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Water Use in High-Performance Buildings

Summary

An objective of EL’s Net-Zero Energy, High-Performance Buildings research program is greater sustainability and energy-efficiency across the built environment. Premise plumbing systems are a key element of building sustainability since living and thriving in buildings is highly dependent on efficient access to clean water. According to the U.S. Geological Survey, water use in the country is approximately 355 billion gallons per day,  and the operation of buildings accounts for nearly 12 % of that quantity.  Increasingly, the nation’s water resources are strained: severe droughts have affected two-thirds of the continental U.S. and groundwater levels nationwide are being depleted at alarming rates.   

The plumbing industry, including the International Association of Plumbing and Mechanical Officials (IAPMO) and International Code Council (ICC), have called for updated data and tools for redeveloping plumbing codes. Plumbing systems are being designed with codes and standards that were intended to provide safe water and remove waste from buildings at higher flow rates. Additionally, there are health concerns about a possible link between plumbing system design and the growth and transmission of pathogens such as Legionella. Thus, researchers, building practitioners, and policy makers are all keen to update plumbing systems to meet both water efficiency and water quality needs.

In the first two years, this project has generated several products, including: a workshop to bring together stakeholders in the water efficiency and water quality communities  and a research agenda addressing premise plumbing issues. Upcoming products focus on gathering data and developing plumbing simulation tools and models to support improvement of plumbing codes considering the issues stated above.
 

Description

Objective:  To develop data and tools that quantify performance of premise plumbing systems in high-performance buildings, and to support the development of building water efficiency standards and codes.

What is the technical idea?  
Building designers and standards makers have traditionally focused on energy efficiency when developing high performance building standards and codes. There has been more activity to incorporate water metering and conservation into these codes and standards (e.g., ICC Plumbing and Mechanical Code, IAPMO Green Plumbing Code, IAPMO Water Demand Calculator, ASHRAE Standard 191P). Buildings are being designed with features such as efficient water heating appliances, low-flow fixtures, and efficient landscape water use. Water labeling of residential buildings, such as EPA’s WaterSense Labeled Homes program and the RESNET HERSH2O program, are gaining traction as well. On the other hand, minimal water use has also had unexpected consequences in premise plumbing systems. Institutions such as the EPA have stated that lower flows can impact water quality, costs, energy consumption, and public health.   Currently, there are few tools that can predict physical conditions in low-water flow plumbing that can result in disinfectant loss, chemical accumulation, and biofilm growth. 

In response to this activity, the technical idea is to develop new measurement methods, collect data, and develop models to address efficiency and safety concerns for modern plumbing systems. 

 

What is the research plan? 
Discussions with individual stakeholders have led us to conclude that experts in water conservation, plumbing design, water quality, and public health desire more engagement with each other. This engagement would inform water use and plumbing guidelines for buildings that would satisfy their respective concerns for building occupants. The first product was a workshop in FY18 that successfully identified premise plumbing research needs.  Major outputs in FY19 were a document that summarized the workshop discussion and a research roadmap articulating the measurement science needed to improve the efficiency and quality of water delivered through new and existing premise plumbing systems.  Subsequent activities in FY20 will disseminate the research roadmap and promote its implementation among key stakeholders in the plumbing industry.

Plumbing codes cannot be improved without an understanding of how pipe design impacts plumbing system performance. A FY20 focus will be to develop several plumbing models that will predict conditions in pipes of various sizes, materials, and configurations. A survey of current tools revealed that, while many have the capability to model hydraulic phenomena or materials transport in pipes, no tool to-date combines thermal, hydraulic, chemical transport, and reaction modeling to comprehensively predict water quality conditions in pipe networks. Data from such a model will be helpful for determining conditions such as stagnation or low-flow that are detrimental to water quality. In FY20, we will begin by using currently available, open-source simulation tools to integrate a simple thermal model with a hydraulic model. Using this model, we will simulate the Net Zero Residential Test Facility’s (NZERTF’s) cross-linked polyethylene (PEX) plumbing system under its current water use profiles, as these types of plumbing networks are becoming more prevalent in high-performance buildings. A subsequent simulation is planned for a plumbing network sized for the NZERTF, but with a traditional trunk-and-branch architecture and standard-sized copper pipe to compare the NZERTF to a conventional home with regard to plumbing thermal performance. Finally, we will integrate a water quality simulation into our model and use water quality data taken at the NZERTF to validate that model. These efforts will lead to journal publications in FY20 and FY21.

This project will continue the effort to better characterize the connection between water efficiency and water quality in low-flow residential building plumbing systems by publishing water quality data on samples collected at the NZERTF. Data taken of sediment concentrations in water heating tanks, concentrations of disinfectant residual and microbiota, and biofilm growth in the plumbing system in FY19 to FY20 will help characterize the overall performance of the plumbing system. The output, a journal publication, will be written in conjunction with collaborators at the end of FY20.


[1]   U.S. Department of the Interior, U.S. Geological Survey, “Estimated Use of Water in the United States in 2010,” http://pubs.usgs.gov/circ/1405/pdf/circ1405.pdf

[2]   U.S. Green Building Council, http://www.usgbc.org/articles/green-building-101-how-does-water-efficiency-impact-building

[3]               U.S. Geological Survey. http://groundwaterwatch.usgs.gov/net/ogwnetwork.asp?ncd=lwl

[4] U.S. Environmental Protection Agency. https://www.epa.gov/research-grants/national-priorities-impacts-water-conservation-water-quality-premise-plumbing-and

[5] NIST Technical Note 1660. 2010. http://ws680.nist.gov/publication/get_pdf.cfm?pub_id=905024.

Created February 28, 2018, Updated October 17, 2019