In 1997 John and Gail bought a modern
split-level house which was about 20% smaller than their prior
house, so they decided to build an addition right away. One reason
they bought the home is its unobstructed view to the south. With
such a great southern view, the addition was designed for passive
solar, with a great room and a study extending due south from
the heart of the existing home's kitchen and dining areas. The
addition is the 3rd lowest of now 4 floor levels in the house,
so solar-heated air can easily rise without blowers into the upper
levels of the existing house.
The addition faces 125 s.f. glass due south in fixed panels 4
panes thick, the 2 outer panes glass and the 2 inner panes HeatMirror88
film. The center-of-glass R-value is nearly 8 and the overall
R-value about 5, nearly twice that of typical low-e argon windows.
HeatMirror films also block 99% of ultraviolet radiation. A patio
door and smaller windows with low-e/argon and HeatMirror tri-pane
glass face east, west and north. All windows have generous overhangs
of 2' or longer. A tube skylight was added to provide daylight
to an existing windowless bathroom.
New trussed ceilings are insulated with R-50 blown fiberglass
and vapor-barriered. 2x6 walls are R-3-to-6-foam-clad on the exterior,
all seams taped, then blown with R-20 icynene insulation and vapor-barriered.
The 4" floor slab, thermal storage for the passive solar
heat, is insulated with R- 15 extruded polystyrene at its edge
and R-10 beneath. Existing ceilings had insulation increased from
R-30 to 50. The icynene insulator insulated and sealed wire, pipe
and fixture penetrations in existing ceilings and the crawl space.
Nothing was done to the existing exterior walls. Top and midlevel
floor walls contain only about R-14, but the lowermost walls have
R-25 insulation.
The original electric furnace was replaced in late 1997 with an
efficient heatpump, rated SEER 13, HSPF 8. A programmable thermostat
replaced the original constant temperature unit. The home's conditioned
area increased by about 40%, but the heating capacity was not
increased. Cooling capacity was raised 25%, but increasing the
SEER, reduced the energy needed to run the new AC by over 25%!
The high-SEER heatpump qualified for a rebate from the electric
utility.
A high efficiency, low-emissions wood-burning fireplace is also
installed in the addition's great room. Rated for about the same
heating capacity as the furnace, it is a backup heater in case
electricity goes out on a stormy winter night. The fireplace is
an airtight combustion type, with dedicated outside air supply
and triple-wall chimney for extra flue safety.
The 1997-8 electricity bills for this house (before the addition)
totalled $764.10, which included 8 months with an outdoor hottub.
John hopes that with the new passive solar performance, wood heat
and a future solar hot water heating system, this bill can be
lowered to below $500 per year!