Excavationless Exterior Foundation Insulation Exploratory Study

Abstract

These authors would like to thank Jed Lahti, Wagner Zaun Architecture, for field work and neighborhood mapping analysis; and Don Fugler, Canada Mortgage Housing Corporation, retired senior researcher, for sharing historical perspective and building science expertise in an interview.

Excavationless Exterior Foundation Insulation Field Study

“…In each case, the walls were waterproofed, draintile was added or remained, and extruded polystyrene (XPS) rigid foam insulation was mechanically fastened to the existing foundation wall, from top of foundation wall to top of footing. The final costs for this type of approach was within the cost range estimated for current advanced approaches to deep energy retrofits at $7-$15/ft 2 (Mosiman et al 2012). Figure 3 illustrates the negative impact of insulating an existing foundation wall from the interior compared to the benefits of applying it to the exterior.…”

“…There is a growing body of research and field experience indicating that applying insulation to the exterior of the foundation during new home construction and implementing proper bulk water management strategies greatly reduces the risks related to water/vapor flow and foundation wall temperature differential. (Mosiman et al 2012) The results are indicating a more comfortable, durable basement environment along with energy efficiency gains. The following illustration ( Figure 1) highlights the key elements for insulation and water management on the exterior side of the foundation wall.…”

“…In the previous NorthernSTAR report (Mosiman et al 2012), two recently completed projects in northern Minnesota provide examples and current cost information about the "conventional" approach to exterior foundation insulation retrofits. A similar backhoe insulation strategy was employed on the two foundations.…”

“…Noted, however, is the cost to upgrade an existing wall using conventional backhoe methods that often prevents homeowners from pursuing this option. The previous BA report (Mosiman et al 2012) also presented results from a Neighborhood Obstruction Analysis of five Minneapolis, Minnesota neighborhoods to try to quantify the type and occurrence of obstructions that would interfere with full access to the foundation walls. Most of the time 75% or more of the foundation perimeter appeared to be accessible to some form of excavation without removal of the obstacle.…”

“…Gaining access to the foundation walls may also mean the removal and replacement of stoops, patios, porches, and landscaping with significant cost and coordination to attend to underground utilities. In a previous Building America (BA) report (Mosiman et al 2012), the NorthernSTAR Building America Team identified a new, minimally invasive excavation and insulation technique for existing home foundation, referred to as excavationless. It is based on existing hydrovac and airvac technology that is capable of precisely excavating a trench directly adjacent to the foundation wall.…”