Building a Solar Home for Less

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The Helio Thermics prototype solar house may look conventional. . . but looks can be deceiving!
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The eight simplified drawings illustrate how the various heating and cooling cycles of the Helio Thermics system work. In modes 1 through 4, the vents in the eaves (and atop the attic) are closed to retain heat during cool weather. In modes 5 through 8 (warm weather), these same vents are opened... thereby allowing the attic to cool through convection. Mode 4 illustrates the most complex - and least often used - heating cycle, in which water is pre-heated by the collectors in the attic, then brought to even higher temperatures by a gas-fired heater, and finally passed through the heat-exchange coils in the "air handler".
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This cutaway view of the Helio Thermics solar home illustrates the "storage to house" mode of heat transfer, in which the "air handler" draws warm air (red) from rock storage to - and through - the edge-laid cinder blocks... the lower level of the central duct... the blower within the air handler itself... the upper level of the central duct...and finally, ducts (directly beneath the floor) leading to the inside of the house. Cool air (blue) enters the return duct (at right) and travels to the far side of the rock storage area, where it absorbs stored BTU's prior to re-entering the cycle. Heavy insulation, and a virtually airtight house, are what make it possible.

Is this the world’s first competitively priced solar-heated and cooled home that qualifies for federal housing authority and veterans administration backed financing?

Until just a few weeks ago anyone who wanted to live
in a solar-heated and -cooled house found the construction
of that dwelling to be pretty much a do-it-yourself affair.
(There simply weren’t any “ready-made” sun-powered homes on
the market.)

And who could really afford the expensive construction of a
custom, one-of-a-kind solar-tempered building anyway? For
that matter, who (other than the local banker’s favorite
grandchild) could even obtain financing for such a “crazy”
idea? Who indeed?

Here Comes the Dawn!

Some folks down in Greenville, South Carolina (folks who go
by the name of Helio Thermics,
Inc.)–however–have now changed all that.
They’ve changed it by designing, building, and making
readily available [1] a “standard” solar-heated and -cooled
dwelling that [2] is very competitively priced and [3] is
among the very first–possibly the
first–such structures to qualify for both FHA and VA
mortgage insurance.

As impressive as the name (Helio Thermics, Inc.) may sound,
this threefold “breakthrough” in the use of solar energy
wasn’t made by any overstaffed and over-financed
foundation, government agency, or corporation. Helio
Thermics is actually little more than three brothers . . .
Randy, Mike, and Larry Granger. Three brothers who–in
their backyard, so to speak–studied some U.S.
Department of Agriculture research data (which is freely
available to anyone) and then–based on that
information–designed, built, and refined an
exceptionally clever solar-heating and -cooling system.

First Things First

One of the most impressive things about the Granger
brothers is that, unlike far too many experimenters in the
field, they didn’t try to design their sun-powered system
“wrong end to”. That is, they did not become so
embroiled in the usual “my collector is more efficient than
your collector and my method of heat transfer is better
than yours” competition that they wound up–as other
experimenters have–“proving” themselves “right” with
a funny looking, lopsided, uncomfortable house that cost
two or three hundred thousand dollars.

Instead, they “began at the beginning” by concentrating on
the more prosaic (although, in some ways, far more
important) components of their system. Things like studding
and insulation.

The exterior walls of the prototype Helio house–which
has been in operation since February of 1976–are all
framed with 2 X 6’s instead of the customary 2 X 4’s. This
makes it possible for those walls to contain batts of
fiberglass insulation that are a full five and
inches thick, rather than the “standard”
three and a half inches used in most contemporary
structures. And the ceiling of the building is insulated
with a thick 12 inches of the fiberglass . . . which is
twice the six inches recommended as “heavy” insulation for
the Greenville, South Carolina area by many authorities on
the subject.

This “extra” insulation, plus the fact that every window in
the Helio Thermics house is glazed with thermopanes (double
layers of glass), makes the building extremely easy to heat
in the winter and to cool during the summer. Or–to
put it another way–by spending a little more to
insulate their structure in the beginning (by putting
“first things first”), the Granger brothers were able to
drastically reduce the size, complexity, and cost of
everything that followed.

The Solar Collector

The economies of Randy, Mike, and Larry’s approach to the
construction of a sun-warmed and -cooled house are perhaps
most obvious when you inspect what is usually one of the
most expensive of all the components that go into such a
system: the collector. The Grangers’ building–in the
strictest sense–doesn’t even have one!

What the boys did was take something (the attic) that
virtually all houses have anyway and, at very little
additional qxpense, modified it into a “hot air solar
absorber”. This modification was actually quite simple.

