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Specifying Decking for High-Moisture Exposure Applications

Posted on 9/4/2015 9:40 AM by Brent Gwatney

Georgia's Port Royale Marina is installing high-performance composite decking throughout its facilities, including in this children's spray park. PHOTO CREDIT: Port Royale Marina

Moisture exposure is a leading cause of deck deterioration, whether from precipitation, waves or water splash from pools and hot tubs. The volume of moisture exposure can be huge. If you build a modest-size commercial deck in a city on the Gulf Coast, every year it will be exposed to more than 200,000 gallons of rain – that’s nearly six full rail cars of water pouring on the deck annually. The same size deck far inland would still receive more than three rail cars of rain each year.

Since the lifespan of a treated wood deck is only about 10 to 20 years, depending on the wood species, treatment and the exposure, building professionals are increasingly specifying higher-performance alternatives like composite decking to extend the lives of their projects. When selecting a composite decking, it is important to evaluate the product’s moisture resistance to ensure its long term performance.

Moisture resistance factors for composite decking

Composite decking is a combination of wood fibers and plastics that are specially engineered for high performance. Because composites include wood, any exposed wood fibers are still susceptible to moisture absorption, which can lead to the twisting, warping, or cracking that is common with traditional wood deck boards.

The most effective way to ensure durable and long-lasting composite decking is for the manufacturer to fully encapsulate the wood fibers in water-resistant plastic. Yet, this is technically difficult to do. So, when evaluating composite decking, it is important to ask the manufacturer the degree to which the wood fibers are encapsulated and if their decking has experienced any field failures.

Because of the manufacturing challenges of achieving full encapsulation, some composite manufacturers developed another approach to managing moisture: adding a plastic cap to their decking boards. Although caps offer several benefits, they still fall short in defending composites against water damage. The problem is threefold: 1) protective caps are almost never included on the ends of boards; 2) many capped composites only wrap three sides of the board, leaving the bottom undefended; and 3) screwing or nailing the boards penetrates the cap leaving the core of the board unprotected.

Each of these areas provides an entry point for moisture. Therefore, as with uncapped composites, it is crucial to check if the composite core is made with fully encapsulated wood fibers. Although caps alone aren’t sufficient to prevent water infiltration, their benefits can include enhanced stain, fade, scratch and slip resistance.

In addition to confirming that the wood fibers are fully encapsulated, when specifying capped composites, it’s also important to ask the manufacturer how they attach the cap to the composite core. In some cases, improper adhesion can lead to the cap separating from the core, directly exposing the wood fibers to moisture. Some specialty boards integrate the cap with the core for a stronger and longer-lasting bond that continues to protect the core from exposure to the elements.

Though it means asking a few questions to find the right product, many commercial facility owners and operators have found that the increased moisture resistance of high-performance composites with fully encapsulated wood fibers makes for more long-lasting decks, docks and boardwalks.

One extreme example of moisture resistance is composite decking installed on a submerged canoe and kayak launch at the Blue Run of Dunnellon Park on Florida’s Rainbow River. The 15-foot section of the ramp that goes into the river stays underwater year-round, yet the decking remains strong and good looking, unlike wood which would quickly deteriorate in these conditions.

Conclusion

The next time you’re planning a deck, dock or boardwalk for your facility, picture a train of rail cars full of water coming down the tracks to drench the surface and ask yourself if the option you’ve selected is durable enough to withstand this onslaught year after year. If you’re not sure, consider tougher options like moisture-resistant composites with fully-encapsulated wood fibers.

Brent Gwatney is Senior Vice President for Sales and Marketing for MoistureShield composite decking. Contact him at bgwatney@aert.com.



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How to Make Better HVAC Refrigerant Decisions

Posted on 9/1/2015 10:19 AM by Brian S. Smith

With increasing frequency, manufacturers of HVAC equipment are fielding questions from customers, dealers and building owners and operators regarding the status of various refrigerants used in North American chillers and HVAC equipment today. Here are considerations around three of the most frequently asked questions, as well as factors to consider before making a refrigerant change:

What are the refrigerants currently being phased out?

The CFC and HCFC class of refrigerants are in the late stages of being phased out under the terms of the 1987 Montreal Protocol. These refrigerants include chlorine, which has been shown to cause damage to the Earth’s protective ozone layer when the molecules get into the upper atmosphere.  CFCs (such as R-11 and R-12) are largely eliminated already, while HCFCs (such as R-22 and R-123) are still used in existing installations. HCFCs have been targeted for elimination by 2020 for developed countries and by 2030 for developing countries. The refrigerants of choice to replace HCFCs in existing and new equipment are HFCs (such as R-134a, R-410A, R-404A and R-507).

