We build homes mainly to protect ourselves from the surroundings and the environment. Aside from extreme environmental events, remember that climate is part of the environment and the overarching system surrounding our homes.
Understanding the climate system and the microclimate around your home should be one of the first steps in designing or retrofitting a home.
Designing your home for the climate zone it is in has two key merits:
- It helps maintain thermal comfort for occupants at all times with minimal active heating and cooling, resulting in significant energy savings.
- It increases the house's resilience and durability for many years with minimal impact from mold, decay, and pests. It also ensures a healthy and safe environment and lowers maintenance bills.
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 construction and can be reduced significantly when retrofitting existing homes (depending on the scope and budget).
Data from recent years shows the acceleration of extreme climate events. We should expect significant climate changes, some gradual (rising temperatures, droughts, sea-level rise) and some harsh and unexpected (extreme storms, precipitation, wildfires).
Designing a home for the current climate or based on historical data is a good start. That’s exactly what building codes help us achieve. However, assuming houses are built to last two to three generations, today’s designs should be able to meet future challenges while demonstrating consistent efficiency and durability throughout those years. To achieve true sustainability, we must adopt best practices that adhere to local climate zones, micro-climates, and predictable extreme events.
This blog focuses on the basic need to adhere to your local climate zone. You shouldn’t design the same home in Arizona, 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, and the risks from wildfires, floods, and earthquakes differ. Therefore, we want to stress two key considerations:
- All the mentioned climate factors command a thoughtful approach to the design and the alignment of a home’s elements. It includes the elevation of the house, the slope of the roof, the size of the overhangs, and the location of rooms, windows, solar panels, and essential energy and water systems. A design that considers its climate zone will perform better while keeping the indoor ambiance cool in summer and warm in winter. It will also help your house dry quickly after water exposure and improve resistance to mold, decay, and pests, to name just a few benefits.
- Consider the use of materials, assembly, and detailing. For example, a humid climate poses different challenges from a dry climate. The materials and their assembly can change a house from one that accumulates moisture and develops mold and decay to a house that dries quickly and healthily performs for many years.
Our blog is not a substitute for proper design and construction. Awareness, research, and hiring the right professionals will help you make the right choices and save you money and aggravation from day one.
Which brings us to the prevailing question: what about the cost?
Cost is a leading factor in decision-making for any type of investment. There is a misconception that designing and building with sustainability, resilience, and efficiency in mind increases costs and tends to be above middle-of-the-road solutions. Check out our blog ROI (Return on Investment), which aims to demystify these conceptions.
When calculating your overall costs, you should consider the following in addition to the upfront expenses:
- Rising prices of energy and water
- The rising cost of usage (operational costs) of energy as the climate becomes more extreme.
- Losses and discomfort due to energy and water grid outages
- Maintenance and repair costs of house elements due to climate impact
The difference between a truly resilient house and standard construction isn’t necessarily the cost. Many times it is awareness, asking the right questions, and implementing the knowledge by proper design and assembly, and by using adequate materials.
U.S Climate Zones
Building America, a program funded by the Department of Energy (DOE), provides ample information and data on design and building practices based on 8 different climate zones in the U.S. Its main aim is to help homeowners achieve the most energy-efficient homes. They also provide critical strategies for durability and adaptation to relevant climate zones, providing additional safety, comfort, and cost savings. To learn more about the difference between adaptation vs mitigation climate change, check out our blog about the two terms.
To determine the climate zone relevant to your property, check Building America Best Practices for a list of counties and climate zones. Or, you can use our tool by submitting your zip code and getting your relevant climate risks and your climate zone.
The climate zones defined by Building America are based on heating degree-days*, average temperatures**, and precipitation. The International Energy Conservation Code ( IECC) has a slightly different method for dividing and defining the U.S. climate zones. We rely on both resources. However, in this blog as in other sections of our website, we follow Building America’s climate zones.
