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Musings of an Energy Nerd

New Green Building Products — February 2012

Photovoltaic shingles, three new insulation products, high-performance windows and skylights, and HVAC register covers for duct tightness tests

Dow Powerhouse Solar Shingles are a type of roofing that generates electricity. For the time being, Powerhouse shingles are only available in Colorado. It's unclear why the roofer in the photo forgot to install roofing underlayment.
Image Credit: Dow
View Gallery 10 images
Dow Powerhouse Solar Shingles are a type of roofing that generates electricity. For the time being, Powerhouse shingles are only available in Colorado. It's unclear why the roofer in the photo forgot to install roofing underlayment.
Image Credit: Dow
Apollo PV shingles have high-quality polycrystalline PV cells. However, the protective layer of glazing is made of plastic, not glass.
Image Credit: Martin Holladay
EnerGen PV shingles, like Powerhouse shingles from Dow, use a thin-film PV product that is less efficient than polycrystalline PV cells.
Image Credit: CertainTeed
InsulFoam HD Composite rigid insulation consists of a 1/2-inch-thick top layer of polyisocyanurate sandwiched to a thicker lower layer of EPS.
Image Credit: Insulfoam
EnGuard batts are made from polyester fibers. The 3 1/2-inch-thick batts are rated at R-13.
Image Credit: Vita Nonwovens
Breathe batts are manufactured in the United Kingdom from a mixture of hemp fibers and flax fibers.
Image Credit: Martin Holladay
NaturHemp batts are manufactured in Quebec from hemp fibers imported from Europe. The insulation is sold in Quebec under a different brand name (NaturChanvre).
Image Credit: M.E.M.
The Lumira EF Aerogel skylight is manufactured by Wasco Skylights of Wells, Maine. The skylight has two layers of polycarbonate glazing that are insulated with a translucent aerogel insulation product.
Image Credit: Wasco Skylights
The window on the left is a 4500 series tilt/turn window from Wasco Windows of Wisconsin. On the right is another one of Wasco's tilt/turn windows: one with a low-U-factor frame that uses the Geneo profile by Rehau. Both windows are triple-glazed.
Image Credit: Wasco Windows
Vent Cap Systems sells temporary register covers used to seal HVAC registers and grilles during Duct Blaster tests.
Image Credit: Vent Cap Systems

My folder of interesting new building products is getting thick, so it’s time for another new product roundup. I’ll review three brands of photovoltaic roofing designed to integrate with asphalt shingle roofs. I’ll also discuss several new types of insulation: a new type of rigid foam, batts made from plastic fibers, and batts made from hemp.

I recently discovered two manufacturers with similar names: one in Maine (Wasco Skylights) that makes high-performance triple-glazed skylights, and another in Wisconsin (Wasco Windows) that makes high-performance triple-glazed windows. Finally, I’ll describe a handy device for energy raters who perform duct leakage tests.

Powerhouse PV Shingles from Dow

Dow Building Solutions is selling thin-film photovoltaic (PV) modules designed to be integrated with an asphalt shingle roof. Called Powerhouse Solar Shingles, the PV modules use thin-film (copper indium gallium selenide) cells made by Global Solar. Because the PV shingles don’t have to be mounted on an aluminum rack that sits on top of the roofing — the Powerhouse shingles are roofing — the resulting PV array is inconspicuous.

The shingles must be hand-nailed by installers who have been trained by Dow; no nail guns are allowed. Each shingle is designed to plug into the adjacent shingle, minimizing wiring connections. All wiring penetrations are covered by the shingles.

For now, Powerhouse shingles are only available in Colorado; Dow hopes to expand the geographical reach of its distribution network in the future. Although Dow hasn’t released pricing information, it’s safe to say that these shingles are less efficient and more expensive than conventional PV modules. The efficiency of Powerhouse shingles is only 12%, while conventional crystalline PV modules have efficiencies of 18% or more. That’s why Powerhouse shingles need a larger area for the same electrical output as a comparable array of conventional PV modules.

