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Musings of an Energy Nerd

New Green Building Products — September 2010

Every energy-efficient home needs a tight air barrier. Here are some products that might help: a cover for recessed cans, a caulk for polyethylene, and a handful of new housewraps

A cover for recessed can lights. The manufacturer of the Tenmat cover for recessed can lights has chosen to illustrate the product with one of the worst fiberglass-batt insulating jobs ever photographed. The Tenmat cover has been cut vertically to illustrate how it fits over the light fixture.
Image Credit: Tenmat
View Gallery 6 images
A cover for recessed can lights. The manufacturer of the Tenmat cover for recessed can lights has chosen to illustrate the product with one of the worst fiberglass-batt insulating jobs ever photographed. The Tenmat cover has been cut vertically to illustrate how it fits over the light fixture.
Image Credit: Tenmat
UV-resistant housewrap. Delta Fassade S is a housewrap designed to resist ultraviolet light. It can be installed behind open-joint cladding with 2-inch wide gaps between the boards.
Image Credit: Cosella-Dörken Products
On-road testing. After covering his trailer with Fassade S housewrap, building scientist John Straube drove 6,000 miles, through snowstorms and desert heat, and reported that the WRB held up remarkably well.
Image Credit: John Straube
If you don't need a housewrap with UV inhibitors, consider Delta Vent S, which costs less than half as much as Fassade S.
Image Credit: Cosella-Dörken Products
It's orange. WrapShield SA is a vividly colored self-adhered housewrap.
Image Credit: VaproShield
Plastic battens. In addition to manufacturing housewraps, VaproShield sells plastic strapping called VaproBattens to create a rainscreen air gap between siding and sheathing.
Image Credit: VaproShield

In this new-product roundup, I’ll look at a cover for recessed can lights, a new caulk for polyethylene, and several new water-resistive barriers (WRBs) that promise better performance than Tyvek or Typar.

A fire-resistant hat for recessed can lights

A Delaware manufacturer named Tenmat is selling an airtight hat for recessed can lights. Tenmat light covers are made from mineral wool; according to the manufacturer, they are fire-resistant.

Tenmat covers are installed from the attic. After making a slit in the cover to accommodate the electrical cable, the cover is pushed down to the drywall ceiling. The cover should be glued to the drywall with canned foam or thermal caulk. Needless to say, the slit or hole made for the cable needs to be sealed with housewrap tape or canned foam.

Once the Tenmat covers are installed, the ceiling can be insulated with almost any type of insulation, including fiberglass batts, cellulose, or spray polyurethane foam.

Tenmat covers come in two sizes: “regular” (9 inches high and 14 inches wide) and “oversized” (10 3/4 inches high and 16 inches wide). Energy Federation Incorporated sells regular size Tenmat covers for $19.65 each.

Besides the high price, there’s only one catch to Tenmat covers: the covers can only be used for recessed can fixtures equipped with CFL or LED bulbs. If a homeowner inserts an incandescent or halogen bulb in the fixture, it can overheat.

Dow Corning 758 caulk

Dow Corning has come out with a new caulk that sticks to a great variety of materials, including polyethylene.

The new sealant, Dow Corning 758, is a silicone caulk that the manufacturer claims will stick to polyethylene, polypropylene, vinyl, polyolefin housewrap (for example, Typar), peel-and-stick flashing (including Vycor and Tyvek window flashing), and peel-and-stick membrane (including Ice and Water Shield). The broad range of materials to which it sticks makes the caulk particularly useful for window installation.

Dow Corning 759 is said to be a low-VOC product.

A warning to anyone seeking technical information from Dow Corning on this product: my repeated attempts to obtain answers to a few basic questions about 758 sealant were ignored by the company. If any GBA readers can provide further information, please post a comment below.

Delta-Fassade S

Did you ever wonder why housewrap manufacturers can’t come up with a tougher product — something that doesn’t rip away from nail heads or get damaged by ladders?

If you’re tired of Tyvek and Typar, and willing to pay for something tougher, you might want to look at four housewraps from Cosella-Dörken Products.

In ascending order of price, Cosella-Dörken’s tear-resistant weather-resistive barriers are Vent S, Delta-Foxx, Delta-Maxx, and Fassade S.

Rated at 69 perms, Vent S costs about 45 cents a square foot — roughly three or four times the price of Tyvek or Typar. Delta-Foxx (214 perms) is more permeable than Vent S, but also pricier — between 65 and 90 cents a square foot. In Europe, Delta-Foxx is used on roofs as well as walls.

At 14 perms, Delta-Maxx has a lower permeance than Cosella-Dörken’s other WRBs. However, it has the greatest tear resistance.

If you need a WRB that can withstand a certain amount of UV exposure — for example, a WRB for use behind open-joint cladding systems — you can use Cosella-Dörken’s top-of-the-line WRB, a product called Fassade S. Delta Fassade S (74 perms) costs between $1.10 and $1.20 a square foot.

Fasssade S has UV inhibitors that allow it to be installed behind unusual cladding systems — for example, a screen made of gapped boards that admit some sunlight. Gaps may be up to 2 inches wide. “Basically it is designed to be exposed to some sunlight throughout its life,” said Peter Barrett, product manager.

Although it can withstand quite a bit of UV exposure, the manufacturer recommends that it be covered with cladding within 3 months of installation. Fassade S does not qualify as an air barrier.

To make sure that fastener penetrations are watertight, the manufacturer recommends the use of tape or a foam gasket between the WRB and any girt or strapping attached to the WRB.

Building scientist John Straube tested Fassade S by attaching it to the exterior of a small trailer. After driving the trailer for more than 6,000 miles, through snow and heat, he says that the housewrap “is still going strong.There was not a bit of deterioration or fraying that I could see in the wrap.”

WrapShield SA

VaproShield is selling a self-adhered WRB called WrapShield SA. Although it’s a peel-and-stick product, it’s not a rubberized membrane; it’s a vapor-permeable housewrap.

The fact that it is a self-adhered wrap gives it several advantages: since it’s self-adhering, fewer fastener penetrations are required to install it; it doesn’t flap in the wind or suffer from “wind pumping” problems; and it’s very airtight.

In addition to being a WRB, WrapShield SA can be used as part of an air barrier system. According to the manufacturer, it sticks well to plywood, OSB, DensGlass sheathing, and concrete blocks. No primer is necessary.

WrapShield SA seals well around small fasteners, although larger fasteners like #12 or #14 screws might require sealing. WrapShield SA works well with a rainscreen application; the manufacturer also makes a vinyl batten called VaproBatten to complete the installation.

WrapShield SA is rated at 50 perms and costs between 82 and 95 cents per square foot.

Henry Blueskin VP

Henry Company, a manufacturer with plants in Ontario and El Segundo, Calif., also manufactures a self-adhered WRB, similar in many ways to WrapShield SA. Henry Company’s product is called Blueskin VP.

Blueskin VP has a permeance of 29 perms. It needs to be applied at temperatures of 40°F or warmer. Like WrapShield SA, Blueskin VP has a peel-away paper backing; it can be adhered to a wide variety of substrates (including OSB, plywood, DensGlass, and concrete blocks) without fasteners. A primer must first be installed if the product is used over concrete or concrete blocks.

Last week’s blog: “Using Rigid Foam As a Water-Resistive Barrier.”


  1. J Chesnut | | #1

    WRB behind open joint cladding
    The open joint cladding system which is commonly referred to as a "rainscreens" in local architectural circles is a very popular look these days. There was always a question about what to put beyond the "rainscreen" apart from another siding product, so the Delta Fassade S option is good to know about.

    I have read health and environmental concerns regarding "fire retardants" and "blowing agents". Any known concerns with "UV inhibitors"?

    How do the felt papers and Grade D building paper hold up to UV light? Are these products known to fail behind open joint cladding installations?


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

    Response to J Chesnut
    J Chesnut,
    Neither felt paper nor Grade D building paper are suitable for weather exposure or exposure to UV light. That's why people living in tar-paper shacks have to buy a roll of tar paper every 6 months.

  3. Tom Magney | | #3

    Can light covers
    Well, that's great for CFLs and LEDs - any products out there for everyone else? Or what's the best way to make your own? I've got ICE (I think!) can lights throughout the dining room and front area, and would love to make them a bit more airtight.

  4. User avater GBA Editor
    Martin Holladay | | #4

    Response to Tom
    If you have access to the can lights from above (the attic), you can build a box out of drywall or rigid foam. The seams of your box should be made airtight with housewrap tape or canned foam.

    The larger you make the box, the less likely the fixture will overheat (and trip the overheat sensor on the light). Of course, once the box is installed (with canned foam sealing the cracks between the box and the drywall ceiling), cover the box deeply with insulation.

  5. Suzanne | | #5

    can light dams
    I'm a professional insulation blower and sometimes I will have an attic with 10-20 can lights which are not IC rated. The material I used to use to easily build a dam around the cans before blowing was recently deemed unacceptable by our local utility provider, who offers rebates on insulation and therefor gets to call the shots. I have not been able to get a recommendation from them, however. Any ideas for something easily installable (they're frequently in all-but-inaccessible places) which will cost my customers less than $20 per unit? Thank you.

  6. Anonymous | | #6

    Can I put the blueskin primer over top of tar? A building supply store in the area sain it make the tar gummy, and blueskin would come off eventually.

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

    Response to Anonymous
    I'm not sure what you mean by "tar." You should direct your question to a technical representative at Henry Company (800-486-1278 or 800-598-7663).

  8. ArtieNJ | | #8

    airtight hat for recessed can lights
    A solution posted on an insulation site awhile back, said that he used cheap styrofoam insulation coolers to cover the lights and caulked or foamed them in place. He used coolers large enough to exceed the 3" minimum contact with insulation that his inspector required. I thought is was brilliant at the time.

  9. Anonymous | | #9

    hat for can lights
    A contractor showing a home on a parade of homes recently said he uses foam winter rose covers as can hats. Any comments about this material and method?

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

    Response to Anonymous
    I've never seen a "foam winter rose cover," but if it's an airtight cover made of EPS, and if it's big enough, I don't see any reason why it wouldn't work.

  11. Jacob | | #11

    Instead of can light covers, use LED LR6 lights
    I spent hours and hours building drywall boxes, moving insulation, cutting the boxes to fit, and foaming them to the ceiling, only to be disappointed as to the air seal achieved. By the time I was done, I probably had nearly 1 hour into each box built, installed. For that cost including the time and materials, it cost the owner over $125 each and they still had the old can lights. Later, I discovered the LR6, a light manufactured by Cree, which is an airtight LED canlight retrofit fixture, that installs in minutes. They cost around $100 each, but considering the reduced labor costs to install them, I'd say they are well worth it. A bead of caulk around the rim, snap it in and you're good to go, for 15 years. They are dimmable too.

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