General rule of thumb is that the WATER barrier goes on the exterior wall, just under the outer cladding, and the VAPOR barrier goes on the warmest side of the wall, up against the sheathing.
Add a vapour barrier on the warm side of the wall within the first third of the thermal resistance value of the overall wall insulation.
Thickness: The vapour barrier must possess a minimum thickness of 0.2mm (200 µm) and demonstrate resilience against impacts, punctures, and moisture penetration. Installation Standards: The film should provide a 200mm overlap at all joints, with penetrations meticulously sealed or taped using a snug-fitting sleeve.
Vapor barriers resist moisture penetration, keeping humid interior air from reaching cold surfaces where it could condense. In cold climates, vapor barriers go on the warm side of insulation. In hot, humid climates, they go on the exterior side.
Lastly, the geographic location of the construction needs to be taken into careful consideration when deciding the proper placement of a vapor barrier in relation to the wall assembly. Properly placed vapor barriers should be installed on the warm, humid side of a wall.
Vapour control layer building regulations
12 require that all new builds have an approved VCL fixed to the warm side of all insulation and cover the external framed wall area. It must be fitted at 250mm centres to the top and bottom of frames, around openings, at laps and wherever there has been any damage.
4.505. 2 Concrete Slab Foundations
A 4-inch-thick (101.6 mm) base of 1/2 inch (12.7 mm) or larger clean aggregate shall be provided with a vapor retarder in direct contact with concrete and a concrete mix design, which will address bleeding, shrinkage and curling, shall be used.
On most projects where insulation meets the under-slab vapor barrier, we have found that the project teams elect to install their insulation first and to lay the vapor barrier over top. Various industry leaders have commented on the advantage of placing the vapor barrier directly beneath the slab.
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.
Even if there is no huge water leak such as from a hole in the roof, the steam and moisture of showers, bathtubs, and boiling pots can potentially affect the structure and safety of a house or building. This is why vapor barriers are needed in areas that are more moisture-prone.
In practice, we now understand that when VDRs are installed on the interior of an assembly, they also prevent inward drying. This can lead to significant moisture problems and mold; problems occur when walls get wet during construction or more often throughout the home's life.
Depending on where you live, the vapour barrier will either go on the inner surface of the insulation (if you live in a cold climate) or the outer surface of the insulation (if you live in a hot climate). It's safe to say that a vapour barrier will be needed for almost all projects.
Multi-Purpose - Our 10 mil black plastic sheeting can be used as a moisture barrier, vapor barrier, protection barrier for painting, dust containment, spray barrier and more!
Carton board air barrier paper is an excellent alternative to vapor barrier plastic.
Panel 1: In the late 1940s, residential building codes in the U.S. began requiring the installation of vapor barriers on the interior side of walls and ceilings. These requirements had complicated historical origins but were not based on credible building science.
Joe Lstiburek, an engineer and principal with Building Science Corp. in Westford, Mass., responds: Installing a vapor barrier on both sides of a wall is never a good idea in any climate.
Vapor barriers are installed along, in, or around walls, ceilings, and floors. Of course this is done to prevent moisture from spreading and potentially causing water damage.
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.
However, if not installed correctly or if damaged, vapor barriers can actually contribute to mold growth.
A vapour barrier is placed on the inner side of the insulation and is designed to stop moist air from passing through it. A breathable membrane, by contrast, is installed on the outer side of the insulation. Breathable membranes must repel water from the outside while still allowing moisture from the inside to escape.
Yes, an air gap can significantly improve the effectiveness of insulation. This is because air is actually a good insulator in itself.
Extend vapor retarder at least 6 inches up walls, columns, and footings. Use physical attachments where practical and necessary for long-term adhesion of vapor barrier to vertical surfaces. Overlap all seams at least 12 inches using a reverse or upslope lapping technique.
When using this approach, it is important to ensure that the vapour barrier is installed correctly. The vapour barrier should be installed on the warm side of the insulation to prevent moisture from penetrating the insulation and potentially causing damage or reducing the insulation's effectiveness.
Failure to use a vapor barrier can lead to higher energy costs and an ideal environment for mold and mildew growth.
A continuous underslab vapor barrier is the most effective against moisture control, but in most cases the material has to be cut to size, so using the appropriate tape to overlap seams and seal holes is very important.