|2014 UECC Newsletter, Volume 2 February
DOE Plugs Energy Rating for Homes, Similar to MPG Rating for Cars
January 13, 2014 – 10:25 AM – by Susan Jones
(CNSNews.com) – The Energy Department on [Tuesday, January 13, 2014, rolled] out new, improved software to help Americans measure the energy efficiency of their homes.
DOE says its energy-scoring software — called the Home Energy Scoring Tool — is like a vehicle’s mile-per-gallon rating because it allows homeowners to compare the energy performance of their homes to other homes nationwide. It also provides homeowners with suggestions for improving their homes’ efficiency.
The software is part of the government’s effort to reduce the nation’s energy consumption; but it’s also billed as a way to keep home-retrofitting going, at a time when stimulus funds for weather-proofing have run out.
The Home Energy Scoring Tool “can be a powerful motivator in getting homeowners to make energy efficiency improvements,” DOE says. “It’s also a great way to help trained workers enter the private sector energy improvement market as funding for weatherization efforts decline.”
DOE says its Home Energy Score is useful if you are a homeowner looking to renovate or remodel your home, lower your utility bills, improve the comfort of your home, or reduce your energy usage. Moreover, “the score serves as an official way to document these improvements and thereby enhance your home’s appeal when you’re ready to sell.”
Right now, getting your home scored is voluntary.
To produce a Home Energy Score, a trained, “qualified assessor” comes to your home — for a fee — and collects approximately 40 pieces of data about the home’s “envelope” (e.g., walls, windows, heating and cooling systems) during an hour-long walk-through.
Based on the home’s characteristics, the DOE software estimates the home’s annual energy use, assuming “typical homeowner behavior.” The software then converts the estimated energy use into a score, based on a 10-point scale (10 being the most energy-efficient). The 1-10 scale accounts for differences in weather conditions by using the zip code to assign the house to one of more than 1,000 weather stations.
In addition to showing the home’s current energy efficiency — or inefficiency — the score also shows where a home would rank if all of the energy-saving improvements identified during the home walk-through were made. That may prompt some homeowners to buy new windows or doors, for example, boosting the market for home retro-fitters.
DOE recommends getting a Home Energy Score “as soon as the program becomes available in your area.” The program launched in 2012, and at this time, only single-family homes and townhouses can be scored.
The scoring is available only through DOE’s participating partners, which include state and local governments, utilities, and non-profits. DOE does not determine how much an assessor charges to score a house. “It will depend on what the local market supports.” But DOE says its partners “have indicated plans to charge between $25 and $125 for the Home Energy Score.”
And yes, the size of the home matters because larger homes use more energy.
The Home Energy Score and the associated report is generated through DOE/Lawrence Berkeley National Laboratory software. The 2014 version of DOE’s Home Energy Scoring Tool will be introduced at a webinar on Tuesday. So far, DOE says more than 8,500 homes have been scored by the Energy Department’s growing network of more than 25 partners and 175 qualified assessors.
See more at: http://cnsnews.com/news/article/susan-jones/doe-plugs-energy-rating-homes-similar-mpg-rating-cars#!
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UC Davis Extension, the continuing and professional education division of UC Davis, has been an internationally recognized leader in educational outreach for individuals, organizations and communities for more than 50 years. With more than 50,000 annual enrollments in classroom and online university-level courses, UC Davis Extension serves lifelong learners in the growing Sacramento region, all 50 states and more than 100 countries.
|Duct Leakage Testing
Posted on Feb 19 2010 by Martin Holladay, GBA AdvisorTesting Ducts with a Duct Blaster.
A Duct Blaster can be connected to a residential duct system at a large return-air grille or near the furnace. Once the duct system has been pressurized or depressurized to 25 Pascals, the air flow of the fan gives an indication of the duct system’s leakiness.For years, Americans who would never put up with leaky plumbing pipes have been willing to accept leaky ducts. While water damage is hard to ignore, the damage caused by leaky ducts is more subtle. Yet leaky ducts not only waste huge amounts of energy — they can also lead to comfort complaints, moisture problems, mold,and rot. Most green certification programs require builders to pay attention to duct tightness. Now that duct testing requirements are starting to appear in some local building codes, more and more builders are asking questions about the ins and outs of duct leakage testing.
If you’ve never had to worry about duct tightness before, you may want to read the “Forced Air” section of the GBA Encyclopedia.Most green builders already know their duct basics:
- Duct leaks are very common; in many homes, duct leaks are responsible for significant energy losses.
- For ducts located in an unconditioned attic, any leaks in the supply system tend to depressurize a house, while return-system leaks tend pressurize a house. Either condition can cause problems.
