Green Means
Energy Efficiency from the Ground Up
Intelligent
design and quality construction of foundations and floors will prove critical
to the comfort and sturdiness of your home.
Don’t skimp on costs or details. Begin
designing an energy efficient, green home from the ground up.
Common Foundation
Elements
Most all
foundations have firmly established footings on solid, unmovable ground. Footings are what bear the entire load of the
house and transfer the load to the earth.
Frost levels in an area will contribute to the determination of footing
depth. In our area, this is usually 3
feet 6 inches below the natural grade.
Footings will be concrete reinforced with steel of a height and width to
suit the home’s design.
Atop
footings will be stem walls or basement walls.
Stem walls are used for slab or crawl space foundations. Either stem or basement walls will extend
just above grade, to heights specified on blue prints.
Above are 3 types of common floor
structures: slab, crawl space, and basement wall. Not all details are shown and
there are many construction options for each style. Often basements must include French drains
outside the periphery or sump pumps that extend beneath the slab. Your structural engineer and/or the county
building inspector will specify what you need.
Slab
Concrete
slab floors have, from top down: reinforced concrete, sand (a good place to
embed floor radiant tubing) or stone; rigid foam insulation; vapor barrier; and
compacted fill dirt.
Concrete
subfloors are ideal for passive solar applications. They offer greater thermal mass than crawl
spaces or main floors above a basement. When
a home’s design has its longest wall facing south with sufficient glass to
allow in plenty of direct winter sun, and flooring is of sufficient density and
color, the sun’s heat is absorbed and retained.
This warmth will migrate slowly down into the sublayers of concrete and
sand. Heat will radiate from this
thermal mass into finished living space long after the sun has set. This passive solar gain reduces the amount of
heat needed from fuel sources.
Crawl Spaces
Crawl space
floor structures can also be energy efficient if careful consideration is given
to finish materials, quality of construction, and heating system. Finished floor materials should, again, be
thick and dense such as tile or natural stone that absorb and retain heat
well.
Subfloors,
the substrate beneath finished floors, must be well insulated so that cold air,
that filters through the crawl space to keep it dry, does not penetrate up into
the home. Rim or band joists, that run
the periphery of the foundation between the stem walls and the subfloor, must
also be heavily insulated. It’s a good
idea to use rigid foam insulation on the inside of stem walls as well. To keep out cold air, caulk or otherwise seal
all openings where plumbing, electrical, or ductwork protrude from the crawl
space into the finished home.
Basements
Daylight or
walk-out basements can function as efficiently as slabs as long as the finished
flooring is of a sufficiently medium or darkish color and receives direct
winter sun. Main or first floors above
the basement won’t have the same mass as the concrete and sand combination, but
can still collect and radiate heat with adequate southern exposure and dense
flooring materials. The interiors of
basement walls must be insulated.
Whatever floor
configuration you decide upon, remember to have structural engineers finalize
your scaled home designs into blue prints. Use engineers with reputations for good, clean
work. It will pay off with easy to
decipher blue prints, more expedient permits, and a rock-solid home.
Here in
northeastern Nevada, we used Lostra Engineering. They generated high quality, easy to read
drafts free of errors or omissions. The
Lostra firm was familiar with straw bale design and charged a flat fee, not a
per square foot price. We received many
positive comments about the extensive use and tidy layout of steel in our foundation
and slab edges. Plus, we had building
permits 4 days after submitting prints to the building inspector’s office. Using a good structural engineer will be
money well spent.
Think green
from the bottom up! A home, just like a
relationship, doesn’t last unless the foundation is solid and healthy –
building a strong, energy-wise base will literally be the building blocks for
an efficient home.
Photo by S. Scott: What’s underneath
the garage floor? Plenty of steel
reinforced concrete for a stout structure. All work
completed by R. Pogoda and S. Scott.
Are you
interested in learning how to build your own straw bale home from foundation to
finish? Please drop me an e-mail. I am considering offering a class building an
instructional model straw bale studio.
The class would include concrete work, plumbing, bales, lime and clay
plastering, masonry, wiring, roofing, and likely mechanical systems. The class would take place over a couple of
seasons. Cost to be determined.
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