For more information, see Brent Ehrlich’s report at

Photovoltaic roofing products from CertainTeed

A Dow competitor, CertainTeed, is offering two types of PV shingles designed to integrate with asphalt shingle roofing: one uses conventional polycrystalline PV cells, and the other uses thin-film laminate PV manufactured by Uni-Solar.

The product that uses conventional polycrystalline cells is called Apollo Solar Roofing. While most conventional PV modules are protected by a layer of glass, Apollo shingles have plastic glazing. Each 12-pound shingle contains 14 PV cells, so the output is about 7 volts DC.

Each shingle includes a plug and a receptacle to allow adjacent shingles to be electrically connected. An array of Apollo shingles has a rated electrical output of about 12 watts per square foot. According to CertainTeed, the shingles cost about $6 per watt.

CertainTeed’s other roofing product — the one that uses thin-film laminate PV — is called the EnerGen Photovoltaic Roof System. As might be expected for a thin-film product, EnerGen is less efficient than Apollo. An array of EnerGen shingles has a rated electrical output of 5 watts per square foot — only 42% of the electrical output of a similarly sized Apollo array.

These new roof-integrated PV products from Dow and CertainTeed face stiff competition from cheaper conventional polycrystalline PV modules. Chinese factories are churning out such modules at a frantic pace, and the price of conventional PV modules is dropping every month.

InsulFoam HD Composite roof insulation

A manufacturer of expanded polystyrene (EPS) has come out with a new type of rigid foam insulation for low-slope roofs. The product, InsulFoam HD Composite, is a sandwich consisting of a top layer of 1/2 inch high-density polyisocyanurate adhered to a thicker layer of expanded EPS. Since InsulFoam HD Composite can be ordered in a variety of thicknesses (ranging from 1.5 inch to 7 inches), the thickness of the EPS varies; in all cases, however, the polyiso layer on top is 1/2 inch thick.

The main advantage of including a layer of polyiso on the top of the foam sandwich is that the polyiso has a high density and compressive resistance (100 psi) — higher than EPS, and high enough to resist foot traffic when used on a low-slope roof. Most types of membrane roofing can be installed directly on top of the foam insulation, without the need for a separate facer board like Georgia-Pacific DensDeck.

It’s possible to install a fully adhered roofing membrane directly to InsulFoam HD Composite — something that can’t be done on ordinary EPS. In short, InsulFoam HD Composite provides a good combination of compressive strength, high R-value, and low price.

The R-value of 7-inch-thick InsulFoam HD Composite is R-28. InsulFoam has 10 manufacturing locations and maintains a nationwide distribution system.

EnGuard polyester batt insulation

For the third time, a North American manufacturer is attempting to promote polyester batt insulation. The first two manufacturers who tried to launch polyester batts — Rtica Corporation of Stoney Creek, Ontario, and Dow Building Solutions of Midland, Michigan — have both given up and abandoned the market. Rtica is out of business, and Dow’s product (SafeTouch batts) was discontinued in 2011 due to dismal sales.

The latest entry into the market is Vita Nonwovens of High Point, North Carolina; the company recently launched polyester batts under the EnGuard brand.

Does polyester have any advantages over fiberglass batts or mineral wool batts? Well, maybe — they’re not as itchy as fiberglass batts. Other than that, though, there’s not much to say about polyester batts except that they are made of plastic and contain recycled content (obtained in part from old plastic beverage bottles).

EnGuard batts have no formaldehyde and no VOCs. The batts for 2×4 walls are rated at R-13. EnGuard batts cost between 50% and 100% more than fiberglass batts.

Two distributors of hemp insulation

Insulation made from hemp has been available in Europe for over a decade. Now two North American companies are selling hemp batts on this side of the Atlantic.

A distributor in Chicago, American Lime Technology, sells batts made from 45% hemp fiber and 45% flax fiber. The batts, called Breathe insulation, are imported from the United Kingdom.

