Air Sealing With Sprayable Caulk
Two new brands of goop — Owens Corning EnergyComplete and Knauf EcoSeal — are designed to cut down on air infiltration
Homes insulated with fiberglass batts are leakier than homes insulated with cellulose or spray polyurethane foam. Until recently, fiberglass batt manufacturers shrugged off the damning air-leakage data, insisting that their batts could deliver the R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. promised on the packaging — and then changed the subject.
In recent years, however, manufacturers of fiberglass batts have begun facing up to their product’s Achilles’ heel — the fact that fiberglass batts are so air-permeable that they usually perform poorly. Worried that competing products are beginning to gain market share, batt manufacturers are finally addressing air infiltration.
A new kind of goop
Two leading fiberglass manufacturers, Owens Corning and Knauf, have developed similar air-sealing products that are best described as sprayable caulk. The Owens Corning product is called EnergyComplete, while the Knauf produce is called EcoSeal. When installed to seal leaks in wall assemblies, floor assemblies, and ceiling assemblies, these sprayable caulks improve the performance of air-permeable insulations like fiberglass batts or blown-in fiberglass.
Here’s how the systems work: an insulation contractor takes a high-pressure spray rig and sprays goop to seal leaks in stud bays and other framing bays. Once the sprayable caulk has cured, the cavities can be filled with batts or blown-in fiberglass.
It's not flash-and-batt
To many builders, these systems sound like a variation on flash-and-batt (a system combining spray polyurethane foam and fiberglass batts). But sprayable caulk should not be confused with spray foam. A flash-and-batt job requires the installation of a 2-inch-thick layer of closed-cell spray foam on the interior side of the wall sheathing; the foam layer has a measurable R-value.
EnergyComplete and EcoSeal are different; they aren't supposed to provide any R-value. Instead of installing a layer of foam that covers the sheathing completely, these products are used to seal the edges of each stud bay (in a “picture-frame” installation). The idea is to seal air leaks at the perimeter of each bay rather than to provide an insulation layer.
The products have a lot in common
EnergyComplete and EcoSeal are similar:
Owens Corning EnergyComplete
EnergyComplete is an air-sealing product made of synthetic latex, glycerine, and plasticizers. It is a two-component system; a special high-pressure Graco sprayer draws material from two separate buckets and mixes them. A foaming action occurs as the product is sprayed in place. Once the product is cured — a process that takes about 20 minutes — the framing bays can be filled with insulation. After curing, EnergyComplete remains flexible.
EnergyComplete can only be installed by licensed contractors. To become licensed, contractors must complete a two-day training course. Owens Corning charges contractors $15,500 for the two-day training; the price includes the necessary Graco sprayer, but not a compressor. If the contractor wants to buy a compressor at the same time, the cost rises to $16,500. Gulp.
The interior air temperature of the building where EnergyComplete is being installed must be at 20°F or above. EnergyComplete is very vapor permeable; it has a dry-cup permeance of 40 perms and a wet-cup permeance of 110 perms.
Because EnergyComplete is rated for use as fireblocking, it can be used to seal through-floor penetrations — for example, electrical or plumbing penetrations. EnergyComplete shouldn’t be used for cracks that are wider than 3/8 inch. According to Dave Wolf, an Owens Corning technical program leader, “If a gap is between 1/2 inch and 3 inches wide, you can’t install EnergyComplete without first chinking the gap with some type of backer rod. Instead of backer rod, you can use a scrap of fiberglass insulation. Then you can spray the EnergyComplete over it.”
As long as the crack isn’t too wide, EnergyComplete can be used to seal between a window frame and a window rough opening (although in most homes, installers prefer to use conventional canned spray foam at this location).
According to the manufacturer, EnergyComplete effectively seals air leaks, even through narrow cracks — for example, the cracks between double top plates or double studs — as long as the material is installed in a bead that is no more than 3/8-inch thick. “A 3/4-inch glob would challenge the compressiblity of the foam," says Wolf. "If there is too much — more than 3/8 inch — you have to take a utility knife and cut off the excess [after it is cured]. You cut the top half of the bead off.”
