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Ask the Green Architect: Resources for Occupant Surveys; Fly Ash in Concrete

Green architect Eric Corey Freed answers your questions on sustainable building performance, materials, and design.

  • The University of Minnesota's Center for Sustainable Building Research (CSBR) has conducted POEs of the sustainable design efforts of several state agencies.

    For example, their researchers discovered when more daylight was incorporated into green buildings, too little thought was given to shading and light control. Excessive glare from the natural light, especially at computers, was lowering productivity.

    Occupants had invented "unique" strategies to minimize the glare, from hanging blinds to covering windows with cardboard or using umbrellas over their desks. Normally, architects would be unaware of the repercussions of such measures. A POE reveals new design opportunities.

  • The Probe studies in the U.K. were a unique collaboration between researchers, designers, government and publishers to undertake POE studies of 16 commercial and institutional buildings. They addressed the efficient operation of buildings, generating valuable information about the success of a variety of green building strategies.

  • Keen Engineering carried out POE surveys of seven green buildings in the Pacific Northwest using a Web-based Occupancy Satisfaction Survey developed by the Center for the Built Environment at the University of California-Berkeley.
Despite the valuable information gained from a POE, they are rarely undertaken. Green and high-performance buildings are particularly good candidates for POEs, since they provide a way to learn about the performance or unexpected side effects of new products, technologies and techniques.

POEs may also help to evaluate whether LEED-certified and other green buildings deliver on their promises, and they can provide the hard evidence that green building advocates need to make their case.

Some suggestions for fully benefiting from Post-Occupancy Evaluations:
  • Include POEs in your proposal to ensure you get paid for your work.

  • Remember the old business adage: If it gets measured, it gets managed.

  • Publish your findings in-house to the other teams so everyone may learn from past projects.

  • Use the findings from one POE to benefit current and future projects. You will be able to say with great accuracy how much energy a particular design can produce; how happy occupants are with a particular amount of natural light.

  • Share your findings with your client and offer staff trainings as part of a possible additional service.
Further Reading:

Improving Building Performance
This guide from the National Council of Architectural Registration Boards introduces the three different types of POE—indicative, investigative, and diagnostic—as well as its phases—planning, conducting, and applying.

Quick-Response Studies Guide
February 2003 handbook from the California Department of General Services.

Facility Performance Evaluation
A helpful backgrounder from the Whole Building Design Guide.

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What is fly ash? What are the positive and negative affects of using it in concrete?

Fly ash is the fine residue powder byproduct from coal-fired electric generating plants. Since the burning of coal provides up to 85% of our electricity (depending on where you live), a great deal of this powder is produced. Some 63 million tons of fly ash were produced in 2002, resulting in 63 tons of mercury byproduct.

Currently, the fly ash is released into the air, buried in a landfill or illegally dumped into our oceans. fly ash contains approximately 1 part per million of mercury (NOTE: The maximum level of mercury in drinking water permitted by the EPA is 2 parts per billion.) The mercury seeps into our groundwater and contaminates our fish. Humans eat the fish, and the mercury accumulates in our bodies.

Mercury has been linked to numerous health problems, including autism in newborns, endocrine disruption and cardiovascular disease. Since 1990, there has been a 10-fold increase in the incidence of autism. One can quickly see a need for an alternate use of this fly ash.

(NOTE: It only takes 1/70th of a teaspoon of mercury to contaminate a 20 acre body of water and make all fish within it toxic to humans. This is about the amount of mercury in a typical medical thermometer.)

Concrete is a mixture of sand, water, stone, and Portland Cement. The cement is the key ingredient in concrete, comprising about 12% of the mix weight, acting as the binding agent that holds sand and other aggregates together in a hard, stone-like mass.

Energy consumption is the biggest environmental concern with Portland Cement, requiring a great deal of energy to mine out of the Earth, grind up, heat in a kiln and process into the final product. Cement production is one of the most energy intensive of all industrial manufacturing processes. One can also see a need to find an alternative for cement.

Offsetting the Environmental Effects

Depending upon the use of the concrete, fly ash can be substituted for 20% - 50% of the Portland Cement in the concrete mix. There have been reports of some people using as high as 70% fly ash substitution.

By taking a waste byproduct that was previously releasing mercury in our environment, we are also reducing the amount and impact of cement, therefore killing two birds with one stone (no pun intended).

The use of fly ash in concrete already saves about 44 trillion Btus of energy annually in the US. Increasing the rate of fly ash substitution from the current 9% to a conservative 25% would save an additional 75 trillion Btus.

Other Benefits

Fly ash also offers numerous other advantages. It improves the performance and quality of the concrete. fly ash affects the plasticity of concrete, improving workability and reducing the amount of water needed. In addition, fly ash will increase strength, reduce permeability, reduce corrosion of reinforcing steel, increase sulphate resistance, and reduce alkali-aggregate reaction.

In terms of costs, fly ash is actually less expensive than concrete, giving you no reason to not use it on every project.

The Drawbacks of Fly Ash

Since a concrete mix is essentially a big chemical reaction, adding fly ash slows the curing of the concrete. This can be an issue in situations where the concrete must reach a certain percentage of its maximum strength in a certain time.

In addition, if you are using a spray on concrete (shot-crete) type of installation, you may have problems with adding fly ash and the consistency of the mixture.

Otherwise, no other features of adding fly ash would be seen as a drawback.

Specifying Fly Ash in Concrete

There are at least a dozen companies providing fly ash to concrete producers. Talk to your contractor or concrete supplier and find out if they are willing to add fly ash to the mix. Your structural engineer should be consulted before changing the structural concrete mixture.

Other Uses

Faswall is a fiber-cement block Insulated Concrete Form (ICF). These ICF's are made of cement with fly ash content to reduce the amount of cement used.

Syndecrete is a precast lightweight concrete containing fly ash and recycled waste from carpet manufacturing. The product is more resistant to chipping and cracking than conventional concrete, tile, or stone making it a great choice for countertops, table tops, fireplace surrounds and sinks.

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Got A Question?
Send your questions about environmental management issues to [email protected]
We can't guarantee that we'll answer every question, but we'll try.

Eric Corey Freed is principal of organicARCHITECT and teaches sustainable design at the Academy of Art University in San Francisco and University of California Berkeley. He is on the boards of Architects, Designers & Planners for Social Responsibility (ADPSR), Green Home Guide, and West Coast Green.

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