Life Cycle Assessment: Getting to the “Why” of Making Sustainable Decisions

RTAblog_2013_0412_LifeCycleAssesmentRyan was invited to participate in a panel discussion on “The Green Appraisal Process” at the Region IX meeting of the Appraisal Institute today. The following are notes for some of the issues he’s been asked to address.

The term “life cycle assessment”  (LCA) is often used interchangeably with “life cycle cost” (LCC) and “life-cycle cost analysis” (LCCA). For the purposes of our discussion, we’ll use the term life cycle assessment with the understanding that it means accounting for the cost of purchasing, installing, operating maintaining and disposing of a building or building system. Building systems are systems in buildings like the air conditioning system, plumbing system or air conditioning system.

The design for a house or building system should respond to its environment. The components need to be integrated so they can perform as efficiently as possible. We get a lot of guidance from building codes though building codes should always be thought of as a minimum standard.

We use life cycle assessments to guide our design so we can make the best use of the project budget. This helps us compare different design solutions. For example, can you tell the difference between the two sections of wall in the image below? They’re both 8′-0″ wide, they’re the same height and they both use 2×4 wood framing.


The design on the right uses wood studs at 24″ on center while the design on the right uses wood studs at 16″ on center. By our calculations, the design on the left offers a material savings of 22% and 3.5% additional insulation. If we used 2×6 wood studs in the wall on the left, we’d get 39% more insulation in the wall.

Insulation is a passive system, it has no maintenance or operational costs. Increasing our use of passive systems like insulation and air sealing help us reduce our use of active systems like air conditioners. Since air conditioners are one of the primary consumers of energy in our homes, it makes sense to try and reduce the size of the system (and thus its costs) by using more passive systems.

This strategy may have a higher first cost though a life cycle assessment helps us estimate how quickly the first cost will be paid back. We want the payback period to be shorter than the life expectancy of the product.

There are a couple of factors that can skew decisions driven by life cycle assessment. Health and special needs are both issues that typically take priority over life cycle assessment results because they’re immediate needs. For example, you may choose to invest in a higher level of sustainable building than is common if you’re sensitive to environmental triggers for allergies and asthma. You may choose to invest more in design for aging in place or wheel chair access if you have special needs.

Regardless of what decisions you make, we have two cautions for you:

1) Don’t put too much faith in complex models for sustainable construction if you’re not able to invest time in studying the variables. For years, our industry has questioned the accuracy of energy modeling used to make design decisions. This has lead to the commissioning of studies to compare actual energy use with projected energy use in sustainable homes.

2) Be sure you have your building systems inspected or commissioned so you know they were installed and initially functioning correctly. We’re still having huge problems with execution on construction sites (things aren’t installed as designed) so oversight is necessary.

Also, we don’t like to include design for resale as a primary driver in our design decisions unless the owner is planning to sell the property within a very short time horizon. Designing for people we’ve never met at a time when we don’t know what technologies and trends will be popular shouldn’t be your focus. Changing interior finishes, appliances, exterior cladding and landscaping are all relatively simple changes that shouldn’t significantly affect building orientation, space planning, building systems selections and other decisions that were driven by thoughtful life cycle assessments.

If design for resale is your primary driver, we hope you’ll take care not to look at the building exclusively as a commodity. That’s one of the point’s Harvard’s Office of Sustainability makes when presenting it’s green building resource for life cycle costing. They note the importance of thinking through operating costs, even if you plan to sell the project, so we have better buildings that make the best use of our resources and cause less pollution. Those decisions effect all of us at some scale: the cost for providing power, water and other services to wasteful buildings is assessed to all the users of those service providers – we all pay for the infrastructure, we all bare the costs for scare resources like water and we must all resulting the health issues like air pollution from power plants.

While the Harvard office is focused on commercial projects and we’ve used the term “buildings”, don’t forget that our houses consume huge amounts of resources and are typically built to a less stringent standard (building code) than commercial buildings. As metrics like the HERS Index Score begin to appear in the MLS listings for houses, it will be more difficult to sell poorly designed and constructed homes because we’ll be able to filter homes with higher operating costs out of searches on services like Zillow and Trulia.

In 1987, the City of Berkley, California adopted a Residential Energy Conservation Ordinance (RECO) to reduce resource consumption and pollutions. It’s triggered by the sale or renovation of a house. We expect the popular adoption of local requirements and better metrics like the HERS Index Score to eventually encourage state requirements. We expect these changes in the very near future so states can remain competitive. We think the next few years are going to be an adventure.

A few other resources: 1) Our National Renewable Energy Laboratory (NREL) maintains a U.S. Lifecycle Inventory Database to account for energy and material flows. 2)You can find a list of Georgia’s construction codes on the GA DCA website. 3) You can find a list of the building code certifications on the ICC website.

Photo by Plutor used under creative commons license.

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One Response to Life Cycle Assessment: Getting to the “Why” of Making Sustainable Decisions

  1. Pingback: The Opportunity of Earth Day | Ryan Taylor Architects LLC

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