Since the optimum angle for the placement of a solar
collector is generally considered to be latitude plus 15
degrees, and since Greenville, South Carolina is located
approximately 35 degrees north of the equator, the
south-facing slope of the attic’s roof was set at 50
degrees to the horizon. Translucent, reinforced,
tedlar-coated, corrugated fiberglass sheeting (“Filon”, the
brand named panels used on some greenhouses) was then
attached with weatherproof screws directly to the rafters
on that side of the attic in place of standard roofing

This created 400 square feet of “collector” . . . at the
rock bottom cost of only about $2.50 per square foot! That’s
an exceptionally low figure, as anyone experienced in the
construction of solar collectors will tell you. Especially
low, in fact, since two layers of the Filon were
fastened to the whole 400 square feet of collector surface.

The double thickness of corrugated translucent sheeting
that covers the Helio home’s “solar absorber” is
cross-laminated both to add rigidity and to increase the
insulating value of the Filon panels. The first layer of
the sheets was laid horizontally on the attic’s south face
and then the topping layer was run vertically (to better
shed rain, snow, and other moisture). The half-inch-thick
plywood floor and opposite wall of the attic’s interior
were then painted flat black so the collection chamber
would absorb the incoming rays of the sun more efficiently.

This was all done, quite obviously, to make the
attic/collector a better heat trap during the winter. But
what about those hot South Carolina summers? What keeps
that double layer of translucent plastic and those absorber
panels of black plywood from turning the attic into an
unbearably hot solar oven during the months of July and

V-e-r-r-r-y simple. By opening a series of vents along the
ridge of the attic’s roof and immediately under its eaves,
the Grangers have found they can create a surprisingly
effective natural “air conditioner” for that part of the
house. The more the air in the loft is heated, in other
words, the faster it rises out the ridge vents and the more
it draws cool air in through the openings under the eaves.
Believe it or not, USDA tests have shown that this entirely
natural flow of air can keep summer temperatures in the
attic as much as 40 degrees Fahrenheit lower than
the attic temperatures in “ordinary” homes located in the
same neighborhood as the Helio Thermic dwelling.

So: By merely opening the vents along the ridge and eaves
of the attic, that section of the Granger house can be
naturally air conditioned during the summer. And by just as
Simply closing those same vents, the modified attic can be
converted into a very effective solar collector.

The Delivery and Storage Systems

Of course, if Randy and Mike and Larry had stopped right
there, they wouldn’t have had much of a solar-tempered
house on their hands. Few people spend all their time up in
the attic. Besides, taken just this far and no farther,
there’d be no way to store the attic/collector’s excess
warmth or cold during any given period and then use it at a
later time.

So the boys tucked 1,100 cubic feet (60 tons) of washed,
egg-sized rock under the building. And they connected this
“heat sink” to the attic with a network of ducts, dampers,
and louvers so that–among other functions–a
blower (the Grangers call it an “air handler”) can draw
air–either hot or cold–from the attic. And that
air can be used to heat or cool either the building’s main
floor or the crushed stone in the storage pit underneath.
And–if stored–the captured warmth (or coolth)
can always be extracted from the storage area on demand and
blown into the house’s living space. by the
1,600-cubic-foot-per-minute fan (driven by a half-horse
electric motor) that is the heart of the building’s air

The Little “Black Box”

All very well and good. It’s easy to see how the Helio
Thermics house can capture hot air in its attic on a sunny
winter day (or cold air on a cool August night) and then
either blow that air into the structure’s living quarters
or down into its rock storage area for use at a later time.
But it’s also easy to see that the mere switching of vents
and louvers and dampers could soon turn into a full-time
job for someone.

(“Let’s see now. I’m collecting excess Btu’s in the attic
and the house is cold so I’ll pump some heat from the attic
to the living area. Whoops! Too much. Better switch a
little down to the storage pit. Wait a minute! A cloud just
went in front of the sun . . . shift all the warmth we can
collect to the house again. Yes . . . NO! Too much. Maybe
if we . . . on the other hand . . . WAIT A MINUTE!!!”)

So the Grangers built a full-time “someone”–an
electronic control unit–right into their house to
continuously take care of this chore. The “solid state
black box” is about as big and as complex as a small TV set
and, just like most modern color TV’s, has removable
circuit boards for easy service and repair.
“Unlike the average `boob tube’, however,” say the
Grangers, “our black box is designed to work darn near

The control unit (actually a mini-computer) constantly
monitors the temperature in five locations: [1] the Helio
Thermic building’s collector/attic, [2] the structure’s
living area, [3] the central portion of the rock storage
pit, [4] the outer edges of the storage area, and [5] the
atmosphere surrounding the house. With this continually
updated information always “in mind”, it then decides which
heating or cooling source and what mode of operation (there
are eight modes) will most economically keep the building’s
living space at the temperature set on the black box’s
console dial.