Here is a summary of considerations in designing or building in the different climate zones in the U.S:
All content below is credited to Building America and the DOE, although we have refined and added some nuggets! Building America is a professional, reliable, and motivating source to follow for further information.
A cold climate is generally defined as a region with approximately 5,400 heating degree days* (65°F basis) or more and fewer than approximately 9,000 heating degree days (65°F basis).
States that are partially or entirely within the Cold and Very Cold climate zones:
Portions of the cold climate are subject to frequent and intense rain and snow storms, severe thunderstorms, and hail. Some areas are at high risk for tornadoes and high winds. Large portions of the Midwest and Northeast have been subject to flooding, with most of the counties of these areas experiencing four or more presidential disaster declarations due to flooding since 1965.
Portions of the cold climate are prone to landslides, especially in the Rocky Mountains and the Appalachian Mountains.
The region is at low risk of earthquakes except for localized areas in Idaho, Wyoming, and Utah and the border of Tennessee and Missouri.
The cold climate zone is at low risk of volcanic eruption except in Alaska, Washington, and Oregon. The region is at low risk for hurricanes except along the Eastern seaboard (USGS 2010)
These two zones cover a significant territory with broad and varying challenges. Notable weather phenomena are extreme, prolonged low temperatures and snow accumulation in the winter, extreme and sudden precipitation events, high winds, and high humidity (along the Mississippi). Extreme natural events that can occur in these climates include flooding, earthquakes, and forest fires.
In this climate region, you should mainly focus on:
- Moisture and precipitation management
- Air Sealing
- Thermal control techniques for foundations, walls, and roofs
- Hurricanes, Tornadoes, and Strong Winds
- Solar radiation
- Wildfires in risk zones
- Earthquakes in risk zones
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:
- Most importantly: properly design and build your walls, roofs, and the foundation floor (crawl space/basement). A solid design will help drain water quickly and allow materials to dry. The design defines the layers you should use such as sidings, vapor, air, and water barriers, insulation, drywall, etc., the order by which you will lay them from the outside in, and the materials you use. The build is how well you attach them and run the detail so there are no cavities/leaks and thermal bridging. Check our blog on “water” for further details.
- Design the right size and angle of overhangs (eaves and gables) with a proper gutter and drain system that is capable of routing water from heavy storms away from the house.
- Landscaping is key. By digging a ditch or creating a small barrier/slope, and planting the right plants, you can help stop excess rainwater from running off and damaging your property or overwhelming the local sewer system or water reservoirs.
- Use door jambs that are designed for water and rot resistance.
- When installing windows use sill wrap, corner shields, and adhesive flashing tape to protect against water intrusion.
- Use cement backer board behind tubs, showers, and kitchens
- Install a dehumidifier - these systems suck wet air, cool it down, and condense the water back into a container or a pipe system and back into the world, preferably for good use and/or away from the house.
- Install a thermostat with humidity controls.
- The EPA still allows the use of paints containing mildewcide which can potentially repel bacteria but is also deemed toxic. Instead, look for VOC-free, or Low-VOC (some of the low-VOC become free after drying for a couple of weeks).
Unintentional airflow robs a home of conditioned air. This airflow can result from poor assemblies at the seams (through walls, roof, foundation plates), through-wall penetrations (of electricity, plumbing, nails), or through leaks around doors and windows, and cracks in the roof,
Not only decreasing thermal and energy control, air leaks are also pathways for moisture flow, poor air, pests, and reduced overall comfort levels.
If water vapor carried by air leaks condenses, it can cause mold and other moisture problems.
Controlling air infiltration is one of the most cost-effective and simple energy-efficient measures in modern construction practices. Air sealing is required by the 2018 International Energy Conservation Code (IECC) which identifies several areas for air sealing and requires verification with a blower-door test or visual inspection.
Air barrier systems hold the vital role of separating conditioned from unconditioned spaces. The key to the control of airflow is the use of a continuous air barrier. It should provide an unbroken barrier between conditioned space (indoors) and unconditioned space (outdoors, attic, crawlspace, and garage).
