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Musings of an Energy Nerd

New Green Building Products — September 2011

High-performance windows, doors, and tapes for your next superinsulated home

This high-performance tilt/turn window was manufactured in Maine by Linwood Windows. The company uses European shaper blades to mill the Douglas fir frames. Most customers order the windows with triple glazing.
Image Credit: Lindwood Windows
View Gallery 9 images
This high-performance tilt/turn window was manufactured in Maine by Linwood Windows. The company uses European shaper blades to mill the Douglas fir frames. Most customers order the windows with triple glazing.
Image Credit: Lindwood Windows
Vinyl tilt/turn windows from Intus Windows are among the least-expensive high-performance windows sold in the U.S. Manufactured in Lithuania, the windows can be ordered with high-solar-gain triple glazing.
Image Credit: Intus Windows
Intus Windows offers both vinyl-framed windows and wood-framed windows.
Image Credit: Martin Holladay
Inline Fiberglass, a Toronto window manufacturer, is producing double-hung fiberglass windows that can be ordered with triple glazing.
Image Credit: Inline Fiberglass
This cutaway shows an Eternity window from Inline with triple glazing. The Eternity glazing pocket allows the use of glazing up to a maximum thickness of 1 1/8 inch.
Image Credit: Inline Fiberglass
Drewexim doors are manufactured in Poland. This 68 mm-thick pine entry door from Drewexim is installed at Jesse Thompson’s house in Portland, Maine.
Image Credit: Jesse Thompson
This detail of an 88-mm-wide Drewexim door shows the perimeter rabbets and multiple weatherstripping.
Image Credit: Drewexim
Siga Rissan tape is used to seal air-barrier seams. It is appropriate for interior use only.
Image Credit: Siga
Siga Wigluv tape is appropriate for sealing air-barrier seams on the exterior of a building.
Image Credit: Siga

About every six months, I report on new products that catch my eye. This round-up features products from both sides of the Atlantic Ocean: high-performance windows from Maine, Ontario, and Lithuania; high-performance doors from Poland; and high-performance tapes from Switzerland.

Linwood Windows

Linwood Windows is a small window manufacturer in Tenants Harbor, Maine. Owned by Richard Cohen, the company makes European-style tilt/turn windows out of Douglas fir. All windows are custom made; the usual lead time is 12 to 14 weeks.

The fir frames are milled in Maine using European shaper blades. According to Cohen, windows using frames milled with similar shaper blades have met the strict Passivhaus Institut standard for certified Passivhaus windows.

Linwood Windows can be ordered with double, triple, or quadruple glazing. A wide variety of glazing options are possible, including triple glazing with a center-of-glass U-factor of 0.13.

Linwood’s triple-glazed tilt/turn windows cost between $120 and $160 per square foot.

Intus Windows

Intus Windows are manufactured in Lithuania and distributed by Intus Consulting in Washington, D.C. Intus sells both vinyl-framed and wood-framed windows. All Intus windows are tilt/turn style windows with triple weatherstripping. The company’s triple-glazed vinyl windows are some of the least expensive high-performance windows available in the U.S.

Most of the windows that Intus sells in the U.S. have triple glazing with two low-e coatings and warm-edge spacers. (However, if the customer prefers, double glazing can also be ordered.) The windows are glazed at the Intus factory in Lithuania. Intus assembles its own insulated glazing units (IGUs), using Saint Gobain glass for Intus wood windows and Guardian glass for Intus vinyl windows. High-solar-gain triple glazing is an available option.

Intus vinyl windows use vinyl lineals (profiles) manufactured by Deceuninck Group (Belgium). None of Intus’s vinyl windows are Passivhaus-certified.

Intus sells two lines of vinyl windows; the less-expensive brand, Elite, costs about $35 to $38 a square foot for operable triple-glazed windows.

The higher-performing brand, Eforte, has vinyl frames with a lower U-factor than the Elite frames. The Eforte window accommodates glazing that ranges from 1 inch to 2.2 inches thick. Operable Eforte windows with triple glazing cost about $40 to $45 per square foot.

Intus wood-framed windows are called Premmier windows. Premmier windows all have exterior wood cladding. The less expensive Premmier windows, Premmier 78 windows, cost about $75 to $80 per square foot for operable windows with triple glazing and aluminum cladding.

The high-quality Premmier windows, Premmier Passiv, are certified by the Passivhaus Institut in Darmstadt, Germany. These Passivhaus-certified windows cost about $95 to $100 a square foot for triple-glazed operable windows. Passivhaus-certified windows include a layer of insulation between the wood frames and the exterior aluminum cladding.

According to Intus representative Aurimas Sabulis, the lead time for an Intus vinyl window is 10 weeks. Wood windows take a little longer — about 10 to 12 weeks. Intus windows do not have NFRC ratings at this time.

