What is moisture control?
Moisture control is exactly what it sounds like – controlling the moisture levels of your home. Is very important to control the level of moisture in your home because if the levels are too high it will cause problems such as mold growth and health issues.Moisture in some levels is normal, but too much can damage your home and your health.
Internal moisture levels should never exceed 20%. It can be measured by purchasing a hygrometer. If levels are higher than 20% you should use a dehumidifier for your home. Something else you should be careful of is the moisture levels in the crawl space, where wood beams help form the foundation of your home, it should never exceed 19-20%.
Here are some warning signs of increased moisture in your crawl space include: indoor humidity and condensation, crawl space condensation, and rot forming in floor joints. If you notice any of these, your crawl space moisture levels should be checked as soon as possible.
You should call trained technicians to come to your home and conduct a moisture reading. The next step includes placing a crawl space dehumidifier in the moist area and sealing it off. This will remove the excess moisture from the area in the crawl space.
One month after the installation of the crawl space dehumidifier, it should be checked to determine if the issue has been resolved.
Moisture Control Principles
To control moisture for long building life and good indoor air quality,everybody should follow these three principles:
- It’s important to control liquid water.
- It should prevent excessive indoor humidity and water vapor migration by airflow and diffusion.
- Another important thing is to select moisture-resistant materials for unavoidably wet locations.
Moisture Damage in Buildings
It is known that moisture can damage building materials and components. For example:
- Prolonged damp conditions can damage building materials and HVAC systems by molds, bacteria, wood-decaying molds and insect pests (e.g., termites and carpenter ants).
- Chemical reacting with building materials can cause, for example, structural fasteners, wiring, metal roofing, and conditioning coils to corrode and flooring or roofing adhesives to fail.
- Water-soluble building materials (e.g., gypsum board) can return to the solution.
- Wooden materials can warp or rot.
- Brick or concrete, it can be damaged during freeze thaw cycles.
- Also, paints and varnishes can be damaged.
- The insulating value (R-value) of thermal insulation can be reduced.
How Water Causes Problems in Buildings?
When we say water damage we can imagine is liquid water in the form of rain, plumbing leaks, or floods. Many water leaks are easy to detect. For example, when it rains, water may drip around skylights, or crawl space may be filled with water. If a toilet supply line breaks, the floor will be flooded. On the other hand, a lot of water-related problems are less obvious and can be difficult to find.
Or, humid indoor air may condense on the cool backside of vinyl wallpaper that covers an exterior wall, creating the best environment for mold to grow. When the damage is being done out of sight under flooring or behind wallpaper, that’s a big problem, not a leak. Moisture problems are preventable. They occur when water moves from a source into some part of a building that should be dry. The actual damage begins after enough moisture is accumulated inside sensitive materials. To prevent a moisture problem, there are 4 elements you should keep in mind:
1. Typical symptoms of moisture problems. Like: corrosion of metals, the growth of surface mold, insect infestations, peeling paint, failing floor adhesives, stained finishes and health symptoms.
2. Sources of moisture. For example rainwater, surface water, ground water, plumbing water, indoor and outdoor sources of humidity.
3. Transport mechanisms. They include liquid water leaking through holes, going through porous materials.
4. Common failures of moisture control elements and systems. Moisture controls include site drainage, gutter systems, above- and below-grade drainage planes, effective flashing, condensate drainage and humidity controls
Sources Of Excessive Moisture In Buildings And Their Reduction
Excessive moisture in buildings can result from a number of causes:
- Rainwater leaks through roofs and walls
- Leakage of moist air
- Diffusion of moisture through walls, roofs, and floors
- Groundwater intrusion into basements and crawl spaces through walls and floors
- Leaking or burst water pipes
- Indoor moisture sources and
- Rainwater Leaks: The control of rainwater leaks has been the main topic of good building practices for a long time. Even serious leaks during heavy storms or slow leaks can lead to mold infestation, and can cause serious damage to buildings and their contents.
- Leakage of Moist Air: Warm and moist indoor air condenses on cold surfaces can lead to moisture damage.
- Diffusion of Moisture through Walls, Roofs, and Floors: Diffusion, as a result of differing vapor pressures across walls or roofs moves mold through the building. There are materials with low permeance that allow little vapor transmission and by the other hand materials with high permeance allow more moisture transmission.
- Groundwater Intrusion: Intrusion of groundwater into basements and crawl spaces is a very common problem. Because most basements and crawl spaces are connected through cracks, pipe chases, moist air from wet basements and crawl spaces will find their way to spaces above.
- Leaking or Burst Water Pipes: The prevention and repair of burst or leaking pipes is one of the responsibilities of plumbers. Except for old steel and iron pipes and frozen pipes.In some areas ,installed copper pipes have been found to develop small pinhole penetrations leading to slow but constant leaks.
- Indoor Moisture Sources: Human occupancy: breathing, perspiration, cooking, bathing, and clothing washing can lead to significant amounts of moisture to buildings. Kitchens and bathrooms should be independently vented and also washers need to be vented outdoors.
If you’re building a new home,pay particular attention to how water will be managed around the foundation.Please see below:
- Keep all wood materials away from earth contact so it won’t have contact with water.
- The drainage system is really important. Install well-designed guttering and downspouts connected that can divert rainwater completely away from the house.
- Establish drainage swales to direct rainwater around and away from the house so you won’t have these kinds of problems.
- You should put a gasket under the sill plate to provide air sealing.
- Install a protective membrane, between the foundation and the sill plate to serve as a capillary break and reduce the wicking of water up from the masonry foundation wall.
- Place a continuous drainage plane over the damp-proofing or exterior insulation to channel water to the foundation drain and relieve hydrostatic pressure.
- Install a foundation drain directly below the drainage plane and beside (not on top of) the footing. This prevents water from flowing against the seam between the footing and the foundation wall. Surround a perforated 4-inch plastic drain pipe with gravel and wrap both with filter fabric.
- Underneath the basement or on-grade slab floor, install a capillary break and vapor diffusion retarder, consisting of a layer of 6- to 10-mil polyethylene over at least 4 inches of gravel.
Hygro thermal Regions in North America
A severe cold climate is defined as a religion with approximately 8000 heating degrees days or greater
A cold climate is defined as a religion with approximately 4500 heating degrees days and less than 8000 heating degrees days
A mixed humid climate is defined as a religion that receives more than 20 inches of annual precipitation and where the monthly average temperature remains above 45o F.
A hot humid climate is defined as a religion that receives greater than 20 inches of annual precipitation and where the monthly average temperature remains above 45o F.
Hot Dry/ Mix Dry
A hot Dry climate is defined as a religion that receives less than 20 inches of annual precipitation and where the monthly average temperature remains above 45o F and a mixed dry climate is considered a religion that has approximately 4500 heating degrees days or less.