- Duct leaks outside of a home’s thermal envelope waste more energy than duct leaks inside a home’s thermal envelope.
- Even if ducts are located inside of a home’s thermal envelope, duct leaks can still connect to the outdoors. For example, supply system leaks in a ceiling between the first and second floors of a two-story home can pressurize the joist bay, forcing conditioned air outdoors through cracks in the rim joist area.
- It’s much easier to seal duct seams during new construction than in an existing house.
Characteristics of a good duct system
A good duct system:
- Has been designed to meet ACCA Manual D requirements, with each duct carefully sized to provide the airflow needed to meet room-by-room heat loss and heat gain calculations;
- Has been designed so that duct runs are as short and straight as possible;
- Does not use building cavities (for example, panned joists or stud bays) as ducts;
- Locates all ducts within the home’s thermal envelope;
- Includes ducts or air paths that allow return air to flow back to the air handler from every room with a supply register;
- Has all seams sealed with duct mastic; and
- Has been tested for duct leakage.
Code requirements for duct sealing
Although model codes have included duct-sealing requirements for years, enforcement has been spotty or nonexistent. For example, a 2001 study of 80 new homes in Fort Collins, Colorado, found that the number of homes that complied with code duct-tightness requirements was zero. Astonishingly, the average duct leakage in the studied homes was 75% of total system airflow.
Another 2001 study found that Massachusetts Energy Code requirements for duct sealing were widely ignored. Researchers who inspected 186 new Massachusetts homes reported that “serious problems were found in the quality of duct sealing in about 80% of these houses.”
The 2006 International Residential Code (IRC) requires (in section N1103.2.2) that “Ducts, air handlers, filter boxes and building cavities used as ducts shall be sealed.” Elsewhere, in section M1601.3.1, the IRC requires that “Joints of duct systems shall be made substantially airtight by means of tapes, mastics, gasketing or other approved closure systems.” Hardware-store duct tape is not an approved tape.
Builders will soon need to get up to speed on duct testing, since recent code changes will require that all residential duct systems except those that are located entirely within a home’s thermal envelope will need to be tested for leakage.
If some ducts are outside of the thermal envelope, the 2009 IRC will require duct tightness to be verified by either a “rough-in test” or a “post-construction test.” Either test requires all register boots to be taped or otherwise sealed during the test.
The threshold for the rough-in test is total duct system leakage of 6 cfm per 100 square feet of conditioned floor area (when tested at 25 Pascals). If the air handler is not installed, the total leakage must be less than or equal to 4 cfm per 100 square feet of conditioned floor area.
The threshold for the post-construction test is duct system leakage to outdoors of 8 cubic feet per minute (cfm) per 100 square feet of conditioned floor area when tested at 25 Pascals. Alternatively, total duct system leakage must be less than or equal to 12 cfm per 100 square feet of conditioned floor area.
Testing for duct leakage
Energy auditors have developed several methods for testing duct tightness. These methods vary from fast and dirty to time-consuming and accurate. Builders interested in tight duct systems should familiarize themselves with the range of available duct testing options:
- Using only a blower door;
- Using a blower door and a pressure pan;
- Using a Duct Blaster;
- Using a Duct Blaster and a blower door; and
- Using a theatrical fog machine.
A fast, rough test
In Residential Energy, authors John Krigger and Chris Dorsi describe a quick (but not particularly accurate) method for estimating duct leakage: “The simplest way to estimate duct leakage in cfm50 is to perform two blower-door tests: one with the home’s registers sealed with paper and tape, and one without. Subtracting the two readings provides a very rough estimate of total duct leakage.”
Because of the inherent inaccuracies of this method, it is rarely used.
The pressure-pan method
A pressure pan is a diagnostic tool consisting of a metal pan (similar to a cake pan) connected by a tube to a manometer (that is, a pressure gauge). The device is used to temporarily cover a forced-air register to measure the pressure exerted on the pan by a blower door.
To conduct a pressure-pan test, you need a pressure pan and a blower door. Here are the basic steps:
- A blower door is used to depressurize the home to 50 Pascals.
- The air handler fan is turned off.
- The tester then blocks each register (one at a time) with the pressure pan and records the reading of the pressure-pan manometer. (The manometer shows the pressure created by air leaking into the duct system.) Typical readings of the duct system pressure (with respect to the house pressure) range from 1 Pascal to 45 Pascals.
- The higher the reading, the leakier the duct run.
In a Home Energy magazine article, “Pressure Pans: New Uses and Old Fundamentals” (January/February 1998), Jeffrey Siegel and Bruce Manclark explain, “A duct system at 0 Pa is entirely within the pressure envelope of the house and has no leaks to the outdoors. A system approaching 50 Pa is essentially outside the pressure envelope, meaning that it has catastrophic leakage to the outdoors.”
