However, putting new plastic over an old vapor barrier is not a recommended approach. Whenever you embark on a vapor barrier installation, take the time to assess the condition of the existing barrier, clean up any debris, and ensure a clean slate.
Like you suspect you must not apply an additional vapour barrier over the existing one. You will trap moisture and produce trouble.
Yes, double vapor barriers are counter-intuitive but they do work – within the limits noted above – especially the points about humidified and pressurized buildings and control of condensing surface temperatures6.
Unless otherwise indicated by the design professional(s) of record, unfold the vapor barrier to completely cover the placement area. Overlap all joints/seams a minimum of 6 inches. Ensure the vapor barrier is clean and dry when applying a manufacturer's engineered seaming tape or approved method.
A high-quality crawl space vapor barrier can be an effective solution for many years, as long as it is not damaged or punctured along the way. Generally, a crawl space vapor barrier that has been correctly installed by a professional and made of high-quality materials can have a lifespan of 20 years or more.
So, before you put in a new vapor barrier, be sure to remove the old one. That's how you get started in properly managing crawl space moisture.
Typically a home's vapor barrier should last for many years, but there are times when circumstances warrant the vapor barrier being replaced.
Because a vapor barrier is a low permeable barrier, it keeps moisture from passing through. This is beneficial to keep moisture away from a dry surface but will trap moisture behind it if installed on a water-damaged concrete wall, causing the wall to fail further.
With vapor barriers, it's important to have a thicker rather than thinner mil thickness. Why? Because you want a material that accomplishes a few things. First, it needs to be durable, meaning puncture and tear resistant.
We don't recommend you seal your vapor barrier down to the concrete, as that can damage your subfloor.
Is DuPont™ Tyvek® a vapor barrier? No, DuPont™ Tyvek® is not a vapor barrier. It is made with unique material science to keep air and bulk water out while allowing moisture vapor inside walls to escape.
2 Sided Butyl Tape: Butyl tape is often preferred for its strong adhesive properties. We offer a reinforced butyl tape that won't stretch during installation. It's ideal to use between overlapping vapor barriers panels and to seal the vapor barrier against other surfaces such as concrete walls and wooden beams.
Roll out Vapor Barrier membrane into desired location. Be sure to stagger end laps and overlap side laps by a minimum of 3” as indicated on the surface film of the products. End laps should have a minimum of 6” of overlap and end lap "T" joints should be cut at a 45° angle.
The Cons of Vapor Barrier Installation
Although vapor barriers aim to prevent moisture from entering the structure, they can also trap moisture inside. If not properly installed or upheld, this could result in the proliferation of mold and other issues related to moisture.
Materials such as rigid foam insulation, reinforced plastics, aluminum, and stainless steel are relatively resistant to water vapor diffusion. These types of vapor retarders are usually mechanically fastened and sealed at the joints.
This reduces condensation on surfaces, helping to protect against moisture damage. It's also important to ensure that the barrier is completely sealed so that no moisture can get through it. Using staples or tape along all edges and seams will help create a strong seal.
In most cases, crawl space vapor barriers should be at least 12 mils thick poly, but it depends on the floor, how often the crawl space will be entered along with if the crawl space will be used for storage.
Both are designed to keep moisture out of your home and can be made from various materials. But there are a few key differences, the most apparent being that moisture barriers are better at keeping out liquids, and vapor barriers are better at keeping out water in its gaseous state.
When properly installed, a vapor barrier should last twenty years or more. But certain circumstances require more immediate action. If you've experienced any of these telltale problems, you should consult a professional to analyze the state of your vapor barrier and see if it needs to be replaced.
However, if not installed correctly or if damaged, vapor barriers can actually contribute to mold growth.
Not every wall does. A vapor retarder is a material used to prevent water vapor from diffusing into the wall, ceiling or floor during the cold winter. Whether or not you need a vapor retarder hinges on three main factors your climate, your home and the location of the wall you're insulating.
In climates that are hot and humid, a vapor barrier should be installed on the warm side (for walls, this would be just beneath the exterior cladding, over the insulation). For very cold climates, the warm side is the interior, so the insulation should have a vapor barrier separating it from the interior wall.
Average Cost of Vapor Barrier Installation
Vapor barrier installation could cost anywhere from $1,200 to $4,000 on average. This estimate includes materials and labor. A thicker barrier provides more protection for your home. It also costs more to install.
You should seal the vapor barrier around the perimeter of the crawl space and where the vapor barrier overlaps with another panel. You should also seal around the foundation support columns or pillars.
If a vapor barrier is damaged during a drywall installation or repair, it may be patched with housewrap tape, but small holes only marginally impact effectiveness. When patching drywall on an exterior wall, it's almost impossible not to damage the vapor barrier.