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6 juillet 2006 4 06 /07 /juillet /2006 09:19

American Plastics Council

Dear Emmanuel Crivat,

Welcome back to our six-part Expert Report, Natural Disasters vs. Synthetic Stability. In our last installment Roger Lohman of ChemQuest Group Inc. traced emerging trends in polyurethane adhesives and sealants, noting that, when used with mechanical fasteners, such adhesives provide strong resistance to hurricanes, earthquakes and other natural forces.

Then Deniz Carroll, public affairs manager for the EPS Molders Association, examined insulated concrete forms (ICFs) and structural insulated panels (SIPs), expanded polystyrene systems that add strength to walls and roofs while increasing energy efficiency as well.

In this issue, Deniz Carroll continues her discussion of ICFs and SIPs, demonstrating their structural integrity and unique thermal performance. In coming reports, we'll continue to get the opinions of top experts regarding emerging trends in building construction and new materials. This Expert Report, focusing on how to maintain structural integrity under adverse conditions, is another service of the American Plastics Council's Green Building Solutions. We provide this important information free of charge so that industry professionals can utilize resources more efficiently to create healthier, energy-efficient construction.

Feel free to forward this to interested parties as long as www.GreenBuildingSolutions.org is credited as the source. If you want more information, or have ideas for other Expert Reports you'd like to see, just contact us anytime.

Thanks for subscribing!

Best regards,
D'Lane Wisner
Green Building Solutions

--------------------------------

Natural Disasters vs. Synthetic Stability: How New Materials Hold Their Ground, Even When Nature Gives Way

Part 4: Good Things Come in Insulated, Strong and Flexible Packages

And now Deniz Carroll of the EPS Molders Association takes a look at thermal performance, structural integrity and design capabilities of EPS....

Thermal performance and structural integrity

When evaluating insulating performance criteria, R-value is the only variable taken into consideration. However, there are a host of other conditions contributing to the performance of the entire building envelope, including air infiltration, moisture, thermal mass, insulation settlement, and thermal drift. Insulated concrete form construction and structural insulated panel systems effectively address all these issues, offering the performance attributes sought by designers concerned with rising energy costs and the importance of green building products in design.

Due to their monolithic assembly, insulated concrete forms can create a shell that inhibits air infiltration--there are no air leaks or drafts due to insulation settlement. The forms and concrete stay in place for the life of the structure and expanded polystyrene rigid foam maintains its performance without experiencing thermal drift. Structural insulated panels also allow tight construction for eliminating air leakage--one of the most significant sources of a structure's energy loss.

For example, the Cement Association of Canada (CAC) tested a home with insulated concrete forms above and below grade wall construction for air tightness. The 362-m2 (3900-sf) structure was found to have an air leakage rate of 0.22 air changes per hour (acph), indicating reduced air infiltration compared to other wall assemblies.[1] A typical air exchange rate for a standard home is approximately 1.1 air change per hour, so this is significant air leakage prevention.

The Northwest Territories Housing Corp. (NWTHC) conducted the same type of test on a structural insulated panel sytem demonstration house, achieving a rating of 0.49 achp.[2] Due to the air tightness of insulated concrete form/structural insulated panel construction, the designer must take into consideration building ventilation systems to maintain indoor air quality (IAQ) and humidity.

Testing has shown a roofing assembly's expanded polystyrene insulation can retain its original thermal performance rating even after 15 years in situ.[3] A more recent research study conducted by the National Research Council (NRC) of confirmed these results--expanded polystyrene sheathing was installed below grade, without protection for 180 days. Again, the expanded polystyrene foam exhibited no deterioration.[4]

Concrete encased with expanded polystyrene foam has been repeatedly proven in the field to provide exceptional structural integrity under the harshest circumstances. Many homes constructed with insulated concrete forms in Florida withstood the hurricanes of 2004, and the Federal Emergency Management Agency (FEMA) promotes the use of insulated concrete form construction for safe rooms in hurricane- and tornado-prone areas.

The Insulating Concrete Form Association (ICFA) partnered with the military to conduct blast testing on insulated concrete forms. Stationary explosives were detonated at various distances from insulated concrete form walls resulting in minimal structural damage. (Additional testing is planned with Air Force personnel.) Structural insulated panels have also proven able to withstand high winds, snow loads, and seismic activity.[5]

Design capabilities

Architects, engineers, and specifiers may be hesitant to incorporate innovative building assemblies due to restrictions on aesthetic design. Indeed, looking at insulated concrete forms, one might assume these blocks would lead to cookie-cutter construction. However, insulated concrete form manufacturers have developed various block-types to open up the possibilities of design. Anything imaginable--curves, angles, bows, and bays--can be created using insulated concrete forms

Once the concrete is poured, electrical contractors use 'hot knives' to cut holes, chases, and rectangles into insulated concrete forms to house cables and electrical wiring. The latter may require a metal sheath or conduit when installed in these routed channels, and electrical switch and receptacle boxes should be specified as shallow depth to fit within the expanded polystyrene layer of the insulated concrete form wall.