It’s important to note that the pressure pan readings don’t really provide measurements of duct leakage; rather, they provide a method for comparing the relative leakiness of several duct runs in the same home.
That hasn’t prevented some energy experts from recommending thresholds for pressure-pan measurements. According to Krigger and Dorsi, “Registers of newly installed ducts should read less than 0.5 Pascals and existing duct registers should read less than 1 Pascal after being sealed.”
In “Duct Improvement in the Northwest,” (Home Energy magazine, January/February 1996), author Ted Haskell provides this advice for existing homes: “Houses with fewer than three pressure-pan readings above 2 Pa are unlikely to be cost-effective to seal.”
The pressure-pan test has several virtues. First, it is fast — especially when an auditor is already conducting a blower-door test. Second, it identifies which of a home’s duct runs are the leakiest, so that a contractor knows where to focus duct-sealing efforts.
However, many experts warn contractors not to jump to conclusions based only on the pressure readings recorded during a pressure-pan test.
As with many other diagnostic tests — infrared scanners come to mind — it takes an experienced auditor to interpret the results of a pressure-pan test. “Pressure-pan readings are difficult to interpret, and the same number can reflect quite different leakage rates in different houses,” wrote Siegel and Manclark. “The disadvantage of the pressure-pan test is that it is more art than science. The one exception is when homes have very similar duct geometry and installation, as is the case with manufactured homes or identical homes in a subdivision.”
The Duct Blaster test
The most common method for testing the tightness of a duct system is the duct-blower test (also known as the Duct Blaster test). A duct blower resembles a miniature blower door; the most common brand is the Duct Blaster, manufactured by the Energy Conservatory in Minneapolis.
Here are the steps:
- All supply registers and return grilles are sealed with polyethylene and tape.
- The air handler fan is turned off.
- The Duct Blaster is set up and attached to the duct system (near the furnace or at a large return-air grille).
- The manometer’s reference probe is inserted into the air handler plenum.
- The Duct Blaster is turned on to pressurize the duct system to 25 Pascals (a pressure which represents typical operating pressures for forced-air systems). The airflow through the Duct Blaster fan (which is displayed in cfm on the Duct Blaster’s manometer) equals the flow escaping through leaks in the duct system. The results are reported as “cfm @ 25 Pascals” or “cfm25.”
Although this test reveals the leakiness of the duct system, it doesn’t tell the tester where the leaks are located; nor does it quantify what percentage of the leakage is leakage to the outdoors. Moreover, it doesn’t tell us how much a duct system leaks under normal operating conditions — conditions which may differ from Duct Blaster pressurization to 25 Pascals.
According to Krigger and Dorsi, “Leakage ranges from less than 50 cfm25 for a fairly tight duct system to more than 500 cfm25 for a very leaky duct system.”
Builders hoping to comply with the 2009 IRC duct-testing requirements will need Duct Blaster test results showing total duct leakage equal to or less than either 6 or 12 cfm (depending on whether it is a rough-in test or a post-construction test) per 100 square feet of conditioned floor area.
Using a Duct Blaster to test duct leakage to the outdoors
Energy auditors often want to know how much of a duct system’s leakage is leakage to the outdoors. Leakage to the outdoors can occur when air escapes through a leak in a duct installed in an unconditioned attic. It is also possible for a portion of the leakage through a duct that seems to be within a home’s thermal envelope to turn out to be leakage to the outdoors, since such leaks can pressurize joist bays, forcing conditioned air through rim-joist cracks.
One quick-and-dirty indication that a duct system has sizable leaks to the outdoors occurs when an auditor notices obvious air flow from forced-air registers during a blower-door test. Since the house is strongly depressurized, the airflow represents exterior air; and since it’s coming from the duct system, the airflow is a sign that the duct system has leaks that connect with the outdoors.
To determine how much duct leakage is leakage to the outdoors, a tester needs a blower door and a Duct Blaster. Here are the steps:
- A blower door is set up in an entry door.
- All supply registers and return grilles are sealed with polyethylene and tape.
- The air handler fan is turned off.
- A pressure tap is temporarily installed in the duct system to measure the pressure of the duct system with respect to the house.
- Another manometer or tube is set up to measure the outside pressure with respect to the ducts.
- The Duct Blaster is set up and attached to the duct system (usually near the furnace).
- The blower door is turned on and the house is pressurized to 25 Pascals.
- The Duct Blaster is turned on to pressurize the duct system; the Duct Blaster fan is adjusted until there is no pressure difference between the ducts and the house. At that point, all of the air going through the Duct Blaster is going outdoors through duct leaks. The airflow indicated on the Duct Blaster’s manometer (in cfm) quantifies that duct leakage to the outdoors.
