We will start with the roof and work down since the roof has the largest potential impact on a green building or home. This is due to the multiple roles that roofs can play.  Besides the obvious of keeping rain and hot sun out of a living area, roofs also are the best surface for producing energy and collecting water. 

So what is the best green roof?  Here is a very straight personal opinion answer to a much debated question - If your roof is sloped, the best green roof is a SIP structure with metal roofing. A SIP roof is super strong, super insulated, uses fast growth trees in a structurally very efficient way, installs easilly and quickly, and provides 'free' living space that is otherwise wasted attic space.  But there is a catch - you need to design your roof to work efficiently with SIPs (not design SIPs to work with your roof design).

The above image is a rendering (somewhat realistic image drawing) that we created for the date of 12/1/2007 using a 3D BIM (building informational model) CAD design we created from a customer's architectural design.

This SIP (structural insulated panel) home shows installation for semi-buried rain water harvesting cisterns, a BP solar panel array, and an Urban Turbine wind generator.

We like to equate a roof system to the engine in a car. There is a lot going on under that hood that we never think about. Currently, almost all residential roofs and vented attic spaces are custom shapes that are field manufactured, one-of-a-kind artistic assemblages formed from 2x6, 2x8, and 2x10 sawn wood members. Rafters are covered with OSB decking and ceiling joists covered with sheet rock.  If absolutely done correctly, a vented attic heats the the volume of attic air until convection causes it to rise. Outside air is then filled into the attic space and the process repeat, air flowing (when hot enough) from low areas (soffit vents) to high areas (ridge vents). Within this semi-sealed volume (that is often easily 1/3 as large as your entire home's volume), a spaghetti bowl of air conditioning duct work must work perfectly to keep 'expensive', low humidity, cold, filtered air separated from a natural environment that is hot, humid, dusty, moldy, pollen and pest laden.

For simpler roof design shapes, the best alternative to a typical dusty moldy spaghetti bowl attic space might be a SIP roof home like the above. For this project a SIP floor created a sealed crawl space, SIP walls support a SIP roof  which creates a semi-conditioned attic space of low humidity or dust that will never gets warmer that 85 degrees even in a Texas 105 degree summer day.

To this engineer, the current roof and attic 'system' does not sound very well designed. A good comparison would be a 2007 auto engine compartment versus a 1970's era auto engine compartment. That 1970's auto had a well designed passenger compartment, but it had an engine compartment that was a jumbled mess. Hoses, wires, black boxes, ducts, and other 'stuff' was bent and crammed in an unorderly fashion, This sloppy 'design' changed only after Japanese auto engine compartments demonstrated how good design looked, and in doing so, how well it could run.

A well designed roof and attic area will lead to better home performance (more efficient use of materials, lower energy, and lower maintenance costs). To consider a better designed greener roof system please contact your designer, ECO, or come back at a later date. ECO recommends designing an unvented attic with MEP chase-ways. Consider using SIPs or 2X framing with spray foam insulation, with metal roofs combined with a small roof garden area all oriented with the sun.