Your roof works hard to protect you and your family from sun, wind, and rain, but it’s a bit simplified to think of your roof as a single object rather than as a complex system. A roof is made of different layers which all work together to keep your home dry and safe from the elements. Today, we’d like to talk about one of the most important parts of any roof: the vapor barrier.
A vapor barrier is typically a plastic or foil sheet underlay, and it has two important jobs. First, it’s there to prevent water and moisture from getting into your house. Secondly, if humidity is already in your home (from a leak or normal activities like showering or cooking), the vapor barrier should allow the moisture to escape from your house into the atmosphere. Vapor barriers are often confused with air barriers, but while an air barrier will prevent the flow of air entirely, a vapor barrier retards just the moisture mixed with the air, so gasses like oxygen, nitrogen, etc can still pass through. What’s important to remember is that air barriers are vapor barriers that also block other gasses, while vapor barriers can’t function as air barriers and just block moisture.
Anyone who’s ever had a mould problem in their home knows that too much moisture in a house is bad news. Your vapor barrier goes beneath your shingles, rubber, or other outer-layer roofing product, and it protects your home from any rain, snow, and other forms of precipitation that seep in. This thin sheet is an integral part of keeping your roof deck safe from water and preventing mould problems in your home.
If you’ve ever tried to mix oil and water, you know that some liquids just refuse to touch. This fundamental inability to mix with water is why asphalt and other oil-based products are so good at keep moisture out. However, not all vapor protection takes advantage of the hydrophobic properties of oil. When an air barrier is an acceptable solution, materials like aluminum foil, other sheet metals, and glass can be used to keep humidity out by keep all air and gasses out.
Your roof system is a collection of many different important parts that all work together to keep your home warm and dry. While your vapor barrier is just one cog of the machine, it’s an important one. If you have any questions about vapor barriers or how flat roofs keep you dry, the experts at Vanderleek would be happy to give you the answers you need.