Obviously, duct leaks to the outdoors represent heating or cooling energy that is lost.
Testing ducts with a fog machine
To find the location of duct leaks, nothing beats a theatrical fog machine.
Gary Nelson, the founder of the Energy Conservatory, describes the method: “You tape up all the registers and you pressurize the ducts. Then you introduce fog into the Duct Blaster — you aim the fog nozzle at the fan blades, without letting the fog get drawn into the vent holes in the motor, and you watch where the fog pours out. Sometimes you may be working with an HVAC contractor who says, ‘This is a good duct system. This is the way we have always done it. This is normal.’ Well, when you show them the fog coming out of the leaks, they shut up really fast.”
For more information on this technique, see “Pinpointing Leaks With a Fog Machine.”
Sealing the leaks that matter most
The mechanics of duct sealing are beyond the scope of this article, but it’s worth noting:
- Duct seams need to be mechanically fastened (using sheet-metal screws for galvanized ducts and compression straps for flex duct) before being sealed.
- For sealing most duct leaks, mastic works better than any tape. (Bruce Manclark calls tape “the band-aid of the HVAC industry.”)
- Mastic is messy, so wear old clothes when you apply it.
- Install mastic “as thick as a nickel.”
- Cracks or seams wider than 1/8 inch need to be repaired with fiberglass mesh as well as mastic.
It’s important to prioritize duct-sealing efforts so that the most important leaks are addressed first. As Philip Fairey, the deputy director of the Florida Solar Energy Center, likes to say, “Duct leakage is like real estate — it’s all about location, location, location.”
- In existing homes, it’s surprisingly common to find disconnected duct components — takeoffs that are coming loose from ducts or ducts disconnected from register boots — in attics or basements. Such disconnected ducts can waste tremendous amounts of energy.
- Leaks connected to the outdoors are more important than leaks inside the home’s thermal envelope.
- Holes that see high pressures — in other words, holes near the air handler — are more important than distant holes that see relatively low pressures. Bruce Manclark’s mantra is, “Follow the pressure: boots for show, plenums for dough.”
- Most furnaces have many bad leaks close to the blower fan, including leaks in the furnace jacket seams, leaks between the furnace and the plenums, and leaks between the duct takeoffs and the plenums.
- Supply system leaks waste more energy than return system leaks.
For more information on sealing duct leaks, see Duct Tape and Mastic.
Measuring air flow
Anyone who commissions a duct system needs to learn how to measure airflow at registers and grilles. Manufacturers offer an array of accurate (and expensive) instruments to measure airflow. However, builders who need to troubleshoot problems may be interested in several low-cost methods of measuring airflow:
- The August 2002 issue of Energy Design Update describes how to build a homemade flow hood using a cardboard box and a $90 digital anemometer.
- Two Lawrence Berkeley National Laboratory engineers, Iain Walker and Craig Wray, have written a paper describing a method of measuring airflow with a “calibrated” laundry basket and a manometer.
- Terry Brennan promotes a method of measuring bath exhaust fan airflow with a cardboard box and a credit card.
- The easiest way to measure airflow at a supply register is the garbage bag technique developed by Don Fugler of the Canada Mortgage and Housing Corporation.
Duct testing is coming to your job site — soon
For decades, plumbers have routinely tested newly installed supply and drain pipes. Meanwhile, most HVAC contractors have gotten away with leaky, untested duct systems. However, the tide is now turning. In the future, testing residential duct systems for leaks will become a routine part of residential construction.
|Should Home Builders Pay the Energy Bills?
Posted on Feb 19 2014 by Allison A. Bailes III, PhD, GBA AdvisorRick Chitwood suggests that as one of seven measures to transform the new home construction industry.
Three questions have been nagging at Rick Chitwood over the past 5 or 6 years. First, why is the HVAC industry in California, where he lives and works, so pathetic?
Second, why have California’s strict energy standards, which have been in effect since 1978, not corrected the problem?
Third, how is it that he, who came to the HVAC business through a nontraditional route, has become a leader in the industry?
The origin of a radical idea
This week at the Forum on Dry Climate Home Performance, Rick gave a short talk on the difference between what the models show and what has actually been achieved, and he concluded by suggesting seven measures which he believes should be required in California. The measures originated from some deep thinking he did upon re-reading Leverage Points: Places to Intervene in a System by Donella Meadows while he was on vacation last year. In that paper, Meadows argues that your best bet at achieving transformation is to change the paradigm. The least effective avenue is through standards and codes.
