GLUMAC - Engineers for a sustainable future

Larry Oliver, CPD, LEED^® AP, Sacramento Associate Principal

This article is to provide an overview of potential LEED^® points available in a building and sustainable features focusing on the plumbing system. So what is LEED^®?

The U.S. Green Building Council (USGBC) developed the Leadership in Energy and Environmental Design (LEED^®) rating system in 1998. This rating system provides a point system score card to evaluate the environmental performance from a whole building perspective (non-residential). The rating system is organized into five environmental categories: Sustainable Sites, Water Efficiency, Energy & Atmosphere, Materials & Resources, and Indoor Environmental Quality. For the purpose of our discussion we will be focusing on Water Efficiency.

The Water Efficiency category of the LEED^® rating system is the least emphasized, with a potential of three LEED^® points obtainable through Innovative Waste Water Technologies and Water Use Reduction. The LEED^® rating system for Water Use Reduction is based on the U.S. Energy Policy Act of 1992. This Act set maximum plumbing fixture flow rates.

ENERGY POLICY ACT OF 1992

We now have a basis to evaluate sustainable features in a non-residential building. The purpose of LEED^® is to make buildings more efficient and sustainable than the maximum required levels. I will not differentiate between new or existing construction, it should be clear which features will be easiest to implement in the type of building you are evaluating or designing.

Innovative Waste Water Technologies: WE Credit 2, 1-Point

(Based on LEED^®-NC Version 2.2 Reference Guide)

Intent:

To reduce generation of wastewater and potable water demand, while increasing the local aquifer recharge.

Requirements:

Option 1

Reduce potable water use for building sewage conveyance by 50% through the use of water-conserving fixtures (water closets and urinals) or non-potable water (captured rainwater, recycled graywater, and on-site or municipally treated wastewater).

OR

Option 2

Treat 50% of wastewater on-site to tertiary standards. Treated water must be filtered or used on-site.

My experience is that the collection of rainwater is a fairly straight forward method of obtaining this credit point. I recommend the collection of rainwater from the roof rather than parking lots which contain oils and other hazardous waste contaminants which are more difficult to filter and handle for disposal to be used in the plumbing system. The collection of rainwater requires the rainwater drainage system be collected and piped to a collection tank(s) (underground or above ground). The rainwater is in most cases pumped from the collection tank through a series of filters (5 micron to collect the large particles and 50 micron to collect any other solids) and then passed through a UV sterilizer to kill any bacteria. The collected rainwater is now ready to be used to flush the water closets and urinals, keep in mind this is non-potable and should be treated as such. In my designs I provide a backup connection to the potable water system in the building in the event no rainwater is available. The backup connection of potable water is protected by a reduced-pressure backflow device to protect the building potable water system from the cross-connected reclaimed rainwater. This system is most likely to be designed in new construction, since an existing building retrofit would be cost prohibitive.

Example Case:

In this example, we will show potable water calculations for sewage flows for a non-residential building with an occupant capacity of 100 (50 males and 50 females). The calculation is based on a typical 8-hour workday. Male occupants are assumed to use water closets once and urinals twice a day. Female occupants are assumed to use water closets three times.

BASELINE CASE

Total Daily Volume (GAL) 420

Annual Work Days 260

TOTAL ANNUAL VOLUME (GAL) 109,200

DESIGN CASE

Total Daily Volume (GAL) 290

Annual Work Days 260

Annual Volume (GAL) 75,400

Rainwater Volume (GAL) (25,000)

TOTAL ANNUAL VOLUME (GAL) 50,400

The baseline case flow rates use the maximum flow rates based on the U.S. Energy Policy Act of 1992. Using a combination of water conserving fixtures and rainwater collection the design case building indicates a 54% reduction in potable water volume used for sewage conveyance; this therefore qualifies for the one point credit.

While the reduction of wastewater by use of rainwater is achievable the easier method of wastewater reduction as well as overall water use reduction is the application of water efficient fixtures. We will now look at the LEED^® credit water use reduction.

Water Use Reduction: WE Credit 3.1, 1-Point

(Based on LEED^®-NC Version 2.2 Reference Guide)

20% Reduction

Intent:

To maximize water efficiency within buildings to reduce the burden on municipal water supply and waste water systems.

Requirements:

Employ strategies that in aggregate use 20% less water than the water use baseline calculated for the building (not including irrigation) after meeting the Energy Policy Act of 1992 fixture performance requirements. Calculation based on estimated occupant usage and shall include only the following fixtures as applicable to the non-residential building: water closets, urinals, lavatory faucets, showers and kitchen sinks.

Water Use Reduction: WE Credit 3.2, 1-Point

(Based on LEED^®-NC Version 2.2 Reference Guide)

30% Reduction

This credit employs the same requirements as above except 10% more efficient.

It has been my experience that water saving methods of employing water efficient fixtures is both easy and cost effective for both new and retrofit construction. My standard designs employ all the requirements to comply and achieve these LEED^® credits. We can use our example above to demonstrate just how easy it is to be sustainable and water efficient at no additional cost.

BASELINE CASE

Total Daily Volume (GAL) 608

Annual Work Days 260

TOTAL ANNUAL VOLUME (GAL) 158,080

DESIGN CASE

Total Daily Volume (GAL) 315

Annual Work Days 260

TOTAL ANNUAL VOLUME (GAL) 81,900

The baseline case flow rates use the maximum flow rates based on the U.S. Energy Policy Act of 1992. Using a combination of water conserving fixtures the design case building indicates a 48% reduction in potable water volume; this therefore qualifies for the one point credit for the 20% reduction plus an addition one point for exceeding the 30% water use reduction for a total of two LEED^® points. What makes this so simple is the fact standard fixtures are available from all the major fixture manufacturers to meet these criteria. If we only used a 0.5 GPF urinal and water saving metering faucets on the lavatories we would still realize a 35% water reduction without changing the water closets.

The LEED^® point system also allows for Innovative & Design Process points (maximum of 4). These allow the designer to submit to the USGBC an innovative design concept that might not be covered within the existing point structure, such as Press-Fit copper piping or CSST gas piping. These systems may qualify for an innovative credit point because they use recyclable materials and are solder-less and oil-less which is environmental friendly.

Hopefully you see that providing a sustainable plumbing design to obtain LEED^® related points is fairly easy when thoughtful choices are made, in fact you may already be designing to meet these requirements. Although I discussed non-residential buildings all of these measures can be applied to residential as well.