- Ask the Expert
Ask the Expert: Best Practices for Healthy Condensation-free Walls
A few months ago, we covered how to avoid condensation and water damage in building walls. The article explained how condensation forms, why it is a problem, and the top four ways to prevent costly damage to homes. The good news for builders and homeowners is that preventing condensation from getting into walls is fairly easy to do with both new construction and retrofits.
One important take away from the article is that the dew point in a home fluctuates – it changes by the season, by the week, and by the day depending on the weather and humidity levels.
With that in mind, Gary Parsons, Fellow, Dow Building and Construction, walks us through some best practices for healthy condensation-free walls to ensure a homeowners’ investment is protected.
1. Reduce water vapor in the air:
One of the best tactics to prevent moisture from getting stuck between the walls of a home is to reduce the available water vapor by lowering the relative humidity of the home environment.
Water typically enters a wall in three different ways: via diffusion through walls, through air transfer, and because of a lack of drainage flashing of windows, doors and other wall penetrations.
Due to a variety of factors, such as: geographical location, weather conditions and the home ventilation system, the degree of humidity and water vapor will vary. But the majority of homeowners across the country, regardless of location, should utilize dehumidifiers to wring excess moisture out of the air, and install ventilation systems, to not only keep air in the home conditioned, but also increase occupant comfort.
Homeowners in especially humid areas, such as building zones 2 and 3, are even more vulnerable to water vapor damage and for them, dehumidifiers should be a standard practice.
2. Allow surfaces to dry when they get wet:
It may seem obvious, but it is important for walls that come into contact with moisture – due to weather or other factors, be allowed to fully dry. Lingering water or condensation often leads to mold and mildew accumulation.
A common source of moisture damage is vinyl wallpaper. In humid areas, condensation can get trapped between the wall and wallpaper and linger there, leading to mildew accumulation. During summer months, or in year round hot climates, this wallpaper is especially vulnerable. Homeowners should avoid impermeable (poly or vinyl) wallpaper on walls that can trap warm, moist air flowing from the outside to the inside causing interior walls to rot.
If you love the wallpapered look, choose something that’s vapor permeable or add a few layers of latex paint to the wallpaper to for greater protection against moisture damage.
3. Design homes to keep building envelope surfaces conditioned:
Proper wall construction is perhaps the primary way that homes can avoid future moisture damage. Building right the first time, and viewing the building envelope as a total system that needs to be insulated and sealed, can help prevent condensation problems from the start.
Local and state building codes vary greatly, but all homes, regardless of geographical location, should use insulation - particularly exterior foam sheathing insulation to keep interior wall components relatively warm to reduce condensation potential. And builders should use as much insulation as the project affords – as the greater the difference in temperature between the interior and exterior, the greater chance for condensation to build. Insulation works to mitigate these differences.
There is a common misconception in the southern region of the country that because it doesn’t get cold, insulation isn’t needed. However it is just as important. Having proper insulation and keeping the wall cavity insulated and climate controlled will save homeowners money on air conditioning over the life of the building. More insulation now equals lower air conditioning bills later. The same goes for heating bills. It is simple math for every geographic region.
Prevent air leaks:
Air leaks are one of the primary pathways for water vapor to penetrate through walls, especially in older homes. According to the U.S. Department of Energy (DOE), random air infiltration through gaps and cracks is a leading cause of energy loss in homes, accounting for 25 to 40 percent of the energy loss in most residential structures. Energy loss through gaps and cracks is highest in uninsulated or under-insulated homes.
Even with wall insulation systems installed, special attention must be paid to sealing these penetrations. The Air Barrier Association of America estimates that the typical 2,500 square-foot home in the United States has over a half-mile of cracks and crevices. Homes in cold climates tend to notice air leakage more – it is often referred to as “drafty.” To prevent a drafty home, caulks and sealants can plug cracks and crevices to significantly reduce air flow, save money on energy bills and prevent condensation from forming in walls. This is a great option for existing homes. Even if the walls are fully built, sealing gaps and cracks is a simple do-it-yourself project that can make a big difference.
Keeping these best practices in mind will help insure the comfort and protection of homeowners’ investment for years to come.