An initial step in this project was to identify a common, locally available home design. Then, through a series of design reviews, all aspects of the home's design were systematically reviewed to explore opportunities to improve the performance of the home based on NAHB's Model Green Home Building Guidelines, and on the five PATH goals.
With these modifications in place, the house design's score under the Model Guidelines changed from one that did not warrant a Bronze rating (161 points) to one that easily achieved a Gold rating (400 total points). For more information on this process, and the technologies chosen, see Greening a New Home (PDF) - a case study which details how the existing plans were modified.
Research and analysis of the chosen technologies is now underway. Results are posted as they become available; click on technology name for an overview of that technology.
Fly Ash Concrete
- For concrete pumped into ICF foundation walls, LCCTC specified that a minimum of 30% of cement should be fly-ash or slag; concrete vendor supplied a product that contained 40% fly-ash and slag.
- Total amount of concrete used to fill voids in ICF foundation walls was 17 cu yd.
- The cost was $84 per cubic yard, which was the same as vendor’s normally-supplied concrete.
- During rating according to the NAHB Model Green Home Building Guidelines, credit was given for using concrete with fly-ash or slag (Resource Efficiency section -- Recycled Content Building Materials).
Insulating Concrete Form (ICF) Foundation Wall Construction
The foundation walls for the LCCTC project were constructed using Insulating Concrete Forms (ICFs). Prior to construction the Working Group considered using precast concrete wall panels; however, precast concrete foundation wall panels would have required manufacturer or subcontractor's certified personnel and equipment. The LCCTC instructors recommended the use of ICFs so that the construction could be conducted by students. The students would be trained by ICF technical personnel. As it turned out, both Carpentry and Masonry students were trained in the installation of ICFs.
New Holland Concrete supplied the Reward Wall Systems, and supplied training and onsite supervision of students for erection of ICF foundation walls. Reward Systems supplied standard details for window flashing and connection of structural floor framing members to ICF walls. ICF forms contain plastic inserts at 6 feet o.c. horizontal spacing to be used for attachment of siding and drywall.
Construction of foundation walls first involved the placement of continuous concrete footings formed by "Form-A-Drain," which is a perimeter footing drain system that remains in place. ICFs were then stacked-up and braced, and vertical and horizontal steel reinforcing bars (rebar) inserted in the voids. Bracing was required at the bay window area, in two locations at angled walls, where there was a vertical seam and ICF blocks did not interlock. A locally available dimple-board drainable layer was attached to the exterior for waterproofing.
Concrete was pumped into forms following American Concrete Institute (ACI) and building code requirements. The minimum concrete strength was 3000 psi and 40% fly-ash and slag was used in the cement. The total amount of concrete used in the ICF walls was 17 cu yd, at a cost of $84 per cu yd.
- A high level of insulation (typically R-17 to R-26) provides continuous insulation without "thermal bridges" and deadens sound transmission.
- Reinforced concrete has high seismic and wind load resistance. Additionally, foam and concrete are resistant to decay and rot.
- Under the NAHB Model Green Home Building Guidelines, the dimpled foundation membrane received 7 points, and the fly ash in concrete received 5 points.
Feedback from instructors
- Carpentry Instructor - "It was a good learning experience for the students. We had a good product to use. Offsets, or bump-outs, added time because of the bracing required. The waterproofing system with dimple board worked well and protects the foam and provides a drainage plane."
- Masonry Instructor - "Everything went well. We had no blow-outs when pouring concrete. The rain and mud really slowed us down. Student training was easy; we had an ICF rep by our side throughout the process. We’re confident we could go all the way up to the roof next time without added supervision."
Technologies under review: