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11.05.2010

Will Clean Energy Manufacturing Create US Jobs?

Will Clean Energy Manufacturing Create US Jobs?

By Jennifer Runyon, Managing Editor   |   November 1, 2010   |   
In this series of articles on the state of clean energy jobs in the U.S., we delve into the clean energy job market outlook for 2011. Here the focus is on manufacturing.
New Hampshire, USA – In the U.S. manufacturing jobs have slipped to level not seen since before 1945 (see chart, below). From 2000 to 2009, manufacturing in the U.S. shed upwards of 7 million jobs. It's no wonder that politicians all over the country are hoping that the promise of the new clean energy economy will result in a restoration of a strong manufacturing base in the U.S.



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Vapor Retarders and Vapor Barriers

Answers to persistent questions about vapor diffusion

Vapor Retarders and Vapor Barriers


Posted on Mar 12 by Martin Holladay, GBA Advisor

Although building science has evolved rapidly over the last 40 years, one theme has remained constant: builders are still confused about vapor barriers.

Any energy expert who fields questions from builders will tell you that, year after year, the same questions keep coming up: Does this wall need a vapor barrier? Will foam sheathing trap moisture in my wall? How do I convince my local building inspector that my walls don't need interior poly?

To begin a discussion of vapor retarders and vapor barriers, I'll answer just a few of these persistent questions. Since I plan to return to this topic in a future blog, I invite readers to submit further questions.

Q. Why would I want a vapor retarder in my wall or ceiling?

A. Vapor retarders help slow the diffusion of water vapor through a building assembly. During the winter, a vapor retarder on the interior of a wall will slow down the transfer of water vapor from the humid interior of the home into the cool stud bays. During the summer, a vapor retarder on the exterior of a wall will slow down the transfer of water vapor from damp siding towards the cool stud bays.

However, a vapor retarder is a double-edged sword: while under some circumstances it can have the beneficial effect of helping to keep a wall or ceiling dry, under other circumstances it can have the undesirable effect of preventing a damp wall or ceiling from drying out.

Q. How often does water vapor diffusion through walls and ceilings cause problems?

A. Very rarely. In many cases, in fact, an interior vapor retarder does more harm than good. The main mechanisms by which moisture enters a wall are from the exterior (usually due to flashing defects that admit wind-driven rain) and via air leaks that carry "piggy-backing" moisture that condenses in a wall cavity. Vapor diffusion is a relatively insignificant cause of moisture problems in walls. (For more information on why air barriers matter more than vapor retarders, see "Air Barriers vs. Vapor Barriers.")

Q. Under what circumstances can vapor diffusion cause problems?

A. Although vapor diffusion problems are rare, they can occur. Dangers of vapor diffusion problems are higher:

  • In very humid rooms (for example, greenhouses or rooms with an indoor pool);
  • In homes with humidifiers; and
  • In homes located in extremely cold climates.

Even in a home with one of the characteristics listed above, the mechanism for moisture transport into walls and ceilings is much more likely to be air leakage than vapor diffusion.

Q. What's the difference between a vapor barrier and a vapor retarder?

A. A vapor barrier stops more vapor transmission than a vapor retarder. A vapor barrier is usually defined as a layer with a permeance rating of 0.1 perm or less, while a vapor retarder is usually defined as a layer with permeance greater than 0.1 perm but less than or equal to 1 perm.

Q. What does the code say about vapor retarders?

A. Codes vary; older versions of model building codes often included more sweeping requirements for vapor retarders than more recent versions.

The 2006 International Residential Code (IRC) and the 2006 International Energy Conservation Code (IECC) both define a vapor retarder as a material having a permeance of 1 perm or less. This definition includes such materials as polyethylene sheeting, aluminum foil, kraft paper facing, and vapor-retarding paint.

In section R318.1, the 2006 IRC requires: "In all framed walls, floors, and roof/ceilings comprising elements of the building thermal envelope, a vapor retarder shall be installed on the warm-in-winter side of the insulation." It should be emphasized that this code requirement makes no mention of polyethylene; vapor-retarding paint fulfills this code requirement.

The 2006 IRC includes exceptions to the vapor-retarder requirement. It allows a vapor retarder to be omitted:

  • In Climate Zones 1 through 4 (an area including most of the West coast and the South);
  • In walls, floors and ceilings made of materials (like concrete) that cannot be damaged by moisture or freezing;
  • "Where the framed cavity or space is ventilated to allow moisture to escape" — an apparent (although poorly worded) reference to vented attics and walls with rainscreen siding.

