The existing conditions present several challenges (opportunities) to the design team. With both above-grade and below-grade habitable space, the solution became complex, and a result, required a transition from exterior insulation, air, vapor, and water control layers to interior control layers. The buildings all have partial basements and crawl spaces, housing mechanical and laundry space, with roughly two-thirds of the footprint occupied as crawl space. The basements had experienced considerable bulk water intrusion during extreme weather events of 2013, adding to the imperative of risk management.

Washington DC is in a mixed-humid climate zone and is increasingly experiencing high exterior temperatures and relative humidity, and has been subject to increasing frequency of extreme weather events including torrential, and wind-blown rain events. In response to these conditions, the design team made efforts to design a long-lasting, low-risk assembly which ameliorates current bulk water issues and provides maximum drying potential. Due to already restricted available square footage and the non-descript the design solution was to externally insulate, air seal, and re-clad the envelope. The original design was for a liquid applied membrane to be applied to the surface of the existing brick façade. Eight inches of Roxul rigid insulation was to be attached between 9.5” vertically hung wood I-joists bolted to the façade to carry the cladding and allow for a ventilation gap between cladding and insulation.

After schematic set pricing, the builder proposed several VE items that were envisioned to provide cost savings at no cost to performance. The impacts of these proposals were a key learning experience.
The resulting enclosure assembly is constituted of vertically hung wood ‘I’-joists, wrapped with a vapor-open, air-tight membrane, dense-packed with fiberglass insulation, with a vented rainscreen of fiber cement cladding. (fig. 2) Foundation walls are insulated on the exterior with Roxul Drainboard. Exterior insulation, air-sealing and waterproofing is extended to 3 ft. minimum below finished grade -well below the finished first floor of the interior. IN addition to external foundation insulation, the below grade, thermal, air-tight and vapor control layers are bound to the inside face of basement and crawlspace walls and floors and extended to the underside of the first floor structure, such that there is ample overlap with the exterior assemblies from above.
Two of the 3 buildings face due East and West while one is 45 degrees from the cardinal points, exposing the main facades of the buildings to undesirable summer and shoulder season morning and afternoon sun, and limiting the use of winter-time available solar radiation. Peak cooling loads could be considerable. Fixed, tapered, external shading boxes were designed to mitigate cooling season gain and preserve heating season gains to the greatest extent possible with fixed shading devices. (fig. 4)