Lecture notes
Department of Architecture, Cornell University

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ARCH 2614/5614 Building Technology I: Materials and Methods

Jonathan Ochshorn

contact | office hours

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Materials: Life Cycle Assessment and Life Cycle Costing

Materials and sustainability

Based on LEED (Leadership in Energy and Environmental Design) 2009 Green Building Design & Construction Reference Guide and Building Design & Construction Reference Guide, v4 from Nov. 2013.

• See my summary and critique of LEED (on materials and resources) from the 2009 version and from the latest LEED v4.

• Extra and optional: See my Critique of Milstein Hall

Life cycle assessment and costing

Life cycle assessment (LCA) deals with environmental impacts over the life of a building

Life cycle costing (LCC) deals with the "dollar" costs of a building measured over its life

"According to International Standard ISO 14040, LCA is 'a compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product system throughout its life cycle'"

Also understood as a "circular economy."

Environmental performance

"Generally measured in terms of a wide range of potential effects, such as:

• fossil fuel depletion
• other non-renewable resource use
• water use
• global warming potential
• stratospheric ozone depletion
• ground level ozone (smog) creation
• nutrification (excess nutrients)/eutrophication (oxygen deficiency) of water bodies
• acidification and acid deposition (dry and wet)
• toxic releases to air, water, and land"

Notes on embodied energy
The embodied energy in building products may be much smaller than the operating energy for a building over its life. On the other hand, certain environmental "embodied" outcomes (water pollution, strip mining, etc.) may be much greater due to the production of building products than from the use of the building over its life.

Both types of outcomes are important
"The essence of LCA is to cast the net wide and capture all of the relevant effects associated with a product or process over its full life cycle."

LCA includes secondary effects

"LCA of a given product should take account of the production and use of other products required for cleaning or maintenance during its use phase."

Limitations
Uncertainty of outcomes, especially with long (50-100 year) expected building life: occupancy changes unknown; demolition or disposal or renovations unknown.

Site-specific effects of resource extraction.

LCA Tools:
BEES (Building for Environmental and Economic Sustainability)

• Measures both LCA and LCC, combined into a single weighted "score" (although the preferences can be set to see disaggregated results without weighting)
• Useful at the specification or procurement stage
• Weighting factors used to "score" building design
• Developed by the NIST (National Institute of Standards and Technology) Engineering Laboratory

BEES online tool: found here

BEES measures the environmental performance of building products by using the life-cycle assessment approach specified in the ISO 14040 series of standards.

ISO is the International Organization for Standardization

ISO 14040:2006

• Definition of the goal and scope of the LCA
• Life cycle inventory analysis (LCI) phase
• Life cycle impact assessment (LCIA) phase
• Life cycle interpretation phase
• Reporting and critical review of the LCA
• Limitations of the LCA
• Relationship between the LCA phases, and conditions for use of value choices and optional elements.

BEES LCA method

• All stages in the life of a product are analyzed:
• Raw material acquisition
• Manufacture
• Transportation
• Installation
• Use
• Recycling and waste management.

Notice that energy use, per se, is not measured. What is measured are the environmental outcomes associated with energy use (burning fossil fuels).

How does BEES measure environmental impact?
BEES examines a number of environmental impacts, e.g., global warming. For any particular building product, BEES compares that product's impact on, say, global warming with the impact that an average person in the US has, per year, on global warming.

Now, take all the environmental impacts (including global warming), give them weights, and sum them all up for the total environmental product score:

Comparison of two products: Lower values are better!

[BEES images above are taken from the BEES "Score interpretation" PDF linked from the "help" page here]

How does BEES measure economic life cycle cost?
The Economic Performance summary graph displays the first cost, discounted future costs and their sum -- the life-cycle cost.

All life cycle costing must convert future building product costs to their equivalent present value.

So why is a future cost different from a current cost (or value)?

Because that is the nature of capital: capital is value that accumulates or increases.

• If you (as a capitalist) invest $100 today and expect a rate of return equal to 10% per year, then you expect to have $110 at the end of the year.
• The "present value" of that "future" $110 is therefore $100.
• In other words, the present value is what you would need to invest today in order to have an increased value in the future.

• Important conclusion about life cycle costing: The greater your expectation of return on your investment (the greater your assumed discount rate), the smaller is the present value of future costs.

• Here's what the BEES tutorial says: "The higher the discount rate, the less important to you are future building product costs such as repair and replacement costs. The maximum value allowed is 20%. A discount rate of 20% would value each dollar spent 50 years hence as only $0.0001 in present value terms. The 2010 rate mandated by the U.S. Office of Management and Budget for most long-term Federal projects, 2.7 %, is provided as a default value." Discount rates set by OMB for other years can be found here. You can see that a later 30-year discount rate (2015, compared with 2009) turns out to be much lower:
  

• In other words, if you invest $1 today and the rate of return on your investment (e.g., the "interest" on your savings; or the "discount rate") is 20%, then your $1 investment grows to $10,000 in 50 years.
• Note that all of this abstracts from any impact that inflation would have on what your $10,000 would actually buy 50 years from now.
• If the discount rate is less than 20%, e.g., 2.7%, then the present value is much higher. An anticipated expense of $10,000 fifty years from now with a 2.7% discount rate would have a present value of $2,639 rather than $1. In other words, it would be a much more significant element in any life cycle costing if the discount rate were 2.7% rather than 20%.
• Want to play with present value calculations? Here's an online calculator
• Or make your own calculator with a simple spreadsheet.
  
• Formula for present value: P = A/(1 + r)ⁿ
  • P = present value
  • A = amount of money (at some future time), e.g., $10,000.
  • R = discount rate per year (interest, rate of return) expressed as a fraction (e.g., 20% = 0.20)
  • n = number of years into the future for the amount, A, e.g., 50.
• In spreadsheet language, the present value is:
  =A2/POWER((1+B2/100),C2) where A2, B2, and C2 refer to the values in the spreadsheet cells shown above.

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Disclaimer: Students are responsible for material presented in class, and required material described on course outline. These notes are provided as a tentative outline of material intended to be presented in lectures only; they may not cover all material, and they may contain information not actually presented. Notes may be updated each year, and may or may not apply to non-current versions of course.

first posted Sept. 21, 2012 | last updated: Oct. 16, 2019

Copyright 2007-2017 J. Ochshorn. All rights reserved. Republishing material on this web site, whether in print or on another web site, in whole or in part, is not permitted without advance permission of the author.