In section 402.5, the 2006 IECC requires: "Above-grade frame walls, floors and ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder. The vapor retarder shall be installed on the warm-in-winter side of the thermal insulation."

In the 2006 IECC, the exceptions to the vapor retarder requirement are very similar to the exceptions listed in the 2006 IRC, except for an additional exception: "Where other approved means to avoid condensation are provided." This last exception gives broad latitude to the building official — and places a heavy burden on any builder intent on convincing a local official that a certain building assembly complies with this exception.

The 2007 Supplement to the IECC and the 2007 Supplement to the International Residential Code (IRC) introduced a new vapor-retarder definition. (Of course, many jurisdictions in the U.S. are still using local codes based on the 2006 — or even earlier versions — of the IRC and IECC.) Vapor retarders are now separated into three classes:

  • Class I: Less than or equal to 0.1 perm [e.g., polyethylene];
  • Class II: Greater than 0.1 perm but less than or equal to 1.0 perm [e.g., kraft facing];
  • Class III: Greater than 1.0 perm but less than or equal to 10 perm [e.g., latex paint].

Since 2007, the IECC has required (in section 402.5) that walls in climate zones 5 (e.g., Nevada, Ohio, Massachusetts), 6 (e.g., Vermont, Montana), 7 (e.g., northern Minnesota), 8 (e.g., northern Alaska), and marine zone 4 (Western Washington and Oregon) have a Class I or Class II vapor retarder — in other words, kraft facing or polyethylene.

The exceptions have also been rewritten. Three of the exceptions are listed in section 402.5 of the IECC, which notes that vapor retarders are not required on a basement wall, on the below-grade portion of any wall, or on a wall constructed of materials that cannot be damaged by moisture or freezing.

Further exceptions are allowed in section 402.5.1, which states that in climate zones where a Class I or Class II vapor retarder would normally be required, a less stringent vapor retarder — a Class III retarder like latex paint — can be used under the conditions listed in Table 402.5.1 (see accompanying figure). Only certain types of wall assemblies are worthy of this exception; they must have either an adequate layer of exterior foam sheathing or "vented cladding."

Q. Clearly, I can get in trouble with my building inspector if I omit a vapor retarder in certain climates. Are there any situations where I could get into trouble for including a vapor retarder?

A. Yes. Although it's perfectly legal to install interior polyethylene or vinyl wallpaper in any climate, these products can lead to moisture and mold problems in most of the U.S. Unless you're building in Canada, Alaska, or somewhere close to the Canadian border, you don't want interior polyethylene or vinyl wallpaper — especially in an air-conditioned house.

Interior polyethylene and vinyl wallpaper prevent a wall from drying to the interior during the summer, when inward solar vapor drive (a phenomenon associated with so-called "reservoir claddings" — for example, brick veneer and stucco — that absorb and hold moisture) can cause condensation on the exterior side of the wallpaper or poly. Unless the moisture introduced into the wall by inward solar vapor drive is able to dry to the interior, wall damage can result.

Q. When it comes to vapor retarders, what do the experts recommend?

A. Here's a sampling of statements by leading building scientists on the subject of vapor retarders:

  • Anton TenWolde: "The calculations show that even with very low air pressures across the assembly, and even with a very good air barrier, sufficient moisture can bypass a poly vapor retarder, degrading its performance. In practice it doesn't matter what the permeance of the vapor retarder is, because the air leakage will go around it for moisture transfer. I came to the conclusion that the idea that we need a vapor barrier to keep our walls dry doesn't hold a lot of water, so to speak."
  • John Straube: "The whole reason we're talking about vapor barriers is not because vapor diffusion control is so important, but because people believe it is so important. The question comes up, have we seen diffusion-related building failures? And the answer is, very few — maybe in rooms with a swimming pool. Assuming that the vapor came from the inside, you would have to have a very high load before you would see a problem. I think that solar-driven vapor is much more important. The moisture is coming from the other side of the assembly."
  • Joseph Lstiburek: "In North Carolina, for whatever reason, they build their walls with fiberglass insulation and with poly on the inside. Depending on the cladding — brick and stucco being the worst — the walls rot like crazy."
  • AndrĂ© Desjarlais: "We can't assume that the building envelope is perfect. We have to assume some level of failure: some rain will get into the wall, and there will be imperfections in the air barrier."
  • Achilles Karagiozis. "It's all related—the vapor control strategy, airtightness, and whether or not there is a ventilation cavity behind the exterior cladding. If you have a ventilation cavity behind the cladding, it doesn't matter what kind of vapor retarder strategy you use."
  • Bill Rose: "In the South, no vapor barrier. In the North, as long as you have insulated sheathing that meets the dew-point test, also no vapor barrier."
  • Anton TenWolde: "When you put enough foam sheathing on the wall you get away from the cliff rapidly, and there's no reason to worry about vapor barriers any more."

