Prefab for Humanity

In the realm of affordable housing first cost is often a driving factor, howeverthe cost to own and operate a house will outpace this initial outlay ofcapital. According to the Alabama Association of Habitat Affiliates (AAHA)families eligible for Habitat homes spend up to 30% of their income onutility bills. The majority of those bills are directed toward the heating andcooling loads of the houses. Within the affordable housing market, andparticularly in Habitat Affiliates, stick built construction offers the utilizationof free, unskilled laborers, but also limits the potential for the housesto develop and implement new energy saving systems. Any modificationsto an existing, time-tested Habitat template would require the addition ofskilled, paid tradesmen, who add cost and complexity to a bottom line drivenmarket. Habitat for Humanity is scrambling to find solutions that wouldenable them to create more energy efficient homes, but at the same timemake them simple enough that unskilled laborers can still piece the homestogether without too much overhead. There is an opportunity to advancethe energy efficiency of affordable homes by dividing labor and deliveryinto two categories; prefabricated construction and stick built traditionalconstruction. By separating the construction sequence of Habitat Homesinto two distinct tracks, opportunities arise for the integration of low-cost,energy saving prefabricated elements that could easily be integrated into aminimally modified stick-built habitat house utilizing the same unskilledlaborers. One of these prefabricated systems, and a focus of this paper, isthe development of a radiant envelope system.Radiant assemblies for space heating (floors, walls, ceilings) are not a newsystem, early forms of these assemblies can be found in Roman Villas aswell as traditional Japanese house construction. Originally these systemsrelied upon the use of air as a heat transfer medium. Air, heated in a furnaceand directed into cavities within the wall and floor assemblies provided heatto the interior of the building. This technology ceased to be utilized with thedevelopment of more efficient fireplaces, stoves and systems of transportuntil being replaced with fan forced air-heating systems. Current materialtechnologies are allowing for a renewed interest in conditioned air space forboth heating and cooling. Radiant cooling is a more recent technology thatpromises to provide a cooling system that requires less energy than a conventionalall-air compressive refrigeration system. The use of water (whichcan hold more heat than air) as the transfer medium yields a system thatcan operate at lower temperatures for both heating and cooling. This paperseeks to couple these approaches within a prefabricated radiant assemblythat can provide an alternative low energy solution to heating and cooling aresidential structure.

Volume Editors
John Quale, Rashida Ng & Ryan E. Smith

ISBN
978-0-935502-85-5