As with our Homes for Our Troops (HFOT) project home, building an energy free or Near energy free home takes careful and detailed planning. Building these types of homes is in many ways different than standard construction. Everything from the ground up in the construction process must center around minimal air infiltration and frame tightness. In addition, maximizing thermal efficiency and insulation performance is a must! This will then allow for downsized and highly efficient mechanical systems to do their jobs at minimal cost.
Our HFOT project home will be constructed over a crawl space due to site soils conditions. In this case, we dropped our floor joists 12″ from top of concrete wall to eliminate the standard wood rim joist installation. The floor joists will rest upon an “interior brick ledge” resulting in the floor decking to be at the same level as top of concrete foundation wall.
This construction technique eliminates extra connection points and areas where air could infiltrate past the typical floor joist/ rim board construction installation detail. In addition, the edges of the floor joists at the foundation wall space will be spray foamed with closed cell insulation to ensure a tight seal around the perimeter.
The earthen crawl space floor will be sealed with 10 mil plastic air barrier mopped up 24″ onto the concrete foundation walls. Finally, the concrete foundation walls themselves will be draped with a continous R11 insulation blanket for thermal performance. This creates a crawl space with a special problem: The need for controlled ventilation.
Our next blog will explain how we will deal with ventilating the crawl space in the HFOT project home.
