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Existing Commercial Buildings Energy Performance Ordinance: Overview
I wrote this blog for my friends who are just too busy and did have a chance to attend the meeting at PG&E. I will try to rewrite the most important notes of the meeting and Benchmarking exercise but do feel free to go to www. sfenvironment.org/ecb for more information.
The intent of the existing Commercial Buildings Energy Performance Ordinance is to help the local market maximise energy efficiency in San Francisco by empowering owners, managers, operators and occupants with the key inormation to control utility costs, and to know exactly how they will benefit by improving energy efficiency.
For exisitng nonresidential buildings 10,000 sf and larger the ordinance requires:
An Actionable Plan: An energy efficiency audit identifying specific cost-effective measures that would save energy.
A Benchmark: Track and annually summarize the energy used by the entire building, enabling tracking of trends and comparison to similar buildings under similar conditions across the nation.
Transparency: Annually share a concise overview of each building's energy benchmarking results with the Department of Environment will ultimately be required to make this type of information available to the public. The Annual Energy Benchmark Summary Report is intended to encourage improvement in Energy management, as well as sustained excellence.
It is the building owner's decision how to benefit from opportunities identified in the energy efficiency audit. Commercial properties in San Francisco are eligible for rebates (such as the San Francisco Energy Watch program: www.sfenergywatch.org and special financing that enhance both your bottomline and cash flow.
There are of course obvious benefits: effective recommendations from experts reduce operating costs; reduce if not avoid utility rate increases and improves you asset value.
BENCHMARKING
Each whole non-residential building larger than 10,000 square feet must be benchmarked using Energy Star Portfolio Manager.
(www. energystar.gov/benchmark). Portfoilo Manager is an online tool provided at no cost to the user by US Environmental Protection Agency. The benchmarking requirment is being phased in over three years.
Building owners or their representatives must annually electronically share a brief report of key benchmarking results with the Department of Environment and tenants. This reprt is an "Annual Energy Benchmark Summary", and is based on data from the prior calendar year. For example, a 2011 report will be based on energy used from January 2010 to December 2010.
The ANNUAL ENERGY BENCHMARK SUMMARY REPORT will include:
Contact Information and square footage.
Energy Use Intensity ( how much energy the building used per square foot for the year)
1- 100 Performance Rating provided by Portfolio Manager, where applicable
Greenhouse gas emissions from energy usage.
(Soon they will add water usage). The Annual Energy Benchmark does not include commodity energy use (KWh or Therms) for the whole building or for any meters.
Benchmarking with Portfolio Manager will also be required under California Public Resources Code 25402 ( AB 1103) Where the San FRancisco Existing Commercial Buildings Energy Performance ordinance requires annual benchmarking and public disclosure of limited statistics summarizing overall performance.
The complimentary State Law will require private disclosure of all energy usage information between parties to the sale,lease or refinance of the entire building. For additional information:www.energy.ca.gov/ab1103/
For the first year that an Annual Energy Benchmark Summary Report is required for a given building, the Department of Environment must keep the report confidential. In subsequent years of reporting for that same building, the Department of Environment is required to make the Annual Energy Benchmark Summary public. Classes are available online at PG&E Pacific Gas & Electric, US EPA's ENERGY STAR program provides both live webinars and recorded training on how to benchmark with Portfolio Manager.
EXEMPTIONS to Benchmarking Requirements:
An Annual Energy Benchmark is not required for:
NEW BUILDINGS (The certificate of Occupancy from the Department of Building Inspection is dated less than two years prior to the Annual Energy Bechmark due date).
UNOCCUPIED BUILDINGS:
IN ALL OTHER CASES, THE ANNUAL ENERGY BENCHMARK SUMMARY IS REQUIRED. To obtain an exemption to benchmarking requirments, please write to: Bechmark@sfenvironment.org. In the message inlude:
Contact Information for the owner, and the owner's agent if applicable.
Assesor Parcel Number (Block and lot)
Gross square footage of the building(s).
Reason for exemption:
Certificate of Occupancy or a copy
Signed Statement that the building was unoccupied for the 12 months prior to calendar year.
Benchmarking Timeline:
AEBS reports will generall be due April 1 In 2011, the reports are due October 1. 2011 will be based upon measured energy performance January 2010 through December 2010.
How to submit an AEBS:
To fulfill the benchmarking requirment, the Annual Energy Benchmark Summary 2011 report template must be used: http://bitly.com/rtAK9C or visit www.sfenvironment.org/ecb This link leads you to Portfolio Manager login page. By accessing your account through this web link, a custom report template for compliance with the ordinance will be available in your account. By using the AEBS report 2011 template, you will securely submit to the Department of Environment only the data required to meet the ordinance and no more and data willbe shared with the Department of the Environment ehnw you click "Release Data" at the end of the process.
Energy Efficiency Audits Benchmarking provides the perspective about how a building performs relative to its peers.To identify specific opportunities:
for savings,
weigh cost against benefits
prioritize investments
an energy audit is necessary.
The owner of each non-residential building larger than 10,000 sf must obtain a comprehensive enrgy efficiency study of the entire building from your qualified energy auditor at least once every five years.
The Auditor or Project Engineer/Architect is responsible for submitting a detailed report to the building decision makers. The idea is to provide a catalog of opportunities to cost effectively improve energy efficiency, improve over 2008 Title 24, gain net zero emmission. It must meet ASHRAE Procedures for Commercial Building Audits.
The full Procedures for Commercial Energy Audits are available directly from ASHRAE:
Bottom line: Saves Energy will save you money and save your healthy life and create sustainable electricity for the community.
