Climate Variations and Wood Flooring

As a wood floor installer, a general understanding of the exterior climate zone where your floor is being installed can help you understand the facility’s interior requirements. When working with the builder and property owner, a brief discussion about this can help them understand the importance of ensuring the new wood floor will be placed in an environment that allows it to perform as intended, and ultimately ensure a successful installation.

The average outdoor temperature and humidity vary from region to region. Across every region, wood floors can be installed successfully; however, all wood floors cannot be installed in the same manner in all climates.

The facility must align with the flooring requirements. In many parts of the country, humidification and/or dehumidification systems are necessary to maintain an environment appropriate for the flooring specified for the project. The U.S. Department of Agriculture (USDA) Forest Service suggests the following moisture content (MC) average and ranges for interior wood products:
• Most areas of the United States:
Average = 8 percent MC, ranging from 6 to 10 percent MC
• Dry southwestern regions:
Average = 6 percent MC, ranging from 4 to 9 percent MC
• Damp, warm coastal areas:
Average = 11 percent MC, ranging from 8 to 13 percent MC

Actual moisture content conditions in any location may differ significantly from these numbers.

These interior moisture content averages are based loosely on the exterior climate regions in North America, which are universally known as Climate Zones. Climate Zones are geographic regions based on climate designations as defined by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), and as specified by the International Residential Code (IRC), and as used by the International Energy Conservation Code (IECC). The climate zone map was developed by the U.S. Department of Energy (DOE), and researchers at Pacific Northwest National Laboratory with input from Building America team members, in particular, Joseph Lstiburek of Building Science Corporation.

The climate zone map was developed to provide a simplified, consistent approach to defining climate for implementation of various codes. It was based on widely-accepted classifications of world climates that have been applied in a variety of different disciplines.

The map was defined on an analysis of the 4,775 U.S. weather sites utilized by the National Oceanic and Atmospheric Administration (NOAA). The U.S. Department of Energy divided the United States into eight temperature-oriented climate zones. These zones are further divided into three moisture regions designated A, B, and C. Thus, the IECC map allows for up to 24 potential climate designations.

It is critical to properly identify what region you are in to determine best practices for selection of wood flooring, moisture control systems, installation methods, HVAC requirements, and long-term maintenance of the wood floor being put to use. Be sure to refer to the climate zone listings of most major counties and cities throughout the world as listed in the new NWFA Regional Climate Variations publication (No. C300).

The climate region definitions are based on heating degree days, average temperatures, and precipitation, and are defined as follows:

  1. Hot-Humid: This is defined as a region that receives more than 20 in (50 cm) of annual precipitation and where one or both of the following occur:
    • A 67°F (19.5°C) or higher wet bulb temperature for 3,000 or more hours during the warmest six consecutive months of the year; or
    • A 73°F (23°C) or higher wet bulb temperature for 1,500 or more hours during the warmest six consecutive months of the year. In these regions, it is common for the interior space to be air-conditioned year-round. This causes water vapor to move from the exterior toward the interior.
  2. Mixed-Humid: A mixed-humid climate is defined as a region that receives more than 20 in. (50 cm) of annual precipitation, has approximately 5,400 heating degree days (65°F basis) or fewer, and where the average monthly outdoor temperature drops below 45°F (7°C) during the winter months.
  3. Hot-Dry: A hot-dry climate generally is 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.
  4. Mixed-Dry: A mixed-dry climate is 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.
  5. Marine: A marine climate generally is defined as a region that meets all of the following criteria:
    • A mean temperature of the coldest month between 27°F (-3°C) and 65°F (18°C).
    • A warmest month mean of less than 72°F (22°C).
    • At least four months with mean temperatures more than 50°F (10°C).
    • A dry season in summer. The month with the heaviest precipitation in the cold season has at least three times as much precipitation as the month with the least precipitation in the rest of the year. The cold season is October through March in the Northern Hemisphere and April through September in the Southern Hemisphere. Climate Variations (Continued)
  6. Cold: A cold climate generally is 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).
  7. Very Cold: A very cold climate is generally defined as a region with approximately 9,000 heating degree days (65°F basis) or more and fewer than approximately 12,600 heating degree days (65°F basis).
  8. Subarctic/Arctic: A subarctic climate generally is defined as a region with approximately 12,600 heating degree days (65° basis) or more.

Regional Climate Zones affect the interior conditions of the facility. With a clear understanding of what climate zone the facility is in, the builder and property owner can focus on getting the interior of the facility adequately prepared and ready for the flooring being installed in it. Having this information at your fingertips should give you the necessary tools to help educate your builders and property owners of what will be necessary for their new wood floors.

The job site should always meet or exceed all manufacturer requirements and NWFA Wood Flooring Installation Guidelines prior to wood delivery and before, during, and post-installation. It is the builder and property owner’s responsibility to get it there and keep it there.

4 thoughts

  1. I installed 4″ Q/R White Oak floor over radiant heat in Sept. 2019, zone 5 Massachusetts. Here’s what happened. Upon arrival to install the flooring I was informed there was no acclimation done in the home. The radiant heat hadn’t even been hooked up or pressurized yet. The flooring had been delivered 2 weeks prior. I recommended to the Builder / Home Owner that the install be rescheduled. He explained that he had to choice but to move forward because his lease on the home he was renting was going to expire and he did not want to renew it. Also kitchen cabinetry was scheduled for installation a couple weeks later so the flooring had to be put in. Assuming we had an understanding that this was not recommended, I installed, sanded & finished the job (1500sqft). Even worse I didn’t have him sign anything. Everyone can stop shaking their heads please, I know! As you can expect the worsted happened. Flooring separated & squeaking everywhere. He wants me to take full responsibility and replace entire floor. He denies that he & I ever had a conversation about the acclimation prior to installation. Of Course! My question is, Does the home owner / builder / GC, have any responsibility here or is this all my fault for not walking away? I appreciate your feedback, good or bad.

    1. He had a responsibility to provide acceptable jobsite conditions to perform the work. He did not. That said, commencement of work is acceptance of conditions. At that point you relieved him of that responsibility. Without a disclaimer (and these often don’t hold up), unfortunately you are on the hook.
      I never lost money on a job I didn’t do. This should have been one of those times. Sorry Dude.

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