ICF (Insulating Concrete Forms)
Flexible, integrated wall construction
Insulating concrete forms (ICFs) are hollow “blocks” or “panels” made of expanded polystyrene insulation (EPS) or other insulating foam that construction crews stack to form the shape of the walls of a building. The workers then fill the center with reinforced concrete to create the structure. There are over 20 brands of ICFs in North America, each providing variations in design and materials.
|Completed ICF home. Architects Best Small House - Better Homes and Gardens magazine, August 1997 (PCA No. 4086)|
ICF construction sandwiches a heavy, high-strength material (reinforced concrete) between two layers of a light, highly insulated one (EPS or foam). This combination creates a wall with many desirable properties: air tightness, strength, sound attenuation, insulation, and mass.
ICFs are used for walls in residential and commercial, industrial, and institutional buildings.
Concrete walls built with insulating concrete forms (ICFs) give a building enhanced comfort, solidity, durability, resistance to natural disasters, quietness, and energy efficiency. Use of ICFs is growing rapidly. They offer owners and builders many advantages compared to wood or steel frame walls. Comfort.
Buildings constructed with ICF walls have a more even temperature throughout the day and night. They have virtually no “cold spots”, and far fewer drafts. ICF walls have negligible air infiltration.
Solidity. The solidity of concrete construction reduces flexing in floors, as well as shifting and vibration from the force of the wind or the slamming of a door.
Quiet. About one-sixth as much sound gets through an ICF wall compared to an ordinary frame wall.
ICFs offer a range of sustainable building solutions. See associated sustainability solutions and technical briefs (right) for more detail.
Improved Energy Operations. The superior insulation, air tightness, and mass of the walls can reduce the cost of operating HVAC in the building by up to 40%. In addition, ICFs allow the installation of smaller (generally, less expensive) heating and cooling equipment. The high R-value combined with thermal mass means ICF walls exceed most energy code requirements. If the building is like most buildings, it is using fossil fuel. By reducing the building’s fossil fuel requirements, the ICF plays an important role in reducing the negative environmental impacts associated with fossil fuel use. May contribute to LEED Credit EA 1.
Natural disaster resistance. Concrete buildings survive high-force winds like hurricanes far better than wood or metal frame buildings. When properly reinforced, they should also withstand earthquakes well.
Fire resistance. Of all construction materials, concrete is one of the most resistant to heat and fire. Experience shows that concrete structures are more likely to remain standing through fire than are structures of other materials. Concrete walls have also proven more resistant to allowing fire to pass from one side of the wall to the other. This is a significant benefit in areas where brush fires are common, or where high density zoning increases the risk of fire spread.. Unlike wood, concrete does not burn. Unlike steel, it does not soften and bend. Concrete does not break down until it is exposed to thousands of degrees Fahrenheit—far more than is present in the typical residential or office building fire.
Since ICFs are filled with ready-mixed concrete, also see cast-in-place
for further examples of sustainable attributes.
|ICF foundation during construction|
One of the main concerns when using an alternative construction type is whether the system requires major adaptations on the part of most construction firms. How steep is the learning curve?
Stacking blocks is intuitive for most crews, and the cutting and leveling required, draw on standard carpentry skills. Most carpentry crews will have to brush up on the use of concrete, however, and electricians will need to learn how to cut channels in the surface of the foam to house their cable. But these are not complex tasks, and training is available from manufacturers and industry groups.
|Filling ICFs with concrete|
Since insulating forms are light and power equipment moves the concrete, labor costs tend to be below those of frame construction. Because of low labor requirements, total construction cost is only slightly above the cost of frame construction. See resources at Concrete Homes (link below) for manufacturer listings and cost comparisons.
ICF houses can be completed with almost any interior and exterior finish, including siding or brick veneer. ICFs can take any shape as easily as wood or metal frame. In fact, some interesting effects, such as curved walls and frequent corners, can be less expensive to build into an ICF wall.
|Placing insulating concrete forms for a curved wall. Photo courtesy of Quadlock |
|Energy Use of Single-Family Houses With Various Exterior Walls
Gajda, John, R&D Serial No. 2518, Portland Cement Association, Item Code CD026, 50 pages.
Available for free.
