Greenbuilding Archive for January 2001

[Bruce Marshall <marshall@cp.duluth.mn.us>]

Bion,

For Duluth, Mn, (52% "possible sunshine") think 8% "savings" on home heating
from passive solar. (Bion wrote: "By the way a 15% savings on heating seems
pretty high as a generalization, and folks should think in a range of 8% - to
18% depending on climate, building design, and occupancy (residential only)."

The reference case was the 2000 Minnesota Energy Code, which is a little
better than the 1995 Model Energy Code. We reduced the heating load by 70%,
relative to the reference case, before getting to passive solar--i.e., by
design, "optimal" thermal envelope, programmable thermostats controlling
setbacks in multiple zones, efficient boiler, heat recovery ventilator.

We reduced the heating load an additional 8%, relative to the reference case,
with passive solar. However, the reduction was 26% relative to the (call it)
"superinsulated house design" (i.e., the reduction achieved by design,
"optimal" thermal envelope, etc.)

All these numbers are estimates using Energy 10.

For more detail, see the Home Energy article on this house, Nov/Dec 2000
issue. For even (considerably) more detail, contact me for the booklet the
article is based on.

Regards,
Bruce Marshall






"Bion D. Howard" wrote:

>  Fundamentally, you are right.  However there are some communities and
>  individual developments that have kept sun-rights in mind.  It is the
>  mainstream developers and code officials who don't get it.
>
>  Just try running this through the code change apparatus, and you will be
>  opposed tooth and nail by builders and developers who are perfectly content
>  with current sprawl and crawl.
>
>  Remember these are folks who cry about a nickle cost difference on their
>  door-knobs, and it is historically very difficult to sell them any change
>  at all.
>
>  Since the early 1970's I have built, instrumented, tested, simulated and
>  lived in passive solar homes and the work on every level.  Some times the
>  "solar-engines" approach melted candles on the living room table, but we
>  learned.  Some times they were a bit too leaky, but we learned.  A
>  breakthrough was in 1982 when at the ASES conference that year there was a
>  session -- attended by about 600 people -- where the issue of passive solar
>  "versus" superinsulation was debated.  When people left the hall, most of
>  them I think were thinking "yes!" and got it.  A balanced approach between
>  conservation and solar leads to better efficiency implementation.  Passive
>  solar works better in a well insulated leak free structure, with a right
>  sized HVAC system.  PV solar works better when you have optimized the
>  efficiency of the electrical loads served.
>
>  However, even our well educated and modern "green-building" community has a
>  problem with solar too, I am sad to say.  Passive solar per say -- almost
>  unbelievably -- has been "opposed" in the creation of the LEED Residential
>  Energy & Atmosphere section; because "it's too hard" and "points for
>  passive solar would double dip' with other sections, such as the siting.
>  In LEED R ex-energy section, it appears solar conscious siting will be a
>  feature.
>
>  By the way a 15% savings on heating seems pretty high as a generalization,
>  and folks should think in a range of 8% - to 18% depending on climate,
>  building design, and occupancy (residential only).
>
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