Frequently Asked Questions
About Geothermal Heating and Cooling
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Q. Geothermal is only for new construction, right?
A. WRONG in many cases geothermal can be retrofitted in
existing homes, but there are a couple of things to keep in
mind:
- Geothermal does not match up well with hot water
radiator and existing hot water baseboard systems.
- The existing forced air ductwork in the home
most likely is undersized and some of it may need
reworked for the geothermal system to function as
efficiently and quietly as possible.
- Even the smallest bore hole installation still
requires getting a 40ft long drill rig on the
property and would need to avoid any overhead
obstructions such as power lines.
Q. I have a 2,400 sq ft 2 story house, how big of a
geothermal system do I need and how much is it going to
cost?
A. Answer \96 We can\92t tell you without ALL of the necessary
information. There are so many factors that are involved
that we need more information in order to give you an
accurate estimate. However, if we have all the information
we can provide you with a highly detailed and accurate
estimate.
Q. What is a blower door test and how does it work?
A. A blower door test is a test that is done to measure the
actual air changes per hour of a particular structure.
Basically a large fan is put in a temporary door in one of
the exterior doorways into the home. The fan is used to
\91depressurize\92 the house, ideally to a -50 pascals. This
\91depressurization\92 is like simulating having a 20- mile per
hour wind hit all 4 sides of the home at the same time. This
shows where there are \91leaks\92 in the insulation envelope of
the home. This reading along with the dimensions of the home
allow the infiltration rate of the home to be calculated.
Q. What is infiltration and why is it so important?
A. Infiltration is the measure of the amount of air leaking
into or out of the home. It is measured in Air Changers per
Hour (ACH). If a home has an infiltration rate of 1, then all
of the conditioned air inside of the home is switched with
unconditioned air that was outside of the home, once in an
hour. An infiltration rate of .5 ACH means that \BD of the
volume of conditioned air inside the home switches places
with unconditioned air from outside the home. If you had a
very small home, for example: a 10ft wide x 10ft long x 8 ft
high and it had an air change of 1 ACH, then 10 x 10 = 100 x
8 = 800 cu ft or conditioned air would be leaving the home
every hour and a new unconditioned 800 cu ft would be coming
in and would need heated or cooled. Keep in mind that a
basketball is roughly equivalent to 1 cu ft. Imagine if you
have a 2,000 sq ft home with 8 ft ceilings now that 1 ACH is
the equivalent of the throwing 16,000 basketballs of heat at
the window and brining in 16,000 basketballs of cold. Air
Infiltration is the SINGLE largest contributing factor to
heat loss.
Q. What is a load study and what is involved in it?
A. A load study is the \93Manual J\94 calculation that
determines how large of a heating and cooling system needs
to be installed in a building. It is based on a number of
factors including: Square footage, Ceiling Heights,
insulation properties, window properties, direction the
building faces, how many stories, how much is below grade,
how many bedrooms are in it, how many people are will live
in it, how many kitchen\92s, and most importantly how \91air
tight\92 it is or is going to be built.
Q. Isn\92t geothermal very expensive?
A. Geothermal has a much greater upfront cost than
conventional systems, but also has a much lower operational
cost. In reality if the price of a geothermal unit was
compared to an absolute top of the line conventional system
(95%+ efficient variable speed gas sealed combustion gas
furnace coupled with a 18+ SEER Air source heat pump and the
necessary connections between the two), there would not be
much difference. The additional costs happen with the
piping, pumping and primarily the loops in the ground.
Without Tax Credits or rebates taken into account, a typical
payback on a well built newly constructed home is about 5 \96
7 years. On a retrofit, in comparison to replacing the
existing conventional system, it is usually about 10-12
years.
In typical new construction, if the cost of the geothermal
system is added to the mortgage on the home, the amount of
money saved in utility bills is usually greater than the
additional cost added to the mortgage. The real question is
not "Can I afford to do geothermal system?" it is "Can I
afford NOT to do it ?"
Q. Can\92t geothermal make my \91domestic\92 hot water?
A. While there are a few geothermal units that are designed
to make domestic hot water \91on demand\92 the most common form
of creating hot water is called a \91hot water assist
generator\92 or a \91desuperheater\92 This is an additional coil
that is installed in the geothermal unit and is used to
\91supplement\92 the hot water in the standard hot water tank.
It is ONLY functional when the geothermal unit\92s compressor
is running. Typically, it is more effective when the
geothermal unit is running in cooling mode than when it is
running in heating mode.
Q. Can I use my existing well for the geothermal system?
A. Possibly, but we don\92t recommend it. In order to use a
well for a geothermal system two very important criteria
must be met \96 1. Extremely clean and pure water \96 not easy
to find in Western Pa. and 2. A LOT of WATER \96 flow rates
for open loop systems need to be 1.5 gallons per minute per
ton of system, so a 4-ton system would need a well to
produce 6 gallons per minute 24 hours a day, seven days a
week, 52 weeks a year, even when the laundry and dishwasher
are both running in the middle of an August afternoon.
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