A typical 2,450 square-foot single-family house with a current design was modeled for energy consumption in twenty-five locations across the United States and Canada. Locations were selected to represent a range of climates. Energy simulation software utilizing the DOE 2.1E calculation engine was used to perform the modeling.
Concrete Systems for Homes and Low-Rise Construction
Vanderwerf, P., Portland Cement Association, Item Code SP405, 576 pages
For purchase for $75.
Fast gaining on more traditional homebuilding materials, concrete systems save builders time, money, and headaches. Offering durability, cost savings, energy efficiency, and eye-pleasing aesthetics, concrete systems now account for large shares of the walls, floors, roofs, finishes, and landscape products in small buildings in the United States.
But are concrete systems right for you and your construction crew? And if so, which ones? This is the place to find out. Written by experts from the Portland Cement Association, Concrete Systems for Homes & Low-Rise Construction provides expert, straightforward answers on concrete systems. Open these pages for everything you want to know about availability of products, evaluating concrete systems for homes and low-rise buildings, requirements for application, managing projects, and much more. Based on case histories, field research, and hands-on-the-hammer experience, and with more than 325 photos and illustrations, this one-stop resource shows and tells what you want to know. It's a huge time and money saver!
For each new concrete system for residences, you'll find:
• Properties and advantages
• Logistics of construction
• Connections to other concrete systems
• Materials and labor costs of installation
• Code and regulatory issues
• Technical and testing information
• Sources of additional information
Investigation of Wind Projectile Resistance of Insulating Concrete Form Homes
Portland Cement Association. Item Code: RP122
Available for $10.
This report presents in-depth results of laboratory testing comparing the impact resistance of residential concrete wall construction to conventionally framed walls. The damage inflicted on ten wall specimens subjected to the impact of a 15-pound wood stud "missile" traveling at up to 109 miles per hour is described. The study compares the differences in inherent resistance to debris driven by high winds, between concrete wall systems and standard residential construction.
Life Cycle Assessment of an Insulating Concrete Form House Compared to a Wood Frame House
Medgar L. Marceau and Martha G. VanGeem, Portland Cement Association, Item Code: SN 2571, 167 pages
Free to download. This report is an update of Life Cycle Assessment of an Insulating Concrete Form House Compared to a Wood Frame House (Marceau and VanGeem 2002). It presents the results of an assessment of the environmental attributes of concrete construction compared to wood-framed construction. A life cycle assessment (LCA) was conducted on a house modeled with two types of exterior walls: a wood-framed wall and an ICF wall. The LCA was carried out according to the guidelines in International Standard ISO 14044, Environmental Management - Life Cycle Assessment - Requirements and Guidelines. The house was modeled in five cities, representing a range of U.S. climates: Miami, Phoenix, Seattle, Washington (DC), and Chicago.
The 228-square meter (2450-square foot), two-story, single family house has four bedrooms and a two-car garage. The system boundary includes the inputs and outputs of energy, materials, and emissions to air, soil, and water from extraction of raw materials though construction, maintenance, and occupancy. The house energy use was modeled using DOE-2.1E and the life cycle impact assessment was modeled using SimaPro.
The results show that for a given climate, the life cycle environmental impacts are greater for the wood house than for the ICF house.
Sound Transmission Loss Through Concrete and Concrete Masonry Wall
Albert Litvin and Harold W. Belliston, Portland Cement Association, Item Code RD066
Many building codes require minimum sound transmission loss values, expressed as sound transmission class (STC), of 45 to 50. Tests of sound transmission loss were made on 8-in.-thick (203-mm) concrete masonry walls and on 6- and 8-in.-thick (152- and 203-mm) cast concrete walls finished with materials intended to increase sound transmission loss. Using furring, acoustic insulation, and wallboard attachments, STC values up to 59 and 63 were obtained for the masonry and cast concrete walls, respectively. Selected STC values, reported by other investigators, for a variety of walls are included for reference.
Built-In Safety with Concrete Homes
Portland Cement Association. Item Code IS306.
Available for free.
This document summarizes the results of laboratory testing to compare the impact resistance of residential concrete wall construction to conventionally framed walls.
Comfort and Quiet with Concrete Homes
Portland Cement Association. Item Code IS305.
Available for free.
This document highlights the benefits derived from combining the mass of concrete with the insulating value of insulating forms. Together they provide a home that lessens the intrusion of outside noise, while improving the thermal performance of the home.
