Hardwood Flooring’s Impact on Natural Resource Depletion

“Increasing wood fuel use, a carbon-neutral process, would lower the environmental impact of hardwood lumber manufacturing and increase its use as a green building material.” (i)

With increased interest in the building industry in sustainable practices and environmental impact, the process and energy costs of producing hardwood flooring need to be examined. Every wood products manufacturing process has its price in both resource and energy costs.

For hardwood lumber, the green lumber is dried usually in conventional-type dry kilns. The heat sources used in these kilns are wood and fossil fuels. The majority of the hardwood lumber dried in the US uses wood from the milling process as the primary fuel source.

A study published in Wood and Fiber Science in July of 2008, titled “Environmental Impact of Producing Hardwood Lumber Using Life-Cycle Inventory,” reported that wood has two significant advantages over non-wood substitutes: Wood is carbon neutral and carbon can be sequestered.

Therefore, using wood as a fuel or in a finished wood product from hardwood lumber could be considered a sustainable practice. Other non-wood products do not have the benefits of a carbon-neutral product to use both as a fuel and a finished product. (ii)

Summary of Green Building Research

While keeping in mind that energy use varies by region, wood species and fuels used in production, the goal of the study was to arrive at the most definitive carbon footprint for hardwood flooring.

Here are some relevant results of the study: (iii)

• Sawing consumes the highest proportion of electricity in hardwood manufacturing. Thus, installing optimization equipment would lower electrical consumption by reducing errors during the sawing process. Thinner saws reduce electrical consumption and reduce the volume of green wood residue produced.
• Drying consumes the highest proportion of fuel. In this study, wood fuel accounted for 87% of the thermal energy used. Lowering overall energy consumption by upgrading or overhauling existing older and inefficient dry kiln facilities is indicated.Increasing on-site wood fuel consumption would reduce fossil greenhouse gasses but increase other products, such as particulate emissions. Particulate emissions may be reduced by re-injecting fly ash. 
• The region of production affects the environmental impact of this product; coal is the largest off-site material used for electrical power generation in the Northeast. Most power in the Pacific Northwest is produced from water and then natural gas, while most power in the Southeast is produced from coal and uranium, just like the Northeast.
• Increasing the level of air drying lumber and percentage of air drying prior to kiln drying, especially for species where color is not a problem, would lower the amount of energy required for the drying process. Therefore, improving air drying methods would lower energy use while maintaining lumber quality and reducing the environmental impact of hardwood lumber.

The Mixed Benefits of Hardwood

Wood holds two ecological advantages over non-wood flooring products: Wood is carbon-neutral, and wood sequesters (stores) carbon [vi]. Of course, wood lovers know and cherish other benefits, such as a pleasing scent, aesthetic beauty, and performance.

Many stakeholders may have purely visceral reasons for installing hardwood floors in homes adorned with environmental consideration.

However, hardwood production is more energy-intensive than that of softwood manufacturing. This is due to hardwood’s generally higher density, which requires more energy to cut. Since hardwoods are also dried to lower equilibrium moisture content (EMC), kiln charges are run longer than on softwoods.

Typically, hardwoods are also cut to thinner dimensions, so more saw passes are required, and more energy consumed.

The Wood Itself

Increasingly, flooring stakeholders are questioning the risks and rewards of using regular hardwood, engineered wood or bamboo flooring products. Different species are beginning to make a presence in the eco-flooring market as well.

However, really, the simplest answer is: All flooring options available for purchase contain very different performance properties due to the structural features of the materials and how they are produced.

Every natural wood species on Earth has specific properties which can be traced to the very cellular structure of every tree. Although this may seem daunting, it just requires that homeowners and builders inform themselves of the species-specific properties prior to purchasing and installing hardwood floors.

Engineered wood flooring combines 3-12 multiple ply layers that are cross layered, glued and pressed together. The inner core layers are usually either a hardwood or softwood plywood-type of material. The top surface is usually a thicker hardwood veneer wear layer, which is available in almost any wood species.

The top layer is glued and pressed on the top surface of the core layers. The process works, and so does the end result. However, even though engineered wood flooring is more resistant to higher moisture levels than traditional solid wood flooring, moisture content (MC) measurement is still important.

A bamboo is a form of grass which is very different in terms of strength and performance properties than that of traditional solid wood flooring. Its cell structure differs from wood, and bamboo flooring strength depends on how it was harvested and how it was manufactured.