Intus also sells a line of aluminum windows with thermally broken frames.

Inline Windows makes triple-glazed double-hungs

Lots of manufacturers sell fiberglass-framed windows with triple glazing. Builders who need an operable window usually choose from just three style options: casement, awning, or tilt/turn. Although double-hung windows with triple glazing are available from a few manufacturers, most such windows have low-performance glazing and leak a lot of air.

Inline Fiberglass has just released a new double-hung fiberglass window, the Eternity. Unlike most double-hung windows, the Eternity can be ordered with triple glazing; not only that, but it actually has good performance specifications.

Making a triple-glazed double-hung window usually results in compromises, and Inline’s new window, dubbed the Eternity, is no exception. The biggest compromise: the window’s glazing pocket only allows glazing with a maximum thickness of 1 1/8 inch. That’s a little thin.

If you are using argon gas, the best triple glazing is 1 3/8 or 1 1/2 inch thick; such glazing won’t fit in the Eternity. If you want to include high-performance glazing in an Eternity window, you’ll need to order it with krypton, a more expensive gas than argon. (Thin krypton-filled IGUs perform better than thin argon-filled IGUs.)

Inline offers several glazing options. An Eternity window with triple glazing with two low-e coatings and krypton gas has NFRC ratings of U-0.16 and a solar heat-gain coefficient (SHGC) of 0.18. If that dismally low SHGC depresses you — and it should — you can order Inline’s Synergy glass package. This option consists of triple glazing with 2 low-e coatings and krypton gas; the NFRC whole-window rating is U-0.17 and a SHGC of 0.46 — very respectable specs indeed.

When tested for air leakage according to ASTM E283-04 (Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen), an Eternity window with an area of 17.2 square feet had infiltration and exfiltration results of 0.07 cfm. This is an excellent result for a double-hung window.

Drewexim doors

By now, most builders of energy-efficient homes have settled on their preferred window supplier. Buyers can select a U.S.-made triple-glazed wood window, a Canadian-made fiberglass-framed window, or a European-made Passivhaus window. When it comes to entry doors, however, there have been few choices available.

American entry doors are thin flat slabs that close against a single stop, and many entry door brands include just one layer of weatherstripping. European doors are built differently. For one thing, they are thicker, which means they feel more solid and often have a higher R-value. They also have rabbeted edges that step down: the door’s perimeter has rabbets that mate with a rabbeted jamb equipped with two or three layers of weatherstripping.

Almost everyone agrees that German doors are built to high quality standards than typical U.S. doors. The main drawback to German doors is that they are very expensive. However, U.S. builders who are frustrated by the low performance of U.S. doors and the high price of German doors now have a third option: Polish doors.

Drewexim doors are manufactured in Koszalin, Poland. One U.S. importer and distributor of Drewexim doors is Fenestrations Plus of Bangor, Maine. According to owner Nate Campbell, the territory served by Fenestrations Plus includes most of New England.

Drewexim doors are available in pine, meranti, oak, and mahogany. If the door will be painted, finger-jointed pine is available at a lower price than stain-grade pine. Aluminum-clad doors are also available. Door panels are manufactured with a core of foam insulation sandwiched between two layers of veneer.

Drewexim doors can be ordered with either double or triple glazing. The standard door thickness is 68 mm (about 2 5/8 inch), significantly thicker than standard U.S. doors (1 3/4 inch). Drewexim also offers extra-thick 88 mm (3 7/16 inch) doors.

A pine Drewexim entry door with a triple-glazed light costs between $1,800 and $2,300; more exotic wood species cost more. The necessary lead time is at least 12 weeks; delivery may be delayed by the need to fill a container before a shipment can be scheduled.

One U.S. purchaser of a Drewexim door is architect Jesse Thompson of Portland, Maine. Thompson described some of the features of his entry door, pictured below: “This is a 68 mm standard solid stained pine door (not the thermally broken 88 mm style). The inset panel is a laminated insulated wood panel, and the light is triple-glazed. Hoppe hardware is standard and included.

“The hinges are adjustable: an Allen key inserts into the drilled holes, allowing the door panel to be raised, tilted, and lowered to adjust inside the frame easily through the years.

“The door has a European ‘threshold.’ It’s not a full width and depth sill; it’s more like an extrusion rabbeted into the bottom of the door panel that holds the jambs together. It’s designed to allow the door unit to be placed on top of a finish floor that runs continuously under the door — if you’re in a 300 year old stone building, for example — without having to cut a slot lower than the door unit like U.S. doors. We installed it by setting the door unit on a strip of Advantech the same height as the finish floor to come, so we could later slide the finish floor under from one side, and a trim sill under from the other side. U.S. doors are designed to sit on the subfloor; these aren’t. That was confusing at first.”

