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Slam dunk a two point
energy swish
Copyright © 2009 by Dave Yates, all rights
reserved, republished with permission,
dave.yates@fwbehler.com
Imagine you live in a home with no insulation,
single-pane glass windows and solid wood doors: the kind of home
many inner-city and country folk live in that was built prior to
1960. Your fuel bills have been keeping you in the poor house -
literally. You're aware that you could be upgrading your home's
energy envelope and reducing energy lost by adding insulation in
the attic, and installing new windows and new doors - the
low-hanging fruit on the energy-loss tree. But is that the best
first investment you can make when putting your home on an
energy diet, or would a new heating system be the wiser place to
begin?
Your
imaginary house is a two-story, 2,500-sq.ft. home with
single-pane clear-glass wood frame windows that makeup 20% of
the walls' square-footage, including two 21-sq.ft. exterior
solid-wood doors. It's an older home, so we'll set the
infiltration in our RHVAC Elite Software program to “poor.” The
home will be in SEPA with design-day temperature set for 10°F.
Heat loss equals 162,611 Btus per hour. Natural gas prices per
Ccf (100 cubic ft.) were $1.80 the previous year, but are now
$2.34 - your 12-month budget plan went from $542 to $704. You've
got to do something to cut those costs, other than setting the
thermostat to sub-arctic discomfort levels below last winter's
65°F indoor chill. You're ready to call in the contractors. You
have budgeted $12,000 to spend on upgrades for your home.
So
begins the parade of contractors. Ironically, every one of them
will take the time to do a heat loss/gain
calculation and project how much you will reduce energy
consumption. (I also believe in Santa, the Easter Bunny and the
Tooth Fairy!) First up are the insulation, window and door
contractors who each do their best to sell you on the notion
that their products will give you the best bang for your buck.
The attic insulator's report shows a drop in heat loss to
115,315 Btus. If you hire them to install R-19 fiberglass batts,
and if you toss in new windows and doors, your adjusted
heat-loss total will be 92,653 Btus. The gas company
representative calculated that your new monthly budget bill
would be lowered to $401. Your $12K budget will be depleted if
you go this route.
The
mechanical contractors come next. You're getting two separate
opinions regarding efficiency upgrades based on the 78% rated
model you have: atmospheric chimney-vented appliances are rated
at 84%; and Modcon (modulating condensing) appliances are rated
at 98%. You've told them the equipment must be sized for the
home as it is and that any other upgrades will come at a later
date, if and when you can afford them.
The
atmospheric chimney-vented appliance's up-front cost is very
appealing, in spite of its lower efficiency rating, and you'll
need to save for just two more years until you can add that
attic insulation. Doors and windows will have to wait. Your
monthly budget for heating, however, is projected to be $654.
The 98%
efficiency rated Modcon will, you've been told, adapt to your
home's heat loss by modulating its input/output to match the
heat loss at any given moment in time. In spite of there being
just a 20% difference in listed efficiency-ratings, this
contractor is telling you that your fuel usage will be cut by
40% or more, and proof-positive is being provided with
references and documented cases. If true, your monthly fuel
budget plan will be $422.
Ding-ding-ding - we have a winner! The Modcon is the best
choice. Why is this? After all, the other upgrades were
projected to cut monthly budget payments ever further - an
additional $21 per month. Here's the deal: a heating appliance
is only going to be 78% efficient at design conditions and
that's assuming it was sized correctly in the first place.
Oversized equipment short-cycles lower operating efficiency, and
by adding the insulation, windows and doors, the appliance is
guaranteed to be grossly oversized. Here's the clincher: as
outdoor temperatures modulate, actual efficiency for on/off
heating appliances suffers and can be as low as 45%. So, even
though the fuel usage will be lower, so too will the efficiency
and a new issue will rear its ugly head - sustained flue gas
condensation, which will rot out the heat exchanger and damage
that old unlined brick chimney. The potential for carbon
monoxide issues loom larger. A Modcon appliance does just the
opposite: as outdoor weather moderates, the efficiency gets
better or remains the same.
As the
homeowners add other improvements to cut energy losses in coming
years, the Modcon will simply adapt to the newly-reduced
heat-loss, and fuel consumption will be further reduced. Does
this sound far fetched?
Here's
a documented case from our files regarding an 82% rated
efficiency heating plan using 7,800-Ccf per year (on average).
In 2002, cost was $3,900 at 50 cents per Ccf, and in 2003 cost
was $5,850 at 75 cents per Ccf. A 95% rated efficiency Modcon
was installed, in 2004, to add more heating since the great room
was too cold. After the installation, the cost was $3,300 at 75
cents per Ccf (4,400-Ccf had a 43.6% reduction in spite of the
13% listed efficiency rating difference) for 2004 and 2005.
Metal-framed single-pane windows were replaced and insulation
added to cut heat losses in 2006. After these two updates were
made, the cost was $3,000 at $1.25 per Ccf (2,400-Ccf had a
45.5% reduction) in 2006 and 2007. The overall, total reduction
in fuel consumption with no change in lifestyle equaled 69%.
Nothing but net!
Dave
Yates owns F.W. Behler, a contracting company in York, Pa. He
can be reached by phone at 717/843-4920 or by e-mail at
dave.yates@fwbehler.com
All
Dave Yates material on this website is protected by Copyright
2008. Any reuse of this material (print or electronic) must
first have the expressed written permission of Dave Yates.
Please
contact via email at:
dave.yates@fwbehler.com
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