Unlike hardwood flooring, there are no official guidelines or manufacturing standards for bamboo flooring.

As such, MC measurement can be difficult due to this lack of standards, but it is still critical because bamboo flooring is still susceptible to moisture-related problems if not installed at the correct MC levels.

Free Download – Wood Flooring Installation: What To Expect

Green Building Primer

According to McGraw-Hill Construction, 52 percent of home builders believe that green building projects are best initiated at the concept design phase[i]. As of 2006, a full 92 percent of builders used green materials because it was the “right thing to do” as compared to “lowering lifecycle costs” (87%)[ii]. “Competitive advantage” placed third.

Best ecological building practices are based on the most ecological materials. In the McGraw-Hill study, builders identified that they preferred to use oriented strand board (OSB) rather than plywood in engineered building materials [iii].

OSB uses up to 50 percent more of a log than conventional lumber, and it utilizes tree species which would not otherwise be mixed into wood building materials.

The authors of a 2008 study [iv] included specialized wood treatments in their assessment of how lumber production energy was used. Thermal processes such as walnut steaming, facility heating and cogeneration were deemed as “significant” contributors to overall carbon emissions in hardwood lumber production.

The same report goes on to recommend several energy-saving strategies to lower the carbon cost of hardwood lumber production:

• Upgrade, or refurbish, aged dry kilns (including progressive drying kilns for hardwood).
• Improve sawing practices (as outlined by the US Department of Agriculture [v]).
• Increase air drying of lumber.

Moisture Content Management

As part of the hardwood flooring lifecycle, moisture content management helps to optimize eco-friendliness by ensuring that hardwood flooring lasts as long as possible. This can be 100 years if the wood flooring is properly installed and maintained. Talk about the ultimate return on investment, both environmental and financial.

Moisture content is the proportion of water vapor held in wood cell walls and nuclei, and MC fluctuates with relative humidity (RH) levels. This is not a malfunction, but a natural imperative. However, it is crucial to assure that hardwood flooring does not contain excess moisture content.

A wood moisture meter is a handy and precise tool to measure hardwood moisture content. Technology provides a number of key features for the modern wood moisture meter. It can be programmed to account for species-specific wood density, and a pinless wood moisture meter can non-invasively assess moisture content up to three-quarters of an inch into the wood.

Assessors can assure maximum hardwood longevity by keeping a hand-held wood moisture meter in the utility drawer. That’s an answer that will carry beyond the building into environmental conservation as well.

Moisture Content (MC) & Longevity

Ultimately, conservation and limiting environmental impact in forestry-related products are ensuring that hardwood that has been processed for flooring or other building uses is maintained to achieve its maximum service life.

Hardwood flooring achieves its optimum longevity when its MC is well-managed both before and after installing the hardwood floors. As the relative humidity (RH) of the surrounding air fluctuates, so too does the MC of the wood flooring. This is a very natural dynamic process, but excessive MC in the hardwood flooring can cause future problems.

Using a wood moisture meter is the best way to measure and assess MC. Users can purchase meters that are programmable and can program the wood species directly into the meter so that its MC reading truly reflects the actual MC of the flooring.

With today’s pinless wood moisture meter technology, the modern wood moisture meter can measure the flooring’s MC up to ¾” below the wood surface without doing any damage to a new or existing floor. Put simply, a wood moisture meter is a proactive tool for protecting hardwood flooring and guaranteeing that the flooring has a long service life once installed.

In terms of environmental impact, well-maintained and properly installed, hardwood flooring can last for many years to come. Hardwood flooring is an option with enormous ecological future returns on investments.

Additional Reading:

[i] Bowe, Scott A. and Richard D. Bergman  “Environmental Impact of Producing Hardwood Lumber Using Life-Cycle Inventory.” Wood and Fiber Science: 40(3), pg. 448 Abstract Monona, WI: The Society of Wood Science and Technology (SWST), 2008.

[ii] Ibid (pg. 456).

[iii] Ibid (pg. 457).

Troy Edwards

Troy Edwards is Technical Service Supervisor for Wagner Meters, Inc., where he oversees manufacturing, quality control and IT service for their electronic measurement products for the building and construction industry. Troy holds an AAS in Electronics Technology and has over 20 years’ experience in various electronic manufacturing and production positions.

Last updated on September 26th, 2023