Q: I’m building a new living space in a downtown area on top of an existing poured concrete structure. I wanted to use insulated concrete forms, but I have great concerns about the weight and the cost. Are there any comparable solutions that provide solid walls, thermal mass, great insulation, ease of use and green tint? I’m also looking into alternatives to drywall as well as geothermal climate control and wind turbines. —Kirk Saylin, Long Beach, California
A: Assuming that your existing poured concrete structure includes a foundation, your first step is to hire an engineer to analyze its structural capacity. Then you won’t have to guess whether a given green wall system is too heavy.
There are many green wall systems: sustainably forested wood, structural insulated panels (SIPs), light straw-clay, many types of insulated concrete forms (ICFs), straw bales, earth masonry, and so on. What makes a wall system most green, however, is selecting it in response to your site, climate, and distance from the source of a material.
Many green wall systems that intermix thermal mass and insulation end up doing neither job well. Depending on your climate, you probably want your insulation on the exterior and your thermal mass exposed on the interior.
If your foundation won’t support a thermally massive wall, you can build a well-insulated exterior wall and provide thermal mass elsewhere. If your existing concrete structure includes a slab or a wall, consider designing your home to take advantage of that thermal mass. Otherwise, you might want to create “distributed mass” by applying a thick coat of plaster to your interior walls. Plaster provides thermal mass, can be as “green” as you like, is a great DIY material, allows for creative freedom, and eliminates the need for paint.
As for geothermal climate control and wind turbines, if your budget is tight, you might be better off using energy conservation and passive heating and cooling techniques as your primary strategies. Good climate-responsive design is the greenest thing you can do; it will save you many dollars and headaches.
Carol Venolia is an architect, author of Healing Environments: Your Guide to Indoor Well-Being (Celestial Arts, 1988), and former publisher of Building with Nature newsletter.