Using EnergyComplete to make site-built gaskets
Since the cured product is compressible, it can be used for two distinct applications: as a sprayable caulk or a sprayable gasket. “It is extremely compressible,” says Wolf. “When installed between double studs at a window, its function is to seal the infiltration through gap between the studs. When installed at the top plate of a wall adjacent to an attic space, it functions as a gasket.”
In this second application it is being used like a gasket installed as part of the Airtight Drywall Approach (ADA). Owens Corning advises installers to run a bead of EnergyComplete along the top plate of any partition wall under an attic. Later, this bead is compressed when drywall is installed against it.
“These are two application categories,” says Wolf. “The first is the classic joint-sealing category, where you seal leaks at a wood-to-wood joint. The other category of joints that we seal — for example, along the top plate of a partition wall under an attic — are gasket-like applications. This is a drywall-to-framing joint, not a wood-to-wood joint. Another example is at a common wall separating the house from an attached garage. If the wall is open at the rough-framing stage, then when the air-sealing person comes to seal up that wall, there isn’t any drywall or OSB to seal against. In that case, we seal the framing the way you would for the Airtight Drywall Approach. From the living-space side of the wall, you install the EnergyComplete along the bottom plate, the top plate, the end studs of the wall, and around the door opening. You have nothing to seal against, so you need a gasket. In the gasket category, we also recommend that installers use it around the flange of a duct boot the comes from an attic. You should spray the flange of the register boot so that when the drywall is later installed, it serves as a gasket.”
One disadvantage of EnergyComplete: because of possible problems with overspray, contractors have to mask many surfaces before work can begin. The manufacturer recommends, “Cover all windows and doors with plastic sheeting. Cover all bath tubs, toilets and sinks with plastic sheeting.”
Owens Corning doesn’t allow its installers to use EnergyComplete with cellulose.
The manufacturer declined to provide any estimates of the installed cost of its product. According to Owens Corning representative Matt Girand, “Quotes are typically provided by our contractors after they have had a chance to look at the specific builder plans.”
EcoSeal is a water-based latex caulk that is installed with an airless paint sprayer. (Knauf recommends the Graco Ultra Max 795 sprayer.) The company has developed a marketing name for the EcoSeal system: the Knauf Insulation and Sealing System (KISS).
Knauf offers training for contractors interested in becoming certified installers of EcoSeal. The training is free; if you need to buy a Graco sprayer, the cost of the equipment is $3,900. (This contrasts sharply with the very high cost of Owens Corning training.)
EcoSeal is a one-bucket system, not a two-bucket system like EnergyComplete. One 5-gallon bucket produces a bead of caulk about 2,000 to 2,500 feet long. Knauf says that EcoSeal can be applied at temperatures ranging from 20°F to 115°F. The product cures in a few hours. Cleanup requires only soap and water. (EnergyComplete cleanup is somewhat more complicated, since chemical cleaning is required for the B component of the spray rig.)
EcoSeal can be used with cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection., although Knauf would prefer contractors to use fiberglass insulation manufactured by Knauf.
Knauf sells EcoSeal to anyone — not just certified installers
Unlike EnergyComplete, EcoSeal can be purchased by anyone; you don’t need to be a licensed installer. According to Chris Brown, a business development manager at Knauf Insulation, “EcoSeal can be installed by a do-it-yourselfer. However, one must have an airless sprayer capable of spraying a heavy material. EcoSeal has a consistency out of the bucket somewhere between peanut butter and a heavy milkshake. Although it is a latex-based material, it is much thicker than latex paint and can't be pumped with a lightweight paint sprayer. The sprayer needs to be a piston-type sprayer as compared to lightweight diaphragm machines that will not be strong enough, with a capability of a minimum of 1,750 psi. The recommended spray tip orifice opening is either .013 or .015, with a fan spray size of 4 or 5.”
