how to build a solar thermal roof
TRANSCRIPT
HOW TO BUILD A
SOLAR THERMAL ROOF
by
John Canivan
1
How to Build a
Solar Thermal Roof By
John Canivan
July 2004
Sunny Future Press, Wantagh, NY Copyright © John Canivan 2003
$20.00 All rights reserved. No part of this book may be reproduced or transmitted in
any form or by any means electronic or mechanical without the express
permission of the publisher. On line support is available from www.JC-
SolarHomes.com. If you have any questions or comments about this book feel free to post them on the JC Solar Collector Forum or join the Solar
Energy group or send email to [email protected]. If you find this book
helpful you may also appreciate my other books:
How to Build a Solar Hot Water System Solar Thermal Energy
Energy Independent Housing
Do-it-Yourself-Solar
RECOGNITION: My appreciation extends to many people that made this manuscript possible such as Professor Dathatri, the chairperson of the Solar
Energy Center, at Farmingdale University, Professor Modi, the chairperson of
the Mechanical Engineering department at Columbia University, NY, my hard
working Dad, the general contractor, my understanding mom, my AutoCAD instructor, Mel Riddick, the critic, Loretta, the best cookies baker on the
block and lets not forget about the little woman who had to put up with my
mood swings and grammatical incongruities, my patient loving wife,
Catresea.
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About this book How to Build a Solar Thermal Roof is based on the concepts developed in
the Solar Thermal Energy Workshops at Farmingdale University, NY and my
book, How to Build a Solar Hot Water System. Rooftops are perhaps the
best place to collect the suns energy. All we need to do is find a cost effective method of heat collection. This book is about that cost effective
method. Photovoltaic systems only collect about 10% of the energy available
while solar thermal systems harvest heat energy at the same heat transfer
efficiency as oil burners. Without rebate incentives installed solar thermal roofs systems can pay for themselves in less time than photo voltaic
systems. They can supply a cold climate household with all or most of it’s
hot water and heating needs.
If you build and install your own solar thermal roof you could be saving
thousands of dollars each year with a system that pays for itself in several
years. How to Build a Solar Thermal Roof is a down to earth, easy to
understand, step by step cutting edge book designed to help you become
energy independent. Over 50 color illustrations are used to clarify construction details and facilitate the learning of basic solar thermal energy
concepts. A glossary is included along with a list of suggested materials for
your convenience.
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CONTENTS
I. Basic Concept 5
II. Absorber Plate Jig 8 III. Making an Absorber Plate 11 IV. Installing insulation 14 V. Installing Absorber Plates 15
VI. Installing the Flow Pipes 16 VII. Energy Independence 18 VIII. Radiant Heating 22
IX. Spinning Sunlight Into Gold 26 X. Glossary 41
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PROLOG
It is now possible to build a practical renewable energy system that
everyone can afford by using the entire surface area of a roof for collecting the sun’s energy. Why mess around with a few pitiful eyesores when the
entire roof can be used to harvest energy. Every dwelling needs a roof. With
a little planning that roof could become an asset rather than a liability. Did
you know that most roofs have a life expectancy of 20 years or less? A solar roof could easily outlast conventional roof and keep your house cool in the
summer and warm in the winter.
Of course not all roofs are suitable for a solar thermal application. The best orientation and pitch of a roof will depend on its global position as well local
climatic conditions. If you live in the Adirondacks and all you have to work
with is a North facing roof you might consider growing mushroom. East and
West facing roofs are capable of harvesting some heat energy during those
short winter days but if you’re serious about heating and cooling your house with the sun your roof should face south if you live in the North. Of course
the reverse will be true if you live on the other side of the equator. If you
live on or close to the equator you’re in the twilight zone of solar thermal
roof application and you’ll probably have more sunlight than you know what to do with so this book was not written for you. How to Build a Solar
Thermal Roof was written for you cold climate people who live between the
latitudes of 30 and 60 degrees. Since I live North of the equator at a latitude
of 41 degrees my references with respect to roof orientation will be made with respect to this latitude.
How expensive is a solar thermal roof?
An installed solar thermal roof system complete with heat storage vault and radiant floor heating could easily pay for itself in less than eight years
without government, state or local incentives. With these incentives a solar
thermal roof might easily pay for itself in less than four years. The initial cost
of a system will depend on the size of the roof, the size of the heat storage
vault and the size of the radiant floor heating system.
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I. Basic Concept
A rooftop is an ideal place for harvesting the suns energy if it’s oriented and pitched properly. For a northern climate the best orientation is
normally south and the best pitch would be about 13 degrees plus latitude
for winter heat gain. If you read How to Build a Solar Hot Water System
and built a few serpentine collectors you’ll have an experience that that should make the solar thermal roof project more comprehensive.
People around the world have built and installed serpentine collectors.
These collectors are the same kind we build at my all day Solar Thermal
Energy Workshops at Farmingdale University in NY. They’re cost effective and at least as good as any expensive commercial units that I’ve seen.