Energy Efficiency AuditsTIMELINE:
All building owners must have at least 12 months between the date they are notified an audit is required, and the date when the first Confirmation of Energy Audit is due.Notification of audit requirements is sent to the party by the Office of the Assessor Recorder as the contact for the property tax and the owner is responsible for filing a Confirmation of Energy Audit. The confirmation of Energy Audit will be required and will be filed online. No confirmation of audit is due until October 2012 at the earliest and a reporting mechanism will be provided at least 180 days before any audits are due.
Energy Audit will include:
Contact Information for the building and building owner.
Auditor, their qualifications and when the audit was completed;
A list of all cost-effective retrofit and measures identified. For reporting purposes, "cost effective" means energy measures that are estimated by the auditor to either:
Each have simple payback of 3 years or less
Each have beneficial net present value,
Comprise an integrated package with an overall simple payback of approximately 3 years.
comprise an integrated package with beneficial net present value.
Watch out for this date October 15, 2012 April 1. 2013, April 1, 20142 017 and beyond. Hopefull all of buildings will be Net Zero and will eventually produce some form of electricity for your electric cars, buses and personal mobile train.
EXEMPTIONS Energy Efficiency Audits Requirements:
High Performance Buildings: The building has received the ENERGY STAR in 3 of past 5 years or LEED for existing Buildings certification in the past 5 years.
New Construction: The building was constructed in the past 5 Years. The building thatmeet these above criteria are exempt from an audit the next audit cycle, and will remain exempt if they maintain current recognition for high performance.
Friend in SF, call: 415 992 6373 or You can email: benchmark@sfenvironment.org
Click on this video to get acquainted with what is greenroof is all about!
Green Roofs are Cool!
A green roof system is an extension of the existing roof which involves a high quality water proofing and root repellant system, a drainage system, filter cloth, a lightweight growing medium and plants.
Green roof systems may be modular, with drainage layers, filter cloth, growing media and plants already prepared in movable, interlocking grids, or, each component of the system may be installed separately.Green roof development involves the creation of "contained" green space on top of a human-made structure.
This green space could be below, at or above grade, but in all cases the plants are not planted in the "ground'. Green roofs can provide a wide range of public and private benefits.
A green roof can certainly make a building look nicer, but can it measurably lower energy requirements and improve water management? At Penn State University, engineer Jelena Srebric and horticulturist Rob Berghage are working together on a project to measure and model how a green roof affects the way buildings use energy and water. In Jelena's lab, undergraduate student Tyler Meek does weather experiments indoors to determine the effects of light, wind and water on the roof. Graduate student Paulo Tabares Velasco works with Tyler to make a mathematical model to explain the experimental data and predict what will happen in the real world. The researchers hope that architects will someday use their model to make building designs even greener.
How do "Green Roof" saves energy?
Here are selected videos to show benefits of green roofs from covering office buildings to gourmet garden plots on your home.
Green Roof® Saves Money.
Prevegetated modules discourage weeds and save the time and money traditionally required to develop and maintain a green roof grown from plugs, seeds or cuttings. Other systems may require three or more years for establishment and intensive care is needed during this time period. Well-established LiveRoof® plants and roots mean an instant green, successful, and instantly functional green roof.
Maintenance cost estimates for traditionally planted green roofs vary from $1.00 to $2.00 per square foot annually. LiveRoof® can be maintained for as little as $0.15 to $0.30 per square foot. Being fully grown, LiveRoof® plants act as a living mulch.
Architecture + Landscape Engineering
Here are list of issues that need to be addressed by your architect and engineers on your green roof:
Annual Rainwater Absorption
BIM Components
Downward Force Against Parapet For Sloping
Effect of Supplemental Irrigation
How Much Slope Is Too Little?
How Much Slope is Too Much?
Fire / Spread of Flame
FM Approval
Irrigation vs. No Irrigation
Job Site Safety
Level or Gently Rolling?
Native Plants
Parapet Design
Plant Basics
Positive Wind Pressure
Rainfall Absorption
Rainfall Intensity
Retrofit Roofs
Recommended Plants
Roof Slope
Runoff Basics
Runoff Coefficient
Seasonal Weather and Rainfall Patterns
Soil Characteristics
Soil Depth
Tall Buildings: How High is Too High?
Wind and Sun
Wind Pressure
Wind Uplift?
What Will My LiveRoof Look Like In The Future?
Wind Pressure
As with any roof, high winds can pose a threat to the security of green roofs, and care must be taken to properly design and engineer the green roof so that it retains its integrity during high winds. To do this, consideration of wind pressure and associated variables, such as the building’s geographic location, surrounding terrain, shape, slope, height, building openings, parapet design, and other features is essential.
At the tip of the iceberg, of wind pressure, one must consider the typical high wind speeds for that region. Consulting ASCE 7.95 Figure 6-1 Basic Wind Speed, or Factory Mutual Global Property Loss Prevention Data Sheet 1-28 is a good first step. In addition, the engineer must consider the surrounding terrain; for example, is the building situated along water, mountains, open field, surrounded by tall trees or taller buildings?
Of course the building design itself is very important. Low rise buildings (generally regarded as 60 feet and lower) are less affected than high rise buildings (60 feet and taller) which in addition to direct (positive) wind pressure are more greatly affected by negative wind pressure, often referred to as uplift or suction.
Positive Wind Pressure
Positive Wind Pressure is the force exerted by the wind as it strikes an object, or building. Positive Wind Pressure is evident when a tree (or other object) moves or bends over in a strong wind.
