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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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