The best way to create a system that works well, Rick told me, is not to adopt the wrong paradigms in the first place. “That was me. I never learned the conventional HVAC approach. I didn’t learn the bad habits.”
Four steps to transformation
As Rick thought about those nagging questions, he realized that four things needed to happen.
1. We have to pay attention to human nature. People will take the easier path when there are no negative consequences for doing so.
2. Move from energy models to reality. At the Dry Climate Forum this week, “modeling” has been taboo. It’s referred to here as “the M word,” and speakers who talk about it risk not being invited back to the conference. These folks are into measured results.
3. Take the narrative away from the box manufacturers. Most installed HVAC systems perform like crap because HVAC companies follow the lead of the manufacturers, who just push the heating and cooling equipment and ignore the distribution side and commissioning.
4. Train the workforce. A great many of the installers and technicians are woefully undertrained in proper installation of HVAC systems.
Rick Chitwood’s proposed seven mandatory measures
Rick works in California, which has a lot of requirements due to their building code, Title 24. One of those requirements is for HERS raters to do Title 24 compliance inspections and verification, and most builders, according to Rick, would like to eliminate the cost of that third-party verification.
Here’s his seven-step plan to accomplish that objective and, at the same time, transform the construction industry in California.
1. When modeling, downrate HVAC performance 50%. You can get credit for the other 50% by measuring full delivered performance once the system is installed.
2. Post the energy model results where everyone can see them. Energy compliance documentation includes predicted energy use in each category (heating, cooling, domestic hot water, baseload) in dollars (based on site energy use and the current rate structure) and these predictions must be posted on the electrical panel in every new home.
3. Publish energy modeling results and identify stakeholders. Place predictions (numbers from the computer models) for every new home in the registry and list the builder, energy consultant, HVAC contractor, and insulation/air sealing contractor. Make this information public.
4. Assure quality and hold stakeholders accountable. Installers should test the delivered performance of their work on every system and record the results to the registry. Eliminate all HERS verification. Have the California Energy Commission do quality assurance on 1 in 100 systems. If cheating or errors occur every system installed in the last year must be tested — at the contractor’s expense.
5. Register actual disaggregated energy usage for every house every year. Compare actual with predicted.
6. Exempt home builder from Title 24 requirements if builder claims net zero energy and registers the actual performance every year. Registry is public info and home is connected to the builder, energy consultant, HVAC contractor, and insulation/air sealing contractor.
7. Every builder pays the utility bills on every home he builds for the first three years of occupancy.
Imagine home builders paying the energy bills
I think the last of his seven measures has the power to reconstruct the construction industry. It is absolutely brilliant. I don’t know how much of a chance he has of getting this adopted, but wow, what a change it would bring if he’s successful. In California, it really could work because the builders would get some benefits by doing away with the current third-party verification system.
Just imagine how energy efficient new homes would become if builders were on the hook for the first three years of energy bills! It wouldn’t take them long to get all the air sealing, duct sealing, HVAC location, and insulation effectiveness right.
Can this work outside California? Maybe. It may sound onerous to home builders initially because they’d see it as another cost they’re asked to bear. But I think the good ones would jump on it.
In fact, it could even become something that builders do voluntarily as a sales tool. They probably wouldn’t do a full three years in that case, but home buyers would certainly take notice of a home that comes with the first year’s energy bills covered by the builder. It’s really the next logical step from guaranteed energy bills, which some companies offer.
What do you think?
|Sealing Ducts: What’s Better, Tape or Mastic?
Posted on Aug 6 2010 by Martin Holladay, GBA AdvisorMost residential duct systems have numerous leaks that waste energy and lead to room-to-room pressure imbalances. Unfortunately, though, few building inspectors outside of California bother to enforce existing code requirements that residential duct seams be sealed with mastic or high-quality duct tape.Most model codes, including the International Residential Code (IRC), include duct tightness provisions:
- The 2006 IRC section N1103.2.2 requires that “Ducts, air handlers, filter boxes and building cavities used as ducts shall be sealed,” while IRC section M1601.3.1 requires that “Joints of duct systems shall be made substantially airtight by means of tapes, mastics, gasketing or other approved closure systems.” Hardware-store duct tape is not an approved tape.
- Section 403.2.2 of the 2004 International Energy Conservation Code (IECC) requires that “All ducts, air handlers, filter boxes, and building cavities used as ducts shall be sealed.”
To learn how to test residential duct systems for leaks, see Duct Leakage Testing.
All about mastic
Most energy-conscious builders seal duct joints with mastic. Mastic is a gooey, non-hardening material with a consistency between mayonnaise and smooth peanut butter. Duct joints should always be secured with #8 sheet-metal screws before seams are sealed with mastic.
