Chloe Zhang
Plastic sheeting is often installed behind drywall as a vapour barrier to prevent moisture from seeping into the insulated walls. This is especially important in cold climates, where water vapour can condense and cause damage to the insulation. Plastic sheeting can also help to seal drafts and improve energy efficiency. However, some people argue that using plastic behind drywall can trap moisture inside the house, affecting its breathability and potentially leading to mould issues. The effectiveness of plastic sheeting as a vapour barrier depends on proper installation and the specific climate conditions of the region.
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What You'll Learn
Plastic behind drywall is a vapour barrier
Plastic sheeting behind drywall is a vapour barrier. This is a standard practice in colder climates, such as in Canada, where the plastic is used to prevent moisture from getting trapped within the insulated walls. The plastic also helps to seal drafts and prevent humidity from reaching the insulation.
Vapour barriers are designed to be airtight and are typically made of poly plastic. They are installed directly behind the drywall, with all joints taped or sealed to prevent air from passing through the wall cavity. In addition to the plastic sheeting, acoustic caulking and red "tuck tape" are used to ensure a complete seal.
While some people question the effectiveness of vapour barriers, arguing that they trap moist air inside the house, others maintain that the plastic simply shows the presence of water rather than creating it. The plastic behind the drywall can help to identify any water leaks or sources of moisture, preventing potential damage to the wall.
It is important to note that the plastic vapour barrier should not be punctured, as this can compromise its effectiveness. Any holes or punctures in the plastic, such as those made for outlets or switches, can allow air with interior moisture to stream through. Proper installation and sealing of the vapour barrier are crucial to maintaining its integrity and functionality.
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Vapour barriers are required in some climates
The plastic sheeting behind drywall is a vapour barrier. Vapour barriers are required in some climates to prevent moisture from getting trapped in insulated walls. Installing a vapour barrier on the warm side of a wall in cold climates is standard practice and code in some places, such as Canada.
Vapour barriers are typically made of plastic and are placed between the insulation and the drywall. The plastic acts as a barrier to prevent water vapour from passing through the wall cavity and condensing in the insulation, which could ruin it. While drywall is not highly permeable to moisture, water vapour can still soak the inside of the wall over time. Vapour barriers help to seal drafts and prevent humidity from reaching the insulation.
However, it is important to note that the plastic behind drywall may not be a vapour barrier in all cases. Some older homes may have plastic sheeting applied to cinder blocks in the basement, which is not the same as a vapour barrier. Additionally, the effectiveness of vapour barriers can be compromised if there are multiple holes in the plastic for outlets, switches, or junction boxes. In these cases, interior moisture can still stream through and render the vapour barrier less effective.
The decision to install a vapour barrier and the specific requirements for its construction can vary depending on the climate and local building codes. For example, one source mentions that their building code in Ontario, Canada, requires a vapour barrier directly behind the drywall, while another source from Colorado mentions dealing with frigid, dry winters and the potential for humidity to reach the insulation.
Overall, vapour barriers are an important consideration in construction, especially in certain climates, to prevent moisture-related issues and maintain the integrity of the insulation and walls.
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Plastic prevents moisture from getting trapped in walls
Plastic sheeting is often installed behind drywall as a vapour barrier to prevent moisture from getting trapped inside walls. This practice is especially common in cold climates, where water vapour can condense and cause damage to insulation and other materials. By installing a vapour barrier, water vapour is prevented from passing through the wall cavity and potentially causing issues such as mould or ruined insulation.
The use of plastic as a vapour barrier can vary depending on the climate and local building codes. For example, in Ontario, Canada, building codes require a vapour barrier directly behind the drywall, usually made of poly plastic, to seal drafts and prevent air and moisture from passing through the wall cavity. In other regions, such as Maryland, the decision to use a vapour barrier may depend on the specific conditions and preferences of the builder or homeowner.
While plastic sheeting can be effective in preventing moisture from getting trapped in walls, it is important to consider the potential drawbacks. For instance, if the plastic is not properly sealed, holes or punctures can be created during the installation of outlets, switches, or junction boxes, allowing moisture to enter the wall cavity. Additionally, some people argue that using plastic vapour barriers can trap moist air inside the house, affecting its breathability and potentially leading to issues such as mould.
To address these concerns, proper installation and sealing techniques are crucial. Acoustic sealant or caulking can be used to seal joints and prevent air and moisture infiltration. Additionally, contractors may create small vent holes in the walls to provide circulation and prevent moisture buildup, especially in older homes where ventilation may be a concern. Ultimately, the decision to use plastic behind drywall should consider the specific climate, building codes, and potential advantages and disadvantages of vapour barriers.
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Plastic can help to seal drafts
Plastic sheeting is often installed behind drywall to act as a vapour barrier, which is a standard practice in cold climates. This barrier helps to prevent moisture from getting trapped within the insulated walls. By doing so, it also helps to seal drafts and improve energy efficiency.
In addition to its functional benefits, plastic sheeting can also enhance the structural integrity of the wall. One common method is to use two layers of 3/8" drywall, with plastic sheeting in between, resulting in a very solid wall assembly. This approach has been utilised for decades without any reported negative consequences.
The use of plastic sheeting as a vapour barrier is particularly effective in cold climates, as it prevents water vapour from passing through and condensing within the insulation. This condensation can lead to the deterioration of the insulation and other structural issues.
However, it is important to note that the effectiveness of the vapour barrier depends on proper installation. All joints should be taped and sealed with acoustic sealant to ensure an airtight seal. Additionally, any punctures or holes made in the plastic for outlets, switches, or junction boxes must be kept to a minimum to maintain the integrity of the barrier.
While some people express concerns about trapping moist air inside the house, the plastic sheeting behind the drywall serves an important purpose in controlling moisture levels and preventing drafts, ultimately contributing to a more comfortable and energy-efficient indoor environment.
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Plastic behind drywall is not always necessary
Plastic sheeting behind drywall is commonly used as a vapour barrier, particularly in colder climates, to prevent moisture from getting trapped in the insulated walls. However, the use of plastic behind drywall is not always necessary and there are differing opinions on its effectiveness.
In some regions, such as Ontario, Canada, building codes require a vapour barrier directly behind the drywall, typically made of poly plastic. This creates a seal that prevents air and moisture from passing through the wall cavity, improving insulation and reducing drafts. This practice is also recommended in similar climates, such as Maryland, where high humidity can be an issue.
On the other hand, some people argue that using plastic behind drywall can trap moist air inside the house, affecting its breathability. They suggest that while drywall is not highly permeable to moisture, it still allows for some vapour transfer, and by adding plastic, any moisture present will be absorbed by the drywall instead of being contained by the plastic. Additionally, punctures in the drywall and plastic for outlets, switches, or junction boxes can render the vapour barrier ineffective.
The decision to use plastic behind drywall depends on various factors, including climate, building codes, and personal preferences. While it can be beneficial in certain situations, it may not be necessary in all cases, especially if proper ventilation and moisture control measures are implemented. It is important to consider the specific conditions and requirements of a project before deciding whether to include plastic sheeting behind drywall.
Furthermore, alternative methods can be employed to manage moisture and ventilation. For example, contractors may create small vent holes in walls to provide circulation and prevent the development of mould. This approach may be more suitable in older houses with established ventilation systems.
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Frequently asked questions
Plastic is often installed behind drywall as a vapour barrier to prevent moisture from getting trapped in the insulated walls.
It depends on the climate. In colder climates, it is standard practice to install a vapour barrier on the warm side of a wall.
Plastic behind drywall can help to seal drafts and prevent moisture buildup, which could lead to mould or other issues.