Building and installing a serpentine solar hot water system gives a person
the practical experience needed to understand the value and dynamics of a
heat gain, heat transfer and heat storage, but I believe we can go one better
when it comes to a practical solar thermal energy project. We have become so dependent on energy concentrates that the
transformation to energy independence based on diffuse renewable energy
resources will be difficult. Most homes aren’t oriented with the sun in mind,
and some new housing design embellish poorly insulated cathedral ceilings with gable roofs that waste, materials, space and heat. New, cost effective,
attractive, energy independent houses are possible but the traditions of
wasteful spending and energy inefficient designs make the process of
change difficult. We’re stuck with a lot environmentally unfriendly houses with roofs unsuitable for this kind of application, but if we look hard enough
I’m sure we’ll be able to find a few that could benefit from a solar thermal
roof.
An 800 sq. ft. solar thermal roof with a 3,000 gallon multi tank heat storage vault, radiant floor heating system and total hot water system would
of course be more expensive than two commercial, 20 sq. ft. collectors with
a 60 gallon SHW tank, but the pay back would be less. Instead of saving
$200/yr on a commercially installed system costing $5,000 with a payback
of 25 years you could save $2,000/yr on a do-it-yourself project that costs $6,000 and has a payback of 3 years.
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The main problems with solar thermal roofs have to do with size and
orientation. Not all roofs are suitable. The roof below has a pitch of 45
degrees. 54 degrees would be ideal for winter heat gain in the Long Island area where I live, but a roof with a 45 degree pitch like the one below could
still put a serious dent in the heating and hot water bills. Let’s focus on what
we can do rather than what we can’t.
BEFORE
Here’s a good candidate for a solar thermal roof. Notice the steeply pitched
south facing roof. If the sewer vent could be moved the entire surface area
of the roof could be used for making hot water all year long. Home heating needs could also be supplemented in the winter.
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AFTER
This 600 square foot solar thermal roof is capable of a 190,000 BTU
harvest per hour in direct sunlight which is the fuel oil equivalent of 1.26
gallons. In a location like Long Island a solar energy harvest equal to the
fuel oil equivalent of 1260 gallons of #2 fuel oil are available to a roof like
this. As long as your neighbors don’t go crazy and run you out of town on a rail you’ll be saving lots of money that would normally go down the fuel oil
drain.
If you’re not turned off by the appearance of a roof like this and you’d
like to have a go at it I’ll do what I can to guide you through the processes, but before we go on this solar thermal roof adventure we’ll have to make
some absorber plates. To do this we’ll need to construct an absorber plate
jig.
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II. ABSORBER PLATE JIG
Absorber plates provide an inexpensive method of transferring the sun’s
heat to the flow tubes of the solar thermal roof. Absorber plates increase the
surface area exposed to sunlight. More than 700 linear feet of copper tubing would be required to cover the same surface area that could be covered with
60 linear feet bonded to a well-constructed absorber plate.
Copper absorber plates facilitate the soldering of copper tubes, but they’re
expensive, heavy, difficult to fabricate and unnecessary. Aluminum absorber plates are less expensive, lighter, easy to fabricate and also the best
conductor of heat per pound known. You should be relieved to know that
we’ll be using aluminum absorber plates. Individual absorber plates can be
as long and as wide as you wish. The ones that I use to make serpentine
collectors are 20 inches wide and 100 inches long. The jig plans of for this size absorber plate are the ones detailed in the book but you may decide to
make absorber plates 24 inches wide since the lower bonding strips on the
roof will be 24 inches on center.
The starting length of the plate should be about a foot longer than the
distance between the peak of your roof and the edge of your roof. After
pounding the aluminum flashing, the length of the aluminum should shrink
to fit on your roof. If it’s a little too long you could always trim it to fit.
These jig plans are for 20” wide absorber plates made from 20” wide sheets
of aluminum flashing with a thickness of about .01”. Be sure to alter the
construction dimensions if you decide to make 24 inch wide absorber plates.
Are we ready? Let’s build the absorber plate jig.
1. Cut four 1X6 boards 4 feet long. 2. Cut seven 1X6 boards to a precise length of 20+1/8 inches. The extra
1/8 inch allows the 20” aluminum to slid through the jig without
binding.
3. Rip one ½” strip of wood 2’ long and rip two 1X3’s 24 inches long. 4. On a flat concrete floor place two 1x6x4 boards parallel to each other
as depicted in illustration below.
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5. Attach the 20+1/8 inch boards to the 48 inch boards. They should be
perpendicular to the 48 inch boards, parallel to each other and separated by a ½ inch gap between. Use the ½ reference spacers to adjust the gap
so that the boards will be centered six inches apart.
After screwing the boards together in this manner with the ½ inch gap between them, a third 1x6x4 board may be joined to the bottom of the jig
for additional support. My original absorber plate jig looked like the one
above, but the aluminum flashing is difficult to align so I added guides.