Minor installation confusions aside, Thompson is pleased with the value offered by Drewexim: high quality at a reasonable price.

Siga tapes

I first mentioned Siga tapes over a year ago, in my blog titled One Air Barrier or Two? Since that article was written, an increasing number of U.S. builders have recognized the advantages of high-quality Siga tapes.

Siga is a Swiss company that manufactures a complete line of air-sealing tapes for builders. The tapes are imported and distributed by Albert Rooks of Small Planet Workshop in Olympia, Washington.

All Siga tapes have a tenacious adhesive. However, these high quality tapes aren’t cheap: expect to pay from $30 to $59 a roll for narrow tape, and even more for wide tape.

For taping the seams of an interior air barrier, Rooks recommends Rissan 60 tape. (The number refers to the tape’s width in millimeters; 60 mm = 2.36 inches.) One roll containing 82 feet of tape costs about $33; the price drops to about $30 a roll when you buy 10 rolls.

For taping the seams of exterior sheathing, Rooks recommends Wigluv 60 tape. Wigluv tape works well on unprimed OSB or plywood; concrete, however, needs to be primed. (Rooks suggests that the seam between a concrete foundation and the mudsill or the bottom of the wall sheathing can be bridged with Wigluv tape.) One roll containing 131 feet of tape costs about $59; the price drops to about $53 a roll when you buy 10 rolls.

Both Rissan and Wigluv tape can also be ordered in wider versions; of course, the wider the tape, the higher the price. If you need primer for a concrete foundation that will receive Wigluv tape, Rooks sells that as well. Siga Dockskin primer costs about $35 a can.

Last week’s blog: “Spray Foam Jobs With Lingering Odor Problems.”


  1. User avater
    Armando Cobo | | #1

    DOE's RFP???
    Does anyone knows what ever happened to a DOE’s RFP, a year or two a go, for several window manufacturers to produce a triple glaze window at reasonable costs?

  2. User avater GBA Editor
    Martin Holladay | | #2

    Response to Armando
    As Texans say about fake cowboys, the DOE R-5 window program is all hat and no cattle.

    You can read about it here:

    Basically, the DOE invited window manufacturers to be listed. But no one posted prices; no one guaranteed prices; and there is no evidence that the program resulted in any builders getting a better price than they would have otherwise.

  3. Christian Corson | | #3

    Intus Windows
    Although the Intus uPVC windows are not PH certified, (The wood line is) They do meet the the PH standard of Uw .14 or .85 W/m2K. and are suitable for PH construction in cold climates. We are currently using this product in a PHI and PHIUS pre-certified PH that we are building in Maine.

  4. David Meiland | | #4

    Martin... photo size
    I have found several times that the photos you take and post with your articles are MASSIVE... they take way too long to download and display, and are large enough to print at 8"x10". You could reduce them to 800x600 pixels and well under 1MB and they would be fine for the web.

    Other than that, great article!

  5. User avater GBA Editor
    Martin Holladay | | #5

    Response to David Meiland
    Good suggestion!

  6. Marc Labrie | | #6 size
    David, I understand your point and at the same time I value these images as they are. Only a high definition image can render the details of that gourgeous window! Wouldn't it be nice if we could have our cake and eat it too? Until then, I'd prefer to keep the icing if possible.

  7. David Meiland | | #7

    Martin's image of the double-hung window is more than 3000 x 4000 pixels and almost 6MB. The only reason you need that size is to print it. It could be more like 1000 x 1300 and still be plenty big enough. Take a look at the sizes of the other images in the series attached to this article. They are typical web-sized images and load in a fraction of the time, but are still very detailed.

  8. Carl Mezoff | | #8

    Quad glazed windows

    On a trip to Nova Scotia I saw installations of sliding windows and sliding patio doors where there are two complete insulated glazed sliders in the same opening, with the inner one set just inside the exterior unit. This results in four layers of glass. To open the sash, you first slide the inner one open and then the exterior one, in separate operations. It appears that this is not a home-brew setup but a manufactured item, with all four sashes running on a single track. But I have been unable to find a manufacturer's name on the units or track down a manufacturer on the web. Has anyone else seen this sone?

  9. User avater GBA Editor
    Martin Holladay | | #9

    Response to Carl
    The only examples I have heard of were home-brew set-ups -- two windows in one rough opening.

  10. Bob Coleman | | #10

    i notice at times too the diff picture sizes create a lengthy download delay. the viewer widget works as far as display sizes go, but it downloads the entire full rez file which causes delay.

    it is difficult doing content for the web when you take different sources and publish from the same pc, as you don't see what happens on others, especially if you have local fast access to the content

    i appreciate the detailed pics, but for some images, it is not needed; and i've had to skip them entirely because i couldn't get them to download without a timeout from greenbuildings server.
    might save some bandwidth costs too

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