LSU’s Todd Shupe Explores Importance of Wood Moisture Content in Subfloors of Residential Houses

todd shupe lsuOur houses are often our most valuable financial asset. Of course, nothing is more precious than children and grandchildren. Affordable, durable, and green housing are important issues for all homeowners. In the southern region of the U.S., all three of these issues are of growing importance. This area of the country has high temperature, humidity, flooding, and wind that really can test a house, says LSU’s Todd Shupe, a wood sciences expert and former lab leader.
“Some houses are built on piers and elevated above the ground. I have seen the elevation range from as little as 1 foot to 5 feet or much more, especially near water bodies. The premise is to elevate the house and decrease the risk of flood water entering the house. The problem is that the moisture content of the subfloor may become high enough to facilitate wood decay. Also, there is concern that these houses are energy inefficient,” Todd Shupe, of Baton Rouge, says.

Damp subfloors can lead to numerous problems such as wood decay, insect infestation, mold growth, corrosion of metal fasteners and buckling of wood flooring. Insect infestation is not the focus of this study, although moisture control can limit infestation risk. In untreated wood, the rule is that the moisture content (MC) needs to exceed the fiber saturation point (approximately 30{008418fa022621a2763fa9d266232055702aae032d1d0630e21bb21e294d80ab} MC) for decay fungi to initiate propagation. At levels below 20{008418fa022621a2763fa9d266232055702aae032d1d0630e21bb21e294d80ab} MC, their propagation is completely inhibited. The traditional guideline for protection of untreated lumber from decay has been to keep the moisture content below 20{008418fa022621a2763fa9d266232055702aae032d1d0630e21bb21e294d80ab}. For protection of wood surfaces against mold propagation, it is recommended that the surface relative humidity (RH) be kept below 80{008418fa022621a2763fa9d266232055702aae032d1d0630e21bb21e294d80ab}, and studies have shown that mold growth can occur on wood at moisture contents above 15 to 18{008418fa022621a2763fa9d266232055702aae032d1d0630e21bb21e294d80ab}. Corrosion of metal fasteners in treated wood can occur when moisture content exceeds 18 to 20{008418fa022621a2763fa9d266232055702aae032d1d0630e21bb21e294d80ab}, but this varies widely based on the type of metal, coating and coating thickness. For all moisture-related failure modes, duration at a particular elevated moisture level is also a key factor.

Expansion and/or contraction damage depends on the magnitude of the change in moisture content and the sensitivity of the particular wood product to such changes, says LSU’s Todd Shupe. The main sources of moisture exterior to a house include rain, surface water, groundwater and atmospheric humidity. Indoor sources include occupants (respiration and transpiration), pets, plants, and activities such as showering, bathing, cooking, cleaning and more. Plumbing leaks can occur inside or outside the house, adds Todd Shupe, a resident of Baton Rouge.

“Site grading and management of roof runoff can largely determine how wet the soil becomes under the structure,” says Shupe. There is no substitute for a 3-foot overhang (soffit) and soil graded (sloped) away from the house. Ventilation of the crawlspace with outdoor air may raise or lower wood moisture content depending on outdoor vapor pressure, crawlspace vapor pressure, and wood surface temperature. Other factors that affect moisture levels in wood floor members include indoor temperature during the cooling season, floor insulation and interior floor finish.. “My PhD advisor at LSU, the late Elvin Choong, found that a soil cover had no discernible effect on moisture levels in wood floors over open pier foundations,” says Shupe. “Because this type of foundation is very open to airflow, the air temperature and humidity in the crawlspace may differ only slightly from outdoor conditions. In contrast, houses with wall-vented crawlspaces tend to have a significant thermal coupling to the ground and lower rates of air exchange with the exterior.” These studies were conducted in southern New Jersey (Stiles and Custer 1994), east-central North.
Carolina (Advanced Energy 2005a; Davis and Dastur 2004), and Baton Rouge, Louisiana (Dastur et al. 2009), have shown that, with the perimeter walls and soil covered with a vapor retarder (thereby eliminating these sources of moisture), during the summer months outdoor air served as a moisture source for the crawlspaces, rather than a moisture sink. Admission of outdoor air during summer months led to high relative humidity in the crawlspaces and, in some cases, in significant moisture accumulation in the wood floor members.

An alternative method of construction is the closed crawlspace, which has perimeter foundation walls without vents. With regard to air and water vapor flow, the crawlspace is treated as part of the interior and is intended to be isolated from the ground and the exterior. The ground and perimeter walls are covered with a vapor retarder, and the crawlspace may be provided with conditioned supply air. A number of studies in various climates have shown that this type of crawlspace can remain safely dry (Advanced Energy 2005b; Dastur et al. 2009; Davis and Dastur 2004; Dutt et al. 1988; Duff 1980; Moody et al. 1985; Quarles 1989; Samuelson 1994; Stiles and Custer 1994).

Note: This blog was largely based on the report “Moisture Performance of Insulated, Raised, Wood-Frame Floors: A Study of Twelve Houses in Southern Louisiana” by the US Forest Products Lab.