GUIDES
Guides make all the difference. They’ll save time and labor. They
automatically align the aluminum flashing and also position the steel rods.
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Temporarily screw the 1x3 guide supports into the sides of the absorber
plate jig. Translate the location of the slots onto the guide boards with a pencil. Remove the guide boards to cut out the ½ inch steel rod guides in
the guide board. Now screw the guide boards back into position.
The finished absorber plate bending jig is a little different than the one above. It has more slots for bending but the design principles are the same.
Without the guides pounding grooves into the aluminum is a bit tedious.
See what I mean?
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III. Making an Absorber Plate Now we’re ready to make some absorber plates. With the guides it’s a pleasure.
STEP ONE Lay in a 20 inch wide sheet of aluminum. This one is 50 inches
long but you can make yours as long as you like.
STEP TWO: Place the 7/16 inch steel rods in the slots.
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STEP THREE: After the first rod is pounded into position it’s held in place with a piece of plywood that you’ll kneel on so that the next rod may be
pounded without disturbing the first. This process may be repeated until all
the groves are placed in the aluminum, To pound grooves in sheets longer
than a jig simply shift the sheet down and place the last groove in the last slot in the first slot. Hopefully your absorber plate will look better than this
one done without guide supports.
A finished absorber plate section should look like this from the top:
To press the flow tubes into the grooves you’ll need to paste ½ inch
supports onto the backs of each absorber plate.
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I like to use ½ inch strips of isocynate insulation 5 inches wide on the backs
Of course the flow tubes won’t be in place when the backing supports are installed. They’re only in the illustration to clarify the position of the
insulation on the back of the absorber plate.
It’s a good idea to make all the absorber plates that you’ll need before preparing the roof for their installation. As a mater of fact it’s a good idea to
gather up all the construction materials first.
When you’re done collecting materials you’ll be ready to assemble the solar
roof. Gathering materials is half the work. Mark off the location of the roof raters on the roof’s ridge and edge. You’ll
need this information when it comes time to screw the flow tube supports
into the rafters.
Before attaching the absorber plates and flow tubes you should tack 4x8 sheets of solid insulation onto the roof.
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IV. Installing Insulation
ISOCYNATE INSULATION
STEP 1. Tack down one inch thick 4x8 sheets of isocynate insulation on
your roof like this: You could use other solid foam insulations if you like, but
this commonly available insulation with a foil backing is easy to come by and
preferred by many siding contractors. Place the foil side up to increase the heat transfer efficiency. This soft bed of insulation provides an excellent base
to mount the finished absorber plates. The following page demonstrates how
absorber plates should be tacked down in an overlapping fashion on a 1000
sq ft roof.
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V. Installing Absorber Plates
This is what an array of interlocking absorber plates would look like on a
20x48 sq ft roof. Notice the 28 absorber plate columns. If each absorber
plate section were 10 feet long it would take about 56 absorber plate
sections 20 inches wide to cover a roof this size. The horizontal grooves of the absorber plates should be spaced about 6
inches apart to optomize heat absorption at a reasonable construction and
material cost.
So far, a side view of our roof would look like this.
Don’t lose me now! A side view of the flow tube inserts would look
something like this:
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VI. Installing the Flow Pipes
Notice below how two sections of ½ inch copper tubing are joined in parallel. This is done to eliminate the expense of ¾ inch copper tubing and maximize
flow rate.
Flow tubes are held in the grooves of the absorber plate by 1X2 inch lower
supports screwed into roof rafters at 4 foot intervals. They may need to be notched to accommodate the raised flow tubes. Additional supports between
these main supports should be screwed into the roof sheathing. Since these
additional supports are not needed to hold the Kalwall glazing they don’t
need to be screwed into roof rafters.
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Before securing the 4x8 sheets of Kalwall glazing to the lower supports, the
aluminum absorber plate will need to be coated with a non reflective coating
that can transform sunlight into heat. There are a number of selective coatings on the market such as black chrome that must be mixed with
bonding agents. Some people usearesol barbeque black or flat black latex
but most paints don’t stick to aluminum. You might like to experiment. use
anything you want and spend anything you want but I’ve found that a mixture of mineral spirits and tar work great. I add a little lamp black for the
final coat. Once this mixture cures it stays put and does a great job of
turning light into heat. If you ever walked on a black asphalt roof on a sunny
day you’ll know what I mean.
Let the sun cure the tar onto the absorber plate for you. After the tar is dry
to the touch you can roll out the Kalwall glazing from the top of the roof and
lightly tack it in a few places. After everything’s in place you can screw down the upper supports every four feet where the glazing sections meet. This
upper support could be made from 1x2’s but strips of aluminum would have
a more finished look. What ever you use be sure that the upper supports are
are sealed with something like silicon calking to keep the water out.