Breathe batts are available in two widths (17 3/4 inches and 22 5/8 inches) and four thicknesses (2 in., 3 in., 4 in., and 6 in.) — oddball sizes that meet the needs of the British market. According to Matt Engelmann, a sales manager at American Lime Technology, the R-value of the batts is between R-4 and R-4.5 per inch.

When I asked Engelmann about the cost of the batts, he wouldn’t answer. All he told me was, “If I give prices now I might scare people off.”

A competitor, Matériaux Ecologiques pour la Maison (M.E.M.), manufactures its NaturHemp batts in Québec, Canada. The batts are manufactured from fiber imported from Europe.

NaturHemp batts are available in two thicknesses (3 1/2 inch batts rated at R-13 and 5 1/2 inch batts rated at R-20) and two widths (16 inches and 24 inches). The R-13 batts cost $1.55 per square foot, and the R-20 batts cost $1.99 per square foot.

Brent Ehrlich, the products editor at BuildingGreen, has played with samples of NaturHemp. According to Ehrlich, “installation is likely to be tricky, since hemp is a tough fiber and is not easy to cut. I took a bread knife to our sample, and it was easier to cut than cotton or wool insulations I’ve tried, but finding the right tool/saw/blade will be key to simplifying installation, and be prepared for some hemp on the floor.”

Two companies named Wasco

I probably shouldn’t be reviewing products from two separate companies named Wasco, because confusion is almost inevitable.

Here’s a coincidence: a company in Maine called Wasco Skylights makes high-performance triple-glazed skylights. A totally unrelated company in Wisconsin called Wasco Windows makes high-performance triple-glazed windows. Both companies have interesting products, so they’re both worth a look.

Wasco Skylights

Last year, Wasco Skylights of Wells, Maine, was offering triple-glazed skylights that complied with the so-called “30-30” requirements of the federal tax rebate program. (That is, a maximum U-factor of 0.30 and a maximum SHGC of 0.30.) The good news is that these triple-glazed skylights are still available; the bad news is that, since the tax rebate expired, they are now a special-order item rather than a stock item. That means the price has gone up.

However, it’s still possible to get a 2 ft. by 4 ft. triple-glazed Wasco skylight (NFRC U-factor of 0.29) for between $600 and $700.

For less money, you can order a translucent skylight from Wasco called the Lumira Aerogel. These skylights have polycarbonate (plastic) glazing incorporating high-R Aerogel insulation manufactured by the Cabot Corp. of Billerica, Massachusetts. The Aerogel improves the performance of the skylight, but you can’t see the sky through these skylights. The glazing is translucent, not transparent.

Wasco Skylights has not yet obtained an NFRC rating for their Lumira Aerogel skylights; however, the polycarbonate glazing has an impressive center-of-glass U-factor of 0.22. (Of course, an NFRC U-factor includes the frame, so that number would be less impressive.)

A 2 ft. by 4. ft. Lumira Aerogel skylight costs about $450 to $500. Wasco Skylights has a nationwide distribution system.

Wasco Windows

As noted earlier, Wasco Windows is not affiliated with Wasco Skylights in any way. Headquartered in Milwaukee, Wasco Windows has several locations in Wisconsin.

Wasco Windows focuses on vinyl replacement windows — a type of window that is often disparaged by green builders. However, vinyl windows are relatively affordable, and that’s a virtue. And Wasco Windows stands out from its competitors in two ways: it offers several high-performance glazing options, and (due in part to the fact that the company’s engineer, David Paulus, used to live in Germany) the company has begun embracing European window technology.