EcoSeal can’t be used as a sprayable gasket, because it is not very compressible when cured. According to Knauf representative Brett Welch, "Knauf is not advocating the Airtight Drywall Approach. This isn't a gasket." In order to seal the gap between partition top plates and drywall, Knauf advises contractors to spray the gap from the attic after the drywall is installed. Of course, this probably means that the air-sealing contractor will need to make two trips to the job site: one before drywall hanging, and one after.
If an insulation contractor wants to air-seal the common wall between a house and an attached garage, it’s necessary to first install a layer of OSB or drywall, so that there are surfaces to spray against.
While it’s OK to leave a 3/8-inch bead of EnergyComplete at a joint between double framing members, you can’t do that with EcoSeal. Knauf advises, “Excess EcoSeal material should be removed from the surface of the top plate, wall tee, and all multiple studs using the rubber squeegee so as to not interfere with drywall.” When sealing between double studs or plates, you need to apply just the right amount of material: not too much, not too little.
According to Chris Harris, a GBA reader who posted comments on the Q&A forum, “The tricky part of the [EcoSeal] installation is on headers and between jack studs. The sealant gets scraped to a thin layer and it can end up not fully filling the crack, leaving gaps. … It goes on so thin that the installer really has to make sure that he is putting on just the right amount to fully seal without leaving gaps or building up too much (particularly a problem on the face of studs where it might affect how the sheetrock lays.)”
According to Brown, however, EcoSeal does a good job of stopping infiltration between double studs and plates. “First of all, the product is designed to be applied with a high-pressure airless sprayer set at between 1,800 and 2,100 psi,” said Brown. “This amount of pressure delivers the sealant deep into the crack or crevice sealing the air pathway. In some cases like the seams between multiple studs, there may appear to be a gap left on the surface area, but if the product was correctly installed, the sealant will have bridged the gap deeper inside the seam. In cases where too much product has been installed on the surface of multiple studs, or anywhere else that might interfere with proper drywall installation, yes, it can be smoothed over using a drywall knife, rubber squeegee or even brushed down with a cheap paintbrush.”
When asked about blower-door results, Brown reports, “ACH50 in the 3 to 3.5 range has been most common in these typically constructed homes. ... Test results below 1.7 at ACH50 are starting to be more common.” (For more information on blower-door testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas. results, see the comment posted by Chris Brown on 9/27/2011, below.)
Prep time for EcoSeal is relatively simple, since installers of EcoSeal are not required to mask doors, windows, toilets, and tubs (as is required for installers of EnergyComplete).
According to Knauf representative Brett Welch, EcoSeal is significantly cheaper than EnergyComplete. “EcoSeal costs between $200 and $250 for a bucket that yields 2,000 to 2,500 lineal feet of product,” said Welch. “To produce 2,900 lineal feet of EnergyComplete requires 5 buckets of material costing $1,200.”
The installed cost of EcoSeal (materials and labor) is about 50 to 60 cents per square foot of envelope (wall, floor, or ceiling).
If you are a contractor interested in using sprayable caulk, here’s the bottom line:
- Anyone can buy EcoSeal, while EnergyComplete is sold only to certified installers.
- The equipment used to install EcoSeal is significantly cheaper than the equipment used to install EnergyComplete.
- EcoSeal is a one-bucket system that doesn't require mixing. There is no need to mask windows and doors to protect against overspray, and cleanup is easier than with EnergyComplete.
- Once cured, EnergyComplete is more flexible and compressible than EcoSeal, allowing EnergyComplete to be used for sprayable gaskets — an application that is impossible with EcoSeal.
- EcoSeal can be used with cellulose; EnergyComplete can't.
Last week’s blog: “An Overview of the 2012 Energy Code.”
- Owens Corning
- Martin Holladay
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