Design Build - Sentinel House

Sentinel House

Mary C. Hardin, University of Arizona


In addition to the pedagogical goals of learning from doing, and the outreach goals of contributing to the community surrounding our campus, this design-build project included the goal of investigating “scoria” as a wall system feasible for the construction of low-cost

“Scoria” is a volcanic stone, also known as “cinder” or “pumice”, commonly found in abundance in locations where volcano ejections are part of the surface geology. A mixture of ground scoria, Portland cement, and water resembles a low-strength concrete mix, and can be poured into forms in layers. It has a good thermal value due to the air pockets found in scoria stone, and the 18-inch thickness of the walls creates a thermal mass that slows the transfer of heat from the exterior to the interior of the home.

While scoria is an easily acquired local material in many hot-arid climate zones, it has not been adopted into contemporary building practices. This design-build studio worked to determine the construction properties of scoria as a wall system, carried out the necessary compressive strength tests in order to meet performative building codes for earthen materials, then designed and constructed a low-cost dwelling. The north and south walls are wood framed, insulated and clad with fiber cement panels and polycarbonate panels. After
the residence was purchased by a low-income family, the students and faculty conducted thermal measurements for one year, to assess the actual performance of the scoria walls (with a mid-wall insulating foam insert) in terms of thermal regulation and interior comfort.

The results of the thermal monitoring reveal that scoria walls function well as temperature stabilizers, and help to keep interior temperatures at an average of the daytime high and nighttime low temperatures in a region with a large diurnal temperature swing.