LiveRoof modules, when populated with a base mixture of flexible-stemmed hardy sedums (the backbone of the LiveRoof product line) were wind tested on 1/25/08 with wind speeds exceeding 110 MPH. In this test, the LiveRoof planting (4’ x 5’) was surrounded with Edging and first exposed to 10 minutes of wind at 95 MPH, followed by 1 hour and 50 minutes at 110+ MPH. The wind was impinged directly upon the surface of the LiveRoof planting as would be the case when testing other roof coverings. Remarkably, at the end of the test period, there was no loss of growing medium and all plants remained well rooted and intact. Throughout the test, the plants simply arched over, held in place by their root systems. This test demonstrated the value of full vegetative cover as a means of stabilizing the green roof system.
Negative Wind Pressure, Uplift
Negative Wind Pressure is what causes airplanes to fly, and it’s what causes roofs to want to fly. Negative wind pressure occurs when wind passes over an object that causes the wind to redirect and accelerate. This in turn creates a pressure differential and the pressure differential can be substantial.
In the case of roofs, wind accelerates as it passes over the roof edge or parapet, causing a pressure differential and lifting force, uplift, that is exerted upon the rooftop. Redirected winds of this nature tend to whirl and swirl, often in cone shaped vortices which can aggressively scour roof surfaces and components. Such forces are typically greatest in the corners of the roof, secondarily along the parapet walls, and to a lesser degree in the “field” or center part of the roof. Uplift forces vary with the building shape and height, parapet shape and height, overall exposure, size of openings, etc.
How Much Uplift?
In answer to the question, how much uplift force can a green roof tolerate, there is no simple answer, at least today there isn’t. Available information is mostly anecdotal and research is slow coming. And, because the weight, vegetation, and porosity of green roof systems is variable, and the particular components in which they interface (edging, pavers, parapets, etc.) are diverse, there has been little testing and there is no accepted testing standard or code.
However, in 2010 the American National Standards Institute (ANSI) accepted RP14 Wind Design Standard for Vegetative Roofing Systems as an American National Standard. This document provides design and installation recommendations to help eliminate the risk of wind uplift on green roofs in high wind areas. LiveRoof modules are fully vegetated at the time of installation and have subterranean overlapping lips, which allows them to be sheltered from direct wind exposure.
The LiveRoof Lite System is 2.5” deep and has a dry weight of approximately 10 psf, and thus meets the definition of #4 Ballast (3.13.1). The deeper Standard (4.25”), Deep (6.25”), Maxx 8” and Maxx 12” systems meet the definition of both #4 Ballast and #2 Ballast (3.13.2). This standard serves as a guide but should not replace the involvement of a qualified professional.
Given the absence of empirical data, many engineers treat green roofs as if they were pavers of similar mass, and pay particular consideration to negative wind pressure, at minimum reviewing the items discussed below. LiveRoof mentions these considerations as an impetus to diligent design and engineering, but does not purport to have specific knowledge of engineering principles. Such expertise and accompanying liability is the domain of qualified engineers. Now and in the future, LiveRoof will pursue research in hopes of providing more precise information as a support service to engineering professionals. For now we offer the following list of considerations to stimulate a diligent review of design and engineering considerations as they pertain to green roofs.
Parapet Design
Low rise buildings in areas of moderate exposure may present fewer challenges in regard to Positive or Negative wind forces. But, taller buildings may cause one to have to be more creative. Design strategies that moderate wind uplift forces and disrupt the formation of surface-scouring wind vortices may be employed in the overall green roof design.
Regarding low rise buildings, a lower parapet design may avoid potential air turbulence and help to minimize uplift forces. And, for buildings containing only a single parapet, as is commonly used as a facade for aesthetic purpose, one should keep in mind that the parapet may dramatically increase the uplift pressures in the corner regions. Conversely, on high rise buildings (over 60 feet), higher parapet height can be an effective tool in moderating uplift forces. Studies on parapet height typically indicate that parapets over 3 feet tall can moderate uplift pressure in the corners of the roof on high rise buildings. Likewise, the use of a partial parapet with attached porous screen may be used to reduce uplift pressures and expand design options for taller buildings. And, parapets of different shapes, e.g. saw-tooth configuration, rounded vs. sharp edges, or the application of spoilers are sometimes used.
Keep in mind, that the taller the parapet, the more Positive Wind Pressure against the parapet itself, both windward and leeward sides.
Wind Challenged Applications
In very challenging applications an engineer may have to direct the architect to forego using the LiveRoof Lite system (about 9 to 10 lbs per sf when bone dry) in favor of the LiveRoof standard system (about 18 to 20 lbs per sf when bone dry). And, in the most wind challenged applications, an added means of securing the LiveRoof (either LiveRoof Lite or Standard) may be needed to safeguard the LiveRoof system. Accessory products for extreme uplift designs may include any or all of the following. (A-C).
A. Limiting the LiveRoof to the center “field” of the roof top, and using heavier ballast in the corners and along the parapet edges. Such ballasted perimeter design is referred to as a “vegetation free” zone. Vegetation free zones will vary with the parapet height and geometry.
B. Overlaying the LiveRoof with a mechanically fastened stainless steel netting such as CarlStahl’s Decorcable, flexible stainless cable mesh, sales@decorcable.com, 800-444-6271 or G-Sky Netting.
C. Adhering the LiveRoof modules to a fully adhered rooftop using special two-sided adhesive tape.
Tall Buildings: How High is Too High?
Tall buildings present three substantial challenges for green roofs. The first is wind uplift. This is a physical phenomenon that presents certain design and engineering considerations, discussed in detail under the wind uplift section.
The second is wind scour. This is the physical displacement of soil and/or plants due to the force of the wind. The best defense against wind scour is full-vegetation, which LiveRoof provides. It is also important to remediate any “bare-patches” that might arise in the future. Bare patches can be caused by weed encroachment, nesting, birds, or physical damage.
The third challenge involves the plants and their ability to resist the wind and cold at high building elevations.