Moisture in ICF Walls
Gajda, J. and VanGeem, M., CTL Group, # SN2190a, 65 pages
Free to download.
The potential for moisture problems in ICF walls was investigated to determine if the walls have any inherent properties that make them susceptible to moisture problems.
The investigation was conducted in several phases. In the first phase, wall sections were
constructed and instrumented to determine rates of drying as affected by various combinations of exterior and interior finishes and vapor retarders. After one year of monitoring in a controlled atmosphere, the walls were carefully disassembled and examined for signs of moisture-related distress. No signs of moisture damage or distress were noted.
The second phase involved analyses of the condensation potential of wall sections utilizing various interior finishes, vapor retarders, and exterior finishes. Analyses were
performed for winter and summer seasons for locations throughout North America. Results
of the analyses led to recommendations on vapor retarders.
The final phase involved recommending standard window details to mitigate water entry at joints. Additional details were developed to address proper practices for exterior walls, from the foundation to the eave, for a variety of exterior finishes and construction types. Details were developed with the assistance of construction tradespeople to facilitate effective, yet practical, means of ICF construction.
Residential Technology Brief: Building a Better House with Concrete
Portland Cement Association. Item Code IS301.
Available for free.
This document provides an overview that describes the various types and features of ICFs as well as the many benefits of building with ICFs.
*Due to the setup of the PCI website, you must perform a search for this title at their bookstore.
Residential Technology Brief: The Quality of Concrete Costs Little More
Portland Cement Association. # IS304.
Available for free.
This document compares the cost of building with insulting concrete forms with the cost of conventional wood frame residential construction. It discusses how the cost of building with concrete declines as a crew becomes more familiar with the materials and methods. It briefly touches on the big advantages of paying slightly more for a concrete home.
What's Your IAQ I.Q.?
Environmental Council of Concrete Organizations, #2846
Architects, engineers, and builders are becoming more proactive in assuring the Indoor Air Quality (IAQ) of the buildings for which they are responsible. Concrete is the best building material for forestalling sick building syndrome. Concrete also reduces the outgassing of indoor air pollutants. Because concrete structures are more energy efficient, they lower emissions form furnaces. This document is available for free from Environmental Council of Concrete Organizations.
To find this article: Follow the link provided, then click "catalog" and scroll half way down the page to find the article.
Portland Cement Association
A web resource for general information on concrete homes.
Energy Use in Residential Housing: A Comparison of Insulating Concrete Form and Wood Frame Walls
Gajda, J. and VanGeem, M. CTLGroup, SN2415, 17 pages
Free for download.
A typical 228-square-meter (2,450-square-foot) house with a contemporary design was modeled for energy consumption in five locations. Locations were selected to represent a range of climates across the United States. Energy simulation software utilizing the DOE
2.1E calculation engine was used to perform the modeling.
In each location, three variations of the house were modeled. The first variation utilized conventional wood framed exterior walls constructed with typical materials. The second
variation utilized insulating concrete form (ICF) walls. The third variation had non-mass
exterior walls that met minimum energy code requirements. For all variations, all other
assemblies such as the roof, floors, windows, and interior partitions were identical. In all
locations, the house variations were insulated to meet the minimum levels required in the 1998 International Energy Conservation Code (IECC).
Due to the inherent insulating properties of the ICFs, total energy use (including heating and cooling, cooking, laundry, and other occupant energy) for houses with ICF walls ranged from 8% to 19% below that of the houses with walls that met IECC requirements.
Houses with wood frame walls constructed with standard materials also showed total energy saving over that of houses with walls that met IECC requirements. In all locations, houses with ICF walls had total energy requirements that ranged from 5% to 9% below
those of houses with wood frame walls.
Houses with ICF walls also showed additional savings resulting from a reduction in the
required heating, ventilation, and cooling (HVAC) system capacity. Total system capacity
for houses with ICF walls ranged from 16% to 30% less than that of houses with walls meeting IECC requirements and 14% to 21% less than that of houses with wood frame
ICF Points to LEED
Insulating Concrete Form Systems contribute to LEED credits
This two page .pdf summarizes the credits available to designers and building owners when using high performing insulating concrete forms in wall construction. Documents available for download to ICFA members.