Some Wasco Windows are made from European vinyl profiles that include glass-fiber reinforcement. Made by a German company, Rehau, the profiles (Geneo profiles using Rau-Fipro material) are made from a composite material consisting of PVC with glass fiber reinforcement, with a capstock layer of ordinary vinyl. These Geneo profiles are stronger than ordinary vinyl profiles, and therefore don’t require any steel inserts. Moreover, Geneo profiles have a lower U-factor (between 0.19 and 0.20) than typical vinyl profiles used by most U.S. window manufacturers. Wasco offers the high-performance Geneo profiles on its triple-glazed tilt/turn windows.

Unlike most window manufacturers, Wasco Windows understands glazing options. Wasco Windows promotes a 1.38-inch-thick high-solar-gain triple glazing (Wasco calls it the “Sustainability Glass Package”) that is particularly appropriate for northern climates. The center-of-glass specifications for this type of glazing: U-0.133 and a SHGC of 0.566. Because Wasco is familiar with triple glazing (and sells more of it than most vinyl window manufacturers), upgrading from double glazing to triple glazing only costs between $70 and $90 per window.

Wasco had shipped windows to customers as far west as Wyoming and as far east as Vermont.

Vent Cap Systems

The most common method of testing duct systems for leakage is the Duct Blaster test. To perform this test, all of a home’s registers and grilles need to be temporarily sealed; this is typically done with tape.

An inventor named Corey Breed got tired of using up rolls and rolls of tape to seal registers. His solution: reusable plastic register covers that seal registers tightly enough for a Duct Blaster test.

The rectangular register covers can be installed more quickly that tape. First you insert a plastic hook into the center of a register or grille. The plastic hook is attached to a long cord that is threaded through the center of the register cover. After securing the hook, you slide the register cover along the cord until the cover contacts the ceiling, wall, or floor around the perimeter of the register. The cover stays tight until it’s time to release the lock on the cord and remove it.

Breed’s company, Vent Cap Systems, sells register covers for $44.90 each (or $299 for 10), not including shipping.

Last week’s blog: “Is This Building Passivhaus-Certified?”


  1. Deniz Bilge | | #1

    I don't understand the big deal with traditional roof-mounted solar modules. When properly designed and installed, they look just fine. The BIPV shingle seems like more trouble than its worth. Firstly, thin film is more inefficient than mono or polycrystalline--avg of 10-13% thin film efficiency vs 16-22% for the others. Next is cost, both in material and labor. Each shingle has 2 wires which need to be plugged in series and then parallel. Times that by a thousand or two and you've got labor costs to pretty up that attic ceiling. Don't forget about the cost of the product. At $5-7 per watt, that's between 2-3 times the cost of a traditional module. Finally, I'd be concerned about performance. Traditional roof mounted modules are (or should be) 4 inches above the roof, providing necessary airflow underneath the modules, which helps with the production numbers and also helps to ensure higher cell efficiency over the lifetime of the module. I understand that thin film can take the heat better than silicon, so I don't know how critical airflow is for thin film--just something to consider.

    What about servicing and warranty? I would bet that the mandatory warranty of 5 yrs on this system costs the owner of the system more. What happens if there is a ground fault dead smack in the middle of the roof? With voltages of only 3-6 vs 200 per module, it can be harder to find the problem module during troubleshooting.

    In conclusion, I don't see the true benefit of these BIPV shingles. If a traditional rooftop array bothered me that much, traditional modules can be incorporated as the roof as well. In fact, this is widespread in Germany.

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

    Response to Deniz Bilge
    I agree with all of your points.

    Roofing is roofing; a PV array is a PV array.

    My vote: keep them separate.

  3. Dan Kolbert | | #3

    Wasco Skylights
    Despite being in Maine, I only became aware of their skylights in the past couple of years myself.. Ive installed one and was impressed with the quality, performance and price.

  4. 5C8rvfuWev | | #4

    reply to Deniz and Martin
    I too agree. the "shingles" however may be a manageable way to get around building covenants in some areas. The prez of a local HOA, when I was considering a remodel in the S/D, thought solar shingles might be accepted under the current rules and not require a special waiver etc.

