TechPractices are outstanding housing projects throughout the U.S. where innovative technologies are implemented. Builders and remodelers can use these examples as models for projects of their own.
| The AFM Study House Snapshot |
| Location: |
Minneapolis, Minnesota suburb |
| Builder: |
AFM Corporation |
| Project Scope: |
One 4,964 sf upper-end si4ngle-family home |
| Price: |
Competitive with similar sized upper-end houses |
| Financing: |
Market financed; preferred rate mortgage from Norwest Bank based upon Energy Star Rating |
| Innovations: |
Structural Insulated Panels, Insulating Concrete Forms. By optimizing this house's thermal envelope, energy costs and the size of the HVAC system were significantly reduced. |
Summary
Using readily available building technologies, such as insulating concrete forms (ICFs) and structural insulated panels (SIPs), this 4,964 square foot home has an average winter heating bill of approximately $48 per month. Many of the technologies have the added benefit of reducing on-site labor.
Details
AFM reports that, in comparison with a similarly sized conventional wood framed house built according to the Model Energy Code, its study house saves 60% on energy heating, cooling, and hot water. AFM further states that the house more than doubles the 30% savings provided by a model energy house certified as an EPA Energy Star Home.
These dramatic energy savings are achieved through the combined use of a number of products and techniques: insulating concrete forms (ICFs), structural insulated panels (SIPs), under-slab insulation, insulated window and door headers, low-e windows, and the latest HVAC technology.
Installation/Construction
The basement walls of the AFM Study House are R-20 ICPs, which are rigid plastic foam forms for concrete that remain in place as thermal insulation and facing material for concrete walls. The process minimizes bracing and eliminates conventional form work. ICFs are typically installed on common spread footings. For the AFM Study House, the ICFs contain Borate, a mineral additive that makes the foam resistant to termites and carpenter ants.
The ceilings and exterior walls are SIPs, comprised of a structural
board (OSB or Plywood) or other facing adhered to a foam core.
The panels range in thickness from 4" to 12" and can
be up to 24' long. The AFM house utilizes 10-1/4" R-39.9
panels for ceilings and 6-1/2" R-24.3 panelsfor exterior
walls. Because the SIPs are ordered as a packaged system, the
panels arrive at the site properly sized with precut openings.
Only on-site assembly is required.
Although the interior of the AFM Study House is finished with gypsum board, the ceiling panels have a pre-applied coat of Firefinish™. This AFM product satisfies fire rating requirements and eliminates the need for gypsum board. This finish system is more appropriate for ceiling installations than for walls due to its slight texture.
Benefits/Costs
The use of ICFs and SIPs with other technologies has a number of benefits. The increased efficiency of the thermal envelope results in a smaller and thus a lower-cost HVAC system. The 120,000-BTU furnace and 5-ton AC unit typically used for this size house is replaced with a 70,000-BTU furnace and a 2.5 ton AC unit. Site fabrication is eliminated because the SIPs were ordered as a packaged system, requiring only assembly. As a result, the house was closed in quickly. Additionally, through the use of SIPs with a factory applied finish, gypsum board is not needed on the ceiling. Because the concrete forming system becomes an integral part of the wall, the need to dismantle form work after the concrete pour is also
eliminated.
Code/Regulatory
Most SIPs systems are recognized by all major code organizations. ICFs with flat wall configurations must meet standard prescriptive
structural design requirements for cast-in-place concrete walls in building codes. Plastic foam insulation requires special attention to meet certain fire resistive provisions. Manufacturers usually provide design and engineering assistance to help builders obtain local code approvals.
Feedback
An independent, third-party energy evaluation by Shelter Supply in Lakeville, Minnesota, indicated that the AFM Study House has a Home Energy Rating System (HERS) score of 91.6. A comparable conventional wood framed satisfying the Model Energy Code would receive a HERS score of 80.
Contact(s)
Do you have a specific question? Try the contacts listed below:
AFM® Corporation
P.O. Box 246
Excelsior, MN 55331-0246
800-255-0176
Structural Insulated Panel Association (SIPA)
P.O. Box 1699
Gig Harbor, WA 98335
253-858-7472
Energy Star Homes Program
US Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
888-STAR-YES
www.firstco.com