Note that air sealing is a complementary effort to insulation and moisture control. All three are different systems and must work together to provide a resilient, durable, safe and comfortable environment.
Sealing against air leakage is primarily done for thermal reasons, but when coupled with appropriate mechanical ventilation, this procedure also assists in maintaining good indoor air quality for the occupant.
Health and safety are essential factors to consider when air sealing, especially if the home contains combustion appliances. See Building America’s Air Sealing guide for more information.
Building America researchers have worked with three building approaches that push the air and thermal barriers toward the exterior of the building shell: conditioning crawl spaces and basements or using slabs,
installing insulated exterior sheathing with sealed seams, and conditioning attics.
These approaches make it easier to provide an uninterrupted air barrier. In addition, in homes where ducts need to be placed in the basement or attic, it is recommended to have these spaces conditioned to increase energy efficiency, air quality, and moisture control.
Air barrier components may include:
- Mudded and taped gypsum board serve as an air barrier on the home’s interior.
- Sidings such as Stucco may serve as an air barrier on the home’s exterior.
- Some Sheathing materials can act as air barriers.
- Some house wraps/membrane can serve as both the moisture/water control barrier as well as an air barrier.
- Caulk, tape, and in some cases insulation foam, are air barriers used in cavities, seams, and through-wall penetrations.
The materials and approaches mentioned are common and time-tested. However, these measures must be carefully installed to be effective and must be installed in the proper construction sequence before cavity areas are covered up by insulation, moisture control layers, fixtures, or walls.
- The airflow needs to be controlled from the outside in and inside out to protect both the interior thermal and air quality as well as the structure of the house from moisture that travels with air.
- Different climate zones command the usage of different air barrier materials.
- Building codes and standards define the performance which air barrier materials should meet (note that the materials, the assembly, and the entire enclosure may have different performance requirements.)
The ENERGY STAR for Homes program has compiled the Thermal Bypass Checklist, a comprehensive list of potentially vulnerable spots in the building envelope. It identifies 25 points to inspect throughout the home, covering all major components of the building envelope including exterior walls, floors, ceilings, attics, and shafts. Builders can use the checklist to verify the integrity of the air barriers in the building envelope.
Thermal control techniques for foundations, walls, and roofs
Building America covers many thermal control techniques in their 40% Whole-House Energy Savings in the Cold and Very Cold Climates guide.
These techniques are not only about maintaining comfortable temperatures in the house, or the benefits gained from consequential energy savings. While those are critical strategies for your home resilience, the guide also discusses how to properly implement these strategies to avoid incidental damages from poor design and implementation.
Here are the key takeaways of thermal control strategies done right:
- Beyond properly insulating relevant house elements to gain thermal control, all strategies include proper design and implementation to avoid moisture and condensation which lead to either short or long-term structural damage (such as mold, rot, and decay) as discussed in the Air Sealing section. Placing tons of insulation without properly understanding how air and water flow from the exterior of the house to the inside, and vice versa may end up in substantial agony and financial loss. Proper thermal control strategies include:
- Implementation of Air Control layers.
- Implementation of Water and Vapor Control layers.
- The detailing around cavities, seams, and joints, especially where the foundation meets the walls and the walls meet the roof, windows, and doors.
- Drying techniques of these elements after they do get wet.
- Different foundations - slab, basement, crawlspace - have different thermal control strategies. Insulation is the first step, and it is wise to check out the IECC R-value requirements for insulating different types of foundations.
- The same goes for walls and roofs, check out the IECC R-value requirements for these house elements based on your climate zone.
- All these strategies also include recommendations to properly design foundations, walls, and roofs to reject pests (namely termites).
