pis: john ochsendorf , les norford , and timothy gutowski

PIs: John Ochsendorf, Les Norford, and Timothy Gutowski

The Edge of Concrete: The Edge of Concrete: A Life Cycle Investigation of Concrete A Life Cycle Investigation of Concrete

and Concrete Structures and Concrete Structures

The Edge of Concrete: The Edge of Concrete: A Life Cycle Investigation of Concrete A Life Cycle Investigation of Concrete

and Concrete Structures and Concrete Structures

September 13, 2010

Motivations for LCA work

1) Growing demand for quantifying performance of structures

Industry Day – August 31, 2010



2030 Challenge calls for carbon reductions of:

60% in 2010 (of average carbon emissions for building type)70% in 201580% in 202090% in 2025 Carbon-neutral in 2030



1) Growing demand for improved quantification of green building

2030 Challenge calls for:

60% in 2010 (of carbon emissions 70% in 201580% in 202090% in 2025 Carbon-neutral in 2030




2) Increasing recognition that green design includes the construction phase and the operating phase of buildings




2) Increasing recognition that green design includes the construction phase and the operating phase of buildings

3) Advantages of concrete construction in lowering the emissions in the operating phase


Goals of LCA Project

Identify advantages over full life cycle

Identify areas for improvement

Build foundations for future studies


Software: GaBi 4

Leading life cycle assessment program

Data for LCA is: Obtained from peer-reviewed sources Taken from in-house database Input from outside sources

Convenient impact assessment interface


Pavements: Locations and Materials

Concrete versus asphalt roads Analysis currently based on national averages Concentrating on high-volume highways


Roadway lighting, lane closures, etc.

Model Scenarios

Full Life Cycle Emissions for Different Traffic Volumes

In Summary

Concrete production emissions are higher than asphalt, but concrete use phase emissions are lower High traffic volume concrete highways can have up to 90% lower

emissions for the entire life cycle compared to asphalt highways because of the greater fuel efficiency of vehicles driving on concrete pavements.

But no two pavements are alike The total carbon footprint of a pavement can vary by two orders of

magnitude depending on the traffic volume, rehabilitation schedule, and many other assumptions.

Pavement roughness and deflection are still inaccurate No one has accurately quantified their interactive effects, the effect of

each pavement layer, nor the effect of temperature.

Work for Year Two

Refine our fuel consumption models to better account for pavement-vehicle interactions and to instill greater confidence in fuel savings due to pavement design.

Continue peer review process to have an expert critical review of our LCA study.

Policy Analysis - Analyze scenarios that quantify the carbon emissions associated with proposed renewal and improved upkeep of the national highway system. Combine with life cycle economic costing to understand the

economic impact of reducing greenhouse gas emissions.

Buildings: Locations

Phoenix Chicago

We consider two climate regions in the USWe will expand the studies to other cities


LCA Components


Pre-use phase Use phase End of life

Extraction Heating DisposalManufacturing Cooling RecyclingTransportation Lighting ReuseConcrete Fans TransportationSteel Plug loadsInsulation MaintenanceGlass Energy Mix

Commercial Buildings

Reinforced concrete frames versus structural steel frames in: 12-story commercial office buildings


Results


Total HVAC:

- 5% Chicago

- 6% Phoenix

CHICAGO PHOENIX

Results


Chicago

- 2.5%

Phoenix

- 2.7%

Results


Thermal mass provides energy savings over time

Better estimation needed of concrete recycling rates and end-of-life emissions

Even greater advantages are possible for concrete buildings

Next Steps


Passive strategies Night cooling Passive solar heating

Active strategies Radiant systems Low-lift cooling

“Predictive Pre-Cooling Control for Low Lift Radiant Cooling using Building Thermal Mass” by N. Gayeski, 2010

Envelope systems

Residential Buildings

Insulated concrete form (ICF) structures versus wood frames in: Two-story single-family residences Four-story multi-family residences


• Results based on average quality wood construction, insulated to meet code vs. typical ICF quality construction

• Primary research performed to determine air-tightness of ICF construction• MIT sponsored tests on 15 ICF houses around the country

RESULTS: Single Family Operational Energy

Chicago

- 34%

Phoenix

- 6.3%

Conclusions

• ICF homes deliver substantial energy savings over the lifetime of residential buildings

• Blower door testing revealed that ICF homes offer tight construction with improved energy performance

• Significant further improvements can be made to the life cycle performance of ICF homes

Highlights of LCA Studies in Year One

For a high traffic volume highway, the greater fuel efficiency of vehicles driving on concrete pavements can lead to significantly lower carbon emissions compared to an asphalt pavement. Over a 50-year lifetime, the savings could be as high as 90% of the carbon emissions associated with the pavement selection.

For commercial buildings, the higher thermal mass of concrete buildings can offer savings of 6% of the heating, ventilation and cooling (HVAC) energy consumption for a hot climate such as Phoenix, and 5% of HVAC energy for a cold climate such as Chicago, compared to steel construction. Even greater reductions (up to 25% of operating energy) are possible through improved design of concrete commercial buildings.

For residential buildings, insulated concrete form (ICF) construction can offer HVAC energy savings of 30% or more compared to code compliant wood-framed buildings in a cold climate such as Chicago. Such operational energy savings can compensate for the initial carbon emissions of the concrete within a few decades of operation.


Embodied versus operating


Embodied versus operating


30% reductionspossible

40% reductionspossible

Next Steps

Complete studies and write reports this fall

Finalize work plans for year two

Integrate new team members



Thank YouThank YouThank YouThank You

pis: john ochsendorf , les norford , and timothy gutowski

Documents

lca workgrowing demand

average carbon emissions

concrete use phase emissions

lca study

concrete pavements

concrete construction

lower emissions

operating phaseindustry