Comparative Life Cycle Assessment of Insulating Concrete Forms with Traditional Residential Wall Sections

Buildings account for 30-40% of the energy use. In United States, buildings use 70% of the nation's electricity and emit 40% of the greenhouse gas emissions (GHGs). Green buildings and green building products are increasingly becoming the norm in the construction industry. But there is no consensus on labeling of a green product. There is a need for a holistic system which looks at all aspects of a material or product and then labels it green. This research incorporates the knowledge of building construction and sustainability tools, such as life cycle assessment (LCA), to compare traditional and new building materials and to analyze whether the new building products are truly green and can be used as replacements for the traditional building materials in certain structural components.

Insulating Concrete Forms (ICF) is a building material which is made of polystyrene into which concrete is poured. Unlike conventional construction, the forms are not removed after concrete has cured and act as insulation. Ties made of polypropylene act as reinforcement for the material and additional steel reinforcement can be added where necessary. In this research, this building material is compared with traditional materials like wood using LCA.

Previous studies have compared ICF with traditional materials. A comparative partial life cycle inventory was conducted on 2,450 square feet houses made of ICF and wood. The inventory was conducted at five different locations in the United States- Phoenix, Miami, Seattle, Washington,DC and Chicago. The results of the study show that the initial embodied energy of ICF is higher than wood but the cumulative energy after five years is higher for wood than ICF. The use phase accounts for 99% of the total energy consumption whereas the cement and concrete production account for less than 1% of the total energy consumed. Another study which compared 2,400 square feet houses made of ICF, wood and steel frame stated that the ICF had higher embodied energy than the other two materials. The National Association of Home Builders (NAHB) constructed demonstration homes made of ICF to show people about the alternative materials available in the market and the method to use them. The desirable properties such as serviceability, energy efficiency and durability compensate for the high initial price. An extension of the partial life cycle inventory study was an energy use study conducted in the same locations as mentioned. Energy modeling tools were used analyzing the energy consumption of the building in different locations. The results of the study showed that ICF walls have an inherent capacity of higher insulation than wood framed walls and have 5% to 9% greater energy savings than the wood framed walls.

While there are many benefits of ICF, a detailed study of the material in comparison with traditional materials is required to identify the advantages and disadvantages of the material in its life cycle. Before ICF is labeled as a ?green building product?, the impact of the product in its life cycle must be analyzed.

The goal of this study is to perform a comparative LCA of residential structures using new and traditional building materials. The entire life cycle of the residential building is divided into four phases- manufacturing of raw materials, construction of the structure, use of the structure and end of life of structure. This research has currently modeled the manufacturing phase and the use phase of the structure. Previous residential LCAs have taken the entire house as the functional unit for all phases which shows that the use phase is the highest contributor to environmental impact. If a complete understanding of the various phases in the life cycle is required, using a single functional unit for all phases does not provide a clear picture. Extensive data is required for every project if the whole house is taken as a functional unit which prevents an unclear picture of the true environmental hot spots. This research aims to create a residential model which will identify areas in all the phases of the life cycle which need to be addressed instead of concentrating on just the use phase. For the manufacturing phase of the structure, a functional unit of one square feet of the structure is assumed and the quantity of raw materials required for producing the functional unit is calculated. Data is obtained from a variety of databases like Ecoinvent, IDEMAT 2001 and ETH-ESU and combined and the input along with the material quantity in the modeling tool, SimaPro to obtain an inventory. Data from industry was also collected and used in the model.

For the use phase, the use of the materials in a 2, 450 square feet house is compared. Various scenarios which involves houses purely made of the aforementioned building materials and a combination of the building materials in different structural components are modeled. The basic features of foundations, windows, doors remain the same for all houses. The modeling tool used for this phase is a Department of Energy (DOE) freeware called eQuest.

Preliminary results show that in the manufacturing phase, ICF does not perform as well as wood in environmental impacts. But in the use phase, a house made of a combination of wood and ICF has the minimum energy use. Any house modeled with a combination of ICF performs better than a house purely made of traditional building materials. Subsequently, the less energy use by a combination of wood and ICF house translates to lower electricity bills annually and lower carbon dioxide emissions per year.

A more robust LCA which includes both process based and input-output data needs to be performed in the remaining phases of the life cycle before a decision can be made on the environmental impacts of the material. As we are moving towards a world which faces energy crisis and expensive energy solutions, materials which can reduce the use phase costs become increasingly necessary. LCA results show the hotspots associated in the manufacturing of the raw materials which need to be addressed with alternative strategies. The desirable qualities of ICF should be tapped after a thorough study of the material has been conducted to address the problem of the life cycle use phase impacts of buildings.