As it deems necessary, the control unit will [1] heat the
house with Btu’s drawn down from its attic or [2] stash
those therms away in the storage pit below. Then again, it
may decide [3] to pull some of that collected warmth back
up out of crushed stone and distribute it to the
structure’s living area. It may even [4] tap into a very
small supplemental source of heat to augment the solar
collection and storage system during unusually long periods
of overcast weather.

The control unit can also [5] cool the building with
outside air or [6] cache some of that coolness in the
storage bin. And it can [7] make the decision to draw
collected cold air from the storage area under the house
and blow it into the living space, or even [8] distribute
the output of a regular air conditioner.

The Backup Heating System

The Grangers are quick to admit that–just like most
solar-heated structures–their Helio Thermic house can
be temporarily “put out of business” by three or more solid
mid-winter days of heavy cloud cover. Unlike a great number
of other sun-warmed buildings, though, theirs is so well
insulated that it can be supplementally heated with nothing
but an ordinary 50-gallon, quick recovery, gas-fired
domestic water heater!

The hot (140° F) water is pumped through a heat
exchanger (something like an automobile radiator) within
the Helio Thermic air handler. There, some of its thermal
energy is transferred to the air passing around the heat
exchanger’s coils and the warmed air is then distributed
throughout the house.

Interestingly enough, the water which returns from the
exchanger is still hot enough (130°) to pipe right into
the dwelling’s plumbing for washing, bathing, and other
household uses. And–at current natural gas prices in
the Greenville area–a whole week (which would be, to
say the least, highly unusual) of heating the entire Helio
Thermic prototype with this backup source of warmth has
been calculated to cost only $6.80.

And if that irregular and highly unusual expense bothers
you, you should realize that the Granger boys are more than
getting it back on a regular basis directly from their
building’s attic/collector. What they’ve done, you see, is
paint some copper tubing black, lay it out on the attic’s
floor and then connect one end of the bed of piping to the
bottom and the other end to the top of an electric water
heater’s tank (the unit’s heating element has been
removed). This very simple solar-powered heater can warm
its water to a torrid 170° F and it supplies the Helio
Thermic prototype with a large part of all the hot water
its residents need.

The Backup Cooling System

Even though it was never actually necessary to
supplementally cool the Helio Thermic house during its
first summer, the Grangers did do a limited amount of
experiments with the idea just to see how it would work.

“You can bolt a big air conditioner right into the
building’s ducting and use it to ‘overpower’ any
uncomfortable heat in the house on a really hot day if you
want to,” says Mike. “We think it’s a lot smarter and less
costly, though, to u se a much smaller conditioner and just
run it on the few nights when the outside air temperature
doesn’t drop enough to cool the rocks in the structure’s
storage bin. On such nights, the small conditioner can be
used to cool the storage pit . . . and then the bin of
rocks used to cool the house during the following day.”

And the Livn’ is Easy!

You don’t have to be an engineer with a degree in
thermodynamics to live in the Helio Thermics house, nor do
you have to tolerate idiosyncrasies in the structure that
only an inventor would live with. Quite the contrary. The
dwelling boasts all the modern comforts that most Americans
expect . . . or, at least, have come to want.

Do you like your living space maintained at a constant 68
or 70 degrees? Then just set the control unit at that
temperature. The only additional effort you’ll have to make
to guarantee your year-round comfort will take place in the
spring (when you’ll flip a master switch from its “heating”
to a “cooling” position) and in the fall (when you’ll flip
the same switch back again). Everything else will be taken
care of automatically.

As a matter of fact, you’ll almost think that your heating
and cooling bill is being automatically handled by the
Helio Thermics control unit too. Because the average
monthly cost of operating the prototype house has been only
about $5.00 . . . instead of the $35 to $40 that it
“should” cost to heat and cool a house of 1,100 square feet
in the Greenville area.

What About the Initial Expense?

Then again, everything–even “free” heating and
cooling–generally winds up costing something. And in
the case of solar-powered houses, that “something” is
usually a heart-stopping increase in the original purchase
price. (Yes, Virginia, there really are prototype
solar-heated homes that cost $ 300,000 ! )

Luckily for all of us, the Helio Thermics house ain’t
anywhere close to the $300,000 category. To be more
precise, its 1,100 square feet of living space-2 X 6 studs,
extra-thick insulation, collector/attic, air handler,
storage pit and all–is priced at just $24,000 . . .
complete. And that’s only about $4,000 more than a gas or
electric heated home– without allthe
currently costs in Greenville,
South Carolina.

This means that if the Granger brothers’ prototype saves
its residents $35 a month (as it has already proven it can
do), the house will save enough in fuel alone to make up
the $4,000 difference in less than 10 years. And that’s if
gas and electricity never cost any more than they do right
now. If the price of energy continues to escalate (and it
will) as it has during the past few years, the Helio
Thermic will pay off the you can adapt some of the helio
thermics concepts to your own house difference even sooner.
And after that, of course, its continued year-after-year
savings will be pure gravy.

