HPAC Magazine

By The Numbers

October 1, 2013 | By Rod Yeoh

The plumbing implications of green rating systems for existing buildings.

Today, building owners, managers, and tenants are all looking to make their buildings more sustainable and “green”, but how do they make sure that they are doing the right things? How do they prove that they are making their buildings more sustainable? This is where green rating systems come in. Rating systems provide a framework that building owners and managers can use as a guide to help them take steps to make their buildings greener. Most green building rating systems also have some form of third party review and this provides tenants with some assurance that the buildings they choose to occupy are actually living up to their green ambitions.

There are currently two green building rating systems for existing buildings that are being used and are fairly common in the industry in Canada. These are LEED EB:O&M and BOMA BESt. LEED is administered by the Canada Green Building Council (CaGBC) and stands for “Leadership in Energy and Environmental Design.” EB:O&M stands for “Existing Buildings: Operations and Maintenance.” BOMA is the Building Owners and Managers Association, which administers the “Building Environmental Standards” program known as BESt.

As an indicator of the uptake of each rating system, at the time of writing of this article, there are approximately 50 LEED EB:O&M certified buildings in Canada, as compared to approximately 3000 BOMA BESt certified buildings. As you can see, BOMA is currently used much more than LEED, mainly due to the fact that BOMA BESt is generally easier and less costly to achieve than LEED EB:O&M.

LEED EB:O&M and BOMA BESt are similar in many ways. Both are points based rating systems with various levels of certification based on how many points your building achieves. LEED has certification levels of Certified, Silver, Gold and Platinum, while BOMA has Level 1 to 4, in order of increasing difficulty and “greenness.” Both award points based on building performance in various categories such as energy use, water use, materials selection, site sustainability, and building operation.

While building plumbing systems can affect credits in other categories, this article will focus on the water use credits, which are the main credits associated with them. The building plumbing systems play a vital role in the water efficiency of a given building. Based on industry data and results of numerous water audits that I have been involved in, plumbing fixtures (lavatories, water closets, kitchen sinks, etc.) in the average commercial office building can account for anywhere from 25 to 75 per cent of the total water consumption. The remaining consumption is from irrigation, cooling tower make-up and other cooling water use, process uses (restaurants, pools, and so on) and leaks.

The water consumed by plumbing fixtures is fairly consistent in office buildings on a per occupant basis; however, the percentage of total use varies widely due to the variation in the water consumption of the other uses. For example, in a building with a typical open cooling tower, the make-up water use is quite high and the corresponding plumbing fixture consumption as a percentage is lower. Conversely, if a building has an air-cooled chiller, there is no cooling tower make-up water use, and the corresponding plumbing fixture use is much higher as a percentage of the total consumption.

The first step in reducing water consumption in a building is to perform a detailed water audit. Without knowing where and how the water is being used, you cannot execute a plan to reduce consumption effectively and efficiently. Water audits also help identify any obvious deficiencies or issues with the water consumption. The results of water audits are always very useful in determining the best use of resources to reduce consumption. 

A water audit begins with an analysis of the building’s historical water consumption. A detailed survey of the water consuming systems and equipment is then performed. Based on the historical data and the survey, a breakdown of the building’s water consumption is estimated and is used to provide a guide as to where the best “bang for the buck” is regarding water use reduction. There have been many instances in the past where the estimate based on the site survey could not account for a significant amount of the historical consumption, and subsequent investigation has found various leaks or fixtures or equipment running when they should not have been.

Once obvious deficiencies are corrected, the next step is to increase the water efficiency of the remaining systems. The most obvious step is to install low flow plumbing fixtures where practical. I stress “where practical” because simply installing low flow fixtures everywhere may cause other issues in the future or may not make sense from a practical standpoint.

One example is the installation of dual flush water closets. It is now fairly common to see dual flush water closets installed; however, their use in men’s washrooms should be reviewed, as most men’s washrooms also have urinals. As most men will use the urinals, the low flush portion of the water closet may not get used very much. Another example is the use of waterless urinals. Their installation in existing buildings should be reviewed to ensure that there is adequate flow of water from fixtures upstream of the urinal connection to the sanitary line to ensure that the undiluted urine does not corrode existing copper piping.

A final example is the use of low flow faucets on lavatories and sinks. Ultra-low flow faucets have flow rates as low as 0.5 gallons per minute. This very low flow rate can affect the ability of the existing hot water recirculation system to provide warm or hot water in a reasonable time. The existing hot water recirculation systems were most likely designed to provide hot water in a reasonable time with flow rates of 2.5 gpm or higher. A fixture that would have typically had hot water in 15 to 30 seconds may now take up to 2-½ minutes or longer to provide hot water at the reduced flow rate. However, with proper review and application, the installation of low flow plumbing fixtures can greatly reduce the water consumption and will contribute to whichever certification system the owner may choose to pursue.

Other ways to reduce water consumption include the storage and re-use of rainwater or other waste water sources. Greywater (collected stormwater or waste water from sinks) can be used to flush toilets and urinals, or for irrigation or cooling tower make-up. The use of recycled water for each of these purposes has various challenges, but it is possible in most buildings. Due to the need for entirely separate non-potable systems, the capital cost of greywater recycling can be quite high; however, in areas where water is scarce or costly, such systems may make economic sense.

Other water based credits in LEED EB:O&M include the requirement for metering of water consuming systems. Typically, the systems to be metered include the indoor plumbing fixtures and fittings, cooling tower make-up water, irrigation systems and process uses (restaurants, pools, clothes washers, etc.). In order to meter these correctly, some re-working of the existing domestic water systems may be required as the water supply systems may not be separated in a way that allows these to be metered separately. These systems should be reviewed on a case-by-case basis. 

Building owners and managers have many challenges in today’s economy. Tenants are more sensitive to sustainability issues and they expect the buildings they inhabit to be as sustainable as possible. Green rating systems provide a framework and guidelines for making buildings more sustainable, while providing third party verification of this. <>

Rod Yeoh, P.Eng., P.E., is a LEED accredited professional and a principal, mechanical engineering, with DIALOG in Vancouver, BC. As a sought after thought-l
eader, Yeoh has recently presented on sustainable mechanical systems integration to the Building Owners and Managers Association, BC Hydro, Terasen, Light House Sustainable Building Centre, ASHRAE, APEGBC and at Buildex Vancouver.



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