Sealing duct seams is messy work, so wear old clothes. The mastic is spread over duct seams with a disposable paintbrush, putty knife, or your fingers. (If you spread mastic with your fingers, wear rubber gloves.)
Gaps in ductwork or plenums that are over 1/16 or 1/8 inch wide can be sealed with mastic as long as the gap is first reinforced with fiberglass mesh tape. If you’re using mastic to seal seams in fiberglass board ductwork, use fiberglass mesh tape for all joints.
Sources of mastic
Manufacturers of mastic include: Hardcast (Versi-Grip 181 mastic), McGill AirSeal (Uni-Mastic 181), Polymer Adhesives (AirSeal #22), RCD Corporation (#6 Mastic), and ITW/TACC (Glenkote mastic).
Among the distributors of AirSeal #22 mastic is AM Conservation Group.
All about duct tape
Since common hardware-store duct tape — technically known as cloth-backed rubber-adhesive duct tape — fails quickly when used on ducts, most energy-conscious builders seal duct joints with mastic. Although mastic works well on galvanized steel ductwork, it has its disadvantages: it is messy to apply and awkward to use on clamped flex duct joints.
According to section 503.3.3.4.3 of the International Energy Conservation Code (IECC), any tape used on duct board or flex duct must be labeled in accordance with UL 181A or 181B. In most regions of the U.S., however, local inspectors have little or no interest in the leakiness of residential ducts, and duct tape labels are rarely checked for UL compliance.
“I’ve been to wholesale distributors in Ohio, and I don’t see them displaying anything with UL markings,” says Mark Pulawski, former cloth tape market manager for Intertape Polymer Group, a duct tape manufacturer in West Bradenton, Florida. “When I ask them, ‘Where are your UL products?’ they say, ‘We don’t sell any of those.’ They hold up a roll of [cloth] duct tape, and they say, ‘This is what the guys use.’”
Does UL 181 duct tape perform any better?
In some areas, however, building inspectors insist that duct tapes sport a UL 181 label. Yet the UL 181B standard alone is no guarantee of long-term tape performance. “The UL 181 listing is more of a smoke-and-flame listing,” says Bob Davis, an energy consultant for Ecotope in Seattle. “The testing doesn’t have much to do with whether it will work as a duct sealant.”
At least four different types of tape have met the UL 181B standard, including some cloth-backed rubber-adhesive duct tapes, foil-backed tapes with acrylic adhesive, oriented polypropylene (OPP) tapes, and foil-backed butyl tapes. Unfortunately, according to tests performed at Lawrence Berkeley National Laboratory by Max Sherman and Iain Walker, a UL 181 listing is no guarantee that a tape will last any longer than unlisted cloth duct tape.
“In California, the duct-tape industry wanted the code to approve the use of UL 181-listed products,” says Walker. “But in our lab tests we have found that the UL 181 products fail. Just because it is UL 181 listed does not mean that it performs any better than non-UL 181 listed products. The listed tapes may be of a higher quality — the mechanical properties of the tape are better — but they are not any better in terms of longevity at high temperature. Under those conditions the UL 181 tapes failed as well as the non-UL 181 tapes.”
More important than a tape’s UL 181 label is the material category into which it falls. At least two new types of duct tape — butyl duct tape and oriented polypropylene (or OPP) duct tape — may offer better performance than cloth duct tape, without the messiness of mastic.
Oriented polypropylene tape
For sealing the inner core of flex duct to metal collars, as well as to repair the outer jacket of flex duct, many contractors have begun using oriented polypropylene (OPP) tape. OPP tape is a film-backed (as opposed to cloth-backed) tape resembling packing tape. (Housewrap tape is a type of OPP tape.) The tape has a smooth backing and an acrylic adhesive, said to be more tenacious than rubber adhesive. The backing can be manufactured in a variety of colors, including a shiny “metallized” plastic finish. “In new construction in California, we’re seeing more and more contractors using OPP tape and a clamp to seal the core of the flex duct to a metal collar,” says Walker.
At least three manufacturers make UL 181B-FX listed polypropylene duct tape: Intertape Polymer Group (manufacturer of AC698 tape), Shurtape Technologies (manufacturer of DC-181 tape), and Berry Plastics (manufacturer of FlexFix tape).
Manufacturers of OPP tape take pains to distinguish their product from the gray stuff. Although their DC-181 is a tape designed for use on ducts, Mark Hooks, a product manager at Shurtape Technologies, insists that “it’s not a duct tape.”
As long as joints sealed with OPP tape are clamped, it will probably perform better than cloth duct tape.
Butyl duct tape
Foil-backed butyl tape performs much better than cloth duct tape, although it isn’t cheap.
