“Alas if the space heating limit is 15 kWh per m2 per year you have only a few options to tweak. One of those is sub slab insulation.
Once you have maximized the cost benefit of wall insulation (which is the most expensive because it increases roof area and fastening costs) and the attic is full to 120 how else do you meet the heating? Well even though sub slab is not that effective it is an available option to meet that unyielding target.”
John Straube, BuildingScience.com
“… PH software assumes too low of a ground temperature versus what has been measured in cold climate housing with decent sub slab insulation.”
“Journalism is like skiing in the 50s or 60s. Previously it had been a sport that very few people enjoyed, and they were all very good. But now the doors were opening to amateurs, as it did with skiing. The pros are going to have to share the slopes with people who don’t take the sport as seriously as they do. They’re still going to be able to ski, but the rest of us are not just going to admire them for how skilled they are, we’re going to do it too. They can even earn a living as ski patrol and ski instructors. Or lift operators or more mundane jobs like people who work in hotels and drive the shuttle bus. There are still jobs in skiing after the arrival of the amateurs. But the exclusivity is gone.”
Dave Winer, ScriptingNews.com
“What is the true purpose of the US Government’s and state governments’ subsidies of solar heating equipment? A simple question? Seems so. But when I consider the question carefully I get into trouble! What is the true purpose of the subsidies? Is it to save oil? Presumably not.”
– from “The True Purpose of the Solar Subsidies”, by William Shurcliff
“I really think the problem is that the use of solar energy is
being discussed by scientists and we have a passion for being
a technological society. As such, we almost frown a little when
someone finds a very simple economic way of using solar heat.
That is much too simple for us. And so we have to find something
very exotic, so that we can earn the name of scientist or engineer.”
Walter A Meisen, circa 1972, at the solar energy roundtable in NY
The most popular forms of solar heating seem uneconomical these days, with high costs and low
solar fractions (20% for some FSEC-certifi ed water heaters), so they seem to require customers
who are concerned about climate change, among other things. If solar house heating were to
simply cost less than other forms of house heating, more people might use it.
After hearing lots of doubt that low-cost solar house heating can work with a high solar fraction
outside the Southwest from local architects, reporters, and others who read SBIC guidelines
which say houses in Philadelphia can only be 60% solar-heated at best and seeing lots of “solar
houses” that are only 30–50% solar-heated versus those “with no other form of heat,” we
should dispatch Deployable Doubt Dispellers (“D-cubes”) to regional Infestations of Doubt,
unboltable 8′ cubes with little windows so people can peer in to see big dial thermometers
inside that stay at 70ºF for a few cold, cloudy days.
Lots of people (eg., AIA, SBIC, and SBSE) seem to have forgotten that things like this can be
engineered, notwithstanding high-school physics and houses by PE Norman Saunders, who
calculates needs for “purchased heat” with Gaussian weather stats in the same way that other
engineers calculate 100-year fl oods: The 1954 ASHRAE Handbook gives the 1% and 2½% temperatures for Boston as 0º and 8ºF (–17.8º and –13.4ºC). For –15ºC, the holding time for our
houses is 3 days, giving a standard deviation of 7.8ºC. In December, the 1% temperature is 2.1
standard deviations lower than average, so can be expected to occur about once every 4.5 years.
This calculation suggests the need to purchase heat [or wear a sweater :-)–Nick] in December
once in 35 years.
We might deploy D-cubes to Rifton, Port Jervis, and Harlem, NY; Kempton, Philadelphia, Pottstown,
and Bryn Mawr, PA; at a wintertime MREF or ASES conference; a DOE Solar Decathlon;
the Chicago Museum of Science and Industry; and lots of YMCAs and high schools.
ORIGINAL HERE (PDF)