Protecting the R-Value Of Insulation

A-4

DuPont™ Tyvek® air and water barriers help maintain the installed R-Value of insulation by limiting air movement and providing an added layer of water protection.

Maintaining R-Value by Managing Air Flow
Double-pane windows, or the way a Thermos® bottle is constructed, are two good examples of how trapped air can keep what’s inside warm or cool. Wall insulation works the same way. As long as the air inside the insulation remains still and dry, the insulation will maintain its installed R-Value. The result is a comfortable home.

But, on average, a 2,500-square-foot home has more than half-a-mile of cracks and crevices in the wall cavities. When the wind blows even a little (and it blows, on average, 8 mph across the US), air is forced into the home, causing the heater or air conditioner to run more often, and resulting in higher energy costs.

View Media
View Media
View Media

How Tyvek® Products And Insulation Work Together
The average wall has 3.5 inches of insulation with an installed R-value of R-14, under ideal conditions. (Installed R-value includes the whole wall system, with studs, sheathing board, insulation and siding, and takes wind movement into account.)

Tests have shown that, when outside air moves into the wall through any crack or crevice resulting from normal construction practices, the result can be up to 63% loss of the R-value of insulation.

Properly installed Tyvek® weather barriers create an air barrier system that reduces unwanted air flow and helps maintain insulation R-value, and keeps people more comfortable.

Maintaining R-Value by Resisting Water Intrusion
Wet conditions can dramatically reduce the effectiveness of insulation. Regardless of thickness, wet insulation retains less than 40% of its effective R-value.1. Tyvek®weather barriers resist bulk water penetration, helping to establish a tight building envelope to keep insulation dry. This helps wall insulation perform to its stated R-Value. At the same time, Tyvek® WB allows moisture vapor to pass through, to provide control of condensation in wall structures and reduce the risk of damage to insulation, as well as protect against mold, mildew and wood rot.

1. Source: Controlling the Transfer of Heat, Air & Moisture through the Building Envelope. M.C. Swinton, W.C. Brown, G.A. Chown