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Comparison of the effectiveness of termite shields to termiticides (termite poisons or chemical barriers):
Termite shields compared with chemical poisons, bait traps, & concrete encasement of foam are discussed in this article, whree Steve Bliss outlines the pros and cons of different methods used to avoid termite attack on buildings including structures whose foundations are insulated with Styrofoam™ or similar insulating board products that may form an attack pathway for insects.
We describe what termite shields are, what they look like, and how and where they are installed. We compare the effectiveness of termite shields with termite bait traps and chemical pesticide barriers as methods for controlling termite damage at or in buildings. We also illustrate the careful use of solid concrete encasement as an approach to avoiding insect attack on a building through foam insulation.
How to Avoid Termite Attack Through Foam Insulating Board
Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Our page top photos shows an insulated building slab during construction, leaving styrofoam exposed on the outside of the slab perimeter. Unless protective steps are taken foam insulation board in this location is a potential path for termites or other wood destroying insects to attack the building framing.
The question-and-answer article about avoiding termite damage on buildings where foam board insulation is installed, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. Our sketch (left) shows some identifying characteristics of termites when seen in the "flying ants" or swarming stage.
Question: Several articles in your magazine have mentioned using polystyrene board as perimeter insulation on a slab and covering it with stucco or millboard to protect it.
Building officials in my area won't let me stucco over Styrofoam™ insulating board [POLYSTYRENE FOAM INSULATION] nor can I cover it with anything else for fear that termites will come up between the insulation and the stucco or through the foam board insulation itself, attacking the building framing. Any suggestions?
Answer: a DOW expert recommends chemical termiticide as an insect attack barrier around foam board insulated buildings
What is a Termiticide? What's the difference between a termiticide (chemical treatment) & a termite shield?
Termiticide, not a termite shield, is the solution recommended by Jerry Severson. Severson heads research into foundation insulation at Dow Chemical Company's Granville Research Center, in Granville, Ohio.
Termiticides are chemicals that are applied in soils around a building foundation in order to form a chemical barrier to termites that might otherwise attack the building. Properly placed, a traditional termiticide chemical binds with the soil and remains in place. At least some modern termiticides, having been chemically adjusted to reduce the risk of environmental contamination by escaping toxic chemicals, may be less durable than older, more toxic chemicals used for that purpose. -- DJF
Termites can burrow through many building materials, including all forms of insulation, and no mechanical guard offers complete protection from termites indicated Mr. Severson.
Termite poisons improperly applied to the soil under a building can give off fumes that enter the home, its heating or air conditioning systems (duct work), and can make occupants sick. To avoid contaminating a building through improperly-applied termite chemicals, hire a reputable local pest control expert who is fully aware of the building's HVAC system design and the location of its components, and if the house is served by a private well, make sure that the well is adequately distant from any location where termiticides are to be applied.
Termiticides are not normally applied to soils outside of a foundation surrounding a dirt crawl space, also because of the possible surprise entry of chemicals or fumes into the building through the crawl space soils. However special (more costly) methods may be used such as the excavation of a trench around the building, mixing the termiticide directly with the soil (making certain thereby that no chemical is escaping to where it does not belong), and the soil is then replaced in the trench.
Also make sure that the termiticide chemical [and the solvent used to apply it] to be used in the soil is not one that can harm exposed insulation around the building's foundation.
What is a Termite Shield and Do They Work to Stop Termite Attacks on buildings?
Metal termite shields are widely used
atop foundations in the southern United States and in
tropical climates as a physical barrier to termites. They sit directly on top of foundation walls, piers, and other
supports before the first piece of wood is installed (see Figure 1-3 at left).
At one time termite shields were thought to block the
entry of subterranean termites, the most widespread
and destructive wood-boring insect in the United States.
However, subterranean termites, which nest in the soil,
will exploit the tiniest gaps in termite shields or other
barriers to reach the wooden portions of a house and will
build tunnels along exposed foundation walls and around
termite shields if necessary.
Although the shields do not
stop termites, they slow down their progress and force
them to build their tunnels in the open where they can be
easily seen during inspections.
To work at all, the termite shield must have tightly
sealed joints and be sealed around foundation bolts and
other penetrations. Joints can be either soldered or mechanically
interlocking. If the barrier is unsealed, termites
will find any small gaps and render the effort worthless.
People who advocate using termite shields say that they slow down the pests so that the homeowner can spot their telltale air tubes (mud tubes) and take action against them. Our photo (left) shows a close-up of a termite mud tube climbing a poured concrete foundation exterior wall in New Jersey.
The building had no termite shield, and its sills were termite-damaged. -- DJF
A termite shield is simply a metal barrier placed atop the foundation wall and bent down over the walls to make termite passage difficult, forcing the termites to construct a mud tube around the edges of the shield, thus either making building attack more difficult for the termites, or forcing them to construct the mud tube in a location that is more easily visible to the homeowner. -- DJF
At ROT, FUNGUS, TERMITES we include photographs of termite mud tubes showing a termite attack passing below a termite shield on a building foundation wall.
Below our termite mud tube photos show that a termite shield appears to have been installed along most but not all of the building foundation top. Or was it? We don't know if this is wall flashing that leaves sills exposed just under the wall edge, or whether the flashing extends across the foundation to the interior (as recommended).
But our second termite photo (below right) shows a termite mud tube ascending the same foundation wall and passing under the termite shield. The shield makes it more difficult, but not impossible, for termites to attack a building.
