No Daddy With Deep Pockets
Regarding the ongoing debate over Hispanic labor in the market,
here in my area of coastal South Carolina, I have tried for
many years, through family, friends, and business contacts, to
hire part-time unskilled labor. No experience necessary, just a
body to tote material up the stairs, hold the other end of the
board, and maybe learn something in the process.
The fact is the Anglo kids just aren't dependable. They'd
rather party than work. Hispanic workers, however, are
dependable and honest, and the only problem is they'll work in
the heat way too long if you don't tell them to take a break.
They don't have a mommy and daddy with deep pockets to feed
them. They're just happy to find a job.
These workers are filling an employment niche nobody else
wants. Are they going to dominate the trades of the future?
Probably, but who cares? When was the last time you heard of
anybody — other than the children of builders —
actively pursuing construction as a career choice after high
Lonestar Home Improvement
Little River, S.C.
How can we, as building craftsmen who are aging, encourage our
society to bring back trade schools and a guildlike system to
train the next generation? I haven't found a young person who
wants to work with his or her hands for the last 10 years; we
Yucca Valley, Calif.
I appreciated the article "Building a Strong Cathedral Hip
Roof" (11/04), by David West, which drove home the importance
of resisting the outward thrust generated by sloping roof
members without horizontal ties. After 25 years of structural
engineering, I would say that in residential construction, roof
behavior is by far the most misunderstood concept among
contractors and framers. Without a vertical support at both
ends of a sloping member, there are outward thrusting forces
that must be considered. And collar ties near the top of
rafters will not resist — and are not intended to resist
— this thrust.
My own designs for roofs like the one shown in the article are
very similar to the design presented by Mr. West. It seemed to
be a good solution and design. The question I would pose,
however, is why should the contractor take on the time —
and, more important, the responsibility — of designing
the structure and opening himself up to potential liability? I
would have sent the drawings back to the architects and had
their engineer complete the design.
Arthur LeBrasseur, P.E.
Newton Centre, Mass.
After reading the Q&A regarding attic mold (11/04), I
thought about two other causes I have run into more than once.
One is bath fans vented directly into the attic, and the other
is a plumbing vent pipe not extended through the roof. Both
will cause the growth of mold in an attic.
More on Tandem Compressors
Years ago, I tried to double up my compressors the way Carl
Hagstrom showed (Letters, 11/04), but I had a problem with
"feedback" from one compressor into the other one and usually
ended up with one compressor running continuously. So I fitted
a cross-T with check valves on the compressor sides to prevent
backflow and ran a hose from each compressor to the T. I also
power my compressors on separate electrical circuits. I am able
to run my four roofing guns with no problem.
Stevens Point, Wis.
The article on twin water heaters (Kitchen & Bath, 10/04)
suggests that standard efficiency for domestic hot-water
heaters is around 80 percent. But according to the GAMA
directory (an independent testing agency), standard water
heaters start at about EF (energy factor) 0.49, or 49 percent
efficiency. Power-vented and oil-fired units average around EF
0.60, or 60 percent. Indirect tanks do use the connected boiler
efficiency, which can be from 80 percent up to 98 percent. And
electric versions are around EF 0.90, or 90 percent, but the
fuel cost is high, so the efficiency is moot.
I would not give your readers the impression that average
efficiency of domestic water heaters is 80 percent.
Christopher T. Trolle, P.E.
Mike Gordon, vice president of
engineering at Bradford White, a water-heater manufacturer
headquartered in Amber, Pa., responds: The efficiency ratings
of water heaters and the efficiency ratings of boilers are
determined by entirely different methods. While both test
procedures are useful and valid for comparing like types of
equipment, the ratings don't work when comparing a boiler with
a water heater.
Boilers are tested according to the DOE-prescribed annual
fuel-utilization efficiency (AFUE) procedure. AFUE measures the
thermal efficiency of the boiler operated at 140°F
supply-water temperature and 120°F return-water temperature
and subtracts the amount of heat lost through the venting
during off-cycle. Heat losses through the jacket are not
counted, since the boiler is assumed to be inside the structure
providing useful heat.
Water heaters are rated using the DOE simulated use test
(SUT). The water heater is operated for a 24-hour period with
135°F average tank temperature and 58°F cold water
inlet temperature. The SUT calls for six water draws of 10.6
gallons each at a water flow rate of 3 gpm over a six-hour
period, one draw per hour. The water heater then maintains the
135°F setpoint for 18 hours. The amount of energy provided
as hot water is divided by the amount of energy used during the
24 hours to determine the energy factor (EF). Heat lost through
the jacket and through the venting is counted as losses.
Effective January 2004, the DOE increased the minimum
efficiency level for water heaters. A 40-gallon gas model now
has a minimum EF of 0.59. However, the thermal efficiency of
the water heater typically ranges between 76 percent and 82
percent. Jacket and flue losses, as measured by the SUT,
typically range between 17 percent and 23 percent.
By contrast, a gas-fired boiler has a minimum AFUE of 80
percent. Many boilers measure around 81.5 percent to 84.0
percent thermal efficiency, with 1.5 percent to 3 percent flue
loss. As noted above, jacket losses are not counted.
The different test procedures weight the various losses
differently. To provide an accurate comparison, the
boiler/indirect water heater combination would have to be
tested more like a water heater, with the same draws and
maintained setpoint temperature. Off-cycle losses and losses
from the connecting piping combined with the higher boiler
water temperatures would reduce efficiency.
A simpler method is just to compare the thermal efficiency, as
noted in Dave Yates' article — around 76 percent to 82
percent for water heaters and a bit higher for boilers. It
would be interesting, however, to see what a boiler and
indirect water heater combination would provide using the
water-heater procedure. A big variable would be the amount of
piping between the indirect and the boiler, and whether the
piping was insulated.
WallShield Price Correction
The price given for VaproShield's
WallShield housewrap, featured in January 2005 Products, was
incorrect. The product costs 45 cents per square foot. For more
information, call 866/731-7663 or go to www.vaproshield.com. We
regret the error.