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VII. Energy Independence
Many roofs could benefit from a solar thermal roof application, but as I said
before, some roofs are more suitable than others. We have grown
accustomed to living in standard rectangular houses with ridge or truss roofs. Any deviation from traditional house designs seems to upset building
inspectors and make realestate agents cringe. Change is difficult, but growth
can only take place where there is change. For now I’d like you to put down
your hammer, grab a piece of paper and pencil and design a practical energy independent home of your own. Use your personal experience tempered with
the the concepts presented in this book. Consider cost, aesthetics and
efficiency. After reading this chapter repeat this exercise.
*********************
Ranch houses with a low
pitched roof are still
popular. Attic space is
sometimes used for central air conditioning, but hot
attics with temperatures
beyond 1600 F are not the
best place to lose heat. Low pitched roofs maximize
heat gain in summer when
extra heat is more of a
problem than a blessing.
The south facing surface area of a 50 foot long roof like this is 787 sq. ft. If
a solar thermal roof were installed over this roof all the hot water needs of a
family of four could easily be met but winter heat gain would be minimal.
What would happen if we optimized the pitch of the roof for solar
heat gain for that day with the least amount of sunshine,
December 21?
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December 21 may not be the coldest day of the year but it is the day with the least available sunlight. To maximize heat gain our roof must be
perpendicular or almost perpendicular to the rays of the sun for the best part
of the day. A roof designed to maximize heat gain for this day would have a
pitch around 64 degrees and cast a mean shadow.
What would Santa say about
a roof like this?
I bet Rudolf would have a word or two on the subject.
Carpenters would throw down
their hammers in disgust and
say: “2x6’s don’t come 34 feet long.”
And building inspectors would
just say “Forget it fool! The
roof’s too high. Take it
down.”
It’s a difficult roof to build even if it were allowed. How about changing a
light bulb in the second floor ceiling? Is there anything good about a steep
roof like this? Sure there is. Think about the 1700 sq. ft. of solar thermal
roof heat gain on December 21. In just three hours a roof like this could
harvest the fuel oil equivalent of 9.5 gallons of # 2 fuel oil. After December 21, the roof angle would of course no longer be optimized and by the end of
January when wind chill factors plummet below 00 F you might be wondering
if you chose the best pitch for your roof. A few million BTU’s could make all
the difference between energy independence and another year of fossil fuel dependence.
How would it be if we moderated our tilt angle a bit to meet the height
concerns of the building department, let carpenters use the kind of lumber they’re accustomed to using and also favor those winter months when heat
gain is most needed?
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A roof angle of 550 should keep
everybody happy, but I still think
we could make better use of
construction materials as well as double the living space with a little
more effort. What do you think?
TRREE STORY HOUSE WITH SOLAR THERMAL ROOF
This three story building
has over 3,000 sq ft of
living space compared
with 1,200 sq. ft. for the others. If you’re planning
a second floor addition
you might as well go all
the way as long as you keep the inspector happy
by keeping the height
under 30 feet. An extra
floor doesn’t necessarily
mean more money. If you can live without an
antiquated truss or ridge
roof that wastes valuable
construction materials you should be able to
build a three story house
for about the same cost as a three story house and have a south facing roof
ideally suited for winter heat gain.
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You’re probably wondering what you’re going to do with all that space.
If you have no children to come home and roost you might consider stuffing
plenty of sound insulation between the floors and renting the entire house out to four sets of strangers. Oh I forgot to mention the finished basement.
A properly designed basement with adequate ventilation can provide
additional living space. Your tenants will love the accommodations and you
won’t have to worry about heating bills with a 4,000 gallon heat storage vault under the solar greenhouse. A 10KW array of PV panels on the shed
roof might even eliminate your electric bill. If you need more power there’s
always the possibility of a solar thermal engine that runs on heat from the
heat storage vault, but this is a topic for another book that’s in progress.
Don’t get too attached to this house. I don’t want you to go mad with all
those balconies and open spaces and plants in the greenhouse. I’ve got a
cozy little solar home in mind for you. It’s not spacey. It’s outer spacey and
it’s coming up soon but first let’s talk about radiant heating.
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VIII. Radiant Heating
The diffuse energy from the sun is all the energy we need to live in harmony
with each other and the world around us. When used wisely it can heat our
homes, supply us with hot water for bathing and maybe even give us the power we need to drive electric cars and log onto the internet. Unlike fossil
fuel concentrates, solar energy requires a lot of space for heat collection,
heat storage and also heat distribution.
Radiant floor heating is about heat distribution. The relatively low
temperature of stored solar hot water (1200-1700) F needs to be spread out
over a large surface area to be effective. This is what radiant floor heating
systems do best. Heating of an entire floor is more comfortable than the localized hot spots provided by wood stoves, hot air systems, and radiators.
A warm floor is a warm house. Heat naturally rises so a floor is the best
place to distribute heat. Radiant heated floors eliminate mildew and bacteria
by keeping floor rugs dry. Moisture has a tendency to condense on the
coldest place in the room which is normally the floor. Mildew and bacteria thrive in these cold damp places, but they won’t survive long if the floor is
heated.
