Humidity and moisture are your home’s biggest enemies. Keeping them under control protects your family’s health and well-being as it promotes comfort and upholds your property value.
Insulation with vapor diffusion retarders decreases humidity and moderates temperatures to reduce condensation within walls and ceilings. Moisture accumulation can cause wood rot, metal rust and mold.
Insulation
Insulation is one of the most important components of a well-performing building envelope, providing solutions for thermal, acoustic, fire and impact concerns. In addition, proper insulation will save you money by reducing heating and cooling costs.
Insulations are typically made of wool or fiberglass products that trap small pockets of air. These materials are excellent insulators, and their ability to trap air helps prevent the movement of cold outdoor air into the house, creating uncomfortable drafts and wasting energy.
Another way that insulation helps control moisture is by preventing air and water vapor from moving through the walls, ceilings and attic space. This is important because when water vapor moves through the insulation, it causes condensation which leads to mold, mildew and rot, and also deteriorates the insulation.
The proper type of insulation for a given climate will depend on its ability to keep moisture out and heat in. For example, builders in humid climates often choose to use insulation that is able to prevent the movement of moisture through wall cavities. Similarly, builders in cold climates may choose to use insulation that is able to retain heat. In either case, the insulation selected should include a vapor diffusion retarder to help mitigate moisture problems. These retarders are typically cellulose based, and they have been treated with borate to make them resistant to insect, rodent, termite and vermin infestation, as well as mildew and fungus.
Air Sealing
Air sealing is one of the most effective, cost-efficient ways to reduce heating and cooling costs. It prevents conditioned air from escaping through gaps and cracks in the home’s envelope, such as around windows and doors, attics, and basements and crawl spaces. It also helps to keep outside air and moisture out, improving indoor comfort, durability, and reducing moisture movement that can lead to mold growth and wood rot.
Air leaks in homes often occur around window trim, doors, vents, fireplace and furnace flues, plumbing fixtures, electrical wires, light fixtures, attics, and basements. These leaks can make the building uncomfortable and expensive to heat or cool. In addition, they allow unwanted water vapor, dust, allergens and pollutants into the house.
Adding caulking and spray foam insulation can help to seal the gaps and cracks in these areas. However, it is important to note that this alone may not be enough to control moisture movement, especially in humid climates. Moisture control strategies should be part of a whole-house energy solution, and include the use of vapor barriers and other forms of insulation to manage moisture. An experienced residential contractor can perform a blower door test to assess the airtightness of a house, and recommend additional steps to ensure optimal comfort, performance, and moisture management.
Vapor Barriers
The role of a vapor barrier is to prevent ground moisture from seeping into walls, ceilings and floors. This moisture can cause problems in a wall assembly such as water damage, wood rot, and mold growth. Vapor barriers are necessary in cold climates and are recommended in most North American building codes.
A vapor barrier is also called a vapor retarder. They are materials of varying types and classifications that impede the diffusion of water vapor into wall, floor or roof assemblies and packaging to prevent interstitial condensation.
Vapor barriers are typically plastic sheeting with a low permeance rating. They can be installed under a concrete slab, over insulation or in a crawl space. They are often used in conjunction with insulation to reduce energy costs and improve the performance of a home or commercial structure.
Class I vapor and moisture barriers are considered impermeable (0.1 perm or less) while class II vapor and moisture barriers allow some moisture to pass through them (greater than 0.1 and less than or equal to 1.0 perms). Some examples of these include foil-faced extruded polystyrene, 30-pound asphalt-coated paper, bitumen-coated kraft paper, plywood, cellulose insulation, and unpainted gypsum board and plaster.
It is important to note that vapor barriers do not function to retard the migration of air; this is the role of an effective air barrier. This difference is often misunderstood by homeowners, builders and contractors, who may use spray-on liquid or closed-cell spray foam as a vapor barrier when this is not the case.
Vapor Retarders
In order to protect structures from moisture migration, the cladding type and construction material must be considered along with the climate and other contributing factors. The ABAA has created a helpful chart illustrating how to best utilize air and vapor barriers on projects, based on building type and location.
Vapor retarders are a critical step in controlling moisture problems that result from the movement of ground water vapor through concrete slabs and into wall cavities. This vapor is responsible for many of the issues associated with modern high performance homes, including odors, mold growth, wood rot and greenhouse gases such as methane and radon.
The proper placement of vapor retarders is a key step to preserving insulation integrity and providing the comfort, energy efficiency and durability that homeowners expect from their home. In addition, they can also help to reduce the potential for slab sweating in unconditioned big box warehouses and prevent floor curling in crawl space floors.
In general, a vapor retarder should be placed on the warm side of the dew point temperature to control moisture migration. To ensure this is the case, it must be properly installed and sealed around penetrations such as plumbing pipes or electrical conduit. The vapor retarder should also be free from tears or punctures that could allow moisture to penetrate and cause condensation inside the wall cavity, which can significantly decrease thermal resistance and lead to structural damage over time.