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ARCH 2614/5614 Lecture notes

Jonathan Ochshorn

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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.

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

The next section is based on "Life Cycle Assessment Tools," John Carmody and Wayne Trusty, found here

"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'"
life cycle assessment diagram

Environmental performance

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

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)

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

BEES LCA method

diagram of BEES model

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.

BEES environmental impact diagram for 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:

BEES environmental impact diagram - weighted score

Comparison of two products: Lower values are better!
BEES environmental impact diagram - comparison of two products

[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.