Meta description: Spray foam vs fiberglass insulation in snowy climates: why R-value per inch is simply half the story and why air sealing comes first for ice dams.
After I crawl into an attic in January right here in Eau Claire, the primary issues I verify are darkish smudges on the insulation, frost on nail ideas, and gaps round lighting fixtures and pipes. These clues present me the place heat air is escaping. So when householders ask me about spray foam vs fiberglass insulation, I begin with R-value after which transfer shortly to air.
The Chippewa Valley is a tricky check. In response to the UW-Madison State Climatology Workplace’s 1991 to 2020 normals for the Eau Claire airport, we common 55.4 inches of snow a 12 months, January highs of 23.4 F and lows of 5.8 F, and about 7,923 heating diploma days. The document low is minus 45 F, set January 30, 1951. The teachings from attics right here apply to most snowy locations.
Spray Foam R-Worth vs Fiberglass, Inch for Inch
The US Division of Power makes use of tough estimating figures: fiberglass batts at about R-3.2 per inch, blown (loose-fill) fiberglass at about R-2.5 per inch, and sprayed foam at roughly R-5 per inch. Producers checklist open-cell spray foam round R-3.5 to R-3.8 per inch and closed-cell round R-6 to R-7 per inch.
On paper, closed-cell foam wins the spray foam R-value vs fiberglass matchup simply. On an open attic flooring, although, depth is normally accessible. You possibly can hold including fiberglass till you attain the goal. R-value per inch issues most the place area is tight: rim joists, cathedral ceilings and partitions.
Each a kind of numbers comes with a catch. Lab R-values are measured with no air shifting via the fabric.
Why Air Modifications the Comparability
Fiberglass is air-permeable. The constructing code itself types insulation into “air-permeable” and “air-impermeable” sorts, and fiberglass sits within the first group. It slows warmth shifting by conduction, however air can nonetheless drift via it and carry warmth alongside. These darkish smudges I search for are sometimes spots the place air has been filtering via the fibers.
Spray foam belongs within the second group. It fills cracks and gaps because it insulates. The Division of Power’s Constructing America program says spray foam gives glorious air sealing and might present air barrier continuity at troublesome particulars like rim joists. The identical program notes it should be blended on the correct chemistry to carry out as supposed, which is one purpose the installer issues a lot.
Moisture is a part of the image too. Producers say closed-cell foam acts as a vapor retarder at roughly 1.5 to 2 inches thick, whereas open-cell lets rather more vapor via. In a heating local weather, that distinction impacts the place every kind belongs.
ENERGY STAR estimates householders can save a mean of 15% on heating and cooling prices by air sealing and including insulation in attics, flooring over crawl areas and accessible basement rim joists. Discover the order: sealing comes first.
Ice Dams Begin With Heat Air
Ice dams type when warmth melts snow on the higher roof and the water refreezes on the colder eaves. Many individuals blame skinny insulation. The analysis factors to leaks.
The Minnesota Division of Commerce says the first explanation for ice dams is attic air leaks. It says spray foam or caulking can seal the leak, that insulation alone is inadequate, and that including roof vents, together with powered vents, is not going to get rid of ice dams and infrequently makes issues worse. College of Minnesota Extension says that in lots of properties, air leakage is the key mode of warmth switch resulting in ice dams, and advises making the ceiling hermetic first, then contemplating extra insulation.
The Division of Power’s ice dam steerage lists three steps: absolutely air seal the ceiling airplane, completely insulate the attic, and ventilate the roof. It calls sealing air leaks from the residing area into the attic crucial step. It additionally notes that closed-cell spray foam can go on the underside of the roof deck in an unvented attic, a unique method that brings the attic contained in the insulated shell.
Spray Foam vs Fiberglass Insulation: Value and Commerce-Offs
Spray foam normally prices extra up entrance. Angi’s revealed worth information lists put in spray foam at about $0.60 to $1.60 per board foot for open-cell and $1.30 to $3.10 for closed-cell. A board foot is one sq. foot, one inch thick, so thicker foam prices extra. HomeGuide lists blown-in fiberglass at round $1.00 to $2.80 per sq. foot. If you evaluate spray foam insulation price vs fiberglass, take into consideration the thickness you want and the place it’s going.
Fiberglass has actual strengths. It’s cheaper, it’s simple so as to add on high of what’s already there, and it really works nicely when the attic flooring has been air sealed first. For a lot of vented attics, cautious sealing plus a deep layer of blown fiberglass is a smart, economical job.
Listed below are the spray foam professionals and cons in brief. Foam seals and insulates in a single step, has a better R-value per inch, and closed-cell slows vapor. It additionally prices extra and wishes a educated installer. The EPA advises occupants to go away throughout set up and keep out till the producer’s re-occupancy time has handed. Some producers suggest 24 hours for skilled methods. Anybody evaluating choices for spray foam insulation in Eau Claire or elsewhere ought to anticipate the installer to clarify these timing guidelines clearly.
Selecting the Finest Insulation for Chilly Climates
The most effective insulation for chilly climates is determined by the spot in the home, and the order of labor issues simply as a lot. ENERGY STAR says a superb insulation contractor begins by sealing air leaks, then provides insulation to the really useful degree.
Northern Wisconsin falls in local weather zones 6 and seven. There, ENERGY STAR recommends R-60 for an uninsulated attic, or including R-49 the place 3 to 4 inches already exists.
I lean on foam for rim joists, tight areas, cathedral ceilings and unvented roof assemblies. Fiberglass makes good sense on open attic flooring as soon as the hidden leaks round fixtures, chases, plumbing stacks and wall tops are sealed, usually with foam or caulk.
Wisconsin’s Give attention to Power provides rebates for air sealing and attic insulation. Quantities change, so verify present provides earlier than you intend a venture.
Fast FAQ
Is spray foam vs fiberglass an either-or alternative?
Typically, no. Many cold-climate attics find yourself with each: foam or caulk to seal the leaks, then fiberglass piled deep on high. Closed-cell foam takes over the place depth is proscribed or the roof deck itself is being insulated.
Will extra insulation alone cease my ice dams?
Often not. The Minnesota and federal sources above agree that the leaks should be sealed first. Insulation then slows the warmth that continues to be, and the 2 steps collectively shield the roof edge.
Picture suggestion (free Pexels license, credit score non-obligatory): Icicles hanging from a snowy roof edge, positioned close to “Ice Dams Begin With Heat Air”. Direct JPG: https://photos.pexels.com/pictures/15411336/pexels-photo-15411336.jpeg