The answer to the question “how high up can green roof plant survive?” is not well understood, at least not at this time. Very tall buildings, for example over 20 stories tall, are subject to virtually constant wind. This in itself is not a problem for the plants, as most green roof plants hail form alpine environments where there is also a lot of wind.
The problem seems to be an issue of dehydration and wind chill, particularly in areas of persistently cold winter temperatures. In such cases, the soil will be frozen for prolonged periods of time, and therefore, the plants can not extract water from the soil to replace the moisture lost from wind desiccation. If this occurs for too long of a duration, the plants essentially become “freeze dried”, and their tissue dies.
At the present time, the level of experience and bona fide research with this problem is not sufficient to be able to quantify the effect in such manner that makes it simple to properly plan and design for tall building applications. No one can say “on the 35th floor in New York City, you can effectively grow these five species of plants”. Therefore, at present we must rely upon anecdotal experiences, and upon common sense.
What we suggest is the following:
The issue will likely be more significant in Chicago than Atlanta: The tallest LiveRoof brand green roof, to date, in Chicago is at 28 stories. Installed in 2010, but it has not yet seen a winter. We have, however, installed a LiveRoof brand green roof on a 16th. story exposure during 2008, and it has persisted without a hint of plant damage during wintertime (note: the winter of 2008/9 was one of the coldest in recent history).
Deciduous plants: Plants that drop their leaves are likely better equipped to resist the rigors of constant winter chilling winds. This is because they present less surface area for chilling.
Irrigation is good: In areas where the winters tend to be dry, giving the plants periodic irrigation can help them to resist dehydration during cold spells.
As we learn more about this issue, we will make that information available.
Downward Force Against Parapet For Sloping Applications
The combination of a green roof (unaffixed object), slope, and gravity imply the need to address physical containment and resistance to downward pressures exerted by the green roof against the parapet and mechanical fixtures of the roof especially in cold climate areas where ice crystals may form on the slip sheet/root barrier surface during winter. For this reason, LiveRoof recommends that the slope and size of the roof be assessed in regard to force that will be exerted against the parapet (or other mechanical features of the roof).
For the convenience of engineers, LiveRoof provides force tables for use in designing each particular LiveRoof project. These tables assume “zero” friction and present a conservative model based upon the assumption of ice between the slip sheet membrane and the LiveRoof modules during the winter months. Obviously, this may not be appropriate for frost free zones, but one must realize that certain roofing membranes are coated in talc or other lubricants to prevent sticking. Others membranes may be slippery when wet. Therefore, even in frost free zones, one should assume a degree of downward force on sloping applications.
For long roofs and roofs with great slope, it may be appropriate to incorporate “stops” or buttresses in the design to prevent all of the load from being exerted against the parapet on the low side of the roof. In all cases, it is important to realize that the low side parapet must be built in such manner as to have the structural integrity to resist whatever forces exist given the design of the particular roof.
How Much Slope is Too Much?
Both of the main international green roof organizations, the German FLL and North America’s Green Roofs for Healthy Cities agree that green roofs should not be applied to roofs with slope of greater than 40 degrees. This stems both from containment challenges but also from the extreme difficulty in managing soil moisture on a roof of such pitch.
You may be familiar with the properties of a wet sponge, where it will hold so much water when laying on its side. But, after you prop it up on its end even more water runs out. Soil acts the same way and as the pitch of the roof increases, there is a greater tendency for the water to want to run out of the system. Green roofs above 2’/12’ pitch are commonly dry at the top and moist at the bottom. And, while the segmental or baffled characteristic of LiveRoof may help to mitigate this phenomenon, pitched roofs will certainly require more irrigation than low sloped green roofs.
How Much Slope is Too Little?
While this question is seldom asked, it is important to design for adequate drainage. Most authorities state that a roof needs ¼”/12’ slope to provide adequate drainage. Without this, water may accumulate and damage the health of your LiveRoof plants.
Level or Gently-Rolling?
Most LiveRoof installations simply follow the contour of the roof for a lovely, gently-rolling, meadowlike appearance. If a dead-level LiveRoof is required, it can be realized by applying a tapered closed cell foam to the roof above the waterproofing layer. If this is done, the closed cell foam must allow for adequate water drainage.
Job Site Safety
Remember, wind uplift should be managed during the entire installation process. High winds can come at any time and will not wait for the installation process to be completed. Be sure to cover materials with appropriate temporary ballast.
Retrofit Roofs
Retrofit Projects are exciting as they represent a tremendous upgrade to aesthetics and environmental quality. Of course, they bring their own particular challenges that need to be addressed from an architectural and engineering standpoint. Here are some of the main considerations for retrofit green roofs.
Determination of the construction, condition, and load capacity of the pre-existing roof and suitability to accept a LiveRoof.
Determination of the condition of, remaining warranty lifetime, and terms or warranty of the existing waterproofing system as it pertains to being retrofitted with the new LiveRoof.
Compatibility of the existing waterproofing system with the proposed slip sheet membrane.
All the same issues regarding positive and negative wind pressure, slope, and forces against the parapet as they relate to new construction also apply to retrofit roofs.
In 2010, the American National Standards Institute (ANSI) accepted GRHC/SPRI VF-1, Fire Design Standard for Vegetative Roofs as an American National Standard. This document provides design and installation recommendations to help eliminate the risk of fire on green roofs. A code change proposal has been submitted to the International Building Code to include this standard in the 2012 edition of the International Building Code. Depending on the plant selections, LiveRoof systems meet the requirements to qualify as generic fire-resistant “Succulent based systems” (4.1.1) or “Grass based systems" (4.1.2).
To Irrigate or Not to Irrigate?
