Stewart Brand sent me this interesting bit on a couple of potential long term building materials that have recently been discovered to be improving rather than degrading their environs:
Recently a new building, the Dives in Misericordia Church in Rome, seemed to be reducing the concentration of urban pollutants in its immediate vicinity (36). Upon investigation, it was discovered that the titanium dioxide coating on the large concrete walls of the church was reacting with nitrogen oxide pollutants in a photocatalytic reaction, resulting in a decrease of pollutants in the area. Although the TiO2 was originally specified for its visual qualities and self-cleaning properties, its effect on local pollutants was a surprise to the architects and engineers of the building. Further research is needed to determine efficacy and real benefits, but proposals are already surfacing for the use of photocatalytic coatings in sidewalks and roads to neutralize the concentration of pollutants found in dense urban conditions.
Also, a “new” material-polyamide, or nylon-has emerged in applications as a “smart” vapor barrier in exterior envelopes. Its water vapor permeability increases by a factor of 10 in conditions of very high humidity. This is particularly useful when moisture is trapped inside a wall assembly. The vapor barrier becomes more permeable and allows moisture to escape, reducing the risk of corrosion, rot, and the growth of mold and mildew. Although nylon was discovered in 1931, its properties as a vapor barrier were not described until 1999, and it was recently commercialized for this purpose (37)
Science 30 March 2007:
Vol. 315. no. 5820, pp. 1807 – 1810
DOI: 10.1126/science.1137542Materials for Aesthetic, Energy-Efficient, and Self-Diagnostic Buildings
John E. Fernández