    Personally, I'd rather prep the conduit etc in the attic and then get on the board of the HOA and lobby from strength for what will work better. (i.e., panels)

  5. Deniz Bilge | | #5

    When I was 13, I went to California for the first time. I saw a house getting built and noticed styrofoam dust on the ground by the exterior wall under construction. I knew nothing about construction and thought that they were crazy for building a house out of styrofoam. Almost 25 years later, it's actually starting to happen. What's next, building a house like a surfboard??--foam shell encased within a fiberglass or epoxy protective coating? Should NASA get into airtight home construction that includes air pressure regulators? Where's this industry headed?

    Back to the Insulfoam... haven't seen this stuff, but 2 questions: How is this stuff secured to withstand 115mph? Does it have any shear strength like plywood? Another thing I believe is that extra fire resistance measures should be incorporated into the product, like a cement-based backer or something of similar value. This whole foam idea is pure poison if that roof catches fire.

    Probably more expensive than slate...the Industry needs to get back to the supply-demand curve. Everything's so cost prohibitive anymore for no good reason. I'm convinced that things cost what they do simply because they can away with it, not because of supply/demand. I'm sure a couple extra bucks can be spent to protect the foam from fire and still rake in the profit, without increasing the price of the product.

  6. Deniz Bilge | | #6

    forgot something in comment 1
    I forgot to comment on the photo of the guy installing the PV shingles on the plywood...It looks to me like those wires will be sitting between the unprotected plywood and the shingles, which spells lots of heat with no cooling airflow to me. Electrically, this means the temperature correction factor for determining the PV wire sizes could potentially be great enough that code may require a #8 or larger wire size. Although I never actually held one of these shingles, I'm willing to bet that #10 AWG is what the factory seals in the junction box.

    To remedy the situation, if this shingle were to be installed, I would use lath boards across the rafters and no plywood (as in the old cedar roof installations), or somehow else make sure there is airflow or insulation or both between the plywood and shingle.

  7. User avater GBA Editor
    Martin Holladay | | #7

    Insulfoam questions
    Q. "Does it [Insulfoam] have any shear strength like plywood?"

    A. No. Insulfoam is insulation, not roof sheathing. It is installed on top of the roof sheathing, usually on a low-slope (flat) commercial roof. This is the most common way of insulating low-slope roofs. Tens of thousands of buildings are insulated this way, all over the country.

    Q. "How is this stuff secured to withstand 115 mph [winds]? "

    A. With cap screws.

    Q. "Probably more expensive than slate."

    A. No, it is far cheaper than slate. But slate is roofing; this is insulation. Even if you found a way to install slate on a low-slope roof, you would still need insulation.

  8. Deniz Bilge | | #8

    I didn't realize the
    I didn't realize the insulfoam is installed in conjunction with sheathing or recovery board...thought it was some miracle by itself system....

    Just wondering what the experts here think (while we're in a blog about building products) about magnesium oxide boards as replacement for both drywall and cement board---mold resistant, easier to work with than cement board, unaffected by water saturation due to its ability to dry out and resist mold (the magnesium content), inert (no silica or poisonous chemicals), easy installation (not necessary for joints to land on studs, brad nails & adhesive)...But what about the cons?

    I've heard that they corrode metal (nails and studs) due to a chemical reaction that occurs when the material gets wet..something to do with magnesium chloride...Wondering if anyoyne knows the myth from fact here...

  9. Paul McGovern | | #9

    vent cap systems
    Martin ... I ordered a few to see how they worked ... they are useless at rough-in (no ceiling in place) and they can't be secured tight enough to guarantee no leakage even at +25pa ... they are held in place by line friction, which is not enough ... camera & smoke stick verify leakage ... covers on an adjustable pole, either manufactured or self-made, are more reliable ... we started with tupperware containers, applied self-adhesive weatherstrip to the outside edges, glued drywall sanding pole swivels underneath and inserted adjustable poles ... same procedure only with plywood instead of tupperware, at rough-in. Works great at fraction of cost ... a bit more cumbersome but reliable.

