Flexible membrane on the outside of a house under the siding that forms a weather barrier, sprayed, rolled, or brushed on as a liquid. Replaces building wrap such as Tyvek.
Weather resistive barrier sheathing systems perform three functions: they prevent liquid moisture from entering the wall cavity and interior; they resist the passage of unconditioned air through the sheathing system and into the home; and they allow for the passage of water vapor, thus preventing the buildup of moisture within walls (From EnviroDri weather resistant barriers).
When covering wall sheathing with a water-resistive barrier (WRB), many builders choose plastic housewrap, asphalt felt, building paper, or rigid foam sheathing. In contrast, liquid-applied WRBs come in a bucket and are applied to wall sheathing or concrete blocks with a sprayer, a trowel, or a roller connected to a compressor that delivers the liquid coating directly to the roller. These products cure to form a continuous flexible coating that seals small cracks and penetrations.
Although liquid-applied WRBs cost more than housewrap, they also perform better as, once cured, these rubbery coatings provide a very high degree of airtightness (Holladay, 2010). A study done by the National Institute of Standards and Technology (NIST) and prepared for the U.S. Department of Energy reported that including a continuous air barrier system could reduce air leakage in a building by up to 83%. This reduction of air leakage can translate into increased occupant comfort and as much as 40% savings on the heating and cooling costs of a building (Chamberlin, 2013).
Status:
Baseline Description: Typical Electrically Heated Home Baseline Energy Use: 4.4 kWh per year per square foot
We will consider homes currently heated by electrical resistance, forced air electric heating and heat pumps. The values below for annual electric usage for heat in single-family and manufactured homes in the Northwest are taken from the 2011 Residential Building Stock Assessment. The weighted average is calculated by taking the heating EUI for each category of home and multiplying it times the total electrically-heated square footage for that category, summing all of them, then dividing by the total electrically-heated square footage in the region. This data will provide a rough estimates of energy use. (Baylon, 2012)
"Typical" Savings: 20% Low and High Energy Savings: 0% to 40%
A study done by the National Institute of Standards and Technology (NIST) and prepared for the U.S. Department of Energy reported that including a continuous air barrier system could reduce air leakage in a building by up to 83%. This reduction of air leakage can translate into increased occupant comfort and as much as 40% savings on the heating and cooling costs of a building (Chamberlin, 2013).
Energy Use of an Emerging Technology is based upon the following algorithm. Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Appropriate for new residential construction.
Installed first cost per: square foot
Price range: $0.60-$0.70/ft2 installed. Traditional house wraps from rolls cost at maximum $0.40/ft2. The higher cost mostly comes from the time taken to apply the liquid barrier at detail areas such as windows and doors. Note: this is per sf of covered wall area, not floor area (from "Energy Options Explained, "Liquid-Applied Water Resistant Barriers", http://energyoptionsexplained.com/liquid-applied-water-resistant-barrier/).
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Martin Holladay, 05/28/2010. Housewrap in a Can: Liquid-Applied WRBs GreenBuildingAdvisor.com
John Chamberlin, 09/01/2013. Fluid-Applied Air and Weather-Resistive Barriers: The Better Choice Interface
Technical Advisory Group: 2014 Residential Building TAG (#10) TAG Ranking: Average TAG Rating: 2.79 out of 5 TAG Ranking Date: 04/10/2014 TAG Rating Commentary: 1. Don't know enough. Would it trap moisture?