One of the main reasons we build houses is to protect ourselves from the environment. Setting aside extreme environmental events, climate (which is part of the environment) is the overarching system that surrounds our homes. When designing or retrofitting a home, one of the first steps you should take is understanding the climate system as well as the microclimate around your home.
Two key merits of designing a home for the respective climate zone it’s in:
Adapting to Climate Zones
About 50% of household energy in the U.S is used for heating and cooling (space and water). This rate could be dramatically cut to almost zero in new constructed homes, and can be significantly reduced in existing homes depending on the scope (and budget) of retrofitting projects.
Data from recent years shows the acceleration of extreme climate events, and that we will be experiencing significant changes in the climate, some subtle and growing slow (rising temperatures, droughts, sea-level rise) and some harsh and unexpected (extreme storms, precipitation, wildfires).
Designing a home based on historical data or for today’s climate is a good starting point and that’s what building codes help us achieve. However, assuming houses are built to last two to three generations (say 80 years) the goal should be to ensure those designs can meet the future challenges and demonstrate the same efficiency and durability throughout those years. To reach true sustainability, it is important to adopt best practices that adhere to local climate zones, micro-climates, and predictable extreme events.
Setting aside extreme events, this blog focuses on the basic need of adhering to your local climate zone. You cannot design the same home in Arizona and Indiana, Texas, or Oregon. In each region, the trajectory of the sun, the direction of wind and rain, the ranges and fluctuations of temperatures and humidity, the amount of precipitation, snow, and ice, the risks from wildfires, floods, and earthquakes differ. Therefore, we want to convey two key takeaways:
What about the cost? The difference between a true resilient house and standard construction isn’t necessarily the cost. Many times the difference is being aware, asking the right questions, choosing the right professionals and then properly designing and assembling the house, using the right materials.
U.S Climate Zones
“Building America”, a program funded by the Department of Energy (DOE), has divided the U.S into 8 climate zones and provides ample information and data on design and building practices based on those climate zones. Their main aim is to help homeowners achieve the most energy-efficient homes, but they also provide key strategies for durability and adaptation to the relevant climate zone, providing further safety, comfort, and cost savings.
To determine the climate zone relevant to your property, check the Building America Best Practices Volume 7.3 Guide to Determining Climate Regions by County (DOE 2015) for a list of counties and climate zones.
All content below is credited to Building America and the DOE, although we have refined and added some nuggets! Still, Building America is a great professional, reliable and motivating source to follow.
HOT-DRY and MIXED-DRY
A hot-dry climate is generally defined as a region that receives less than 20 in. (50 cm) of annual precipitation and where the monthly average outdoor temperature remains above 45°F (7°C) throughout the year.
A mixed-dry climate is generally defined as a region that receives less than 20 in. (50 cm) of annual precipitation, has approximately 5,400 heating degree days* (65°F basis) or less, and where the average monthly outdoor temperature drops below 45°F (7°C) during the winter months.
States that are partially or entirely within the Hot-Dry and Mixed-Dry climate zones:
Hot-dry and mixed-dry climates bring several challenges for home building. The intense solar radiation imposes a large thermal load on houses, increasing cooling costs, adversely affecting comfort, and damaging home furnishings. Annual precipitation in these climates is typically less than 20 inches. Nevertheless, a brief period of heavy rain can deposit several inches of water onto and around a building. Besides rain, improper irrigation can be a major moisture source; leaks can cause significant damage, and indoor sources of moisture can be a problem. If water collects in an area that cannot quickly dry, deterioration of building components may occur.
In this climate region you should mainly focus on:
Moisture and Extreme Precipitation
Probably the biggest challenge for maintaining a durable home is keeping its structure dry. Water in its various forms - liquid, solid (ice), vapor (moisture) - finds its way onto the exterior (rain, snow, ice), interior (floods, showering, cooking, breathing), and within the structure (leaks). Here are some key strategies to explore with your architect and contractors when designing or retrofitting a waterproof house:
Solar radiation
Simply put, solar radiation heats up the roof, walls, windows, and doors, and that energy then heats up the interior of the home. In order to have an energy-efficient home (use less energy) and resilient (reduce the dependency on the energy grid and cooling systems, even during extreme heat waves), you should:
Wildfires in risk zones
Wildfires pose a risk for the lives of people who live near those ecosystems and their homes. Moisture is one of the main factors that determine wildfires frequency and since the changing climate in recent years brings dryer winters, the consequences of wildfires are becoming more devastating, and the fire season becomes longer. In fire risk zones consider:
Pest control
Pests do not only risk your property, they are also a threat to your family’s health. As with other hazards, prevention and being on the offense is a better strategy than being on the defence after pests have gained access or control over parts of your property.
The following methods are layers of protection that perform well together to reduce the threats from pests.
Summary:
Climate (which is part of the environment) is the overarching system that surrounds our homes and one of the main reasons we build houses - to protect ourselves from weather and natural phenomena.
The main impacts of the climate on our homes have to do with how we handle moisture and water so house elements dry quickly and do not develop mold and decay. How we handle pests such as termites. How we insulate and provide comfort while minimally utilizing heating and cooling systems. How we take advantage of solar energy as well as protect from it. How we handle “average” winds, earthquakes, wildfires, and floods.
Setting aside extreme environmental events, homes should be designed in a way that adheres to the local climate zone characteristics and the micro-climate around the home, in order to achieve:
Building codes are a good starting point however, they set the minimum requirements and don’t always cover all the best practices. Assuming houses are built to last 50 - 100 years, the goal should be to ensure their design can meet future challenges and demonstrate the same efficiency and durability over such time.
To reach true future sustainability - research and understand your climate zone and study how to mitigate the risks it poses. Tap into information from local governments, communities and neighbors. Hire certified professionals that will help you achieve these goals in the most cost-effective way.
Remember, working with the environment and adhering to the local climate zone is the necessary first step. The next step is being ready for future extreme events, those - “one in a century events” - which now occur more often. These require additional measures and planning.
KEEP COOL. BUILD RESILIENCE. EAMPACT.
References:
https://www.eia.gov/energyexplained/use-of-energy/homes.php
https://www.ncdc.noaa.gov/billions/
https://www.energy.gov/sites/default/files/2015/10/f27/ba_climate_region_guide_7.3.pdf
https://www.energy.gov/sites/prod/files/2013/11/f5/40percent_hot_humid.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/40percent_mixed_humid.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/18899.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/cold_climate_guide_40percent.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/marine_40_guide.pdf
Footnotes:
* Heating and Cooling Degree Days
NOAA defines: “Degree days are based on the assumption that when the outside temperature is 65°F, we don't need heating or cooling to be comfortable. Degree days are the difference between the daily temperature mean, (high temperature plus low temperature divided by two) and 65°F. If the temperature mean is above 65°F, we subtract 65 from the mean and the result is Cooling Degree Days. If the temperature mean is below 65°F, we subtract the mean from 65 and the result is Heating Degree Days.”
A degree day is a solid gauge to calculate if your home improvements have merit. After you take measures to improve your energy efficiency with the proper home insulation and air tightness, energy efficient HVAC systems (or a “passive house” ventilation system), you will be able to observe how the new energy bills fare against the past. While extreme events of high or low temperatures at any given year might skew the results, you should still be better off after installing proper insulation and taking advantage of energy efficient HVAC systems or “passive house” strategies.
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