  10. User avater GBA Editor
    Martin Holladay | | #10

    Response to Paul McGovern
    Thanks for you very valuable comments. A great tip.

  11. Steven O'Neil | | #11

    thin laminate PV on standing seam metal roof
    Certainteeds product looks like it's for asphalt shingles, but I learned about thin PV laminate when i saw it applied to a standing seam metal roof. Is this the same product mentioned here?

  12. User avater GBA Editor
    Martin Holladay | | #12

    Response to Steven O'Neil
    The products mentioned in this article are designed for asphalt shingle roofs.

    You are thinking of a different product from Uni-Solar. Their peel-and-stick product for metal roofing is now called Uni-Solar PowerBond. (It has been sold in the past under a variety of names).

    Here is a link to more info:

  13. Sam Jensen Augustine | | #13

    Thin Film Vs. Crystalline
    I am no expert and these are as much questions as anything but here goes:

    Production under similar high temperature conditions. Thin film do not have nearly as great an efficiency drop off as crystalline. So if you have a large area on the roof in Arizona it may be worth your while to go for Thin Film.

    Similar in climates like the intermountain west, say Utah, where seismic snow and high summer temperatures play a role thin films can beat out crystalline due to weight, bearing capacity and temperature. That is not to say that all of those factors cannot be accounted for in Crystalline, they can and are but that from a whole product, install and climate standpoint a thin film may be a wiser choice.

    I have heard than thin films perform better under low light conditions, not sure this accurate or not. If not should be included in one of Martyn's "myths" (caveat not truly myths) columns.

    Perhaps the greatest reason to go with thin films, and admittedly the least nerdy, is that many HOAs and design review committee, justified or not, have less of an issue with them.

  14. Nicholaus Baxter | | #14

    PV Shingles
    Personally, I've been waiting for these for a long time, and as costs come down, I think they will be quite successful. I can't stand bolt on PV panels. It pains me to see ugly junk slapped on to the outside of a building. There is a zero energy townhouse project near me called the Z-Homes, these townhouses are beautifully planned and designed, but then they slapped bolt on PV panels to the roofs and it made me sad. PV shingles would have really made this project, but unfortunately, green design is still ugly in some ways. PV shingles are an intentional and beautifully incorporated product that I wish all the best for.

    There are valid issues with PV shingles. I just hope the manufacturer and installers are addressing some of the issues. All PV panels or arrays should be independent from one another, monitored by the user, and accessible for maintenance and repair. If these, a decent warranty, and a cost effective solution can be achieved, then PV shingles will be a highly successful product, and something that I will personally invest in and recommend. Regardless, how can you say no to such a beautiful, intentional, integrated PV product?

  15. Richard Ugarte | | #15

    Grace Ice & Water over Insulfoam
    Maryland, mixed humid, 4A.

    I read that I could use fully adhered membrane over the Insulfoam polyisocyanurate layer. Could one place Insulfoam on the walls to the exterior of the sheathing and then lap Grace Ice and Water exterior to that as an air barrier? Like a reverse PERSIST/REMOTE?

    Do you know if Grace Ice and Water would keep the termites from the rigid foam?

    Would the membrane still work as an air barrier if the foam shrinks in the future?

  16. User avater GBA Editor
    Martin Holladay | | #16

    Response to Richard Ugarte
    There are many roofing manufacturers that sell membrane roofing. Products include EPDM roofing and PVC roofing. These roofing products can be installed on the exterior side of InsulFoam HD Composite, as long as the foam manufacturer tells you that they are compatible.

    Grace Ice & Water Shield is not roofing; it is a rubberized asphalt membrane that must be protected from UV exposure by a layer of roofing that goes on top of the Grace Ice & Water Shield.

    There is no need for two layers of membrane. As long as you plan to install a membrane on top of the foam, choose a roofing product, not Ice & Water Shield.

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