Radiant heating systems are fairly easy to install if you have some plumbing and masonry skills. If you don’t have these skills get them or get someone
to help you. If you’re installing a heating system over a cement floor on a
slab house you’ll first have to insulate the floor with solid foam insulation to
prevent heat loss to the ground.
Wood floors are easy. Metal lath on the floor prevents cement from cracking
and crumbling. It also increased the heat transfer from the polyethylene
tubes to the concrete slab.
RADIANT FLOOR ASSEMBLY STEPS
STEP 1. Install solid insulation if necessary and staple wire lath to floor.
STEP 2. Run polyethylene tubing around perimeter of floor area first and than secure it with pipe clamps.
STEP 3. Pour cement over pipe and floor. Rake it out and float cement till it’s
level and smooth.
STEP 4. Connect the tubing to the input and output ends of the heat storage vault and you’re done.
STEP 5. Multiple level houses should have separate heating systems. Zoning
is an excellent way to conserve heat.
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The following radiant floor heating system applies to a three story house
with the solar thermal roof.
There’s more than one way to bend polyethylene tubing, but this should give
you an idea for a possible lay out. I’ve connected two ½ inch tubes in
parallel to increase the flow rate and the heat transfer rate, but you could
use a one inch tube if you like.
The baseboard heating system in the den is the first to receive heat from the
heat storage vault so it should be hot enough to heat this small, isolated
room. The bathroom is next and then the dining room on the north side of the house. The dining room is a central heating area where most of the heat
is transferred. By the time hot water from the heat storage vault reaches the
kitchen/living room area most of the heat has been transferred. After leaving
the living room the cooled water is returned to the heat storage vault to pick up more heat before being circulated back into the den’s baseboard heater.
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THREE DIMENTIONAL VIEW OF HEATING SYSTEM
The dark red lines are connections under the floor from one set of
polyethylene tubes to another. The network of green copper tubes is where
heat is extracted from the heat storage vault.
Notice that one circulator pump and three relays are being used for three
heating zones. Zone one is for the first floor.
The total heating system consists of three zones. Notice that the second and
third floor zones are not using a radiant floor heating system. The have conventional baseboard heating instead.
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Why is radiant heating unnecessary for the second and third floor?
If you feel that a warm first floor would partially heat the second and third
floor you’re starting to think like me. That could be dangerous. For more
dangerous incites into the wonderful world of energy independence you should read my book: Energy Independent Housing.
As far as this book is concerned our adventure together is approaching an
end. We’ve done everything but spin sunlight into gold. Perhaps we should give that a try.
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IX. Spinning Sunlight Into Gold
From an early age I believed sunlight could be spun into gold. Farmers make
money with sunlight. Why couldn’t I? Photovoltaic panels convert sunlight directly into electricity and some feel this is the best way to plug into the sun
and sell sun energy but the PV industry is regulated by the fossil
fuel/government conglomerate and there is little room for profit even with
the excessive rebate programs. Anyhow the idea of energy independence based on sunlight never occurred
to me until May 7, 1973 while I was working on my first house in Peru, NY.
At the time I was putting some finishing touches on a roof that was more
difficult to build than I had originally anticipated. The sun was bright on the swamp grass all the way down to the Little AuSable River, the smell of pine
was in the air and spring peepers were still chattering away in the wet bog
on the other side of the road.
A dark haired woman who I later came to know as Karen Votraw was strolling down the dusty road that led to the place I was working. I called
the road a path since it was overgrown and had numerous ruts that made
navigation difficult. The worn path was important because of the connection
it had between River Road on the north side of the property and Harkness
Road to the south. Few people ventured down the path and when they did I wondered why. As Karen approached I looked down from the roof and she
looked up. The sun was on my back as she strained to see me with her hand
cupped over her forehead.
“Is this a solar home”, she inquired? This was the first time I heard the term solar home. I though about her
question and soon realized my roof was unsuitable for any kind of solar
application since the small amount of winter sunlight available was blocked
by a forest to the south and east and the roof was a patchwork of triangles.
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Hexagonal House
The market for hexagonal housing is virtually untapped
although the living space is
ample and the possibilities for
creative spatial arrangements
seem boundless.
The roof could be a problem, if
the framing gets too involved. In
1973 I framed the roof with a series of right and equilateral
triangles that were not very well
aligned. Roof windows took
forever to install and the grand third floor turned out to be not
as grand as I had hoped.
Since that time I’ve learned from my mistakes. I thought about what Karen
had asked and wondered how the sun’s energy could be incorporated into
the design. I figured a large south facing roof section would be needed to
place a house like this in the solar housing category. Years passed before I discovered a simple roof design based on a cube octahedron.
CUBE OCTAHEDRON
A cube octahedron can be made from a cube that has its corners
chopped off. Another way to
make a cube octahedron
involves attaching squares to the side of a hexagon and
joining them at the corners.