In general, termite shields should be a minimum of
6 inches above grade and extend out 2 inches on either side
of the foundation at a 45 degree angle. In addition to making
termite infestations visible, they also form a capillary
break between the foundation and sill. Areas where a termite
shield cannot be used, for example, where a concrete
stairway abuts a foundation wall, are at high risk for
In termite-prone regions, the only reliable way to prevent
termite damage is to use treated wood in critical locations
and treat the surrounding soil with termiticide.
See INSECT INFESTATION / DAMAGE for termite and other wood destroying insect information in depth, including termite inspection case reports, field photos and advice.
More installation details for termite shields and other building flashing can be found at FLASHING WALL DETAILS. Readers concerned about termite damage associated with foam, fiberglass, or other building insulation materials should also see Insects & Foam Insulation.
Termite Bait Traps: Other Approaches to Avoiding Termite Damage
[The following has been added to the original Q&A, by DJF]
Termite bait traps (photo at left) are a different approach to handling a termite problem: containers holding wood sticks are buried at intervals around the building and inspected regularly by the pest control operator (PCO).
When the PCO detects that termites have begun attacking one or more of the wood baits, the operator exchanges the tasty wood for one that has been treated with a poison.
Concrete Encasement of Foam Insulation as Termite Barrier
Foam perimeter insulation encasement: At a building slab perimeter, another approach to reducing the attack path for termites where foam insulating board is used at the slab perimeter is shown in our photo of a home being built in Minneapolis, MN.
The builder has encased the foundation perimeter insulation in poured concrete, leaving about a 1/2" of solid concrete around the insulation.
Cracks in poured concrete slabs, even very tiny cracks, can form an entry path for termites into the building.
Quality of slab construction and other details can minimize this risk of insect attack, but it's also important to keep water away from the building - wet wood attacks insects.
Construction details to reduce the risk of termite damage: include avoiding placing wood within 8" of the top of any soil, using caulking and flashing to be sure that building leaks do not wet framing lumber (making it attractive to termites), use of insect-resistant treated lumber for building wall sill plates, and similar measures.
Good design and construction practices, combined with keeping water away from building wood, can make a significant difference in the risk of termite attack on a building.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
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Questions & answers or comments about using termite shields at foam board insulated building foundations & walls.
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Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: email@example.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
"House Eating Fungus"Meruliporia incrassata (also called "Poria" the house eating fungus) in the U.S. or Serpula lacrymans in Europe) can cause severe structural damage. Evidence of hidden "poria" may be found by expert inspection methods which include tracing sources and paths of probable Building
leaks and moisture traps. Further, careful indoor particle sampling methods can often permit the presence of this mold to be identified in the laboratory.
Humidity: How Low Should You Keep Indoor Humidity to Avoid a Mold Problem
Termites - Greenhouse Gases, U.S. EPA, Environmental Protection Agency. Web search 09/11/2010, original source: http://www.epa.gov/ttn/chief/ap42/ch14/final/c14s02.pdf Quoting an interesting passage from this brief document: Termites inhabit many different ecological regions, but they are concentrated primarily in
tropical grasslands and forests. Symbiotic micro-organisms in the digestive tracts of termites
(flagellate protozoa in lower termites and bacteria in higher termites) produce methane (CH4).
Estimates of the contribution to the global budget of CH4 from termites vary widely, from negligible
up to 15 percent.
U.S. EPA. Prevention, Pesticides, and Toxic
Substances. 1997. Reregistration eligibility decision:
Diflubenzuron. Pp. 17, 46. www.epa.gov/
U.S. EPA. Office of Prevention, Pesticides and
Toxic Substances. 1994. Pesticide fact sheet:
Hexaflumuron. Washington, D.C.
U.S. EPA. Office of Pesticide Programs. 2003.
Pesticide ecotoxicity database. Unpublished database.
U.S. EPA. Prevention, Pesticides, and Toxic
Substances. 1998. Reregistration eligibility
decision: Hydramethylnon. Pp. 16-18, 43.
U.S. EPA. Prevention, Pesticides and Toxic Substances.
Undated. New chemical New chemical fact sheet:
Noviflumuron. Washington, D.C.
"Protecting Your Home from Subterranean Termite Damage", Journal of Pesticide Reform, Fall 2004, V 24 No. 3, - 6-7, Northwest Coalition for Alternatives to Pesticides/NCAP, POB 1393, Eugene OR, 97440 541-344-5044 www.pesticide.org: Web search 09/11/2010: http://www.hipspro.com/pubs/subterraneantermites.pdf
This document discusses alternatives for termite protection including reducing the attractiveness of the structure to termites (get wood away from the building, fix leaks), use of 16-grit sand (diameter 0.06 - 0.1 in) as a termite barrier 18" wide x 3" deep in crawl areas, or stainless steel mesh for the same purpose under foundations and slabs, boric acid, Diflubenzuron (insect growth regulator, risk genetic damage, EPA classed as carcinogen), Hexaflumuron (insect growth regulator, EPA didn't ID health concerns, waived some testing, partly because of anticipated very low risk of human exposure), Hydramethylnon (stomach toxicant, EPA: Carcinogen, highly toxic to fish), Noviflumuron (chemically similar to hexaflumuron), can cause anemia, EPA didn't ID other health hazards, some testing requirements waived, moderately toxic to fish).
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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