What is the US EPA SNAP (Significant New Alternatives Policy) program, and how does it affect my existing or upcoming chiller purchases?

The SNAP program was established as a means for the EPA to allow a safe, smooth transition away from ozone-depleting compounds by identifying substitutes that reduce the overall risk to human health and the environment. The EPA SNAP program has developed a list of approved alternatives for CFCs and HCFCs. The most common alternative refrigerants are HFCs, as noted in the previous question. Recently, refrigerant producers have begun requesting EPA approval for some new HFO alternatives, too. 

For chiller applications, the best choice for refrigerants continues to be R-134a and R-410A, since most equipment has been highly optimized for efficiency and performance using those refrigerants. Over time, manufacturers will continue testing new refrigerants and will optimize their hardware for these newer alternatives. But cost and availability may be a challenge until the industry settles on the direction and a more widespread adoption occurs. Using systems not optimized for a newer refrigerant can result in higher first costs, higher maintenance costs and lower energy efficiency.

The EPA recently published its final ruling, based on the original July 2014 proposal to restrict certain HFCs.  The ruling targets higher emission applications, such as mobile air conditioning, retail refrigeration and certain aerosol and foam applications. It does not impact commercial air conditioning using stationary chillers, rooftops, etc.

How will I know when it is appropriate to change to new refrigerants?

While regulatory and other actions will evolve over time, governments will, as they have in the past, ensure that building owners are not left with stranded assets and will allow for more than ample time to convert when the time is right. There is no risk to the continued use of HFCs, such as R-134a and R-410A, and no calls to phase out those refrigerants in stationary air-conditioning equipment. It may take a decade or more for new refrigerants to be tested and approved by the various agencies and manufacturers involved, and some experts believe that R-134a and R-410A will be available indefinitely.

Optimal refrigerant selection depends on many factors for any given situation. However, there are five that are the most significant: safety, availability, reliability, performance and cost. Each must be satisfied before considering a change.

Let us review these five factors briefly, one-by-one:

1) Safety has many facets, but flammability and toxicity are the two primary considerations. With the exception of R-123, which has higher toxicity, most commercially used refrigerants are classified as lower toxicity. Some of the newer HFC and HFO refrigerants are slightly flammable. So, building codes and equipment safety standards need to be updated to address this fact before they can be used safely. Also, service technicians will need to be properly trained and equipped to install and maintain systems safely.

2) Many new refrigerants are only recently being made available, and in some cases, full-scale production hasn’t started. Local supplies will need to be established if demand ramps up for individual fluids. From our experience with early HFC alternatives to R-22, there were localized issues with availability until widespread adoption occurred, and today it is not clear yet what new options will gain the needed widespread adoption that will allow suppliers to inventory enough of these fluids to support local needs.

3) Compatibility of materials and refrigerant stability are crucial, not only for reliable, cost-effective operation and maintenance, but also for safety reasons. While much has been learned from past refrigerant transitions, each new fluid requires compatibility testing to ensure that gaskets, elastomers and other materials of construction are compatible with the fluid for the life of the chiller –  lessons learned from the industry’s past experience with new refrigerant types.

4) Performance can be measured in terms of cooling capacity and efficiency. There are no perfect drop-in replacement refrigerants for any of the existing refrigerants. Each has a trade-off, many involving either capacity or efficiency, and sometimes both. Less capacity means a higher first cost for larger compressors and heat exchangers, while lower efficiency results in higher operating costs and potentially greater greenhouse gas emissions through indirect sources (increased use of fossil fuels back at the power plant).

5) Once the above factors are addressed, demand will need to increase to a point to make it profitable for refrigerant manufacturers to bring the costs down to reasonable levels. Today, these HFO refrigerants can be several factors higher cost than HFCs. The newer HFO fluids are more complex molecules and require additional steps in their manufacturing processes than conventional HFCs, which suggests higher prices, even at global production scale.

As the phase-out of ozone-depleting CFC and HCFC refrigerants continues, drop-in alternatives are limited. Although R-134a and R-410A are the subject of much discussion in regulatory and political circles, they remain the best refrigerant choices for most stationary HVAC applications. In fact, HFCs will continue to be the best choices for our industry – at least until the performance hurdles, risks and concerns for safety associated with the many new, emerging refrigerants are addressed and a local supply becomes readily available and cost-effective.

Brian S. Smith is Director, Global Marketing, Chiller Solutions, Building Efficiency at Johnson Controls.

 



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