Last week's blog: "The Energy-Efficiency Pyramid."


Tags: , , , ,

musingsheader imageImage Credits:

  1. Martin Holladay / IECC


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2010 ACEEE Energy Efficiency Scorecard Cites

2010 ACEEE Energy Efficiency Scorecard Cites State Leaders

October 20, 2010

States across the country made strides in energy efficiency, according to the 2010 State Energy Efficiency Scorecard released on October 13 by the nonprofit American Council for an Energy-Efficient Economy (ACEEE). Among the highlights in the fourth edition of the scorecard are: a near doubling of state energy efficiency budgets from 2007 spending levels from $2.5 billion to $4.3 billion; the adoption or active consideration by more than half the states of energy efficiency resource standards that establish long-term, fixed efficiency savings targets; and a one-year doubling of the number of states that have either adopted or have made significant progress toward the adoption of the latest energy-saving building codes for homes and commercial properties.

California retained its first place ranking for the fourth year in a row, outperforming all other states in its level of investment in energy efficiency across all sectors of its economy. Massachusetts again placed second. The four most-improved states were Utah (up 11 spots from 2009 to number 12), Arizona (up 11 spots to 18), New Mexico (up 8 spots to 22), and Alaska (up 8 spots to 37). California, Massachusetts, and Washington have implemented transportation-specific greenhouse gas reduction targets while several other states have adopted policies to encourage the creation of compact and transit-oriented communities.

The fourth edition of ACEEE's State Energy Efficiency Scorecard examines six energy efficiency policy areas: utility and public benefits programs and policies; transportation policies; building energy codes; combined heat and power; state government initiatives; and appliance efficiency standards. See the ACEEE press release, the complete report online, and the Energy Scorecard Web site.



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First Solar Power Tower on U.S. Public Lands

Interior Department Approves First Solar Power Tower on U.S. Public Lands

October 13, 2010

Photo of a large tower surrounded by square solar mirrors in the desert.

The Ivanpah solar project will rely on solar power tower technology, which employs a field of flat mirrors to concentrate the sunlight on a receiver, mounted at the top of a central tower .
Credit: BrightSource Energy

The U.S. Department of the Interior (DOI) approved on October 7 the Ivanpah Solar Electric Generating System, the first large-scale solar energy project on U.S. public lands to use "power tower" technology. Proposed by BrightSource Energy, the project could produce up to 370 megawatts of clean energy, enough to power 111,000 to 277,500 American homes. Located in San Bernardino County, California, the project is expected to generate approximately 1,100 new jobs. The DOI decision authorizes Interior's Bureau of Land Management (BLM) to offer BrightSource a right-of-way grant to use the public lands for 30 years if all rents and other conditions are met. The site is in Southern California's Mojave Desert, near the Nevada border.

The Ivanpah project uses innovative technology that, when completed, will include three solar thermal power plants. The technology employs mirror fields to focus solar energy on power tower receivers near the center of each array. Steam from solar boilers in the towers drive a turbine that generates electricity for the transmission grid. Construction of all three project phases is scheduled to be completed by the end of 2013. To lessen its environmental impact, BLM reduced the size of the project by more than 15%, from 4,073 acres to 3,471 acres; it also reduced the number of heliostats (solar mirrors) from 214,000 to 173,500.

Through the American Recovery and Reinvestment Act, renewable energy developers whose projects begin construction by the end of 2010 can apply for payments of up to 30 percent of the eligible costs of the project. Also under the Recovery Act, DOE awarded BrightSource $1.37 billion in conditional loan guarantees for this project. See the DOI press release and an fact sheet on IvanpahPDF.



