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Wet-Spray
Insulation
In residential construction, cellulose,
fiberglass, and rockwool insulation can be installed in dry blown-in,
loose-fill, or (except for cellulose) batt form. Some builders, however, find
that batts are difficult to fit tightly between the studs, and that loose-fill
and dry blown-in insulation systems sometimes settle over time. The latter
problem usually means that the insulation system will not produce adequate
thermal resistance (R-value).
Wet-sprayed insulation tightly adheres to
walls and anything else it contacts. This reduces air infiltration and increases
the R-value of a new home's wall. For years, it has been used to insulate,
fireproof, and sound-proof commercial buildings.
The primary ingredients of wet-spray
insulation are cellulose, rockwool, or fiberglass, along with water and an
adhesive. Cellulose is the most common material for residential applications. A
special blowing machine that combines the adhesive, water, and insulating
materials sprays the mixture into or over open wall and ceiling cavities. The
insulation provides an R-value of approximately 3.5 per inch if installed at the
product's recommended density.
Blown-in insulation systems use a form
of wet or dry applied wall insulation. Although it commonly uses fiberglass
material with a latex binder to minimize water content, cellulose and rockwool
installation is available through some contractors. Blown-in insulation applicators thoroughly
pack confined cavities with insulation.
Wet-spray insulation has several
advantages. It does not settle; it forms a uniform, continuous blanket
throughout the wall cavity; and it forms an air seal between electrical wiring,
pipes, framing members, and other obstructions. There are also some precautions
you must take with wet spray products. The chemical fire retardants within the
products may corrode the metal fasteners, piping, conduit, or structural members
they contact. The long term stability of some plastics in contact with such
chemicals is also of concern. Unscrupulous installers can "fluff"
blow-in-blanket insulations, installing it at lower density than disclosed to
the homeowner.
Application and Cost
When installed properly, wet-spray
insulation uniformly covers the applied area, completely surrounding any
obstructions within the cavity. The adhesive binds the insulation material to
itself and the applied area. The adhesive is either a liquid that mixes with
the insulation at the nozzle of the blowing machine or a powder premixed in
the insulation material. Latex is a common binding agent.
Wet-spray insulation is most practical
for new construction or unfinished spaces such as basements with exposed
studs. Installing wet-spray insulation is often messy, since some of the
insulation can become airborne or adhere to the stud faces and floor. Stud
faces need to be scraped clean after installation. This insulation is
recyclable into the blowing machine for reuse as long as it is free of debris.
Wet-spray insulation in unfinished
spaces needs time to dry before being enclosed, or sheathed. Sealing up the
wall too soon after application sometimes leads to moisture problems, such as
mold and mildew growth. The drying time for the insulation varies depending on
the type of insulation material and its moisture content, the moisture content
of the framing members, and the climate.
There are wet-spray systems that can
significantly lower wet-spray moisture from about 50% to 28% dry weight
moisture content. One fast drying system uses rockwool, which does not absorb
moisture. Another system uses netting over the studs to help support its
low-moisture insulation while it dries.
When applying wet-spray insulation in
horizontal spaces, such as above ceilings, the weight of the insulation must
never exceed the capacity of the supporting finish material and fasteners. Be
sure to confirm from the insulation manufacturer the maximum allowable
insulation depth for the installed density you plan to use.
In fire testing done at the National
Research Council Canada (NRCC), wet-spray cellulose offered poor fire
resistance compared to dry-blown cellulose or rockwool batts. Since wet-spray
insulation adheres to the wall sheathing, when the sheathing is exposed to the
fire and collapses, it pulls the insulation out of the cavity, exposing the
entire cavity to the fire. This does not happen with friction-installed batt
insulations. This is usually only a problem with party walls-separating, for
instance, habitable dwellings.
Wet-spray insulation systems (including
installation costs) are usually more expensive than batt insulation.
Typically, wet-spray fiberglass or cellulose insulation costs are comparable.
Wet-spray rockwool is often less expensive where available. Prices vary,
however, depending on local supply and on labor rates.
Bibliography
More information regarding wet-spray
insulation systems can be found in the following articles. This bibliography was
reviewed in August 1997.
"Ark Seal BIBS-R-Value, Density, and
Effects of Freezing," J. Nisson, Energy Design Update, (9:4) pp.
6-7, April 1990.
"Batts versus Loose-Fill Wall
Insulation-The Manville Tests," J. Nisson, Energy Design Update,
(8:8) pp. 6-10, August 1989.
"BIBS Versus Batt Insulation-Measured
Air Leakage Rates," J. Nisson, Energy Design Update, (8:7) pp. 3-5,
July 1989.
