Install clear plastic barriers on the inside of windows

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. The humid air is indoors, and the dry air is outdoors. The sheet of poly still cuts off drying to the indoors, but it keeps the water vapor in the humid indoor air away from the cold surfaces inside the wall.

Plastic on the inside of the wall, humid air inside Plastic on the outside 3. Cold Weather. Plastic on the outer surface of a wall in cold weather could cause problems. The humid air is indoors. The cool surface is the sheathing, assuming no exterior insulation. If water vapor diffuses or infiltrates into the wall cavity and finds the cool surface, moisture problems can occur. Of course, you can have moisture problems here even without the exterior vapor barrier because of what Bill Rose calls the rule of material wetting.

That is, warm materials dry more quickly than cold materials. The problem occurs with a vapor barrier when it prevents drying to the drier space. In a building with air conditioning during hot humid weather, the drier space is indoors. The humid air is outdoors. The wrong place to put a vapor barrier is on the inside because any humid air that gets into the wall cavity is blocked from drying to the inside. If the vapor barrier is on the outside, it prevents the humid air from diffusing into the wall cavity and finding the cold surface on the other side of the cavity, the back side of the drywall.

You could be creating the kind of problems I described in scenario 1 above. Understanding moisture is one of the most important aspects of making buildings do their jobs properly and not fail prematurely.

We know now that mid-twentieth century building science incorrectly ascribed magical properties to vapor barriers.

Bulk water from deficiencies in drainage planes , flashing, and other moisture management details caused most of the problems.

Building science has progressed since then. We know that vapor barriers can cause problems, but we still have homes like the one in Charleston with poly in the walls. I saw the one below when Martin Holladay came to Atlanta last year. Allison A. He has a doctorate in physics and writes the Energy Vanguard Blog. He is also writing a book on building science. You can follow him on Twitter at EnergyVanguard.

Vapor Retarder? Vapor Barrier? What the Heck?! What a great deal! I enjoyed the blog, as always I enjoyed the blog, as always, and I respect you for staying on topic. Thanks for sharing your experience with the TodaysHomeowner.

Please enter your comment! Please enter your name here. You have entered an incorrect email address! Recommended For You. How to Install Canless Recessed Lights. All rights reserved. Reproduction in whole or in part without permission is prohibited. A Year of Simple Solutions. Place staples along all four edges of the screen at 3-inch intervals. Staple or nail strips of lath over the edges of each piece of clear vinyl sheeting or plastic to help hold it in place.

Note: An alternative to stapling vinyl or plastic to the screen frames is to build frames that fit inside the framework on the inside of the screen porch. Stretch vinyl or plastic material over the frames and staple in place. Hold the screen covers in place with bent nails, full-turn or half-turn button latches. To remove the screen coverings and staples in the spring, pull the staples from the screen frames with needle-nose pliers. Related Articles. Tip Another option to install clear vinyl sheeting is to cut the sheeting to cover the screen and the frame.

Measure and cut clear vinyl sheeting or other heavy plastic to the appropriate size or sizes. Bind the edges with waterproof cloth. Secure marine dome snaps to through the wrapped edges with a snap set.