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Contributed by Bob Hitchner, Chief Sales & Marketing Officer, Nexus eWater, Inc.

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The California Building Standards Commission recently acted at breakneck speed to implement emergency regulations to address the drought.

On Friday, May 29th, the BSC met, adopted a number of new rules, and put them into effect as of June 1. The normal public comment period will be held in parallel over the coming months.

What impact will these new rules have on residential home builders?

CalGreen, which is California's own Green Building Code, includes both mandatory and voluntary measures. The mandatory measures have the same impact on new building construction as any other part of the State Building Code, while the voluntary portions, as their name implies, are not required but often signal the direction of things to come.

The Emergency Regulations have two important impacts on builders:

1. Cuts in Allowed Water Use Outdoors

The maximum allowed outdoor watering budget for landscapes, the so-called MAWA, has been cut by about 20%.

We estimate the impact to be about 20,000 gallons (annually) for homes with a landscape area of 4,000 sq feet.

2. Encourages On-site Water Recycling

The CalGreen Code now actively encourages builders to implement alternate water systems including rainwater and greywater.

By using On-site Water Recycling to create so-called Special Landscape Areas (SLA), landscapes can earn a larger watering budget under the MAWA calculation.

Reducing Water Use Outdoors

The new regulations reduce outdoor watering budgets through the formula for calculating water budgets in the Model Water Efficient Landscape Ordinance (the MWELO).

The new regulations have lowered an adjustment factor in the formula from 0.70 down to 0.55.

See what this formula change does to the maximum allowable water budget (the MAWA) for a 4,000 sq ft landscape in the City of San Diego:

Formula: Evapotranspiration X Adjustment Factor X 0.62 X Area = MAWA

  • San Diego, old rule: 46.5 X 0.70 X 0.62 X 4,000 = 80,724 gallons
  • San Diego, new rule: 46.5 X 0.55 X 0.62 X 4,000 = 63,426 gallons

As this calculation shows, maximum allowable water budget has dropped 17,000 gallons, or 21%, for this San Diego home with 4,000 sq ft landscape.

If you want need more water for your landscape, what can you do? Look below at how On-site Water Recycling can be leveraged to give you a lot more water in your MAWA.


Encouraging On-site Water Recycling

The Emergency Regulations use the term "On-site Water Recycling" to define the use of alternate water supplies including harvested rain water and grey water. This is a first for a State agency and is music to the ears of advocates for wider use of on-site water resources.

Kudos to the Building Standards Commission for giving it a name that makes sense to everyone.

As a builder, why might you want to use On-site Water Recycling in your next home? Because it creates a larger water budget for your landscape.

Under the MWELO, so-called Special Landscape Areas (SLAs) qualify for a larger water budget under the MAWA calculation.

And what qualifies a landscape to be an SLA? It must either be edible plants (e.g. a vegetable garden) or it must be supplied with non-potable water.

Using the example from above, what happens to the MAWA calculation if the home uses On-site Water Recycling to supply non-potable water and make the entire landscape an SLA? Under this calculation, the adjustment factor for the SLA landscape is raised by 0.45, from 0.55 to 1.0.

Remembering that the Water Budget (MAWA) without On-site Water Recycling was 63,426 gallons annually, see what it is now:

SLA Impact on Water Budget (MAWA)

San Diego, new rule: 46.5 X (0.55 + 0.45 ) X 0.62 X 4,000 = 115,320 gallons

By implementing On-Site Water Recycling, the water budget for the same 4,000 sq ft landscape can be raised by over 50,000 gallons!

(The details of the MAWA calculation will be incorporated into a new MWELO calculator to be announced by the Department of Water Resources for the first time on June 12th. Landscape designers should refer to the most recent draft of these regulations to determine the MAWA).

Now look further at how the Emergency Regulations further encourage and promote the use of alternate water sources in CalGreen's voluntary Tier 1 and Tier 2 standards for exemplary water use efficiency.

To achieve either Tier 1 or Tier 2 status, the home must employ at least one alternative water source.The complete elimination of potable water use in landscapes is set out as an explicit goal.

Implications for Builders

In the short term, builders can address these changes by:

(a) changing plant mix,
(b) using more efficient irrigation technology, or
(c) augmenting potable water with non-potable sources like grey water or harvested rain water.

Longer term, builders should decipher the writing on the wall, and expect even more pressure in the future to reduce the use of potable water on landscapes.

To get ahead of this curve and to provide greater value to homeowners today, builders should incorporate On-site Water Recycling into their landscape plans.

And how much on-site water is available to the homeowner?

  • A family of four will typically generate about 50,000 gallons of grey water annually.
  • A 2,000 sq ft roof in San Diego will effectively capture an additional 15,000 gallons of rainwater.
  • Together, these two key on-site sources are able to completely offset the entire water budget of most new homes in San Diego.

By embracing On-site Water Recycling, home builders can produce Water Performance Homes that will stand completely apart from all previous homes on the market. This will demonstrate to local political leaders the folly of acceding to the demands of anti-growth, NIMBY activists. It also gives new home buyers another reason to buy the shiny new, ever-more efficient home.

On-site Water Recycling is ready for prime time in the home marketplace. It can have a greater impact on the home market than the hybrid engine had on the car market. It delivers a whole new way to think about home water use.

The new Emergency Regulations embrace the implementation of On-site Water Recycling. Builders can use this year's PCBC to learn about the State of the Art.

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