RE: [GBlist] Low E glass
Title: Message
stephen thwaites point has much validity... as a building systems
engineer dealing directly with HVAC issues at our university, i can tell you
occupancy comfort often has very little with a "satisfying" room
temperature. effective comfort control requires a careful look at many
issues, particularly during the heating season:
temperature of the building mass: if the building mass is cold
(concrete floors with vct tile, and/or masonry walls), the radiant effect
on the occupant can be extremely uncomfortable regardless of the room
temperature. since heat is radiated by the warmer surface (your body) to
the walls or floor, your feet or legs will be cold, and you will be very
uncomfortable.
two
issues regarding windows tremendously impact occupancy comfort. the first deals,
again, with the radiant effect. if you have a single pane window
(which could have a surface temperature of 40-50 deg f), heat is being literally
sucked from your body to the window. you are cold no matter what the room
temperature is - particularly if your office chair is only a foot or two away
from the window, which is quite often the case. the other issue is
infiltration. cool air, let alone extremely cold outside air blowing on an
occupant is extremely uncomfortable. you would be amazed at how much
air infiltrates around windows and sills.
too
often in energy analyses the reality of the above issues are not addressed, and
therefore, low e, double paned windows are "not life cycle cost
effective". i have often seen the same analyses prove weatherstripping and
caulking were "not life cycle cost effective" (!!!!!!).
these
analyses missed several important considerations:
-uncomfortable occupants will jack the thermostat up very high to
compensate for their discomfort, no matter what the official policy of their
company is (such as mandated 68 deg f heating and 78 deg cooling setpoints
mandated by in federal govt buildings in the late 70s).
-electric heaters will be used.
-hvac
systems will be rigged to get heat to the occupants one way or the other-causing
a maintenance nightmare for competent hvac technicians
-customer satisfaction with the hvac department will be very low - even
though the cause of discomfort is not their fault.
in any
case, the REAL payback is much quicker than calculated by the life cycle cost
analyses. it is only natural that we wish to be comfortable, and we WILL
do those things to attain comfort. thermostats WILL be jacked up and
electric heaters WILL be brought in. and we have not even discussed the
issue of productivity losses due to lower morale and
discomfort.
stephen is making this point, and i affirm: regardless of the
calculations, installing low e windows are cost effective.
our
proof is in the pudding. we replaced single pane, metal frame windows with heat
mirror technology glazing in one of our buildings, and the occupancy comfort
increased tremendously...
and
this brings up a final point: designers and consultants need to spend a
lot more time in the field performing reality checks instead of relying simply
on the "numbers" calculated.
-----Original
Message-----
From: Corwyn [mailto:corwyn@midcoast.com]
Sent: Thursday, January 03, 2002 1:34 PM
To: Stephen
Thwaites
Cc: Greenbuilding List
Subject: Re: [GBlist] Low E
glass
