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4
Refrigeration rules of
thumb:
Assuming an 11 ft. high ceiling,
it costs about $45 - $50/sq. ft. to
build an insulated cold storage
room. The larger the building, the
less cost per square foot.
You need about 100 BTUs (British
Thermal Unit) per sq. ft. of floor.
So, a 10’ x 12’ room (inside
dimensions) would need 10’ x 12’
x 100 BTUs = 12,000 BTUs. A
one horsepower (hp) compressor
absorbs about 12,000 BTU. As
such, for a 10’ x 12’ well insulated
room you would need 1 hp of
refrigeration.
There are two kinds of
refrigeration.
The first is the window air
conditioner where the compressor
and condenser are together. A
home-type room air conditioner
could do a reasonable job on a
small room (less than 10 feet by
10 feet), but tends to dry out the
products. Window air conditioners
are better than no refrigeration,
but they are not good for keeping
produce any length of time.
The next step up is the refrigeration
unit that has a condenser in the
room to do the cooling and a
separate compressor outside to
get rid of the heat. These are much
more energy efficient and do a
better job of not drying out the
produce.
While you can get 1 horsepower
(12,000 BTU) units, it makes more
sense to buy something in the 3
horsepower range. You get more
and better refrigeration for not
much more money. The larger units
would:
• give a bigger coil, and
therefore a smaller temperature
difference, so the produce won’t
dehydrate as much
• allow you to expand your cold
storage without the need for a
larger refrigeration unit
A lot of the cost with refrigeration is
installation. Purchase a reasonably
sized unit initially so you don’t have
to redo the refrigeration when you
expand your cold room.
A 20 foot by 20 foot room would
need 40,000 BTUs or 3.3
horsepower. So you’d likely be
best to buy a 5 horsepower unit
for a room this size. It will give
you better cooling and allow you
the flexibility to do some forced
air cooling of highly perishable
products.
Tools of the
Trade
Refrigerated Storage
You will need refrigerated storage to
maintain product quality and to give
you some time to market perishable
items:
• build your own in the corner of the
barn, or as a separate building
• purchase a prefabricated cold
storage
• buy a refrigerated (freezer) box off
an ice cream truck and have an
electrical refrigeration unit installed
on it
TIP: The calculator will budget for
cold storage assuming you are getting
someone else to build it, but you can
go into the summary and adjust the
figures based on what you think it
would cost if you built your own.
One way to cut the cost of the
cold storage is to buy an insulated
cube van box from a wrecker.
An ice cream truck should have
good insulation; then have a new
electrical refrigeration unit installed
on it