Excerpts From: How To Build and Benefit From
A PASSIVE SOLAR SPACE HEATER
Chapter 1. Introduction
What it does
We know there is a heat loading on the exposed south wall of a house. We can turn this problem into an asset.
What if we collect this heat and utilize it to heat the house? This device makes the collection and utilization of this heat practical.
Simplified Version
Except when the sun is overhead in the summer, the south wall collects from 200 to 250 BTU per hour per square foot of surface area. Multiply that by the number of hours of sun on the wall, times the area within the collector and there’s plenty of heat just waiting to be used.
The trick is getting this heat into the house. Here are the problems our collector solves:
1. Transfer this heat to the air we draw from the house. It does that.
2. Circulate cool air from inside the house through the collector, and do this without any additional energy usage. It does that.
3. Keep the warm air in the house from being cooled in the collector at night. It does that.
4. Provide a means of keeping warm air from going into the house when we don’t want it. It does that.
5. Automatically function when the sun comes out. It does that.
6. Use materials that otherwise become waste. It does that.
7. Cost little and have minimum maintenance. It does that.
It does all these things? We can’t afford not to have one, maybe more than one.
The book tells us how to build it and how to use it, from start to finish.
How do we get this marvelous thing?
You must build it. Oh, sure, they are on the market, but the price begins around $800, requires a fan and does not protect against cold air coming into the house. This one costs about $100 and does not require a circulating fan, nor does it allow cold air to come into the house. It can be shut off when you don’t want more heat.
Example
Okay, let’s run through the motions of building one:( You need not build this one unless you are extremely doubtful that a solar collector works.)
1. Select a south facing, unshaded, wall area. Mark off a space about four feet wide by eight feet tall, and paint this space black. Black is the most absorbent color.
We also put one on an east facing wall to catch the morning sun as soon as it was up. It worked before the sun gave its heat to the south wall for the rest of the day. It works anywhere there’s sun.
2. Build a frame around the black space with 2 X 4 boards. Set them on edge so they stick out all of their 3 ½ inches from the wall.
3. Punch or saw, ugh, two holes through the wall about 6" by 9". One should be as close to the ceiling as you can get and the other should be close to the
floor. We’ll let you decide which hole is which. Oh, these holes must be within the framed area.
4. Cover the frame with sheets of clear, corrugated, fiberglass.
5. Wait for the sun to come out. Now feel the warm air coming into the room from the top vent. It will get hotter as the day goes on, and will continue to deliver heat as long as the sun shines on it.
Congratulations! You have just made your first passive solar collector. Realize that this one has some serious drawbacks, but we will solve them in the rest of the book.
What About Summer?
In the summer, the sun is high and the south wall gets very little, if any heat from the sun. The collector doesn’t work. In the spring and fall, some sunlight reaches the collector and you have the solar switch to direct the warmed air outside instead of heating the house when you may not want it.
Problem solved.
This collector has the cover removed and shows the details. The cans were fastened directly to the wall. This is an early collector, our third attempt, without the improvements that experience brings.
How Much Heat?
If you started with a 4 X 8 frame, you may receive about 200 to 250 BTU per square foot, or about 6400 to 8000 Btu per hour. It works every sunny day and even on the cloudy ones it will give some heat. From this point, it is free heat. It will still be free whenever the sun shines.
What It Costs To Build
It costs a day or two of your time, a few bucks for wood, paint, plastic, and a little anguish when you punched those holes through an outside wall, just because I said you had to do it. The pain will quickly vanish when you feel that warm air for the first time.
It doesn’t take quarters. It doesn’t need oiling. It doesn’t even have a switch. At the time of the first writing, the cost was under fifty dollars. It costs at least double that now, but so does the heat you buy from the utility company.
What this book is about
This book tells you how to do it. You must supply the Armstrong part and stay with it until you finish the job.
Armstrong? Oh, arm plus strong. Get it?
Not Enough Heat?
Need more heat? Build another collector.
It’s a great way to heat a barn, a garage or workshop, or any of those areas that would otherwise remain cold because conventional heating was just too costly.
Barns and The Garage
If you have animals in your barn, you have just cut the feed bill. They won’t eat as much to keep warm. Even the car will work better if it doesn’t get so cold.
Other Benefits
You boost your integrity when you do it yourself. Add another drop of integrity when you utilize available energy.
The oracle in me says that the time will come when a passive collector on the front of the house will advertise your commitment to energy conservation. They will ultimately be designed into a new home. They will also enhance the selling price if you must move.
More
We ask friends and neighbors to collect cans for us. Cans, as in pet food, soup, etc. Those crazy Ritchies! Remembering us, they remember to collect the cans. We collect them and haul away some stuff that no one could possibly use.
Those Crazy Ritchies...yeah, crazy like a fox!
Cans?
What for? Why would we want cans? They weren’t mentioned before. It turns out that the surface area of tin cans improves the heat transfer to air by a factor of approximately four. We have tried all manner of fins and various materials, but nothing approaches the efficiency of plain old cans, painted black, of course.
A four by eight collector can use about 250 cans. They may take some time to accumulate, but your friends will make it go much faster. The upper can count may go as high as 300 cans, depending upon the can size and how well you arrange them. Have some extra cans ready to go, just in case.
I placed an indoor-outdoor thermometer on the inside wall, with the sensor for outside placed in the upper vent. When anybody sees the incoming air temperature around 150*F, there are no more sanity questions about us, only envy. You can solve that, begin collecting the next batch of cans for them. (Only have them buy their own copy of this book! We’d like to keep eating and paying the bills.)
Getting Ready
Preparation Beforehand
Locate the collector placement, make the size decision. There is a more detailed list later.
Acquire about 250 cans.
Acquire sheet metal for solar switch boxes, Screen frames, Upper vent cover.
Acquire wood, plastic, paint.
Construction
Cut holes, fit switch duct in the holes.
Paint the cans.
Install the frame, then install cans.
Touch up the black paint.
Paint the frame outside to match the house.
Caulk gaps and around the frame edge and for the plastic cover. Install cover.
Indoors, Place a frame around the inside holes and paint to match the wall color.
Admiration Time
It’s time to step back and admire your work, only for a few moments. Then it is time to consider your next project for free heat.
The finished collector does not respond to inflationary cost increases, does not allow utility company cost increases, and the heat will cost increasing less with time, because the original price spent never changes.
Examples
Here are some of the collectors we have built. They all used tin cans and each one was an improvement over the last one. That’s the way it should be.
Mohawk Valley, Oregon
After Encinitas and the studio( See Chapter 5), we moved to Oregon and a more conventional house. It was the first home we had that we hadn’t built. One of the first modifications was the addition of a passive solar collector. The open, beamed ceiling in this part of the three level house allowed a collector 11 feet tall. It gave us about a 20 degree additional temperature increase in the incoming air. At times, with snow on the ground to reflect more sunlight, the temperature went to 184 degrees. That was the highest temperature ever noted.
There was exactly 4 feet of space vacant on this south wall. It was a close fit.
This size collector was capable of collecting 17,600 to 22,000 BTU per hour.
Springfield, Oregon
Our Solar Home in the city. Left of the large window and right of the door are the two passive solar space heaters. The windows have film on them to reduce heat loss and they show black in the picture. Actually, the South light is so strong that the light reduction inside is hardly noticeable. The privacy aspect is obvious.
The greenhouse is on the right and next to it is our solar water heater. It was a roof-designed unit, but we mounted it at ground level so circulation could be accomplished by convection. It does not require a circulating pump. It is the first solar water heater I didn’t build.
The greenhouse, in addition to providing a place to grow plants, adds warmth to the house, sort of an enclosed patio.
The solar electric panels are behind the house and have a clear view over it, but they do not show from the front.
End of excerpt