Floods are the most common natural disaster in the U.S. We tend to think that floods happen mainly around coastlines and during hurricanes, yet America is experiencing more frequent and devastating floods along creeks and rivers (“riverine floods”), lakes and ponds, and areas with inadequate drainage systems. In some cases, extreme precipitation events (“atmospheric rivers”), in-land tornados, and melting snow/ice can also cause floods in unexpected locations.
In flood risk zones, consider:
- Elevating your home above BFE (Base Flood Elevation level).
- Build slab-on-grade foundations and grade lots to drain away from the structure. In areas of likely coastal flooding build on concrete or pressure-treated piers.
- Adoption of Water Resistive Materials.
- Elevating Essential Infrastructure.
- Backing up Critical Systems.
- Install a generator-ready electrical service panel to run generator-powered shop HVAC, fans, and heaters to dry out the house and reduce water damage during post-storm recovery when electric power outages are common.
- Building Rain Gardens and Barrier Systems.
- Buy flood insurance.
Read further on strategies and products to enhance the protection of your home from floods in our blog.
Hurricanes, Tornadoes, and Strong Winds
Damage from hurricanes varies depending on the storm category and the house location. The main risks from hurricanes are falling trees, poles, flying debris, power outages from days to months, major flooding and excess rain, and loss of water supply. In all storm categories, there is a risk of damage or full removal of the roof, sidings, and other exterior elements, structural damage (walls, roof) to complete displacement or destruction of the house.
The following are strategies to reduce potential damage In hurricane areas:
- Structural load design and assembly: designing walls to resist uplift using hurricane strapping and other metal fasteners that provide a continuous load path from foundation to roof.
- Anchoring walls properly to foundations.
- Designing roof geometries that are less prone to wind damage than gable roofs and installing continuous roof underlayment.
- If you decide to go with a gable roof, properly plan the length and width of the gable overhang, strengthen gable ends, and outlooker attachments at gable ends.
- Eave designs with extended fascia providing drip edge, and recessed soffit vents (Zoeller 2006).
- Adequately securing chimneys to the structure.
- Ensuring windows and doors meet appropriate design pressures (“impact windows and doors”) in addition to being protected from windborne debris.
- As with windows and doors, there are hurricane-proof garage doors and tracks. Or reinforce an existing garage door using a garage door bracing kit.
- Safe-room / Shelter - according to the Federal Emergency Management Agency (FEMA), a safe room is a: “hardened structure specifically designed to meet the FEMA criteria and provide near-absolute protection in extreme weather events, including tornadoes and hurricanes. Near-absolute protection means that based on current knowledge of tornadoes and hurricanes, the occupants of a safe room built per FEMA guidance will have a very high probability of being protected from injury or death.”
- Consider steel-reinforced concrete walls.
- Use outswing doors.
- Use hurricane shutters.
Read further on strategies and products to enhance the protection of your home from hurricanes in our blog.
Hail is a form of precipitation consisting of solid ice that forms inside thunderstorm updrafts, sometimes building rapidly and without advanced warnings. Hail can damage homes and landscaping and can be deadly to people, livestock, and pets.
In Hail risk zones, consider the following:
- Harden your roof using impact-resistant shingles (Go for Class 3 or 4 UL2218 tested shingles)
- Protect windows and skylights with either permanent or temporary shutters.
- Cut trees around the house that may fall on the house during hail storms.
- Stowaway (indoors) all backyard and front yard furniture during the storm.
Read further on strategies and products to enhance the protection of your home from hail in our blog.
Solar radiation heats the roof, walls, windows, and doors. That energy then heats the home interior. To have an energy-efficient home (that uses less energy) and resilient (that reduces the dependency on the energy grid and cooling systems, even during extreme heat waves), you should:
- Install a reflective roof and use light or reflective exterior wall colors.
- Install a radiant barrier in the attic.
- Install overhangs, covered porches, awnings, pergolas, or shade trees to minimize solar heat gain (avoid shading the roof due to moss).
- Place the air handler and ducts in conditioned space or go ductless with mini-split heat pumps.