Architects submit their structural insulated panel system designs directly to the factory. Using CAD systems and high-end fabrication techniques, the structural insulated panels are then manufactured to specification and delivered on-site, ready for immediate installation with detailed layout instructions. Door, window, and skylight openings may also be pre-cut. Even the most complicated, multi-faceted roof design can be accomplished in-house without wasting valuable time on-site.

All traditional exterior finishes including vinyl or wood siding, stucco, brick, stone, or--another expanded polystyrene application--external insulation finish system (EIFS) can be used with insulated concrete forms. The same is true for structural insulated panels.

Installation

To maximize the benefits offered by both systems, there are several design options architects can employ.

Insulated Concrete Forms
Insulated concrete forms may be used for below- and above-grade walls, while structural insulated panels can be specified above the grade or for roofing applications. When using insulated concrete forms in below-grade walls and structural insulated panels above grade, an anchor is embedded in the top layer of the forms and then secured to the bottom of the panel. Floor joists (perpendicular to the wall) may be installed in between the insulated concrete forms below the grade and the structural insulated panels above. Again, an anchor is used to fasten the joists to the  insulated concrete form construction. To install structural insulated panels as the roof, a 2x6 stud is embedded in the top insulated concrete form after the concrete has been poured, attaching the structural insulated panels using long (i.e. +254-mm [10-in.]) screws. (Adding an structural insulated panel roof to structural insulated panel walls is straightforward.)

Notes
[1] See Natural Resources Canada's Improving Energy Performance in : Report to parliament under the Energy Efficiency Act 2000-01 (2000).
[2] See CMHC's "Building with Structural Insulated Panels," About Your House: North Series 1 (2001).
[3] See R.P. Tye and C. F. Baker's Development of Experimental Data on Expanded Polystyrene Roofing Insulation Under Simulated Winter Conditions (The Energy Materials Testing Laboratory, 1984).
[4] See NRC's In-situ Performance Evaluation of Exterior Insulation Basement Systems -EPS Specimens (March 1999).
[5] Visit
www.concretemonthly.com.

-----------------------------------
Next Installment, Part 5: "Developing a Green Building Thumb" -- our helpful tips on installing insulated concrete forms can save you time and effort.

______________________________________

American Plastics Council

Dear Emmanuel Crivat,

Welcome back to our six-part Expert Report,

Natural Disasters vs. Synthetic Stability.

In our last installment Deniz Carroll, public affairs manager for the EPS Molders Association, examined insulated concrete forms (ICFs) and structural insulated panels (SIPs), demonstrating their structural integrity and unique thermal performance. In this issue, she gives practical tips on installing ICFs and SIPs, helping you save time and money.

In the next and final report, we'll introduce you to one more expert in new building materials who will take you underground to discover the best and longest-lasting pipe available.

This Expert Report is another service of the American Plastics Council's Green Building Solutions. We provide this important information free of charge so that industry professionals can utilize resources more efficiently to create healthier, energy-efficient construction.

Feel free to forward this to interested parties as long as www.GreenBuildingSolutions.org is credited as the source. If you want more information, or have ideas for other Expert Reports you'd like to see, just contact us anytime. Thanks for subscribing!

Best regards,
D'Lane Wisner
Green Building Solutions

--------------------------------------

Natural Disasters vs. Synthetic Stability: How New Materials Hold Their Ground, Even When Nature Gives Way

Part 5: Developing a Green Building Thumb And now Deniz Carroll of the EPS Molders Association provides helpful tips on installing insulated concrete forms that can save you time and effort....   The National Association of Home Builders (NAHB) Research Center has identified several tips to assist contractors and designers when installing insulated concrete forms:[1]

Additional reinforcement is not necessarily better. Adding more reinforcement than required can hamper the proper placement and consolidation of concrete in insulated concrete forms.

Lintels (or concrete headers) should be as deep as possible. When the lintel span-to-depth ratio is greater than five, shear reinforcement or "stirrups" are necessary. Stirrups can be very difficult to place in insulated concrete forms and overuse can contribute to the concrete placement and consolidation problems mentioned above.

One should not specify very low slump concrete for use in insulated concrete forms. Although this practice may slightly reduce the concrete strength, a slump rate of 6 is good for insulated concrete forms since it helps achieve better concrete consolidation in the forms.

 

 

The design professional may wish to consider laying out building dimensions, windows, and doors to correspond with the modular dimensions of the insulated concrete form materials being used. This design investment can improve labor efficiency and reduce waste, particularly in house plans that will be used repetitively.

 

Thicker walls should be accounted for in architectural plans and details, such as window jambs.