While irrigation may only be needed during protracted hot dry weather (to sustain the plants), there are other reasons to install an efficient means of irrigating one’s green roof. Irrigation allows the green roof to be fully optimized. With the ability to irrigate during hot dry weather the rooftop can be turned into one big cooling unit and save money on air conditioning. Remember water liberates 8000 BTU of energy during evaporation (latent heat of evaporation), and pumping water is efficient and cheap, but running air conditioners is inefficient and expensive. The cooling effect derived by irrigating allows for the conservation of energy in comparison to the energy wasted on cooling by less efficient methods.
According to some authorities, and dependent upon the particular climate, during the cooling season the temperature in the room below an irrigated green roof may be reduced 16 to 27ºF compared to a reduction of about 11-13ºF for a non irrigated green roof. This difference is substantial and can mean considerable savings on air conditioning costs. Estimates of cost savings for air conditioning range from 25% to 50% for the floor under the green roof. Irrigating during hot dry weather allows for the optimization of the green roof’s cooling ability.
In rough figures, when an extensive irrigated green roof shows an average summertime temperature of 80 degrees, the same roof without irrigation will average about 100 degrees. Similarly, the membrane below the irrigated roof might fluctuate an average of only 7 or 8ºF during a 24 hour period, while the same green roof without irrigation may fluctuate ± 20 degrees. Less fluctuation may mean less wear and tear via micro-tearing on membranes, and therefore potential extension of the lifetime of the waterproofing membranes.
Judicious irrigation also keeps the green roof plants fat,
full and beautiful. This means better coverage, fewer weeds, less labor, and happier owners, occupants, and visitors. It also means lower maintenance costs and safeguards one’s investment in the green roof.
Finally, judicious irrigation should not significantly
impact stormwater management as irrigation typically occurs only during low rain/low runoff periods when the roof will dry out quickly from evapotranspiration.
Benefits of Irrigation vs. No Irrigation
• Net energy savings
• Reduced temperature fluctuation (less wear on membrane)
• Less maintenance cost
• Plants will be optimally beautiful
• Avoid plant loss due to drought
• Greater owner satisfaction
Plant Basics
The LiveRoof Standard and LiveRoof Lite systems are “Extensive” green roof systems. In other words, their soil depth is less than 6 inches. And, while extensive green roof systems optimize evaporative cooling and storm water management (in part because they can dry down between rain events), their shallow substrate depth means that the plants they can support must be extraordinary at resisting drought. Practically speaking, the plants that work best in “extensive” green roofs must be exceptional “water conservers” as opposed to “water sourcers”.
Water conservers are plants that store copious amounts of water in their fleshy stems and leaves. Cacti are the poster children for “water conservers”. They absorb water when available, and conserve it by closing their leaf pores during the day, by having a waxy cuticle over their leaves and stems, and by having relatively little surface area. Water sourcers, on the other hand, are plants that have extensive and deep root systems that go deep into the earth in search of water. Good examples of “water sourcers” are prairie plants such as little bluestem, purple coneflower, and prairie dock.
Recommended Plants
The LiveRoof system is typically vegetated with a palette of deciduous, semievergreen and evergreen “base mix”
and “accent plants” that are exceptional “water conservers”. These are succulent, water-holding plants like Sedums, Alliums, Sempervivums, Euphorbias, Delospermas, and other species. The best LiveRoof plants both store water and have a special type of metabolism called Crassulacean Acid Metabolism, CAM for short. CAM plants are unique in that under drought conditions their stomates (leaf pores) are open at night rather than during the day (as is the case with most plants). CAM plants exchange gasses (oxygen and carbon dioxide) in the dark when it is cooler and less windy and therefore conserve water. And, CAM plants are up to ten times more efficient with water conservation than non-CAM plants.
Can Native Plants Be Used?
While it is popular to say that native plants are better adapted because they evolved here, this notion is not necessarily true. A plant’s toughness or suitability, is dependent upon genetics and ecological and environmental adaptation (evolving with time and exposure). There is nothing magical about latitude and longitude as there may be similar or more demanding environmental conditions on the other side of the globe. In reality some native plants are tough, some aren’t, and a few will grow in an “extensive” green roof without frequent irrigation. The list, however, is quite short as the native ecosystem parallel would be a giant rock covered in 2 to 4 inches of gravelly soil with loads of reflected light from bordering rocks. Such “real world” parallels are few and far between.
Even though there is not a long list of native plants for use in extensive green roofs (unless one plans to frequently irrigate), there are a few to choose from. Such species as Sedum ternatum (white flowered sedum, a shade lover), Opuntia humifusa (prickly pear cactus), and Allium cernuum (nodding onion) are such plants. Of course, with regular and frequent irrigation, many others can be sustained, and plants that fall into this category include purple coneflower (Echinacea pallida) and little bluestem (Schizachyrium scoparium). These plants are very drought resistant in conventional landscape settings, because they are great “water sourcers”. On a rooftop with 4 inches of soil, however, they won’t survive for long unless regularly irrigated. Such plants are better suited to the LiveRoof Deep system.
The bottom line: LiveRoof growers are interested in using plants that will be successful, regardless of regional nativeness. Rest assured, LiveRoof growers only use plants native to this planet.
What Will My LiveRoof Look Like In The Future?
All plants are unique, and are opportunistic in one way or another. LiveRoof plants are no exception, and practically speaking, some species tolerate heat better than others, some cold better than others, some dry conditions, and others moist conditions. By combining species of varying growth characteristics, we strive to design each LiveRoof plant assortment to perform optimally in all seasons.
Over time, depending upon the particular plant assortment, geographic site, climate and microclimate, the plant assortment will adapt and evolve. One species will increase its presence while another decreases its presence, from season to season, and from year to year. It is this evolutionary dance that helps to make each LiveRoof fresh and exciting now and in the future.
