RE: [GBlist] attic ventilation

["Ralph Bicknese" <ralph.bicknese@christnerinc.com>]

Alan:

Air conditioning condensing equipment must be well ventilated to operate
efficiently.  I suggest it should be completely outside in an area with at
least 3-4 feet clear all around it.

I recently had a situation where condensing units for a commercial kitchen's
refrigerator and for its freezer were located in an unconditioned mechanical
mezzanine.  The mezzanine is a sizable volume and is fairly well insulated
from the outside.  There is no added insulation between it and the kitchen
below or the adjacent dining room.  After about 2 days of 90 degree plus
outdoor high temperatures the mezzanine reached about 125 degrees.  The
condensers not only suffered from inefficient operation, they shut down and
food was lost.  The client was very unhappy and it cost $9,000 to have them
moved outside.  Thankfully, the condensers for the air conditioners were
already outside.

The indoor mezzanine temp. of 125 degrees surprised me.  In addition to
being reasonably well insulated, the roof was ventilated with soffit and
ridge vents. It turns out that the extracted heat from the condensers was
adding to the heat in the mezzanine.

Regards,
Ralph Bicknese

-----Original Message-----
From: Alan Abrams, A.I.B.D. [mailto:awabrams@starpower.net]
Sent: Friday, August 31, 2001 2:26 PM
To: greenbuilding@crest.org
Subject: [GBlist] attic ventilation


this is to seek advice on whether or not to ventilate an attic area which
will be used for heating and air conditioning equipment and associated
ductwork and mechanical connections.

the attic is above three habitable levels (including full finished basement,
which is 75% below grade).  the house is generally frame construction with
minimum of  3 1/2" of icynene insulation in the walls.  it is located near
washington, dc ("hazy, hot and humid" summers and relatively mild winters,
with a few weeks in mid Jan-early Feb were the temp may not get above
freezing.

the options, generally, are to insulate the upper ceiling with +/-4" of
icynene and 6-8" of batt, and ventilate the attic conventionally with soffit
and ridge vents--or to insulate the rafter bays, either shooting the foam
against underside of the sheathing, or creating baffles and air channels
under the sheathing, and insulating the bays.  baths and laundry will be
carefully ventilated, with provision for exterior make up air.

i would love to seal this space up and reduce the load on the hvac equip,
but i am concerned about moisture buildup.

alan abrams aibd


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______________________________________________________________________
This greenbuilding dialogue is sponsored by REPP/CREST, creator of
Solstice http://www.crest.org, and BuildingGreen, Inc., publisher of
Environmental Building News and GreenSpec http://www.BuildingGreen.com
______________________________________________________________________