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Scott's Contracting
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11.04.2010

Snake Oil Awards and Koch Industry


Dear Scotts Contracting,

Thanks for casting your vote for Koch Industries in the 2010 Snake Oil Awards. You've joined thousands of supporters in shining a spotlight on the fossil fuel industry's dirty tricks.

But it isn't enough just to crown a winner -- we need to spread the word about the vile tactics and outright deceptions of big polluters and climate deniers.

You can make that happen. Tell your friends, family and colleagues about the Snake Oil Awards: ask them to vote for Koch Industries before November 5 at midnight.

http://acp.repoweramerica.org/snakeoil-voteKoch

Thanks for standing up to the snake oil salesmen,

Dave Boundy
Campaign Manager
Repower America



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Scott's Contracting
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Earth Dance: Eco Friendly Invitation in St Louis

EarthDance:

Come join us at their party Saturday night!


PESTO FESTO!


Pesto Festo is EarthDance's premier fundraising celebration of the year and includes live music, local food, live art, a silent auction,
The EarthDance Mission Awards, and much more.

Located at the historic Savoy in Ferguson, Missouri, on Nov 6th, it is a confluence of community and an opportunity to give thanks for the year's harvest. Much of the food that will be served at Pesto Festo is even grown by EarthDance farm apprentices just 1 mile from the event!

St. Louis Earth Day's Recycling on the Go program is assisting EarthDance in making the event near zero waste. Festo-goers will dance to the tunes of the Maple Jam Band, bid on "live" art created right before their eyes, and meet this year's incredible
EarthDance Mission Award honorees!

For more details, visit www.pestofesto.org



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Scott's Contracting
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Review: Water-Conserving Showerheads

8 showerheads that combine performance and conservation.

With the release of WaterSense for showers, bathers can conserve without sacrificing performance.

