In November 2004, the GreenSpec Directory – publishers of the environmental newsletter EBN (Environmental Building News) – announced the Top 10 green building products of 2004. Winner of one of these awards was a product from CertainTeed Corp.: the Membrain Smart Vapor Barrier, which is “smart,” since it has the ability to change its permeability from permeable to impermeable and vice-versa depending on the relative humidity (RH) present in the air within close proximity to it. This allows it to remain impermeable in the heating season (when RH is low) and morph itself into a permeable state by opening pores in the surface of the 2-mil nylon from which it is made when RH is greater than 50 percent, such as is the case during the cooling season. Since water vapor always travels from higher pressure to lower pressure (path of least resistance), this is particularly important in the summer months when outdoor air pressure is higher than indoor air pressure.


The rule of thumb for exterior framed walls (cavity walls) is simply put: Whatever gets into the wall cavity must have a way of getting out of the wall cavity. Membrain Smart Vapor Barrier solved this problem by doing just that: allowing water vapor (water in its gaseous state) to exit a wall cavity by the process of vapor diffusion. This is the ability of water in its gaseous state to move through and past “solid” surfaces like a ghost through a wall. Under low RH conditions, it acts much the same as 6-mil polyethylene remaining impermeable, thus blocking entry of water vapor into the wall cavity from the room or warm-in-winter side (high pressure). In June 2004, an article entitled: “If I Only Had a Brain” appeared in this column. Fortunately, I wasn’t referring to myself but, rather, this innovative and revolutionary vapor barrier.


Recently, CertainTeed has taken Membrain Smart Vapor Barrier to the next logical step by applying it as a facing for both R-13 and R-19 batts and rolls for their line of fiberglass insulation. Though there is a slight cost premium as compared to other faced fiberglass insulation, it’s worth the price of admission for the benefits derived. Just as Membrain Smart Vapor Barrier works in its 2-mil nylon sheet version, as a facing for fiberglass insulation it is permeable under high RH conditions (cooling seasons) and impermeable under low RH conditions (heating seasons). Since the key to controlling mold growth in a wall cavity is moisture control, as a facing for permeable fiberglass insulation, excess moisture is allowed a means of escape through other permeable materials, such as gypsum board, to areas of lower air pressure.

CertainTeed calls this next generation product CertainTeed DryRight Fiberglass Insulation with Membrain Facing. Its intended use as a less-than-full-width batt is for wood framed wall and ceiling cavities – not light-gauge metal framing where full-width batts are always required to fill the web cavity (to avoid thermal short-circuits) – as both a thermal and acoustical insulation in residential and commercial construction. Composed of 2-mil thick polyamide (nylon) film facing adhered to yellow, inorganic glass fibers it is an effective moisture manager regardless of climate type. However, it is most effective in moderate and/or cold climates.

Since permeability – the ability of water vapor to pass through permeable materials – is a chain only as strong as its weakest link, low permeance interior finishes such as vapor retarding paints and/or vinyl wallpaper should not be used. As well, DryRight should not be used as an exterior vapor retarder. For rooms with short peaks of high humidity, such as kitchens and bathrooms, whereby interior finishes (i.e. ceramic tile) provide a buffering action, DryRight is acceptable. However, in rooms/areas where there is constant high humidity, such as pools and saunas, or where humidification systems are set at more than 50 percent RH levels, it should not be used.

Like all insulation, DryRight should not be placed within three inches of recessed (can) light fixtures in a ceiling pursuant to National Electric Code guidelines and it should be kept dry at all times. Fiberglass insulation loses its R-value when wet and the batts/rolls should be placed “behind and in” substantial contact with the unexposed surface of the wall/floor/ceiling finish. DryRight should always be installed on the room or “warm-in-winter” side of the exterior wall. Though fiberglass insulation is noncombustible, the membrain facing should not be left exposed (a flame-resistant facing is available for exposed applications). Staples are not required; a friction-fit between wood studs spaced 16 inches o.c. typically suffices.


DryRight is manufactured, marketed and sold throughout the United States. All CertainTeed fiberglass insulation products used for residential, commercial and HVAC systems are certified by GreenGuard. CertainTeed was also the first insulation products company to have all of its blanket, batt and blown insulation products certified by the National Association of Home Builders Research Center’s Certification and Labeling Program. CertainTeed, in cooperation with the NAHB Research Center, developed the “Certified Insulation Contractor Program” (CICP). The program entails third party testing to ensure quality installations and certification of IAQ (Indoor Air Quality) performance.


The GreenGuard mark is significant not only for the health benefits derived but also for accruing credits/points under the U.S. Green Building Council’s LEED (Leadership in Energy & Environmental Design) Commercial Interiors (CI) program, which recognizes GreenGuard certification. If you consider the fact that we Americans spend 90 percent of our time indoors rather than outdoors and that the indoor environment can be up to 10 times more polluted at levels of concentrations up to 100 times greater, then IAQ performance is very significant. Persons suffering from respiratory illnesses such as bronchitis and/or asthma are particularly aware of good vs. bad IAQ issues.

All GreenGuard products are tested for emissions of:

• Respirable particles

• Volatile Organic Compounds (VOC)

• Formaldehyde

These comprehensive tests are performed pursuant to stringent environmental chamber protocols as outlined by the Environmental Protection Agency for operating and testing dynamic environmental chambers which simulate the typical indoor environment. These EPA protocols include:

• EPA’s own Environmental Technical Verification program

• American Society of Testing Materials

• State of Washington

• Germany’s Federal Environmental Agency

• Other government and industry programs

Under these test protocols, a product is packaged, sealed and shipped to an accredited GreenGuard environmental chamber lab within a few days of manufacture and testing begins within five days of receipt. In this way, testing is performed when the product is new; when emissions are highest and can be measured accurately. For one week, tests are performed to measure for specific pollutants in concentrations measured in PPM (Parts Per Million) or Micrograms per Cubic Meter.

As mentioned, testing data results for respirable particles, VOCs, formaldehyde and other aldehydes are obtained from this rigorous testing. Also, gaseous emissions such as ozone, carbon monoxide and nitrogen oxide are also monitored during testing. Within the five-day test period, exposure concentrations are compared against specific pollutant standards for each product tested whereby they must meet standard levels. Out-gassing and pollutant decay during these five days is thus taken into account.


Though the GreenGuard certification standards are subject to change in the future pursuant to state, federal and international regulations, presently, they contribute significantly to obtaining high IAQ levels, thus, low levels of pollutants in the interior environment. The certification process entails several stages including:

• Raw material and facility reviews

• Annual product certification testing

• Quarterly monitoring tests (at each manufacturing site)

Use of recycled glass, both pre-consumer (mill waste) and post-consumer (curb-side recycling), for manufacturing fiberglass insulation helps reduce waste at the source and uses less energy than does manufacturing from virgin materials. Recycled glass is ground-up, cleaned, re-melted and combined with sand and other ingredients to make new fiberglass insulation. By using recycled glass, 12 BTU’s (British Thermal Units) are saved annually for every one BTU used to manufacture fiberglass insulation. This is good news for the environment since release of CO2 (carbon dioxide) – a greenhouse gas and a by-product of the fiberglass manufacturing process, is significantly reduced.

By having all its manufacturing plants, research and development center and corporate headquarters the first to be registered to ISO 9001-2000 standards and introducing innovative “green” building products such as Membrain Smart Vapor Barrier and DryRight fiberglass insulation as well as conforming to the high standards of GreenGuard, CertainTeed is setting an example of corporate environmental responsibility and initiative for others to follow and emulate.