Notice the large flat, steeply
pitched surface that’s a natural part of the cube octahedron. As
it happens this surface is ideally
suited for mounting a solar
thermal roof.
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Summary of ingredients
needed for a practical energy independent solar heated dwelling
1. A large steep pitched roof facing south to harvest energy.
2. A large heat storage vault.
3. Insulation on the exterior of the foundation.
4. A minimum R factor of 25 for walls and ceilings
5. Thermal drapes and thermal shades. 6. Thermal mass to moderate temperature fluctuations
7. Hydronic radiant heating in the floor.
8. An automatic heat sensing and heat exchange system
9. Photovoltaic Panels, storage batteries and an inverter. 10. Practical use of standard construction materials.
11. Easy, uncomplicated fabrication (low labor costs).
12. Aesthetic appeal.
A geometric shape that contains all
the right ingredients for energy
independence is the cube
octahedron. It has the aesthetic symmetry of a geodesic dome,
makes cost effective use of
standard construction materials
and contains a steep pitched roof/wall to capture the oblique
rays from a winter’s sun.
29
By installing gables on three sides of the building, windows and doors are
protected from the elements. Notice the large solar thermal roof on the
south side of the house and the concentric steps leading to the entrance on the north side.
The entrance is placed on the north side of the
building to optimize south
roof heat gain and internal
spatcial arrangements. The
advantages of a cube octahedron will become
more apparent as you
examine the construction
details.
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CONSTRUCTION DETAILS
After a site is chosen with a good southern exposure a hole should be
excavated about four feet deep and about 40 feet square. Next at least
thirty yards of #2 crushed stone should be dumped into the excavation and
evenly distributed about a circle 35 feet in diameter. The excavated material would later be used to backfill the foundation and raise the grade near the
building so that it appears to be on a hill.
Crushed stone provides a solid base for the footing as well as
insulation from the ground. Wet soil conducts heat away from the
foundation. It’s important to place some of the crushed stone exterior to the footing in conjunction with a drainage pipe. This precaution will prevent
unnecessary heat loss from the footing and foundation walls adjacent to wet
soil. After the stones are nicely distributed and leveled, a steel rod could be
driven into the center of the circle as a reference point. This reference point is used to sketch a circle with a radius of 16’4”. A steel wire of this same
length could then be used to find the end points of hexagonal footing.
Remember the radius of an inscribed hexagon is the same as any side of
that hexagon. This information should be used to lay out the footing forms in the manner depicted below.
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The 16 x 6 inch footing should be poured carefully on a leveled bed of
stones. Felt paper should first be placed on top of the stones to prevent
seepage. Horizontal reinforcing rods are then immersed in the wet cement of the forms. Two foot long vertical rebar pieces should then be spaced every
two feet in the form so that when the cement hardens into concrete the
vertical pieces will be rigid enough to attach 8 foot long sections to support
the foundation.
The exterior corners of the hexagonal footing are 16’ 4”
from the center of the hexagon.
The eight foot high foundation walls are 16 feet wide and measure 32 feet
across. Two basement window openings (not shown) are formed toward the
top of the eight foot high foundation.
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After the concrete hardens six 2x6x16
pressure treated
foundation plates are
installed and the main carrier beam is
mounted on the
support posts.
Next the 2x10 floor
joists are secured to the
face plates. Notice the
area framed out for the stairway.
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The first floor may now be sheathed with two layers
of ½ inch overlapping
plywood.
The installed staircase
is protected with a first
floor wall.
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Three 16x16 foot roof/walls are framed on ground level and raised into
position. The top junctions are bonded with steel plates
The 2x10 top roof rafters
are then nailed in place
16 inches on center.
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Gable roof overhangs
are framed.
Vertical walls are then framed.
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Let’s remove the three roof/wall section for now to get a better look at the
vertical walls. Notice that the entry way is skewed to one side to make room
for the staircase wall.
Here is a close up
view of the entrance
from the south east.
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Here is an overall view of the first floor with finished walls.
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View from South East
Notice the small circle above the front door.
This is where a fan would be mounted to exhaust accumulated summer heat.
Before we leave let’s go down into the basement and take a peek at the heat
storage vault.
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Heat Storage Vault
View from North West of heat storage vault inside basement.
Notice the notch cut out in the basement wall. The well insulated 1,000
gallon heat storage vault has four chambers. For more information about how to build this vault read How to Build a Heat Storage Vault.
So what do you think? Is this enough space for you and your friend? The
total basement plus first floor area is about 1200 sq. ft. If you need more space you could always add a few floors or add a few extensions. Cube
octahedron roofs go well with hexagonal designs.
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HEXAGONAL HOUSE WITH A SOLAR THERMAL ROOF
The living space in a house like this would be about 3,600 sq. ft.
One of the nice things about hexagonal housing has to do with the way
extensions fit together, not to mention the cube octahedron roof with an
ideal pitch for harvesting the suns energy. Many house designs are possible with steep pitched roofs, and I’m sure you’ll come up with a unique design of
your own.
