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Oversized and Inefficient HVAC Systems
Unfortunately, widely used HVAC sizing methods such as Manuals
J and S and the ASHRAE Handbook of Fundamentals are
either cumbersome or do not account for the thermal mass,
high levels of insulation, and/or low air infiltration of
the insulated concrete walls. Additionally, many builders
and HVAC contractors’ size HVAC equipment based on a
“rule-of-thumb” developed for wood framed homes
that equate equipment size with square footage of living space.
The net result is an inefficient HVAC system that is typically
oversized.
An oversized HVAC system will have a higher initial cost than
a correctly sized system, and will consume more energy than
necessary to maintain thermostat set points. In addition,
an oversized system will have a shortened “on”
time, which can lead to larger temperature swings and reduced
thermal comfort. Air conditioning systems with short “on”
times do not remove enough moisture from the indoor environment,
which can promote moisture problems and increase the probability
of occupant respiratory problems.
Based on a wealth of research comparing the energy performance
of concrete homes to wood-framed alternatives, the inherent
energy-saving properties of insulated concrete walls allows
a 15 to 40 percent downsizing of HVAC equipment.
This publication is available online at www.cement.org/bookstore
or by phone at 1-800-868-6733. Cost is $59.95.
Insulated Concrete Walls
Insulated concrete walls include insulating concrete form
(ICF) walls, cast-in-place insulated concrete walls, insulated
precast concrete walls, autoclaved aerated concrete (AAC)
walls, and insulated concrete masonry (CMU) walls. Houses
constructed with concrete wall systems are both disaster resistant
and energy efficient. Energy efficiency is imparted by the
inherent thermal mass, high levels of insulation, and low
air infiltration of these walls.
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About PCA
Based in Skokie, Ill., the Portland Cement Association represents
cement companies in the United States and Canada. It conducts
market development, engineering, research, education, and
public affairs programs.
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