Archive for July 2011
So we left off talking about one of the 8 LEED scoring categories. Water Efficiency. Last week I talked about one of the three sub-categories of Water Efficiency; water reuse.
This week I’ll talk about one of the other two sub-categories; outdoor water use.
Outdoor water use has to do with the irrigation system for the landscaping. You’d think that the landscape design and the kind of plants etc would dictate how much water gets used and to a certain extent it does. But in reality it’s possible to have a completely inefficient irrigation system watering an expertly designed LEED certified landscape plan. That’s why landscape is part of another LEED category called “Sustainable Site”. To earn LEED points for outdoor water use, Irrigation systems must be designed and installed to minimize the amount of water needed to maintain the landscape. Although a lot of this is kind of obvious, you’d be amazed at how much is overlooked and ignored in most of the irrigation systems installed.
There are two ways the maximum amount of points can be earned for outdoor water use. One is install a high-efficiency irrigation system and have a third party verify its efficiency. The other is to use a formula that calculates the amount of water needed to irrigate a specified landscape area that takes into account species, microclimate factors and irrigation equipment and then reduce that amount by 45%. If that sounds complicated and subject to serious interpretation issues, I agree. The first way is much easier to comprehend and implement. Here you get points for adopting at least three of 7 “strategies” that create an efficient irrigation system. Obviously it would be most efficient to adopt all 7 but LEED at this time gives max points if you adopt three.
Design a system with head to head coverage is one. Doing this keeps the water coming out of the heads from overlapping each other causing some areas to be watered more heavily than others. A second way is to use drip irrigation on at least 50% of the landscape beds. This puts more water in the ground and less in the air through evaporation. A third is to create separate zones based on the bedding type. More porous bedding types obviously absorb water quicker and can stand longer watering times while non-porous beds will create runoff in the same time frame. Installing a timer is a fourth way. This allows the landscape zones to be watered at the best time of day to avoid evaporative effects and to only water for a specified time related to the needs of each zone. Fifth is to install pressure regulating devices to maintain proper pressure and avoid misting. Misting water never hits the ground and ends up as humidity in the air. Sixth is to use high efficiency nozzles that control distribution uniformity so areas within the zone receive the same amount of water. And seventh is to install a moisture sensor controller that shuts the system down in case of rain. How stupid is it when you see someone’s sprinklers on while its raining.
As I said its best to use all 7 seven strategies but for LEED purposes you max out in terms of points at three. I think over time in locales that have water issues, all these strategies will be law instead of optional, and in reality they should be. As I said before most of the growth in this country is occurring in areas with water issues and learning how not to “waste” water now, makes it easier in the future.
Next time we’ll talk about indoor water use.
So last time we talked a little about water efficiency. I talked about how water is an interesting natural resource because we definitely need to be efficient in its use, but not because of its scarcity. In fact water is basically an unlimited resource. We need to be efficient in its use because it’s a pain in the ass and costly to procure, treat and distribute. Especially if you live in an area where it doesn’t naturally exist…..like most of the southwestern portion of the United States. Of course that’s ironic because MOST of the growth in this country in the last 50 years has occurred in the southwest portion of the United States.
Remember I also said last time that growth can be severely limited by access to water. As a region tries to grow, if it can’t get water, it won’t grow for long. As the costs of getting MORE water to an area increase, it will eventually become a situation where those costs will exceed the ability of that region to grow. If the costs of getting MORE water are prohibitive, then the only way to grow is to use the water that you ARE getting more efficiently.
LEED awards points in their certification process for building new homes and neighborhoods that use water more efficiently. There are three areas points can be earned.
First is the reuse of water. And there’s three ways points can be earned there. First we can capture and reuse rainwater. Obviously it can’t be used for everything as it isn’t treated for drinking or bathing purposes, but it can certainly be harvested and used for landscaping. Of course it’s a little expensive and impractical to try and harvest rain in an area that has little or no rainfall so we haven’t looked at this option very seriously.
Second is the use of “gray water”. Gray water is untreated household wastewater that has not come into contact with toilet waste, kitchen sinks or dishwashers. It includes used water from bathtubs, showers, bath sinks, and clothes washers. Toilet waste and used water from kitchen sinks and dishwashers is called black water. It cannot be reused. Gray water absolutely can be reused for landscaping purposes. A sewer system must be devised that separates black and gray water and diverts them to different areas. This is where the cost comes in. In most communities ALL wastewater goes into the same sewer system and ends up in city treatment facilities. LEED will award points for a project that devises a system to separate and capture gray water so it can be reused.
Third is utilizing a Municipal Gray Water system. Some forward thinking cities have their own systems in place that separate gray and black water. Building a project that hooks into that system gets LEED points as it helps use water more efficiently.
The other two areas LEED awards points for has to do with outdoor and indoor use. I’ll address them next time