All you need now is a place to store all this heat. That part should be easy compared to the harvesting device. Theory and construction details are
available for a unique, easy to build, cost effective heat storage vault. How
to Build a Heat Storage Vault should solve all your storage and heat
transfer problems. I’m working on a method of using storage vault heat to
generate electricity, but it will be awhile before I put one together maybe you’ll beat me to it. Good luck.
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X. X. X. X. GLOSSARYGLOSSARYGLOSSARYGLOSSARY
Absorber Plate: a heat conductive metallic plate capable of converting light energy into heat energy
Active Solar: solar heating systems that use external power
sources to transport heat from collection areas
to storage areas and from storage areas to living space areas
BTU: British Thermal Unit, a measure of heat or
energy.
140,000 BTU’s are contained within one gallon
of fuel oil.
Calorie: amount of energy required to raise one cc of
water one degree C
Chimney Plumbing: a method of bonding copper tubing to a
chimney for the purposes of extracting heat from a chimney. This method is sometimes
called wood stove plumbing.
Carrier Pipes: large pipes used to transport fluid
Carrier Pipe Fluid fluid transported to and from heat transfer tubes
Circulator pump: a pump used to circulate fluids inside a closed
loop circuit. This kind of pump is primarily used
for heat extraction, heat exchange and heat distribution
Collector Fluid: a mix of water and antifreeze circulated
throughout the collector and chimney heat
exchange system
Collector System: a network of carrier pipes, heat exchange tubes, and collectors connected to a circulator
pump and governed by sensors
Cube Octahedron: a geometric figure formed by connecting
squares with triangles
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Diagonal Glazing: glazing placed at an angle commonly used in
the construction of a solar greenhouse.
Flush Mounting: an ideal method of mounting collectors flush
with a roof
Energy Equivalents: one gallon of #2 fuel oil contains 140,000BTU’s
one gallon of #2 fuel oil contains 41KWH
one gallon of #2 fuel oil contains 130,000 Kcal
Glazing: a transparent covering such as glass plastic or
fiberglass reinforced plastic
Ground Water: well water, city water or town water
Heat: product of temperature and mass
Heat Exchange Tubes: a tube through which fluid is passed for the
purpose of exchanging heat. Such a tube could
be used for heat extraction of for heat exchange
Heat Extraction Tubes: small tubes used to extract heat out of a
medium such as water
Heat Gain System: a method by which heat is gathered. Solar
collector systems and wood stove systems are examples.
Heat Transfer Tubes: small tubes used to transfer heat
Heat Transport Method: a method by which heat is transported from a
collection area to a heat storage area or
from a heat storage area to a living area.
Heat Storage Tank: a container used to store hot water
Heat Storage Vault: an insulated area where heat is stored
Hexagonal Solar Housing: a style of housing suited for solar application because of the naturally occurring steep
pitched roof that results when a cube
octahedron roof is added.
Insulation: a substance used to resist the transfer of heat
like fiberglass, polyethylene foam, sand, gravel or firebrick
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Kalwall Glazing: a light, durable, inexpensive, fiberglass
reinforced plastic used in solar heat gain
applications
Knee Wall: a knee high wall joining a diagonal wall
KWH: Kilo Watt Hours, a measure of power or energy
Multi Tank Heat Storage Vault: a network of water filled tanks used for
the efficient transfer and distribution of heat
Passive Solar: a method of utilizing the sun’s energy without
the aid of an external power interface
Relay: a switch activated when sensors detect temperature difference
Retrofit: an add on structure not planned for in the
original design, an after thought
Solar Collector: a device used to harvest heat from the sun
Solar Greenhouse: a special type of greenhouse designed to add
heat to living quarters
Solar Panel: an array of photovoltaic cells used to harvest
solar energy in the form of electricity
Temperature: the average kinetic movement of molecules
Vertical Glazing: the perpendicular angle of thermo pane
vertical glazing is designed to minimize heat
loss
Wood Stove Plumbing: see chimney plumbing
Zoning: an energy conservation method of heating
specified areas of a dwelling rather than an
entire dwelling
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Author’s Note
I was brought up in a construction environment. My father built houses on
speculation during the depression to
keep food on the table. He worked so
hard that I rarely saw him. As much as I loved dear old Dad I vowed I would
never be like him and work that hard at
anything. Banks often foreclosed on his
construction loans before his houses were sold, but somehow dear old Dad
managed to maintain a crew and a
family during those difficult times. As a
child I spent a lot of time digging holes
and playing pirate. In 1952 at age nine I decided to bury my prize collection of Davy Crocket cards inside a
mahogany treasure chest behind the backyard playhouse. My neighbor, Ned
and I spent the better part of a day digging.
“Is it deep enough, Johnny?” Ned would say. “Deeper,” I would say.
When the sun got low in the sky and supper time was near Ned threw down
his shovel and said: "I quit."
