Control and balancing valves, coil losses, etc. on a critical run should be assessed to see if oversizing is beneficial. Internal pipe fittings can have more than 10 times the pressure drop of external fittings and should be examined closely. Likewise, central-plant components and arrangements should be analyzed for possible savings.

Perhaps the most wasteful practice in HVAC engineering is the oversizing of central-plant equipment. Design teams need to work with owners to reach a better understanding of the benefits of more accurate system sizing.

Engineers should not fall into the trap of thinking that if a little pipe insulation is good, a lot would be better. There is an extreme law of diminishing returns in insulating pipes.

Engineers should verify that actual flow and pressure correspond to design. If they do not, the engineer should work with the contractor to determine why.

The engineering community needs to develop metrics that define distribution-system efficiency.

Energy-efficient design is only half the story. The other half is the materials (e.g., pipe, fittings, glues, solvents, solder, gaskets, sealants, tapes, and lubricants) used to create systems. The following issues should be considered when choosing piping material:

• Toxicity

  Potable water for human consumption should not be exposed to potentially toxic materials. Lead, heavy metals, polyvinyl chloride (PVC), dioxins, and other toxins should be avoided.

• Longevity

  If something is built using half the resources, but its useful life is half as long, the net benefit is zero. When this occurs with piping systems, the net benefit is less than zero because piping-system failures almost always result in collateral damage, such as mold. Making matters worse, pipes often are concealed, allowing damage to progress unnoticed for years, ultimately requiring substantial additional costs for repair or replacement. It is more important to specify top-quality systems that last for the life of a building.

• Recyclability

  Recyclable piping systems do not contribute to landfills and can be made into other useful items. Recycled materials, however, never should be used to make new pipes. By nature, recycling introduces impurities. Impurities affect the toxicity and quality of pipe.

• Thermal integrity

  When hot or cold fluids are being transported, the piping materials chosen should not be able to conduct heat out of the fluid, allowing for the reduction or elimination of pipe insulation and associated costs and the lessening of environmental impacts.

• Chemistry

  Chemical interactions between fluids and piping materials can result in premature failures of piping systems and water contamination. Historically, engineers have tried to protect piping systems from the fluids they carry by adding inhibitors. However, this entails adding chemicals to the mix. More chemicals mean greater chances for unintended consequences, such as chemical incompatibility or environmental contamination. To protect people and the environment, engineers must strive to select the toughest, most inert, and least harmful materials and use as few materials as possible.

• Pollutability

  A detailed analysis of steel, copper, and plastic drinking-water piping systems was conducted by Technical University in Berlin.¹ The ecological impact of each type of piping material from raw-material sourcing through manufacture, installation, and disposal was quantified. The study also evaluated the relative energy required to produce the piping systems. The results showed more intensive ecological pollution loads associated with metal pipe systems. Pipe systems made of polypropylene (PP), cross-linked polyethylene, polybutylene (PB), and chlorinated PVC plastics were found to represent a more ecologically beneficial solution. In terms of energy balance, recycling, and waste disposal, PP and PB piping systems were found to present the most environmentally beneficial alternative to metallic piping systems.

Piping engineers are in the position of being stewards over vital natural resources, and they make decisions every day that have long-term effects on the health of people and the planet. They are being called on more than ever to seek better answers to the challenges facing us. If we are supposed to consider the environment before printing an e-mail, how much more should we consider it before designing a piping system?

1. Kauter, H., Weinlein, R., & Jokel, C. (1994). Final report: Comparative analysis of drinking water systems. Berlin: Technical University Berlin.

President for North America for plastic-pipe manufacturer Aquatherm Inc., Steven J. Clark, PE, P.Eng., has 30 years of experience in building-energy optimization, including performance of design and energy studies for commercial, institutional, and industrial facilities. His building-system designs have won energy-efficiency awards in the United States and Canada. He holds several patents on HVAC and piping systems.