 

The contractor should understand appropriate concrete placement practices and forming details related to the specified insulated concrete form system. A poorly planned construction endeavor can reflect badly on the technology and the designer.

A team approach involving the contractor, builder, manufacturer, designer, and owner is encouraged. This means the entire team should be included in the process as soon as possible after the design concept stage.

 

Plumbing in insulated concrete form construction should be kept in the slab and routed through floor and interior wall cavities to the greatest extent possible.

 

Electrical wiring in the surface of insulated concrete form walls may need protection (e.g. metal sheathed or placed in conduit) when installed in routed channels of the foam forms using a hot knife (usually available through the manufacturer). Additionally, electric switch and receptacle boxes will need to be specified as shallow depth to fit within the foam layer of an insulated concrete form wall.

 

Structural Insulated Panels Structural insulated panels are lightweight and, as such, easily carried and installed by hand. Pneumatic nailers are generally used to fasten the panels to top and bottom plates, and to make vertical connections. The panels must be braced and plumbed just as practiced with stud framing. Beams carrying roof loads may require supports incorporated into wall panels for carrying the point loads downward. Heavier roof panels are usually set in place with a crane. To ensure the insulating capacity of the structural insulated panels, all joints must be sealed properly.

 

The Structural Insulated Panel Association (SIPA) provides best practice connection diagrams for typical joints and details. Using structural insulated panels in the installation of perimeter walls is not only easier and faster, but the interior gypsum wallboard and exterior siding installation is just as simple because there is no need to locate studs. Most panels include a formed chase in the core for electric wiring. The insets for boxes and additional channels must be mechanically routed, then resealed with expanding foam.

 

Green thinking
As the design and construction community integrates environment-related practices and government agencies implement legislation to foster green building products and initiatives, traditional products and systems are being re-evaluated. New green building products such as insulated concrete forms and structural insulated panels are moving to the forefront thanks to their ability to leave a lighter footprint on the environment.

 

Defining green building products is not an exact science. Characterization of a sustainable material is difficult because product environmental attributes can be evaluated differently. As a result, there are numerous sources claiming to have the answers--from online databases to the U.S. Green Building Council's (USGBC's) Leadership in Energy and Environmental Design® (LEED®).

 

In actuality, all insulation materials can be considered "sustainable" to a degree, thanks to their contributions to a structure's energy efficiency. However, not all materials deliver significant enough attributes to classify them as green building products. The expanded polystyrene used in both insulated concrete forms and structural insulated panels offers sustainable R-values throughout the structure's life without thermal drift.

 

Additionally, many expanded polystyrene providers incorporate recycled content--both post-consumer and post-industrial--into their manufacturing process. The amount of recycled content varies as long as the end material meets ASTM International C 578, Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation, performance points. Insulated concrete forms and structural insulated panels also incorporate renewable products via the former's concrete and the latter's OSB panels.

 

Due to the extensive pre-planning process used in both insulated concrete forms and structural insulated panels, on-site waste is also considerably reduced. With structural insulated panel systems, an architect employs CAD drawings to determine the number and dimensions of structural insulated panels needed for a job. The structural insulated panel manufacturer customizes the panels to the design before shipping them to the project.

 

Installers can "build" the structural insulated panel home according to the numbered panels corresponding with the blueprints--no extra materials are needed or wasted. Reduced costs can also be realized through shorter construction schedules and lower labor costs due to ease of installation. Additionally, with minimal thermal bridges, air leakages are rarely a concern with these green building products, as most outdoor pollutants are kept out.

 

Conclusion
Insulated concrete form and structural insulated panel building systems have offered a viable green building product alternative to traditional building methods. They provide the possibility of increased energy savings with flexible design elements and quicker construction practices. Many manufacturers have developed courses and certification opportunities for contractors to ensure installation guidelines are followed.

 

Industry organizations are continuing to level the playing field with the other traditional construction systems through the development of prescriptive code standards for these building systems. Language developed for insulated concrete forms have been incorporated into the International Building Code (IBC) and International Residential Code (IRC), while the standard for structural insulated panels is currently in the works.

 

Notes
[1] For more NAHB tips, visit
www.toolbase.org and select "Design Guides," followed by "Concrete" and finally, "Designing Homes Using Insulating Concrete Forms."

 

About the Author
Deniz Carroll is the public affairs manager for the EPS Molders Association (EPSMA). She has worked with the EPS industry for more than six years. Carroll can be reached via e-mail at
dmcarroll@epscentral.org.

 

Further Resources
EPS Molders Association (EPSMA) -
www.epsmolders.org Portland Cement Association (PCA) - www.cement.org/homes

---------------------------------------

Next Installment, Part 6: "Polyethylene Goes Underground"--high-density polyethylene pipe won't leak, corrode, or crack, even under strong impact. 

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