As he walked home I wanted to say something like: ‘What kind of pirate are you’, but somehow I managed to remain silent and
just watch Ned disappear behind the spruce tree in his yard.
I was still digging when Dad came home from a long day on the road and a
tedious time at the Canivan Brothers Hardware store office.
“Diggin’ a hole to China, old man?” He said.
“No, Dad,” I explained I just want the Davy Crocket cards to be safe.
”I see”, he said, as he lifted his hat to scratch the top of his shiny head.
“You’ll fill the hole in when you’re finished, right old man?” “Oh yes” I said as I shook some mud from my face.
At the supper table Dad told my mom I was digging to China, but I corrected
him on the spot. “What will we do with that boy,” asked Mom?
“Don’t worry mother we’ll find something to keep him out of mischief.”
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In the following year after a difficult time in school, I was looking forward to
summer vacation and two months of blissful goof off relaxation, but Dad had other plans. After breakfast he led me outside and grabbed a shovel from
the garage.
“I know how you love to dig, old man,” he said. I’ve got a wonderful job for
you. We need to make a space under the backyard sunroom extension for Grandma and Grandpa and I believe you’re the man for the job.”
I was really looking forward to goofing off, but Dad made me feel important.
He gave me a mission. He helped me understand the glory of purposeful digging. I stood there for awhile in awe at my new found purpose in life, and
when Dad’s car disappeared down Pine Street I jumped on the shovel. By
noon the pile of dirt in the driveway sloped directly into the hole, but I
managed to wiggle out for lunch. By the end of the day a nice pile was ready for inspection. Dad was impressed but Mom just shook her head.
The next day was almost as much fun as the first but I missed my friend,
Ned, so I invited him to play in the clay and sand. He liked throwing dirt
bombs but digging was a problem. “I think my mother needs me, Johnny” he said, and when I turned around
Ned was gone.
As summer progressed I lost track of my best friend because I was too busy breaking through hardpan with a pick and chipping out an 8” thick reinforced
concrete wall with Dad. Mixing cement and learning how to make concrete
forms from scrap wood also took up a lot of my time.
After the basement room was excavated and the foundation walls were
secure Dad taught me how to glaze windows and frame walls. Soon I
learned how to use all the tools in Canivan Brother’s and before long I was
working with Tom, Harry, Peat, and other members of Dad’s elite outside
construction crew. I enjoyed learning how things were put together. Sunlight energy fascinated me from an early age. Pens were easy to melt with
grandmother's magnifying glass. The Coindre Hall Boarding School boys
asked me why my pens looked funny, but when I explained they lost
interest. In Junior high school I designed and built a conceptual model of a solar power generator that used grandma’s magnifying glass. The lens
tracked the suns position with a crank shaft made from a curtain rod
attached to a string that attached to both sides of the lens suspended in
space with steel supports made from hacksaw blades. The focal point of the lens was a steel end cap. Water was fed into the end cap with a copper tube
a little at a time from a V8 can. I figured a small amount of water would boil
faster than a large amount of water. This is the principle of modern
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vaporizers used today. My science teacher liked it and couldn’t understand
why I didn’t win an award at the science fair.
“You should have had a poster to go with your exhibit.” he said. I didn’t care so much about winning a prize I just wanted the tools to build a
working model.
Shortly after graduating from high school I was given an option of inheriting
the Canivan Brother Hardware/Construction business, but my ambitions were too lofty to be held down by the responsibility of the family store so I
decided to attend college, master the sciences and become a teacher. This
was a decision I soon learned to regret.
My college experience during the 60’s were beneficial toward gaining a
better understanding of chemistry and physics and biology, but I never did
fully comprehend the social disorder of that time, and when it came to
finding a part time job I soon found that college was useless. Muddling through three schools was a long, tedious process. It was fifteen years
before I finally became a certified high school science teacher, and an
additional five years to realize that teaching unmotivated students was not
my forte. During this 20 year time interval I worked in the Plastic Products
Laboratory of RC Hooker, cut lawns, sold encyclopedias, pruned trees, built and repaired boats, installed driveways, delivered flowers, built welding
transformers, delivered furniture, repaired furniture, made and sold
furniture, installed roofs, drove a dump truck, built a few houses and
generally regretted not taking the offer to own and run an established hardware/construction business.
Since 1980 I became a self employed home improvement contractor and
grabbed what ever work came my way like: Dry walling, extensions, dormers, house jacking, block work, foundations, walls, floors, ceilings,
roofs, doors, windows, kitchens and bathrooms. Fortunately, I had the
opportunity to designed and build a few solar greenhouses, collectors and
solar hot water systems along the way. I also transformed basements, attics
and garages into energy efficient living spaces. Home improvement jobs supply food for the table, but my soul hungered for more fulfilling projects.
Many things can be done to improve the energy efficiency of a drafty,
uninsulated dwellings, but the challenge of building cost effective energy
independent houses was all I could think about. Now it can be done with a solar thermal roof.
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