"Blown-In-Blanket Insulation: How
Airtight Is It?" R. Kadulski, Solplan Review, (No. 28) p. 3,
August/September 1989. For more information, contact Robert Adams, Ark-Seal
International, 2185 S. Jason, Denver, CO 80223, (303) 934-7772.
"Blown-In-Blanket Insulation Receives
Canadian Approval," R. Kadulski, Solplan Review, (No. 34) p. 7,
August/September 1990.
"Blow-In-Blanket Solves Insulation
Problems," Energy Business News, (8:5) p. 1, Summer 1988.
"'Blow-In-Blanket' Trade Association
Formed," J. Nisson, Energy Design Update, (9:2) p. 3, February 1990.
"Cellulose Insulation: An In-Depth
Look at the Pros and Cons," A. Wilson, Environmental Building News,
(2:5) pp. 1, 12-17, September/October 1993.
"Dry, Dust-Free (?) Cellulose Walls
without Poly Vapor Retarder," J. Nisson, Energy Design Update,
(14:5) pp. 11-13, May 1994.
"Effect of Wet-Spray Cellulose on
Walls," J. Nisson, Energy Design Update, (8:10) pp. 3-5, October
1989.
"'Facts' About Wet-Spray Insulation
Systems," J. Nisson, Energy Design Update, (10:4) pp. 13-14, July
1989.
"F.A.T.S. Spray-Applied Rockwool Wall
Insulation," J. Nisson, Energy Design Update, (9:7) pp. 10-12, July
1990.
"Fiberglass Wall Spray: Move Over
BIBS?" J. Nisson, Energy Design Update, (16:5) p. 11, May 1996.
"Fire Resistance of Wet-Spray Versus
Dry-Blown Cellulose Wall Insulation," J. Nisson, Energy Design Update,
(14:12) pp. 6-7, December 1994.
"The First Wet-Spray Blowing
Machine," J. Nisson, Energy Design Update, (13:9) pp. 3-4, September
1993.
"Foamed Fiberglass Insulation,"
J. Nisson, Energy Design Update, (8:1) pp. 10-11, January 1989.
"Foamed Fiberglass Insulation,"
J. Nisson, Energy Design Update, (13:5) pp. 9-10, May 1993.
"Guardian Introduces Residential
Spray-On Fiberglass Insulation System," Energy Design Update, (17:6)
pp. 10-11, June 1997.
"Insulation Alternatives," R.
Kadulski, Solplan Review, (No. 37) pp. 8-9, February/March 1991.
A Handbook on Cellulose Insulation,
S. Siddiqui, Krieger Publishing Company, 1989. Available from Krieger Publishing
Company, P.O. Box 9542, Melbourne, FL 32902, (407) 724-9542. 178 pp., $29.50
(hardcover), ISBN: 0-89464-336-3.
"High-Density Fiberglass Insulation
for Blow-In-Blanket Application," J. Nisson, Energy Design Update,
(13:1) pp. 10-11, January 1993.
"Is The Insulation Dry Yet?," Journal
of Light Construction, (10:1) p. 10, October 1991.
"More Caution on Wet-Spray Cellulose
Insulation," J. Nisson, Energy Design Update, (8:9) pp. 1-2,
September 1989.
"The R-Value of Wet-Spray Cellulose
Insulation," J. Nisson, Energy Design Update, (7:4) pp. 5-6, April
1988.
"Sprayed Insulation," P. Fisette,
Progressive Builder, (11:10) pp. 23-27, November 1986.
"Wall Spray Dream Machine with
Automatic Material Recycling," J. Nisson, Energy Design Update,
(16:5) pp. 10-11, May 1996.
"Wet-Spray Insulation For
Houses," J. Nisson, Journal of Light Construction, (7:10) pp. 42-43,
July 1989.
"Wet-Spray Cellulose
Insulation," C. Reiss, Journal of Light Construction, (12:11) p. 24,
August 1994.
"Wet-Spray Cellulose in Steel Stud
Walls," J. Nisson, Energy Design Update, (13:4) p. 6, April 1993.
"Wet-Spray Cellulose-Questions about
Drying," J. Nisson, Energy Design Update, (8:7) pp. 6-9, July 1989.
"Wet Walls Signal Caution for Spray
Cellulose Applications," J. Nisson, Energy Design Update, (8:7) pp.
1,6-8, July 1989.
Source List
Blow-In-Blanket Contractors Association (BIBCA)
Chuck Andris, Executive Director
110 Breeds Hill Road
Unit 3, 3rd Floor
Hyannis, MA 02601
Phone: (800) 451-8862); Fax: (508) 778-0017
EREC is operated by NCI Information
Systems, Inc. for the National Renewable Energy Laboratory/U.S. Department of
Energy. The statements contained herein are based on information known to EREC
at the time of printing. No recommendations or endorsement of any product or
service is implied if mentioned by EREC.
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Clearinghouse (EREC)
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