Table Of Contents
- What materials make suitable air barriers?
- Where are the most common air barrier defects located?
- What’s the difference between air barriers and vapour barriers?
Air-leakage control is a critical but often misunderstood factor of an energy-efficient home. The use of caulking and sealants to tighten the surface has several advantages. Mould and rot are less likely to develop in a tight house because moisture is less likely to penetrate and get stuck in cavities. Tighter homes have better-performing ventilation systems, which can need less heating and cooling equipment. Air leakage, also known as penetration, is the unintended or unwanted intrusion of outside air into a system. When there is infiltration, there is also exfiltration in other sections of the building envelope.
Air barriers may be made out of a variety of materials. Drywall, plywood, polyethylene sheeting, directed strand board sheathing, and rigid foam insulation are among the most common. Although these materials do not allow air to pass through, air may pass through openings and seams. Must seal the air barrier’s joints with tape, gaskets, foam, or caulk that has been certified by the manufacturer for particular materials.
The majority of air barriers are made up of many components in an assembly or structure. The most popular features of most air barriers are sheet polyethylene and gypsum board. There is no need for polyethylene in a gypsum board-based air-barrier device. Polyethylene is a Class I vapour retarder, which means it can protect a wall from drying out. Wood, poured concrete, glass, some rigid foam insulations, some spray foams, plywood, and peel-and-stick rubber membranes are only a few of the materials used to create an air-barrier device. Although air cannot pass through these objects, it can pass through penetrations, corners, and seams. Additional materials, such as tape, gaskets, or caulk, are used to complete a code-compliant air barrier when these materials are used to form an air barrier. The material must not only avoid air movement but also be robust to make a strong air barrier.
The majority of air leaks occur at the intersections of various materials, such as where floors
meet walls and walls meet ceilings. While air leakage may occur around windows and doors, the most severe air
leaks are typically found in secret areas. Here’s a rundown of some of the places that are often under-sealed, resulting in significant air leakage:
- Basement rim joist areas
- Poorly weather-stripped attic access hatches
- Cracks between finish flooring and baseboards
- Recessed can light penetrations
- Utility chases that hide pipes or ducts
- Kitchen soffits above wall cabinets
- Plumbing vent pipe penetrations
- Fireplace surrounds
- Cracks between ceiling-mounted duct boots and ceiling drywall
The purpose of a vapour barrier is to prevent vapour diffusion, while the purpose of an air barrier is to prevent air leakage due to pressure differences. A vapour barrier should be present in any wall system, but air barriers can be numerous. While a vapour barrier can act as an effective air barrier, it does not always prevent vapour from diffusing.
In cold climates like Canada, the vapour barrier should be inside the insulation for the majority of the year. In hot climates, such as the southern United States, a vapour barrier should be mounted outside the insulation to prevent condensation and mould, mainly where air conditioning is used.
Contact WGYC to assist you and provide air barrier specialists to answer your questions and solve your roof repair problems. Call us today at (613)-325-5535.