Monday, May 9, 2016

Design - Sustainable Building Practices

Building green is not just about energy efficient windows, low-flow faucets and lots of insulation.  It starts with site selection, continues through construction and culminates with the owners enjoying a low carbon lifestyle indefinitely.

Site Selection
For site selection, an important issue is personal transportation -- by what mode and how far.  An urban in-fill location, such as ours, is preferable to suburban, exurban or rural because it reduces travel to infrastructure such as schools and churches, shopping, work, medical care and entertainment.  Proximity to public transit is also a plus; we are a few blocks from a bus line and a short bus ride from a light rail station.  And what an advantage is has been during construction to have the lumber yard, the rebar supplier, a home center, wholesale plumbing and electric dealers and a farm and home store -- all within a few miles.

Site Stewardship during Construction
Here the issue is minimal site disturbance -- limited excavation and respect for topsoil and trees. Our ranch design surrounded by an insulation/watershed umbrella unavoidably requires much more site disturbance than would a multistory conventionally-built house of similar size.  To our credit, though, the topsoil has been carefully removed and set aside for future use.  And erosion is being controlled by straw bales, silt fencing and a retention pond (which has had to be dredged twice during the first year and a half).

Erosion control with silt fencing, straw bales and a
retention pond.

Site Stewardship Is More Difficult When Working Alone
A distinct negative is that working alone takes a long time and site disturbance is protracted.  In an attempt to ameliorate this problem, construction was halted in late fall so I could use the track loader for some serious dirt work.  I was hoping that before the ground started freezing and thawing I could install the downhill portion of the insulation/watershed umbrella -- that part in front of the house -- so that the slope to the street could be returned to its original contour and native plants could a be started immediately for erosion control. So the considerable excess dirt in front of the house was moved to behind the north wall as the first 5-6' of backfill and the hillside was graded.

My intention was that, as soon as the proper contours have been established, erosion could be controlled with an erosion control blanket with native plant seeds sown under it for germination in the Spring. Unfortunately, unseasonably wet weather around Christmas interfered and we went into a crisis mode to make run-off from our property stay on our property using additional silt-fencing and another dredging of the retention pond. It is now May and pouring the footings, foundation and slab for the screened porch and pouring the garage floor has delayed installation of the umbrella to the extent that any definitive planting in front of the house will have to be delayed until Fall and may have to be annual rye grass as a temporary cover crop until it can be replaced by something better later.  We are committed to native landscaping but now recognize that it may have to be done more gradually than we would like.

House Size Matters
Of course, the larger the house, the more energy it consumes -- both during construction and during its life.  In my view, a McMansion that touts its structural insulated panels (SIPs), its geo-thermal HVAC system, its top-of-the-line windows and, even, its photovoltaic solar panels or wind turbine is nothing but sophisticated greenwashing.  True, such a home is better than a McMansion with no regard to sustainability, but size does matter. 

Each square foot of floor space has an impact on sustainability -- more concrete, more lumber, more drywall, more copper wiring and plumbing, more floor coverings, more insulation, more roofing, more furnishings, etc.  At a minimum, each additional square foot impacts sustainability by way of its embodied energy.  And window size and placement also have a bearing.  Ever notice the expansive windows that face north and west even in so-called "green" houses?  

However, the real impact on finite resources plays out during the life of the dwelling. More space requires more energy to heat and cool, regardless of how efficiently it is done (unless it is done strictly with renewable energy -- which is our case).

Our floor plan is essentially a 2,800 sq ft two bedroom/two bath ranch with a third bedroom piggybacked on as an abbreviated second floor giving total living space of 3,000 sq ft. About 450 sq ft of the 2,800 sq ft slab is non-living space that the principal author of the AGS system calls a "vertical basement" and we are calling "storage".  Another 110 sq ft comprises the entry air-lock which could be considered quasi-living-space. 

If our plan is overly consumptive, the master bedroom and the living room-kitchen-dining room "great room" might be considered somewhat generous. However, I rationalized this bit of extravagance to some degree in the following ways:
  • Most of the lumber will be either recycled or grown locally
  • The "extra" space impacts sustainability mostly via an increase in concrete for the floor, wood for the ceiling and metal roofing, but concrete does sequester industrial waste (fly-ash), wood ceilings come from plantation-grown trees less than 300 miles away and metal roof panels have recycled content and a recyclable end-life
  • The extra space will have no impact on the amount of wiring because the longest circuits were shortcutted beneath the slab using donated wire; the same goes for the supply side of the plumbing
  • At our age, we will not be the principal owners of the house -- either through inheritance or sale after we are gone, it will be occupied by younger folks with larger families who will appreciate and enjoy the roominess
However, the justification for the added space that is most defensible is that our passive AGS system will provide zero-energy conditioning year-round for the life of the house regardless of the size of interior space.

The next post on sustainable building practices focuses mostly on the construction phase.