Damp structures, whether they’re in the construction phases or already complete, are unhealthy structures as moisture leads to mold growth. In some cases, a new building might have mold growth that occurred before or during construction, which can create serious, ongoing problems. Without proper humidity control for construction drying, the moisture content within a building might exceed industry specifications, resulting in delays and significant losses.
The Life of Mold
In the affected wallboard, the concentration of mold spores can grow up to 10,000,000 per square inch. Mold, a fungus, is a naturally occurring organism that makes up about 25 percent of the biomass on Earth. In nature, mold has a vital role as it breaks down organic matter, creating substances necessary for sustaining animal and plant life. Within buildings, however, the effects are undesirable.
In new construction, moisture in building materials prompts mold growth. This moisture comes from a variety of sources, such as rain, snow, new timber that’s still too wet, free water in concrete, leaking pipes, condensation, or concrete that sweats. When building materials are damp, they become a food source for mold. Similarly, when a mold spore lands on a dry object that later gets damp, it becomes a food source.
When a mold spore encounters a source of food, it secretes an enzyme that dissolves the food, creating a nutrient-rich broth. Using osmotic pressures, the dry spore draws the broth through its outer wall. Once nourished, a spore germinates, generating hyphae coated with the same enzymes that dissolve the food, allowing it to thrive and grow. In wallboards or ceiling tiles, for example, it takes as little as 48 hours for mold to grow past the point of producing branched hyphae.
After materials become wet or damp, the standard calls for humidity control for construction drying within 48 hours. Merely keeping relative humidity levels at or below 60 percent is insufficient because the moisture trapped within affected materials will still feed surface mold. Removing dampness from the air and within affected materials requires a combination of air movement and low relative humidity levels (about 30 percent or below) over the course of several days. This process can delay a project for days or weeks, making mold prevention vital to any construction site.
Mold Prevention Tips for Construction Sites
- During construction, ensure that the moisture content of building materials (e.g., timber) is within specification.
- If possible, hold materials at the manufacturing site or in a storage facility to keep them dry and away from high humidity conditions.
- Ensure that finished products are wrapped and protected before transporting them.
- Use humidity control for construction drying so the air is dry when you install interior walls to reduce the risk of hidden mold growth in the future.
- Install gypsum wallboard with a fire sealant bead that’s 3/8 inch between the edge of the board and floor. The sealant prevents water from floor cleaning or accidental spills from wicking up into the wallboard. It also eliminates the air path that reduces the board’s acoustical barrier properties and fire protection.
- Measure and document the moisture content of taped and sanded gypsum-board walls at two different locations on each wall—at a point halfway between the floor and ceiling and at a bottom edge.
- Measure and document the moisture content of concrete block walls. Do not hang gypsum boards on concrete blocks unless they have the same moisture content as blocks kept away from moist conditions.
- Do not apply interior finishes to gypsum wallboards until they have a moisture content of 0.4 percent or below on a gypsum moisture meter, or 12 percent or below on a wood moisture meter.
- Measure the concrete floor’s moisture level as soon as your close in the building and can bring the slab’s temperature between 65 and 75 degrees Fahrenheit. If the moisture content exceeds standards, maintain relative humidity levels in the space below 30 percent until the concrete meets the flooring manufacture’s specifications.
During a project, keep in mind that traditional HVAC systems are not meant to, nor are they effective at, drying out construction-related moisture. The load from wet materials is too much for an HVAC system, which is a comfortable air conditioning system. Temporary humidity control for construction drying is a better solution because it works faster and is far more effective. In addition, temporary humidity control solutions create the ideal environment for all stages of a project, ensuring your team finishes on time and within budget.
Polygon creates custom temporary humidity control solutions for construction sites that save energy and reduce downtime. Contact Polygon today to learn more and schedule a consultation.
