about the structure's location relative to trees and which rooms face south will help define a building's 'metabolism.' Although we know that incorporating passive design into new buildings can greatly reduce their energy consumption (perhaps by as much as half), no research has been carried out to quantify the effectiveness of such strategies on Texas' existing buildings. Furthermore, no thorough canvass of the state's existing building stock exists that defines a typical structure. Building climatology's potential impact on state energy consumption can only be approximated in the absence of these data.