Todd Shupe Discusses a Greener Alternative to Traditional Insulation

todd shupeWhen Todd Shupe thinks about some of his favorite research projects at Louisiana State University in Baton Rouge, LA, it was bio-based spray foam insulation. Many homeowners are aware of spray foam. For starters, it can be bio-based or not. Regardless, it is an excellent product because it creates an air seal and is a great vapor barrier. According to Advanced Foam Insulation Co., no other type of insulation creates this seal.

Converting attics into a semi-conditioned space in hot climates by closing soffits, gable and ridge vents is a positive design approach in reducing the moisture loads in houses and buildings. This can be achieved by moving the insulation from the floor of the attic and applying spray foam to the underside of the roof deck to seal all the vents. According to LSU’s Todd Shupe, this is the preferred method. This design prevents the moisture-laden outside air from entering the attic and subsequently from getting into the living area of houses and buildings. The air seal also prevents the radiant heat from migrating into the living area. The lower humidity levels create indoor air quality that is much more comfortable to live in. This is very important in all higher-humidity climates such as the coastal regions of the United States.

According to Advanced Foam Insulation Co., combining these insulating methods with “Low E” glass in the windows will help to lower utility bills by 40 percent to 60 percent compared to a building that has conventional insulation. Not only is spray foam insulation an excellent thermal and moisture barrier, the indoor air is also much cleaner. According to wood sciences expert Todd Shupe, spray foam greatly reduces pollen and dust from entering your home or office building, thus decreasing rates of occurrence for allergies and asthma.

Currently, bio-based spray foam has a small percentage of “bio” and a large amount of “non-bio.” This finding is based off of Todd Shupe’s research at LSU in Baton Rouge, LA. According to the US Environmental Protection Agency (EPA), there are health concerns associated with the non-bio portions of spray foam. Most spray foam formulations contain isocyanates and polyols. According to the EPA, spray foam contains a side A and a side B. For side A, isocyanates are the primary compound of interest and are a class of highly-reactive chemicals with widespread industrial, commercial and retail or consumer applications. Exposure to isocyanates may cause skin, eye and lung irritation, asthma and “sensitization.” Isocyanates are irritants to the mucous membranes of the eyes and gastrointestinal and respiratory tracts. Direct skin contact can also cause marked inflammation. According to Todd Shupe, there is no recognized safe level of exposure to isocyanates for sensitized individuals. Isocyanates have been reported to be a leading attributable chemical cause of asthma in the workplace.

Side B contains a blend of proprietary chemicals that provide unique properties in the foam and may vary widely from manufacturer to manufacturer. Amine catalysts in SPF may be sensitizers and irritants that can cause blurry vision, also known as a halo effect.

Flame retardants, such as halogenated compounds, may be persistent, bioaccumulative, and/or toxic chemicals (PBTs). Some examples include:
– TCPP -(Tris(2-chloroisopropyl)phosphate)
– TEP -(Triethyl phosphate)
– TDCP -(Tris (1,3-dichloroisopropyl) phosphate blend)
– Blowing agents may have adverse health effects.
– Some surfactants may be linked to endocrine disruption.

LSU’s Todd Shupe Talks Controlling Mold In Wake Of Flooding Event

todd shupe baton rouge

A flood is a terrible event for any homeowner. A home is typically our most expensive asset and even a few inches of flood water will have a devastating effect on your house. Todd Shupe of Baton Rouge remembers his experience well and wants to recount it so others may learn.

“My house was flooded in 2016 with 14 inches of water. Time is not on your side after a flood event. It is imperative that all wet material be removed from the house as soon as possible. This includes sheet rock, insulation, carpet and drapes. I had to remove all personal items from the house prior to the ‘gutting’ of the house. This is the process by which the sheet rock is cut and removed 4 feet from the floor and the old insulation is removed,” says LSU’s Todd Shupe, whose career in wood sciences has lent him a great deal of construction knowledge. “My house did not lose electricity and no water got into the electrical outlets so I was able to run ceiling fans and bring in large de-humidification units to dry out the house. Everything is removed so that the studs in the walls can dry out. However, all bathroom counters, showers, bath tubs, kitchen cabinets, counter tops, the oven and so much more had to go All that was left was the toilets!”

The studs need to dry so they will not be attractive to fungi and wood-destroying insects. However, as they are drying they can easily be attacked by mold fungi. These fungi will not degrade the strength of the wood but will discolor the surface and in certain cases can causes respiratory problems. For my house, I used Bora-Care with Mold-Care. “This is a safe and economical product that anyone can apply with a typical garden sprayer,” says Todd Shupe, of Baton Rouge. “It needs to be mixed 1:1 with water before application. I sprayed from the sill plate upwards of four feet. I waited a few hours for it to dry and did a second application. I never saw any presence of mold, fungi, or insects in the frame of my house after the flood.”

Some of the personal items grew mold immediately and most had to be discarded. Two days passed before we could return to the house and then another few days before the house could be gutted. This was a trying time for LSU’s Todd Shupe, but the knowledge he’d acquired in the field came in handy here. BoraCare is also an excellent product for new construction or during remodeling or additions of existing houses. It is available on Amazon or directly from the manufacturer, Nisus, at