Rainfall Absorption
From the perspective of civil engineers and city planners, the capture of rainfall may be the greatest perceived benefit to green roofs. Sewage infrastructure and retention tunnels are expensive, and green roofs can have a significant impact on reducing the need for such infrastructure.
Runoff Basics
It is common to ask how much water the LiveRoof system will absorb. Or, how much of the initial rainfall (e.g. first 1/2 inch, 3/4 inch, etc.) will be absorbed prior to system saturation and run off. The answer must always begin with five words: “It depends upon many variables.”
LiveRoof, like other green roof systems is expected to absorb a relatively predictable amount of water throughout a full season (based upon soil depth and many other variables). And, absorption at the onset of a rainstorm may capture all, some, or no water. This depends upon how moist the soil and plants are at the onset of the storm. For example, if Monday evening is cold and drizzly, and Tuesday brings a tremendous downpour, then most of Tuesday’s rainfall would flow through the system. On the other hand, if the system were quite dry at the onset of Tuesday’s storm, then the absorptive capacity of the soil would be much greater, and any runoff would come some time later than the onset of the storm event, as the soil must first reach a point of saturation before it allows water to pass through. This process is referred to as “delay in peak flow” and is important as the distribution of stormwater discharge over a longer period of time allows for smaller more efficiently used stormwater infrastructure.
Annual Rainwater Absorption
Most research (Liesecke, 1998; Moran et al., 2004; DeNardo et al., 2005; VanWoert et all, 2005) has shown an annual runoff reduction of 60-100%, impacted most significantly by climate. The precise amount for any given locale and any given rooftop is not one size fits all. The factors that come into play are numerous and include the following:
Seasonal Weather and Rainfall Patterns
When comparing the average monthly rainfall and daily average temperatures of various cities, the differences are amazing. In Phoenix, temperatures tend to be hot and what little rain falls is spread evenly over the year. In Portland Oregon, the temperatures tend to be moderate with wet winters and dry summers. In Chicago and New York the winters are cold, spring and fall are cool, and the summers are hot; precipitation is spread pretty evenly throughout the year. Miami is warm in winter, hot spring through fall, and has a defined summer rainy season where rain can fall in torrents. With this in mind, each climate will have different absorptive qualities. A city like Phoenix may experience nearly 100% rainfall retention, because it is typically hot and dry with little rainfall. Cities like Chicago or New York may see annual stormwater retention in the range of 60% to 85%. And a city where the rain comes in torrents will experience less annual rainfall retention. Retention will also vary somewhat from year to year as determined by the year’s weather.
Rainfall Intensity
Soil acts as a sponge in capturing and holding onto water. But, soil is less porous than a sponge, and will take longer to absorb and hold onto water. For this reason, if a rain event is very fast and intense, such as 1 inch over 15 minutes, a certain amount of water may sheet across the soil surface to the roof drains, before becoming absorbed by the soil. On the other hand, if a 1 inch rain comes in a gentle soaking drizzle over the course of a couple of hours, the efficiency of water capture is much greater.
Runoff Coefficient
The approximate "flat-roof" runoff coefficient may be calculated using our Flash Calculator. Runoff will be greater with increasing roof slope. On roof slopes over 15 degrees, runoff increases by 10 to 15 percent. In order to use the calculator, one needs three things.
Dry and saturated weight of the medium (soil). 60 pounds per cu. ft. dry and 90 pounds per cu. ft. saturated serves as a ballpark figure. But, verify with local grower as LiveRoof media varies somewhat regionally.
Depth of growing medium. Approximately 4-4¼” for LiveRoof Standard, approximately 2¼-2½” for LiveRoof Lite, and approximately 6” for LiveRoof Deep.
Local Rainfall Data. See MIFAB Rainfall Considerations for Roof Drains website for useful rainfall information: www.mifab.com/pdf/r-sizing-us.pdf.
Note: it is advised that the information rendered from such calculations be considered ballpark, and that an appropriate safety factor of 20% or greater be built into the calculation, and that aggressive rainfall data be used so as to present a conservative view of runoff. LiveRoof, LLC makes no warranty or representation regarding stormwater and runoff calculation. Such information is the domain of engineers skilled in the science of such calculations and matters related to stormwater management.
Wind and Sun
Windy sites, particularly those that are windy during hot dry weather, will dry out more and retain more rainfall on an annual basis. Taller buildings will tend to be windier and those with reflected light or heat will dry out faster and therefore absorb more water as well. Of course, all things being equal, sunny areas are going to have less stormwater runoff then shady areas.
Roof Slope
All roofs must slope in order to drain, and what most people refer to as a flat roof will have a slope of 1/4” per 12’. Such roofs will retain more water than roofs with greater slope. This is because soil holds water by cohesion, but there is a limit to how much cohesive force soil can provide. Practically speaking, soil acts as a sponge. If a moist sponge is angled upward, additional water will run out of it. The same is true of soil. The greater the angle, the less capable the soil is of retaining water. Researchers Bradley Rowe, Kristin Getter, and Jeffrey Anderson have conducted studies regarding slope and water retention with inclines of 2%, 7%, 15%, and 25%, and found that annual water retention in Lansing Michigan ranged from approximately 85% with 2% slope to 76% with 25% slope.
Soil Depth
One might logically presume that the deeper the soil substrate the more storm water a green roof will mitigate. This is not necessarily true as independently discovered by Dr. Bill Retzlaff, et. al., of Penn State and Civil Engineer Drew Gangnes of Magnusson Klemencic Associates of Seattle have published their findings that a 4 inch soil depth performed optimally for storm water retention. This is because at 4 inch soil depth, the combined ability to hold water along with the ability to evaporate water between rain events, created the least amount of runoff. In comparison, a 6 inch system might hold somewhat more water, but won’t dry out as effectively between rain events and a 2 1/2 inch deep system may dry faster but won’t hold as much rainwater.
