Green Home Building and Sustainable Architecture

Sustainable architecture is an exciting and important field, with many people reviving traditional methods of building and others creating innovations to established practices. Kelly Hart, webmaster of the popular website www.greenhomebuilding.com, posts text and photos featuring what he discovers from around the world.

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Location: Crestone, Colorado, United States

Kelly Hart has been involved with green building concepts for much of his life. He has also worked in various fields of communication media, including still photography, cinematography, animation, video production and now website development. Kelly has lived in an earthbag/papercrete home that he built and consults about sustainable building design.

October 21, 2009

Living Walls

We have all heard about green roofs and know about their environmental advantages, but there is a new concept that is taking root, especially in urban environments: green walls or living walls. Better than the old ivy-covered buildings, which can be adversely affected by the vines, these walls are designed to feature a variety of different plants in a vertical environment, and provide all of their needs for moisture and support right on the wall.

These walls can be either exterior of interior, and they provide advantages in both situations. On the outside they will shade the wall from the intensity of the sun, and thus moderate the temperature considerably, as well as provide lovely textural contrast and beauty. Plant surfaces, as a result of transpiration, do not rise more than 4–5 °C above the ambient and are sometimes even cooler. On the inside they will filter and oxygenate the air, providing a healthier indoor environment, while also creating the calming effect that natural plants tends to have on most people.

Vertical gardens can be grown on just about any type of wall, with or without the use of soil. Many living wall kits come with modular forms that are assembled and applied to a frame that then is affixed to the wall. The most common frame for sale today is a panel that is self-supporting and can be set up independently or attached to a real wall. It is then filled with soil or a soil-less medium and planted. Once the initial panels are in place living walls require little maintenance. They are designed so that their upkeep is about the same as a landscaped garden.

When you combine the obvious environmental benefits of living walls with their sheer beauty I anticipate that we will be seeing many more examples of this wonderful art form. For more details and photos see greenhomebuilding.com.

October 17, 2009

Super-Insulated Houses


I am pleased to introduce a new "expert" panelist at www.greenhomebuilding.com. Robert Riversong has created his own form of the Larsen Truss building system, and specializes in super-insulated houses. He teaches these techniques, and many other subjects, at the Yestermorrow School in Vermont.

In an article about his work, Robert states, "I've been using and modifying the Larsen Truss super-insulated wall system for 20 years and can build a 12" thick wall (R-40+) with no more lumber than a conventional 2x6 house, in part because I eliminate exterior wall sheathing and use t-braces and full 3/4" drop siding over housewrap. And, with the air-tight drywall system instead of vapor barrier and dense-pack cellulose, there's almost no thermal bridging and a 3 bedroom house can be heated with less than a cord of wood per year here in New England.
"I also use native, rough-sawn green full-dimension lumber, rough-sawn subfloor and roof deck, and rough-sawn exterior trim. The load-bearing wall is 2x4 24" oc and the exterior chord of the parallel chord wall truss is a 2x3, extending from sill to rafter tail and attached to studs with rough-sawn 1x4 gussets 24" oc."

"The open wall cavities makes the installation of mechanicals simple, since there is little drilling necessary. The three air barriers (drywall, dense pack, housewrap) make the walls virtually impermeable to infiltration. The dense pack cellulose makes the walls highly fire resistant and extremely quiet. Insects and rodents don't like the boric acid used as fire retardant in the cellulose, so these two universal problems are minimized or eliminated. The cellulose is more hygroscopic than wood, so it not only can absorb and release any diffused moisture that might get into the wall cavities but also draws any potential moisture away from the wooden frame, thus protecting it (foam insulations will do the opposite)."

"The only plywood in the house is for door and window boxes, as this makes a better air-tight seal than boards, and for a couple of interior shear walls. Let-in metal t-bracing in exterior and interior load-bearing walls and wooden under-rafter diagonal bracing sufficiently stiffens the structure, particularly once the sealed drywall is installed."

"I find that going from conventional construction to superinsulation adds no more than 5% to the cost of a house and the payback is enormous, both in energy savings and comfort. Some banks are offering higher debt-to-income ratios to mortgagees who buy or build highly efficient homes, since they need so much less income to operate it."

If you have any questions about the Larsen Truss building system or super-insulated homes in general, Robert is happy to answer them. Go to greenhomebuilding.com/ask_the_experts to send your question.