Hardcast, the manufacturer of Versi-Grip 181 duct mastic, sells several types of butyl duct tape; one of them, Foil-Grip 1402, has a UL 181B listing.
Foil-Grip 1402 consists of 12 mils of butyl adhesive (similar to the adhesive used in some flexible window flashings) with a 2-mil aluminum-foil top layer. Hardcast recommends Foil-Grip butyl tape for use with galvanized steel duct, duct board, or flex duct. The manufacturer claims that Foil-Grip 1402 is rugged enough to use outdoors or below grade.
Berry Plastics sells a butyl-adhesive duct tape under two different brands (Nashua and Polyken). Nashua 558CA is basically the same product as Polyken 558CA. The tape consists of a butyl adhesive on a polyethylene-coated cloth backing; it has a UL 181 BFX listing for use with flex duct.
Like OPP tape manufacturers, butyl tape manufacturers want to differentiate their product from duct tape. “We don’t like to use the word ‘tape,’” says David Barnes, a technical service representative at Hardcast. “We’re trying to overcome all of the perceptions associated with duct tape.”
Butyl tapes have fared well in the Lawrence Berkeley tests. “The butyl tapes come with a metal foil backing as opposed to the cloth backing,” says Walker. “The cloth-backed tapes are the ones we see shrinking and failing. The butyl tapes have much more adhesive on them, so they will take longer to dry out and will stay flexible longer. In our testing we’ve done several different orientations over the years, and we haven’t found any failures in the butyl tape.”
Choosing between tape and mastic
Since all duct-sealing products, including mastic and all types of duct tape, have disadvantages, deciding on the best duct-sealing strategy is tricky. Chuck Murray, an Energy Specialist with the Washington State University Energy Program, sees no reason to abandon mastic. “I haven’t seen a tape yet that I like for use in a crawl space,” says Murray. “But we continue to monitor the situation.”
One of mastic’s chief advantages is that, unlike some tapes, it performs well without clamping. Yet mastic will not prevent a joint from opening up. “Mastic is not a mechanical fastener — you still need sheet-metal screws, and scrap metal or fiberglass drywall mesh for big holes,” notes Davis. “You need to be sure that everything will hold together on its own merits. But, unlike with tapes, you don’t have to worry about whether the surfaces are clean.”
Most installers don’t bother to clean their joints before applying a sealant, and Davis feels that mastic holds up better under the circumstances. Yet mastic manufacturers, like duct tape manufacturers, generally require joints to be clean. “You need to clean the joint with soap and water and a rag,” says David Barnes from Hardcast. “The same surface prep is required no matter which sealing system is used.”
High quality duct tape — not mastic — should be used to seal holes in a furnace or air handler. As energy expert Bruce Harley notes, “Mastic would render the cabinet unserviceable.”
Making good duct joints
Here are some tips for creating durable, airtight duct seams:
- Duct seams need to be mechanically fastened (using sheet-metal screws for galvanized ducts and compression straps for flex duct) before being sealed.
- To secure seams in round galvanized ducts up to 12 inches in diameter, use at least three #8 screws per joint. To secure ducts over 12 inches in diameter, use five screws per joint.
- For securing joints in rectangular galvanized duct, use at least one screw per side.
- In most locations, mastic is preferable to tape.
- Mastic is messy, so wear old clothes when you apply it.
- Install mastic “as thick as a nickel.”
- Cracks or seams wider than 1/16 or 1/8 inch need to be repaired with fiberglass mesh as well as mastic.
- Don’t forget to seal collar connections between plenums and duct take-offs.
Sealing joints in flex duct
Flex duct sections are usually connected with a beaded metal sleeve or coupling. Here’s the procedure for sealing flex-duct connections:
- The duct boot or coupling should be inserted at least 2 inches into the end of the duct. The fitting should be attached to the inner sleeve of the flex duct with a drawband (clamp) or #8 screws.
- Seal the joint between the inner section of duct and the fitting with high-quality duct tape or mastic.
- Seal the exterior vapor-barrier sleeve with a drawband and tape.