Soil and Plant Characteristics
Plants and Soil also play a role in stormwater retention. Soil aggregate sizes and composition affect pore space, air space, and absorptive capacity. The volume and type of soil will also influence each system’s ability to absorb water. And, while soil is mostly inanimate, it will gradually change over time due to natural freeze-thaw cycles that can alter particle sizes of some of the mineral components. Neither is the organic component static and can either rise or fall and therefore affect the soil’s absorptive capacity. The process of plant growth and decay (leaves roots and stems) can contribute organic matter, particularly deciduous plants which shed their leaves to nourish the soil. Fully evergreen plants on the other hand may actually reduce organic matter from the soil.
Plants also affect water retention and runoff by their use of water. They extract water from the soil and combine it with CO2 to make sugars, and they liberate water to the atmosphere by transpiration (similar to sweating) when it is sunny and there is sufficient water available. In either case, plants help to keep rainwater out of the stormwater system and the more densely they cover the soil surface, the more absorptive capacity they have.
Effect of Supplemental Irrigation
While irrigation is used to sustain the LiveRoof system during hot dry periods, a particular roof will likely experience little reduction to its absorption of stormwater. Typically irrigation is used, temporarily, during times of sparse rainfall and the added water is mostly evaporated or sequestered by the plants.
Here's time lapse video on the installation of greenroof landscaped roof deck.
Many of our friends are looking for ways to make their homes more eco-friendly.
Whether this stems from a wish to help the environment or a desire to cut heating and cooling costs, the steps are often the same. Some eco-friendly home improvements are small, simple, inexpensive steps. Others require more time, money and expertise. So let's explore some quick ways to show you how:
Let's take a look at 10 popular home-efficiency tips that may work on your budget. These home-improvement options include a number of projects, that could mean energy and cost savings for you and your family.
1. Know your Home weakpoints:Have a home energy audit.
A home energy audit is essentially a thorough inspection of your home, in which you (or a professional inspector) examines such things as air leaks, sites where insulation could reduce energy transfer from outside and the efficiency of your appliances and electrical system [source:
A professional energy audit, if it's in your budget, can include higher-tech assessments such as thermal imaging and precise airflow measurement.
These tools refine the audit, helping the inspector pinpoint exactly where your home's energy weak spots are and how much they're costing you in terms of heating and cooling bills.
There are county that offers free Energy Audit like San Mateo and Sta Clara County. Check your Bay Area counties for energy audit. Its a great first step, that helps you develop a game plan pf projects that can cut energy bills and keep those hard earned savings into something you are planning for, say vacation!
2. Control Air Flow: Keep air leaks tight
Warm or cool air leaking into or out of your house is not the only airflow problem that can cost energy. Air creeping in from a cool room, such as your basement, or from a warm area to a cooler one, can cause additional problems.
Interior doors, improperly sealed ductwork and even small gaps around switches and electrical outlets can lead to energy-consuming air leaks [source: Energy Star]. Be sure to check these areas as well.
Repairing these air leaks requires a variety of techniques and tools.
Simple caulking can seal gaps that don't need to be opened. Something as simple as a draft-catcher placed under a door or along the base of a leaky window can help control airflow through these openings
3. Windows Upgrade: Watch The windows.
It pays good dividend to replace old single pane to double pane windows Low E
Energy-efficient windows typically use a number of features to separate the climate-controlled air in your home from outside air. Your budget may allow you to install multipane windows, in which the space between panes is filled with an insulating gas, such as argon [source: Efficient Windows Collaborative].
Insulating windows in this manner improves their U-factor, a measure of how well the windows prevent heat from escaping. A lower U-factor number identifies a more efficient window
The glass on these efficient windows is often tinted or treated with a glazing material that reduces the solar energy allowed into the home [source: Efficient Windows Collaborative]. This not only reduces glare, but also improves the windows' Solar Heat Gain Coefficient (SHGC), a measure of how the windows prevent sunlight from raising the home's indoor temperature. As with U-factor, a lower SHGC value identifies a more efficient window.
PER Personal Energy Review
4. Positive reflection:
Reflective insulation can help control how the heat from the sun affects your home's temperature.
The sun's effect on your home's energy usage doesn't stop at the windows. If you live in a home that heats up too much in the warm, sunny months, reflective insulation may be a cost-saving upgrade to put high on your to-do list.
Reflective insulation is designed to control solar radiation, the sun's heat-producing energy, which passes through your roof and walls to heat the air inside your home.
Some types of reflective insulation can prevent wayward airflow inside, while others simply bounce the solar energy away from the interior (hence the "reflective" label) [source: U.S. Department of Energy].
Reflective insulation is often a thinner material than the thermal insulation used to keep heat from escaping from the home. It usually consists of a reflective material, such as aluminum, bonded to thin wood or another type of backing. It's typically used along with thermal insulation as part of a comprehensive project: Combining this type of insulation with the options described in the following section can provide year-round protection from the outside temperature [source: U.S. Department of Energy].
5. Basics of Insulation:
Batting, blown fill and rigid sheets of insulation provide energy-conscious homeowners with a number of benefits. These materials prevent the heat transfer that can occur through building materials such as wood, drywall and masonry. They can be installed to act as air dams, preventing airflow inside walls and energy-stealing drafts in attics and crawlspaces. And they provide some of the easiest DIY projects for improving the eco-friendliness of your home [source: U.S. Department of Energy].