Launch Slideshow


Water-Saving Showerheads


Product Review: Water-Conserving Showerheads


8 showerheads that combine performance and conservation.
Water-Saving Showerheads
8 showerheads that combine performance and conservation.
  • 600
    American Standard. The water-conserving FloWise showerhead line now includes a handshower that flows at 1.5 gpm in single-function and three-function models. The bather can set the three-function version to turbine spray, a 2.0-gpm full spray, or a combination of the two, and it includes an auto-return feature that re-sets the showerhead to the lowest flow function when the shower is turned off, says the firm. The showerhead comes in polished chrome, blackened bronze, polished brass, stainless steel, and satin nickel. 800.442.1902. www.americanstandard-us.com.
  • 600
    Delta. Designed to imitate the scallops of a seashell, the Addison Raincan showerhead is WaterSense-certified and flows at rates of 1.5 gpm and 2.0 gpm. The showerhead features H2Okinetic technology, which forms larger droplets for more coverage, the firm says. The showerhead has a 6-inch face and comes in four finishes. 800.345.3358. www.deltafaucet.com.
  • 600
    Jaclo. Pending WaterSense certification, the Leticia showerhead uses a flow regulator to maintain a constant flow rate over fluctuations in the supply pressure, says the company. The showerhead has a 3-inch face, a brass body, a swivel ball joint, and an easy-grip rubber ring for adjusting between five spray patterns: full rain, power rain, power spray, massage, and full rain massage. It comes in more than 20 finishes. 800.852.3906. www.jaclo.com.
  • 600
    Kohler. The Purist oversized showerhead flows at 1.75 gpm and meets WaterSense specifications, the firm says. The showerhead has three spray options—wide, focused, and concentrated utility spray—and it includes a pressure-balancing valve for anti-scald protection and temperature regulation. The showerhead is also available as a handshower. 800.456.4537. www.kohler.com.
  • 600
    Moen. The Envi Eco-Performance rainshower has a flow rate of 2.0 gpm and carries the WaterSense label. The 8-inch-diameter showerhead uses self-pressurizing technology to maximize spray power. It comes in chrome or brushed nickel finishes. The company has 16 other WaterSense-certified showerheads, including wall-mount, rainshower, and handshower models. 800.289.6636. www.moen.com
  • 600
    Niagara Conservation. The WaterSense-certified Earth Massage showerhead flows at rates of 1.25, 1.5, and 2.0 gpm with a pressure compensator to keep the rate from fluctuating. The showerhead has nine jet options and comes in three styles: a wall-mount, a handheld with a 72-inch hose, and the Earth Soap & Soak, which includes a pause valve to stop the water while lathering. The showerhead is available in white or chrome finishes. 800.831.8383. www.niagaraconservation.com
  • 398
    Price Pfister. The 1.5-gpm Eco-Pfriendly showerhead with Air Infusion Technology, which infuses air in the water droplets to amplify pressure, is WaterSense certified. It is available in a chrome finish. 800.422.4278. www.pricepfister.com.
  • 600
    Toto. The Lloyd high-efficiency showerhead has a maximum flow rate of 1.75 gpm and a rubber nozzle to prevent lime scale and calcium buildup, says the company. WaterSense pending, the showerhead is available with a Shape Memory Alloy mixing valve to regulate temperature changes with a coil made of nickel and titanium alloy. The showerhead comes in a variety of finishes. 888.295.8134. www.totousa.com.
Rinsing under dismal dribbles and lukewarm mists can leave bathers with persistent soap lather and a bad impression of low-flow technology. The EPA's WaterSense program seeks to rectify this problem—whether real or perceived—with its new label for showerheads, which requires units to deliver a satisfactory deluge while remaining well below the federal water restriction.
Thirty gallons of water disappear down the shower drain every day in the average household, according to the EPA, which is why the group added showerheads to its labeling program in early March. As with existing WaterSense standards for faucets and toilets, qualified showerheads not only must not exceed a maximum flow rate (2 gallons per minute, 0.5 gpm below the federal standard), but also must meet user-satisfactory pressure and coverage requirements.
"What we don't want to do is take a 2.5-gpm showerhead and put a flow restrictor in there and have it flow at 2.0 or 1.75 gpm and feel different or weak," says Mike Reffner, group product manager at Moen.
Simply choking down a showerhead can leave a weak spray or chilly dead spots; alternatively, blasting the water through smaller spray formers to increase the intensity creates a stinging sensation that is far from satisfying.
In consumer test reports, the EPA found bathers did not enjoy showerheads that spat water from a single, central jet, nor did they like a ring of drenching rain with an empty spot in the middle, so in order to earn a WaterSense label, the showerhead must pass the spray pattern criteria to ensure complete, even coverage. The standard also evaluates pressure compensation (i.e., how well the water flows at different pressures) and spray intensity (how effective the flow is for rinsing soap and shampoo). In addition, WaterSense set the maximum pressure at 80 psi to avoid needle-like sprays.
Makers have taken up the challenge, engineering larger droplets, experimenting with air induction and vacuum technology, or arranging the spray pattern in new ways, all to earn a low-flow label without the low-flow feel.
"A 1.5-gpm feels like a 2.5-gpm because the spray pattern oscillates and feels like it's enveloping you in a lot of water," says Delta representative Christiana Brenner of that manufacturer's new H2Okinetic technology, "but it's because the water droplets are slightly larger and coming at you from many different places."
"We have spent time and engineering resources to come up with solutions," says Moen's Reffner. "If you don't incorporate that kind of thinking into the product ... the efficiency is lost and instead of spending 10 minutes in the shower, you have to spend more time to rinse the shampoo out of your hair. So who wants to be frustrated by more time and really not saving anything?"
Using the mathematic Phi ratio found in organic designs such as plants, animals, and even galaxies, Moen's Biomimicry designs use nature's calculations to fit as many spray formers on the surface of the showerhead as possible for complete spray coverage.
Like traditional showerheads, WaterSense-certified units vary widely in price, from affordable to high-end. "People really don't want to spend a lot more if anything on [these] products. They want to be green, but they don't want to be told, 'Well, you have to pay X number of dollars more to save water,'" Reffner says.
The EPA says a $30 WaterSense showerhead will ideally pay for itself in roughly 14 months via water and energy savings.
And along with reengineering the products, manufacturers also are working to reverse consumer perceptions about water-conserving fixtures. "We like to call them 'high efficiency' because when people hear 'low flow,' they get a little scared and they think they're going to lose their water pressure," says Cecilia Hayward, marketing manager for Niagara Conservation. "The main challenge is educating people that low flow doesn't mean you're losing pressure; it just means you're saving water."
Evelyn Royer is assistant editor


Part 8: 1st Floor Weatherization

Part 9: See the Difference a Little White Paint Makes

Part 10: Interior Framing-Plumbing-Laundry Room

Part 11: Kitchen Framing Tip #36-Benton Rehab Project

Part 12: Water Main Repair- Benton Rehab

Part 13: Benton Rehab Project Drywall Installation and Tip: Number 1172

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