It Can be Financed

Best of all (for us ordinary people who seldom find
ourselves with an unexpected $24,000 to spend in a single
lump), the Helio Thermic solar house can be
financed. The design is one of the very
first–if not the first solar-heated and
-cooled home–that has been approved for mortgage
insurance by both the Federal Housing Authority and the
Veterans Administration. (NOTE: FHA and VA mortgage
insurance is granted at a regional level and what qualifies
in one area may not necessarily be accepted in another. But
the Helio Thermic has been approved by both
agencies in the Greenville, South Carolina area and there’s
no good reason for it not to be approved in other
regions of the country. And soon. Especially if you decide
that you want to build one of the houses where you

Will it Work in the North?

Even though the Grangers constructed their prototype
dwelling down in what most folks consider to be “The Sunny
South” . . . Randy, Mike, and Larry state that their design
should perform as well in cooler climates as any other
solar heating system now on the market. Probably better
than most, since the Helio Thermic house (except for its
add-on water heater in the attic) has no pipes to leak,
corrode, break, or freeze.

So What are You Waiting For?

The Granger boys are quick to add that their particular
design for a sun-powered house–or any particular
design for such a structure–probably won’t please
everybody. But it’s obvious that they have
justifiable reasons for being just a little proud of “the
house that Randy, Mike, and Larry built”.

Let’s face it: The Grangers–without hundreds of
thousands of dollars in government or foundation grants and
without the backing of a multi-million-dollar
corporation–have gone one heck of along way toward
ushering in the Solar Age for John Q. Public almost

Sure others have built some darn good solar-heated and
-cooled houses. (Steve Baer, Harold Hay, and Harry
Thomason, to name just three of the reigning geniuses in
the field.) And other have built those houses almost
single-handedly by themselves, with no help from grants or
big corporations. (Steve Baer, Harold Hay, and Harry
Thomason, to name the same three geniuses again.)

But, as far as we know, this is the first time that anyone
has ever come up with a sun-powered house that both heats
and cools itself, looks the way that Joe Suburb and his
wife think a house should look, carries a price tag that
Joe can afford . . . and has been stamped “approved” by the
FHA and the VA. If that doesn’t open up solar houses to the
mass market, I don’t know what will.

Adapt Some Solar Concepts into Your Own Home

Can you adapt any of the Helio Thermics ideas to your own
house? “You betcha,” say the Granger brothers. “We haven’t
really done anything that is beyond the reach of any
reasonably handy family.”

Even though the pitch of your home’s roof is probably far
from optimum and even if its southern-most oriented slope
doesn’t face exactly south, you can most likely use the
attic to capture enough of the sun’s warmth to be

Just remove the roofing material from the rafters on the
roof’s southern slope (and if it doesn’t have one, a
western slope is a distant second choice). If you do have a
southern slope to work with and you can handle the extra
investment in labor and expense, you can dramatically
increase the efficiency of the finished conversion by
reframing that face of the roof to make its angle equal to
your house’s latitude plus 15 degrees.

Then replace the removed roofing with two layers
(cross-laminated) of tedlar-coated, corrugated fiberglass
(Filon) panels as described in the accompanying article. If
you use the sheeting that is trade named “Filon”, you’ll
find that it’s guaranteed for 20 years …which is probably
about as long as you could have expected the original
roofing to last when it was new.

Additional insulation should then be added to the floor,
the ends, and the north-facing slope of the attic (to hold
the Btu’s you’ll trap once they’re caught), and the whole
attic–except, of course, for the Filon-topped
slope-finished inside with a lining of plywood that is
painted flat black.

As heat is collected in this trap, it can be transferred
(when desired) to your home’s living area through a sheet
metal duct. An ordinary fan mounted in the ducting and
controlled with a manual switch is all you’ll actually need
to do the job . . . but a “semi-automated” system turned on
and off by a double set of thermostats is much to be
desired. Place one of the “stats” in the attic/collector
and set it so that it will only allow the fan to kick on
when there are “surplus” Btu’s in the attic. The second
thermostat is then mounted in a cool corner of the living
area and set to “tell” the fan when additional heat is
needed in that part of the house.

Of course, if you have the time and money and inclination,
you can always take the next logical (though very big) step
by tearing out the basement or crawl space under your
house, installing a heat storage pit, and otherwise
completely duplicating the sophisticated solar-heating and
-cooling system built into the Helio Thermics prototype.
But that would be ridiculous because such extensive
remodeling of an old building would probably cost more than
the price of a brand new Helio Thermics structure . . .

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