Installing insulation can be as simple as unrolling fiberglass batting between rafters in your attic or studs in an unfinished garage wall. Covering blown fill with sheets of lighter insulation can be an effective way to insulate an overhead crawlspace. The use of a reflective barrier as an outer envelope against the inside of a wall or roof adds to the insulation's effectiveness without adding significant time and cost to the installation. More complex installations, like blowing cellulose fill into the space between studs of a finished wall, takes more specialized equipment, and may be best left to contractors [source: U.S. Department of Energy].
6. Grow Low impact Lawn:
Home's yard. Fossil fuel powers lawn mowers and string trimmers, creating harmful emissions. Fertilizers used to grow lush green lawns and bountiful gardens leach into groundwater, creating a pollution problem that can affect drinking water quality. And poorly managed rain runoff can lead to sewer overflows and flooding [sources: U.S. Environmental Protection Agency].
One of the easiest and most cost-effective ways to grow an eco-friendly lawn is to use native plants as ground cover, rather than bagged grass seed.
Try changing your landscaping to frame a small lawn with beds of native wildflowers, rather than growing a lawn big enough for a soccer pitch. The reduced water and fertilizer needs of the native plants will reduce the amount of chemicals you release into the environment, saving both the groundwater and your lawn care budget
I always tell friends that Auntie Celia loves to plant tomatoes and herbs; Mrs. Obama did her garden at the whitehouse which I personally think its cool to set a good example of greening your backyard and fun too!
7 Install Pervious Pavers
I always advise my clients to landscape alley ways and walkways. Its a great way to introduce fruit and flowering trees while providing needed shade. It also prevents run-off. Uncontrolled rain runoff can cause serious problems for your community's environment. Impervious surfaces such as roofs, streets and driveways don't allow soil to absorb rainwater. Instead, the water gets channeled through often-aging sewers and culverts, then dumps into local waterways that evolved to accommodate much lower amounts of water during rain. As a result, erosion from excess runoff damages local streams and rivers, and low-lying communities become more prone to flooding.
As a homeowner, you can make a big difference in your community's runoff problem. Pervious pavement allows rainwater to soak through to the underlying soil. The soil then releases the water into local streams at a measured rate, filtering it and preventing the floods that develop when too much water hits the stream at once.
Some pervious pavement materials can be poured like concrete, while others are modular bricks or tiles that you can arrange into attractive patterns. The type of material you choose depends on the amount and type of use the surface will see, as well as your taste and budget.
A tiled patio may be a weekend project within your reach, while replacing your asphalt driveway with a pervious one may be best left to a professional contractor. Either way, you'll finish the project with the satisfaction of knowing you've put the soil under your property to a very important public use.
8. Watch the Water
Jupiterimages/Comstock/Thinkstock While it may be more expensive, a tankless water heater is the most efficient water-heating option available.
Our estimates including PG&E suggest that heating water accounts for roughly a third of a home's energy consumption [source: Consumer Reports].
Whether you're building a new house or trying to make your current home more eco-friendly, improving your water heater's efficiency can be an effective investment.
Understand one thing, though: This type of home improvement can be an expensive undertaking. Tankless water heaters, which heat water as needed rather than storing it in an insulated chamber, are some of the most efficient heaters available. However, they can cost two to five times as much as a traditional tank water heater, and installing one in an existing house can require costly upgrades [source: Tennessee Valley Authority]. Still, if you want a very efficient water heater and can afford it, a tankless water heater is a good option.
For homeowners on a tighter budget, there are other ways to save on water-heating energy costs.
For starters, make sure your water heater is the right size for your home. While a too-small heater may not meet your needs, an oversized water heater will waste energy. Check the heater's First Hour Rating (FHR), a measure of its ability to produce water during high-demand situations, to get a sense of how well it meets your needs [source: Consumer Reports].
Another measure to consider is the heater's Energy Factor (EF). This standard measurement can give you a sense of how efficient one heater is when compared to another. The higher the EF, the more efficient the heater [source:Consumer Reports].
9. Smart Thermostats
Imagine having a personal assistant who made sure you had hot water just in time for your morning shower, warmed or cooled your house to the perfect temperature at the end of every day and monitored the cost of energy to make sure you only ran your power-gobbling appliances when gas and electricity were at their cheapest, non-peak rates. Thanks to a new generation of "smart" thermostats, this level of control is increasingly available to tech-savvy homeowners.
Thermostats have become much more than temperature-activated switches for heating and cooling systems. Many models can now monitor factors such as the energy use of individual appliances, the cost of energy at a given time of day and the functionality of appliances. Some of the more advanced models are able to contact you via e-mail if something goes wrong with an appliance, and they can be adjusted from your office computer or mobile device.
These thermostats can run appliances when it's least expensive to do so. And when no one's home, they can easily turn off energy-hungry appliances, such as water heaters, and program them to restart in time to provide hot water in the evening.
No matter how efficient your appliances are, you can save even more energy with this precise, instantaneous level of control.
10: Energy Star: Efficient Appliances
Hemera/Thinkstock When your old appliances wear out, consider replacing them with newer, more eco-friendly models.
The first step to making an energy-conscious appliance purchase involves learning how efficiency is measured for that appliance. Knowing what an appliance's ratings mean can help you shop smarter and faster.
Likewise, make sure you know what size appliance you need. Buying an air conditioner that's too small will lead to hot summers and a constantly running appliance. But a too-large air conditioner might not adequately remove humidity in your home and will waste energy when it's running [source: Energy Star].
Once you've found your new appliance, check to see if there are ways you can save energy through better installation.
Can your water heater be moved to shorten the length of your hot water pipes?
Are your air conditioning ducts properly sealed and insulated? Now is the time to address these issues and maximize your energy savings.
New, efficient appliances aren't always cheap. But evaluating your needs and researching your options can help you strike a balance between price and performance that will improve your home's eco-friendliness, regardless of your budget.
