Steve Bliss, of BuildingAdvisor.com, writes: The short answer is: Don't use a vapor barrier in a finished basement. This is asking for trouble, especially with a full bathroom, which generates a lot of humid air. Rigid foam board on the interior, like you have, is the ideal insulation.

Do I need a vapor barrier for basement walls?

Building codes usually require a vapor barrier (4 mil plastic sheeting) on exterior basement walls if the framing is attached to masonry or concrete surfaces, or if the wood framing butts up against the outer basement walls.

Should I put plastic behind drywall in a basement?

It's like sealing a wet blanket inside a plastic bag. Vapour barrier or not, any kind of fiber-based insulation is risky to use in basements. It could work out or it might not. Waterproofing the inside of the foundation wall does reduce the risk, but leaks or vapour infiltration are still a distinct possibility.

Where does vapor barrier go in basement wall?

Not to be confused with a vapor barrier—which is placed on the warm side of the wall just in front of the insulation and behind the drywall— a moisture barrier goes against the basement wall and behind the insulation and framing. The best option for insulating a basement is to use spray foam insulation.

Do you need to insulate basement walls below grade?

Your best bang for the dollar in this instance is to insulate the coldest part of the wall, again typically to 2-feet below grade. However, there are many instances where insulating the full wall is the best option, such as if your walls are stone, or the floor is earth or crushed stone with no vapor barrier.

Vapor Barriers: Need one or not?

How do I install a vapor barrier in my basement?

Tips for Installing Vapor Barrier in a Basement

1. Pull the barrier tightly across, and cover large surfaces as flatly as possible.
2. Make sure not to tear or cut the material.
3. Align the barrier right up to electrical outlets, pipes, windows and other obstructions, and use a sealant to secure the material.

What is the difference between vapor barrier and moisture barrier?

Moisture barriers function to help in preventing water from entering inside of the wall cavity. On the other hand, vapor barriers basically prevent water vapor from the interior of the house to filter through the wall and condense on the warm side of the insulation.

Should I use tar paper on basement walls?

Building inspectors would commonly recommend putting roofing felt (or tar paper) up against a foundation wall before refinishing the inside. Our experience has shown that this is a definite no-no.

Should plastic be used on basement walls?

In exterior walls that are below-grade, like basement walls, plastic should not be used at all.

How do you insulate basement walls to prevent mold?

The ideal Basement wall assembly to prevent mold growth:

1. Install two inches of rigid insulation board directly against concrete. ...
2. Frame an interior 2x4 stud wall at 24 inch centres, pressed tightly against the foam panels.
3. Install mineral wool batts in the cavities.

What happens if you don't have a vapor barrier?

The short answer is: if your wall doesn't have a vapor retarder, there is no need to worry. Builders worry way too much about vapor diffusion and vapor retarders. It's actually very rare for a building to have a problem caused by vapor diffusion.

Should I put plastic behind drywall?

Without poly beneath the drywall, water vapor hits the drywall and diffuses through to the drier (in summer) indoor air. By installing a sheet of poly there, you cut off that drying mechanism and water that finds its way into walls can stay there longer and do more damage.

Do vapor barriers cause mold?

One of the more common problems with crawl spaces that do not have a crawl space vapor barrier system is that they create high moisture levels, which may result in mold growth – as dampness creates the ideal environment for mold growth.

Is vapor barrier necessary?

A vapour barrier is an important component in building construction. Its purpose is to help prevent water vapour from reaching building walls, ceilings, attics, crawlspaces or roofs, where it can condense and cause building materials to rot or grow mould.

Do I need a moisture barrier and vapor barrier?

Vapor barriers are necessary for crawl spaces. A moisture barrier is the minimum amount of protection you should have in your crawl space. Most people will forget about protecting their crawl spaces, and when they do, serious problems arise.

How do you install a vapor barrier on a cinder block wall?

Stick the vapor barrier material to the foundation seal tape and then use mechanical fasteners to hold it forever. Drill holes through the plastic and through the seal tape into the block. If you drill through the seal tape you will prevent the plastic from peeling off when you remove the drill.

Can you use plastic sheeting as a vapor barrier?

Reinforced polyethylene plastic sheeting (poly) comes in a variety of thicknesses and strengths. A 6 mil thick poly is commonly used as a vapor barrier and offers short-term savings to the homeowner.

What is the cheapest way to insulate basement walls?

The smart and inexpensive way to insulate joist bays is to use extruded polystyrene (XPS) foam insulation panels cut to size to fit inside the bay and "glued" in with expanding foam. When the expanding foam hardens, trim away the excess and cover the foam with a piece 1/2" thick drywall to meet fire code.

Will insulating basement make house warmer?

Yes, insulating your basement will help keep your house warmer in winter and cooler in summer. Basements are susceptible to moisture when it's raining or cold outside, which may cause cracks and blisters. Insulation can help heat transfer and restricts moisture from penetrating through the walls.

Does insulating basement walls help?

Basement Insulation. A properly insulated basement can save you money on heating and provide a dry, comfortable living space. In most cases, a basement with insulation installed on its exterior walls should be considered a conditioned space.