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ESCSI INFORMATION SHEET 3201 - NOVEMBER 1999

Energy Efficient Buildings
with SmartWall Systems

When it comes to energy performance SmartWall high performance concrete masonry systems outperform metal stud walls with batt insulation and provide lower heating and cooling cost. SmartWall Systems is helping to decrease the overall global demand for energy.

SmartWall Systems
SmartWall is a high performance lightweight concrete masonry wall system that outperforms other masonry and non-masonry wall systems, especially in terms of energy efficiency, maintenance, appearance, fire resistance, durability and strength to weight ratio. SmartWall is a mason friendly, cost effective wall system that enhances speedy construction and has a very high degree of customer satisfaction.

The SmartWall System is Energy Efficient
SmartWall provides superior energy conservation by optimizing the combination of R-values, thermal mass and low thermal bridging. Wall heating and cooling costs may be reduced by more than 50%! The concrete in SmartWall has more than 2.5 times the thermal resistance of the concrete in a typical heavy block. This significantly reduces thermal bridging, maximizes the effectiveness of core insulation, and results in the high R-value of SmartWall. As shown in Table 1, an un-insulated SmartWall performs as well as core-insulated heavy units! Also, SmartWall with perlite fill offers maximum thermal performance.

In addition to thermal resistance, SmartWall also benefits from thermal mass— the flywheel effect that minimizes peaks and valleys in heat load as a wall responds to daily changes in ambient temperature. Walls with optimized thermal mass reduce overall energy use, compared to non-masonry walls. SmartWall has an ideal balance of thermal mass and thermal resistance for optimum performance.

Calculating the overall effect of thermal mass and thermal resistance in a wall’s dynamic response to the environment is a complicated task. To perform this task, the ASHRAE 90.1 energy code uses a computer program called ENVSTD, and the results can be dramatic. For example, using ENVSTD to compare the energy performance of a 12" SmartWall with perlite core insulation to an R-19 batt insulated metal stud wall shows that SmartWall outperforms the metal stud system! ENVSTD factors many variables besides opaque wall properties, including glass area, shading, overhangs, and building orientation. Using ENVSTD and SmartWall, energy efficient buildings can be designed that comply with energy codes without the need for added-on insulation. In many cases a single-wythe SmartWall does the job.

TABLE 1:
R-VALUES FOR CONCRETE MASONRY
WALLS (1) (Exposed Both Sides)

Nominal
Thickness

Concrete Unit
Weight lbs/ft3
Cores
Empty
With Core
Inserts

Cores Filled
With Perlite

8"

SmartWall (2)

2.5

4.2

6.6

Heavy CMU’s (3)

1.9

2.6

3.2

12"

SmartWall (2)

2.7

4.4

9.5

Heavy CMU’s (2)

2.0

2.7

4.4

(1) R-Values are mid-range per NCMA TEK 6.1A & 6.2A. R in (háft2 áoF)BTU and includes 0.85 air film coefficient. (2) SmartWall at 90 lbs/ft3. (3) Heavy CMU’s at 135 lbs/ft3.

ASHRAE Energy Conservation Standard
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) building energy conservation standard clearly demonstrates that SmartWall Systems incorporating high performance lightweight concrete masonry units are indeed energy efficient.

The Standard, ASHRAE/IES 90.1-1989 provides state of the art guidance regarding the design of energy efficient buildings. Standard 90.1 recognizes the performance characteristics of the materials used to construct the building rather than concentrating on the R-values alone as earlier versions did. These characteristics include the effects of wall thermal mass, thermal bridging and insulation position.

Thermal Mass - Heat Capacity
The effects of wall thermal mass are well known. High thermal inertia walls, such as stone, concrete masonry, SmartWall masonry, poured concrete or clay brick, have the ability (due to their high heat capacity) to delay and reduce the impact of outdoor temperature changes on conditioned indoor environments. This means less heat gain or loss, depending on the season, that must be supplied by energy consuming HVAC equipment. ASHRAE 90.1 quantifies thermal mass effects based on a wall’s heat capacity. Heat capacity is defined as wall weight per square foot times specific heat. Table 2 lists heat capacity for concrete masonry units, and Table 3 lists heat capacity for other common building materials.

Thermal Bridging
In buildings, when insulating material is interrupted by a highly conductive material, thermal bridging takes place. Examples of thermal bridges include steel studs that interrupt the continuity of batt insulation and metal fasteners that go through heavily insulated exterior walls. Simply put, thermal bridges occur where differences in material thermal conductivities result in significant lateral heat flow; e.g., heat flowing along the surface of a wall and then flowing through the wall via a steel stud. ASHRAE 90.1 considers many thermal bridges. Table 4 (table 8C-2 in ASHRAE 90.1) lists the effect of thermal bridging in metal stud walls.