- Install high-performance, low-emissivity windows with low solar heat gain coefficient.
- Locate windows on the sides of the house that can catch coastal breezes.
- Create a tight thermal envelope and install a positive-pressure ventilation system.
- Use non-heat-producing Compact Fluorescent Light (CFL).
- Install ceiling fans and look for solar-powered fans (as backup).
Wildfires in risk zones
Wildfires pose a risk to the lives of people who live near those ecosystems and their homes. Moisture is one of the main factors that determine wildfire 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:
- Avoid new construction in WUI zones and choose a location that is not at high risk of wildfire.
- Use non-combustible or fire-resistant materials for exterior components such as roofs, sidings, windows, doors, vents, and gutters. For example, use Class A-rated roof shingles and borate pressure-treated lumber in framed homes.
- Create defensible space by surrounding your property with non-combustible materials and remove vegetation away from the house.
- There is no “fire-resistant” vegetation. Design the landscaping around the house with high-moisture plants that grow close to the ground and have a low sap or resin content. Choose plants that resist ignition such as rockrose, ice plant, and aloe. Choose plant hardwood, maple, poplar, and cherry trees that are less flammable than pine, fir, and other conifers.
- Install interior and exterior fire sprinklers.
- Find more information in our Building Resilience Against Wildfires blog.
Earthquakes in risk zones
The design and building of new construction should be sufficiently strong and stiff to properly perform during an earthquake. According to FEMA, “actual earthquakes can generate forces considerably higher than those used for code-prescribed design.”
As a minimum, build your home according to local and state codes. But based on the specific risk zone you are in, consider the above-code techniques to further enhance a structure to obtain minimal damage and the best protection for the occupants and belongings. These would be:
- Adopting I-Codes from the International Code Council (ICC) where local codes have not yet adopted them or where no code is currently required.
- Codes define the measures or factors for strength and stiffness. Discuss with your experienced architect, engineer, or contractor if you need to go above these metrics.
- Designing strength and stiffness for both vertical and lateral movements. Often the focus is on vertical, although lateral loads pose the same if not higher risks. Adding strength and stiffness to lateral movement can be beneficial.
For retrofitting your home, there are numerous measures you can take to make your house more susceptible to earthquake forces. Here are some options to explore:
- Replace unreinforced masonry or deteriorating concrete foundations with reinforced concrete.
- Add steel frame and structural sheathing to a soft-story wood frame.
- Secure the frame to the foundation with anchor bolts.
- Inspect exterior masonry walls periodically for cracks and reinforce them. Brace chimneys to the roof structure.
- Inspect for loose roof tiles and properly anchor roofing material to a braced roof frame.
- Strap water heaters to the building frame.
- Secure bookshelves to walls with screws or straps, and secure bookcases to wall studs.
- Secure light fixtures and fans to ceiling joists.
- Strap computer monitors and televisions to walls or desks.
- If your home is heated by natural gas, use flexible pipe connections for gas appliances.
- Install a seismic-actuated gas valve, which shuts off the gas during severe earthquakes.
- Manufactured homes should be tied-down and anchored
Read further about Earthquakes’ risks to homes and strategies to reduce potential damage in our blog.
Climate is part of the environment and the overarching system surrounding our homes. We build homes mainly to protect ourselves from weather and natural phenomena.
Homes should be designed to adhere to the local climate zone characteristics and the micro-climate around the home to achieve:
- Thermal comfort for house occupants at all times with minimal active heating and cooling, resulting in great energy savings.
- A resilient and durable home for many years with minimal impact from mold, decay, and pests - ensuring a healthy and safe environment for occupants (even when the power grid is down) as well as lower ongoing maintenance bills.
Achieving these objectives requires proper design, construction, and choice of materials. 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 time.
To achieve 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. Lastly, 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 which occur more frequently. These require additional measures and planning.
KEEP COOL. BUILD RESILIENCE. EAMPACT.