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200th
User of BTC's Envelope Facility
Tests Recycled Concrete Wall
A building’s
"envelope"—its walls, roof, and foundation—is the thermal
barrier between the indoor and outdoor environment and is one of
the key determinants of how much energy a building uses. The Building
Envelope National User Facility, housed at the BTC, conducts research
on improving roof, wall, and foundation systems, as well as the
insulating materials in these systems.
To
date, this BTC facility has evaluated almost 70 different wall systems
for industry users. Recently, the facility tested a wall system
for its 200th user, the Tennessee Valley Authority (TVA). TVA and
its partner, Babb International, are interested in developing an
autoclaved aerated concrete (AAC) block made with 70 wt % flyash
from TVA’s coal-fired power plants.
Testing
the Flyash AAC Block
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AAC
is an extremely lightweight concrete building material; it
weighs as little as one-fifth the weight of ordinary concrete.
Not only does the flyash AAC building block have good insulating
properties (a high R-value), but it also recycles material
(flyash) that would otherwise have to be disposed of at some
cost to the environment.
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Construction
of a flyash test wall in the BTC.
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BTC
researchers have shown that a test wall using this AAC block has
an R-value of 7.2, higher than values for several other AAC block
walls tested at the BTC. Analysis is under way to determine the
equivalent whole wall performance accounting for its inherent thermal
mass benefit.
Using
the AAC Block for Habitat Houses
TVA
and Babb’s interest in developing the flyash block dovetails with
the interest of Habitat for Humanity International in applying AAC
technologies to affordable housing. Because AAC block walls with
high R-values may not require insulation inside or outside, they
provide the potential for inexpensive and simple construction as
well as energy efficiency.
TVA
plans to test the flyash blocks on both counts in the near future
by building an energy-efficient Habitat house. BTC researchers will
install instrumentation and monitor the energy efficiency and air-tightness
of the house for a year. The results will be compared with data
obtained from the recently completed monitoring of two identical
Habitat houses built in Lenoir City, Tennessee, in 2000.
This
project will help DOE reach both of the broad goals underlying the
most recent National Energy Plan—providing energy supply in an environmentally
responsible manner and promoting energy conservation. It will also
provide more data for the BTC’s Whole-Wall
Thermal Performance Calculator, an interactive calculator that
enables Internet users to compare uniform whole-wall R-values for
more than 40 different wall systems.
For
more information, contact Jeff Christian (christianje@ornl.gov)
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