Example: The effects of thermal bridging in a typical metal stud wall with 2x4 studs 16" on center.

Uncorrected Insulation R-value = R 11
Correction Factor = .5
Effective Insulation R-value = R 5.5

Table 2 lists concrete masonry R-values calculated according to ASHRAE’s series parallel method recommended by the National Concrete Masonry Association. This method accounts for thermal bridging within the CMU. Because of its low thermal bridging characteristic, SmartWall Units with open cores (no insulation) have the same R-values as heavy CMU with core insulation as shown in Table 1.

Calculating Thermal Performance
ASHRAE 90.1 provides two methods for determining how the thermal properties of walls impact building envelope energy-efficiency criteria. The first method is prescriptive and provides 38 Alternate Component Package (ACP) tables. The ACP tables list maximum wall Uo values, Uo = 1/R. The second method is the systems performance method and it employs a computer based program, Envelope Standard (ENVSTD). This approach requires input of many building parameters including wall heat capacity and wall Uo. ENVSTD uses these building-wide inputs to determine if the design meets the Standard’s energy efficiency criteria. Because of this building-wide approach, SmartWall CMU wall systems, with an optimized combination of heat capacity and R-values, are found to be as energy efficient as "highly" insulated steel stud wall systems. For ease of comparison, four energy compliance examples are included on the following pages. The ENVSTD computer program was used to verify the excellent energy performance of SmartWall high performance concrete masonry walls. Each example uses the appropriate changes in the Wall Uo, Heat Capacity values and INsulation POSition with all other building parameters unchanged. Examples 1 & 2 compare an apartment building in Milwaukee, Wisconsin. Examples 3 & 4 compare an office building in El Paso, Texas. CONCLUSION.....For the examples considered, ENVSTD proves that a 12" SmartWall System with perlite insulation uses less energy for heating and cooling than a metal stud frame wall with R-19 batt insulation.

The Bottom Line
There are many ways to incorporate energy conservation into a building. One of the most cost effective and environmentally friendly ways is to consider the overall comfort of the users, as well as the total energy consumption over the life of the structure. This not only helps the person paying the heating and cooling bills, but also decreases the overall global demand for energy— benefitting both the user and the environment.

Thermal mass benefits are not new. Throughout the ages, high mass building materials were the product of choice for building strong, secure and comfortable structures and dwellings. It’s only in the past few decades we have become misdirected with marketing emphasis only on the "R" value. Many have forgotten that the truly comfortable buildings of the past had the energy conservation built into the structural components. Now the ASHRAE 90.1 Standard provides the needed link between energy theory and the real world.

By designing buildings with the high performing SmartWall Systems, owners will get energy conservation built into the structure without complicated and expensive add-ons to insulate the building envelope. SmartWall masonry units are made with expanded shale, clay or slate (ESCS) aggregate. They are mason friendly and up to 40% lighter than obsolete heavy masonry units. Additionally, SmartWall offers superior fire resistance, sound absorption, reduced seismic loading and low shrinkage.

As a building owner or designer you can choose a system with a practical "R" number that when combined with thermal inertia, obtains proven energy performance with quiet comfort. The SmartWall system maximizes all the benefits of traditional masonry: design flexibility, economy, thermal mass and durability. In addition, the lighter weight SmartWall system benefits the mason because of fewer injuries, safer scaffolds, longer working career and the opportunity for female workers. Since increased productivity is a natural consequence of lighter units, overall construction time is often reduced. SmartWall meets the needs of today’s market, and gives specifiers all the best reasons to choose concrete masonry. SmartWall is the Answer!

(The following tables and examples are in    format.)

TABLE 2: THERMAL PROPERTIES
OF CONCRETE MASONRY WALLS

TABLE 3: THERMAL PROPERTIES
OF VARIOUS BUILDING MATERIALS

TABLE 4: (ASHRAE 90.1 Table 8C-2)Wall Sections
with Metal Studs Parallel Path Correction Factors

EXAMPLES 1 & 2 - Apartment in Milwaukee, WI
12" SmartWall Systems Wall compared with typical face brick steel stud wall

EXAMPLE 3 & 4- Office Building in El Paso, TX
12" SmartWall Systems Wall compared with typical face brick steel stud wall

For additional information please contact ESCSI
via Phone: (801) 272-7070, Fax: (801) 272-3377,
e-mail: info@escsi.org or visit ESCSI’s web site
at www.smartwall.org.


ESCSI INFORMATION SHEET 3201 - NOVEMBER 1999