Best Wide Spray Foam

Two of the three makers sell their cans for open wall cavities, and none of the three describes filling a closed one. DAP’s Wall & Cavity sheet says a full cavity fill "for maximum R value" needs a two-layer application, giving a wall cavity and an attic as examples, while calling the can "Ideal for rim joists, touch-ups" or smaller repairs and projects; Kraken Bond lists walls, attics and ceilings among ThermaFoam’s uses; and both give a spraying distance from the surface, DAP approximately 12 in. Great Stuff Wide Spray is "Not approved for full cavity fill", and DuPont’s product page warns that filling enclosed voids "may cause accumulation of hazardous flammable vapors."

One can is rated at 10 board feet on Kraken Bond’s ThermaFoam sheet and up to 11 board ft on DAP’s Wall & Cavity sheet, and DAP defines a board foot as a 12 in by 12 in square at 1 in thick. Kraken’s figure, "10 board feet at 1 inch", is for its 16 oz can; DAP’s is for its 20 oz can, and DAP calls it theoretical, calculated in perfect laboratory conditions, with actual output affected by application method, temperature and humidity. Great Stuff Wide Spray states coverage as a run rather than an area: DuPont’s product page says two 18 oz cans cover up to 60 linear ft at a 4 in band, with no thickness given. Both board-foot figures are at 1 in thick, and Kraken recommends a total thickness of 2 in.

The two wide-spray data sheets set four conditions that bear on it: can temperature, humidity, can position and shaking. DAP asks for the can to be conditioned for at least 24 hours before use and for relative humidity of 40% or higher at the job, and Kraken Bond’s ThermaFoam sheet recommends a can at 68 F and warns that "Lower temperatures may reduce yield" and that any position other than valve down "will reduce foam output and efficiency". Both ask for 30 seconds or more of shaking and an upside-down can, and DAP asks for a test spray on scrap cardboard or into a trash bin before the project. Check the can’s age as well: DuPont’s safety data sheet for Great Stuff Wide Spray says to use it within 12 months, Kraken prints a shelf life of 18 months and DAP 12 months.

Kraken Bond says yes for ThermaFoam: its sheet lists "Sealing irregular, vertical, overhead, or uneven surfaces" among the uses and gives a separate spraying distance for ceilings. DAP’s Wall & Cavity sheet lists attics among its suggested uses and has a nozzle that turns for horizontal or vertical spray patterns, but it says nothing about spraying overhead. The Great Stuff Wide Spray documents we hold, a safety data sheet and DuPont’s product page, say nothing about overhead use either.

Of the three, only DAP’s sheet sets a per-pass limit: no more than 1/2 in of wet foam, which it says expands up to 3x to a 1.5 in cured layer. For the next layer it gives two routes: wait at least 15 minutes and until the first layer is tack-free, or mist the surface and the wet foam with water and wait 5 to 7 minutes, the method it prefers for multiple layers and maximum thickness. Kraken Bond’s ThermaFoam sheet asks for a recommended total thickness of 2 in, applied in at least 3 layers, without a per-layer figure or a wait time. The Great Stuff Wide Spray documents we hold give no layer instruction; DuPont’s Class A claim covers foam "up to 6 in wide by 1 in thick".

Two of the three makers list metal. Kraken Bond’s ThermaFoam sheet names metal among the building materials it adheres to and lists vehicle bodies, trailers and boats among its non-structural insulation uses, and DAP’s Wall & Cavity sheet says the foam bonds to "most: woods, masonry, metals and drywall". Both ask for a clean, dry surface, Kraken one free of dust, grease and rust, and Kraken does not recommend it on polyethylene, polypropylene, silicone, PTFE or oily or contaminated surfaces; DAP also marks its can "Interior use only". The Great Stuff Wide Spray documents we hold, a safety data sheet and DuPont’s product page, say nothing about which surfaces the foam bonds to.

Each states something the others do not. Great Stuff names a tested extent, 6 in wide by 1 in thick, and its certifier, Intertek, without indices. Kraken Bond prints both indices, FSI 15 or less and SDI 40 or less, without a thickness or laboratory. DAP prints both indices and the thickness, 10 and 450 at 2.75 in, and its 450 sits at the Class A ceiling for smoke.

The two numbers are not comparable, which is the answer. DAP states R-4.1 at 1 in as an aged value to ASTM C518, one of the four methods the FTC R-value rule accepts. Kraken states R-5.66 per inch from a DIN 52612 conductivity measurement with no aging basis stated. Different products, different methods, different conditioning: 4.1 is 27.6 percent below 5.66, and none of that gap can be assigned to aging alone without matching product, thickness and method. What it does show is that an aged, method-named figure and an unaged conductivity figure are not the same kind of number.

Per ounce, Kraken Bond ThermaFoam: $119.99 for twelve 16 oz cans on September 7, against $219.49 for twelve 18 oz cans of Great Stuff. DAP sold a single 20 oz can at $21.60 the same day.

DAP 3.1 from 418, Kraken 3.9 from 29, Great Stuff 4.0 from 12, against 4.0 to 4.3 for the single-can insulation kits we rate. We have not read the complaint patterns yet, so we do not know why. It is the open question on this page rather than a finding.