Climate Zone Information
Developers are encouraged to educate themselves about climate zones prior to designing a new construction or rehab project. Modern energy codes for buildings are organized by climate zones, with provisions like wall insulation R-values tailored for each specific zone. The map below shows seven distinct climate zones within the United States, as defined by the 2009 International Energy Conservation Code (IECC). The IECC is a national model energy code which is adopted by many states throughout the country.
Each of the seven zones is based on the extent of heating degree days (HDD) and cooling degree days (CDD). These metrics are used to classify how severe the heating and cooling conditions are for buildings in different regions of the country. For example, Climate Zone 1 (South Florida) has CDD > 9000 and building space conditioning is dominated entirely by cooling. Conversely, in an area like the Upper Midwest located in Climate Zone 6, building energy use is dominated by heating loads, with HDD greater than 7200 and less than 9000.
U.S. Climate Zones based on 2009 International Energy Conservation Code
Source: Building Energy Codes Resource Center, Pacific Northwest National Laboratory, U.S. Department of Energy. Accessed online at: http://resourcecenter.pnl.gov/cocoon/morf/ResourceCenter/graphic/973
Moisture and humidity conditions must also be considered during the design process. Humidity considerations have a major impact on optimizing the energy systems within housing, often dictating which materials or systems work best in terms of both energy performance and moisture control. For instance, in hot and dry climates, evaporative cooling systems can provide the space cooling for homes; typically using less energy than traditional vapor compression A/C systems. Meanwhile, in areas like the hot/humid Southeast, special attention must be given to the vapor permeability of insulation materials in wall assemblies to prevent serious moisture and mold problems in the building envelope.
Using information about the climate setting for a building project — from energy codes as well as local information about any microclimate conditions - will help developers decide which energy efficiency features are best suited for a project and can optimize energy savings.
For a quick glance at the 2009 IECC provisions for any county in the U.S., use this online map tool from U.S. DOE's Pacific Northwest National Laboratory. But keep in mind that these provisions are code minimums, with high performance homes generally exceeding these levels.
NOTE: the IECC Climate Zone map shown above is provided as a widely recognized system for defining climate conditions as they relate to buildings. It is especially helpful because it is referenced in many state building energy codes now, and serves as the basis for energy-related building requirements. In the 2010 NOFA, a climate map with five climate zones produced by the U.S. Energy Information Administration (EIA) in their Residential Energy Consumption Survey (RECS) was used for the purpose identifying and selecting projects from a simple and diverse set of climates within the U.S. In 2011, the NOFAs no longer utilize this tool in the selection process because it did not result in as much geographic diversity in the selected projects as we had anticipated. Climate zone knowledge is important for all applicants but climate zone designation is no longer part of the selection process.