What are the Hot Markets for 2014?Overall the general predictions by leading economic authorities in construction call for modest increases in overall spending in 2014.The construction forecast by McGraw Hill in general presents a 9% increase in construction starts for 2014. Single family housing is expected to grow 24% in 2014 bringing housing starts to 785,000 while multifamily housing starts will continue to improve this year, reaching the 365,000 starts. The commercial sector should experience a modest increase improving to 568 million square feet- warehouses and hotels will lead this commercial sector. Institutional buildings are expected to increase by 7% this year to 275 million square feet. Manufacturing building (particularly high-tech) are expected an increase about 8% in terms of square footage and dollars. Public works and utilities will likely see a reduction of 5% in 2014, mostly in part by government restraint and economic challenges on public works. The electric (power) sector is expected to drop 33% during 2014 due to surplus generating capacity and the switch to natural gas power plants. Highway and bridge construction is
expected to increase by 12% while environmental public works, will increase 8% in 2014. “We see 2014 as another year of measured expansion for the construction industry,” said Robert Murray, MHC’s vice president of Economic Affairs at McGraw Hill
Construction.“We will see 10 to 15 percent improvement in private residential construction and about a 10 percent increase in private non-residential work in 2014,” says Ken Simonson, chief economist for Associated General Contractors of America (AGC).”We will also see a one to five percent decrease in public construction projects, but overall we expect to see a five to 10 percent total gain in 2014 over 2013.”As the economy continues to stabilize, non-residential construction will grow, spurred along by declining office and retail vacancies as well as growing commercial property values. The American Institute of Architects (AIA) predicts that spending will increase 5.8% in 2014 and 8% in 2015.“The 2014 picture bears some similarity to what took place during 2013, with single-family housing providing much of the upward push; multifamily housing showing a slower yet still healthy rate of growth after four years of expansion; and commercial building gradually ascending from low levels,” Bernard Markstein, chief economist for Reed Construction Data said. “One change that’s expected for 2014 is that institutional building will no longer be pulling down nonresidential building and total construction.”FMI predicts moderate growth of 7% for 2014 construction-put-in-place, reaching an estimated $977B from the anticipated $909.6B predicted through 2013.
Nonresidential building activity is expected to increase by 5.8 percent in 2014, according to the American Institute of Architects’ (AIA) semi-annual Consensus Construction Forecast. A stabilizing economy signals a significant improvement in the construction industry, which has been recovering slowly yet steadily over the last two years, AIA Chief Economist Kermit Baker, Hon. AIA, said in a statement. “At a more granular level,” he added, “the surging housing market, growing commercial property values, and declining office and retail vacancies are all contributing to what is expected to amount to a much greater spending on nonresidential building projects.”
Looming concerns for 2014 include rising interest rates, an uncertain economy causing owners and developers to delay projects, shortage of skilled labor, project financing difficulties, and rising costs (Obamacare, liability insurance, rents and new technology investments). “Factors such as the standoffs in Washington, uncertainty in the European economy, and still-tight lending have muted construction growth coming out of the recession, said Bernard Markstein, chief economist for Reed Construction Data, during the “2014 Outlook: Emerging Opportunities for Construction” webinar. “Until these are resolved, there will be uncertainty,” he said. “The growth in construction is barely acceptable.”
New Kitchen Exhaust Reference Guide Available
The new Kitchen Exhaust Reference Guide is now available; click here for more information.
Homes shall meet this Item. Alternatively, the prescriptive duct sizing requirements in Table 5.3 of ASHRAE 62.2-2010 are permitted to be used for kitchen exhaust fans based upon the rated airflow of the fan at 0.25 IWC. If the rated airflow is unknown, ≥ 6 in. smooth duct shall be used, with a rectangular to round duct transition as needed. Guidance to assist partners with these alternatives is available at www.energystar.gov/newhomesresources. As an alternative to Item 8.1, homes that are PHIUS+ certified are permitted to use a continuous kitchen exhaust rate of 25 CFM per 2009 IRC Table M1507.3.
|Senate Bipartisan Energy Legislation to Include SAVE ActSenators Jeanne Shaheen (D-NH) and Rob Portman (R-OH) announced energy efficiency legislation will be reintroduced shortly.
The legislation will include the SAVE Act. The SAVE Act is co-sponsored by Senators Michael Bennet (D-CO) and Johnny Isakson (R-GA), would allow a home’s expected energy cost savings to be included when determining the value and affordability of the property. The proposed legislation recognizes the RESNET Home Energy Rating standards for calculating savings.
Shaheen, who has co-sponsored the legislation (S. 1392) with Portman, told the Senate Energy and Natural Resources Committee’s Energy Subcommittee that the bill had a “great chance” of becoming law due to bipartisan support in both chambers. Portman said Senate action could be expected on the measure possibly in the next month and that formal reintroduction of the bill would likely come the week of Feb. 24.
On the House side the House Republican leadership is reported interested in similar bipartisan legislation (H.R. 2126) in that chamber, sponsored by Representatives Peter Welch (D-VT) and David McKinley (R-WV). The House bill passed the Energy and Commerce Committee by voice vote January 28, 2014.
The 2014 RESNET Building Performance Conference will have a breakout session dedicated to the SAVE Act. There will also be a track on policy and program issues.
Catch the Power of Performance. Register for the 2014 RESNET Conference today!