Are there any easily created passive solar heating ideas . . . : LUSENET : TimeBomb 2000 (Y2000) : One Thread

And I mean real easy. For instance, can you paint concrete blocks black and put them in the sun and then bring them inside in the late afternoon?, (I know you can do it, the question is will it give off any significant heat?) (My house axis is east-west, so it gets very little southern light in the winter. Therefore I'm looking for a portable passive solar solution.)

I've also heard stories of old about people putting hot stones under their bed or their mattress or bedroll or something. How did that work? (or was my leg just being pulled further from its socket)

-- Puddintame (, April 27, 1999


Make that axis "north-south." Whatever. Take my word for it, no southern light.

-- Puddintame (, April 27, 1999.

Sure, it'll work. Stones and concrete have specific heats (measure of capacity to hold heat per unit of mass) lots higher than wood and many other common household items.

Water has one of the highest specific heats, but its transparency lets a lot of sunlight through without absorption. You could try setting a glass jar of water in the sun for a day, but if you move it in and out each day chances of breakage increase.

Whether the heat will be significant depends your ability/willingness to haul those black concrete blocks in and out every day!

-- No Spam Please (, April 27, 1999.

Maybe I'd better add that using a hot stone to heat a small insulated space within layers of bedding is a lot easier than trying to do the job of a gas-burning forced-air furnace with solar-heated daily-repositioned black concrete blocks. Better plan to use the blocks similarly -- that is, to heat a small insulated space. And have contingency plans for moving them in and out.

-- No Spam Please (, April 27, 1999.


Putting concrete blocks outside on a cold day will not work. The blocks will absorb solar energy, sure, but they may be at an ambient temperature of 30 to 40 degrees, so that when you bring them in the blocks are only at 32 or 42 degrees. Solar heat will raise their temperature above ambient.

Water is good. 55 gallon black drums will absorb heat. Put them inside, behind a south facing window (you surely have one or two) and let the sun heat them up. Then they'll release the heat after dark. People have made passive solar walls using these things. Work well.

I have one room in which I have a lot of south facing windows. I have a concrete slab for about 6' in from the windows, with a concrete block wall. The slab sits on 3 feet of gravel, and the wall and the gravel are insulated. This works well, too, but I have a lot of glass in that wall. [The wall and the slab form a sitting area right off the master bedroom. I got the room heated to 72 degrees with outside air at 15 degrees, and the slab kept it at 55, even though the temperature dropped below zero that night. Power outage!]

-- De (, April 27, 1999.

Two things make solar work: siting (how the dwelling sits in relationship to the sun) and insulation of the dwelling.

You are probably out on both accounts.

There really is no 'simple' way to do solar refitting since you end up installing alot of devices which use electricity to push air or fluids around, etc.

Wood heat is basicly 'solar' since the trees had to use solar energy to grow. I think that is about as close as you'll get. Insulate the heck out of the place will get you the most bang for your buck. Also get an electrostatic air 'ozone' machine to help control indoor polution.

-- David (C.D@I.N), April 27, 1999.

I have friends who built an adobe(mud) brick wall around 3 sides of their wood stove. The wall gives off enough heat all night to keep the room warm even when the stove goes out.

-- L stone (, April 27, 1999.

Puddintame, I read a couple of books a few years ago about passive solar heating. The examples of homes built to take advantage of passive solar heat all included three general aspects. The first was to build the house with a large southern exposure. (Guess this one's not for you, huh?) The second was to have some form of shutters or insulated covers for any windows which could be closed at sundown and opened during the daylight hours. Some people made these from the thin insulated panels available at home improvement stores (not very expensive either). Some brands of these panels have one side which is shiny to reflect heat. In the cold northern area where I live, I have heard that these panels cut easily to any size window you might have and when slipped in place at night DO make an appreciable difference in lowering home heating costs. I suppose a lot depends on how conscientious a homeowner wants to be about putting them in and slipping them out on a daily basis, or if he/she can stand having all their windows closed off each night. One lady I know says the reflective side of these panels which she sees sometimes drives her a little crazy, but not only do they help keep the heat in, they also reflect any light in the house and make it seem brighter inside.

The third aspect of passive solar is the concrete blocks you mentioned and/or the large containers of water. These were not put outside and then brought in, though, but were an inbuilt part of the homes. For instance, a padded bench (with back)was part of the furniture but under it was a sealed container of water. Picked up heat during the day, and slowly released heat at night. Other beds or furniture were built either with water or concrete as a hidden base.

While all the homes in the books were built specifically with passive solar heating in mind, I don't see why you couldn't adapt the concepts, even if only in small ways. From what I understand of the principles of passive heating, you wouldn't even have to paint the blocks black. Heat is absorbed by the concrete or stone anyway - assuming there is some source of heat for it to absorb. Bricks, too. A block of soapstone (or other stone or brick of the size wanted, but soapstone was preferred) was often used in earlier times to provide heat for people's feet, either in bed at night or on a sleigh, or even later in early automobiles. The soapstone would be heated near a fire or on a wood stove, wrapped in some layers of flannel cloth, and placed where you wanted it. A great Aunt of mine related many times the comfort she remembered from a soapstone warmer at her feet in the winter. A hot water bottle was also often used for this, too.

If you could figure out an inexpensive way to use the water container idea in the house, it could also serve as a dual or triple purpose plan. Besides the passive absorption/release of heat, you'd have stored water, and if you chose to keep the container open (and refill it as needed), you'd also have more humidity in the air, which also makes a lower temperature feel as comfortable as a higher temp with dry air.

If you've got any used book stores in your area, you might want to check and see if they have anything on passive solar heat. That's where I picked up the ones I read, very inexpensively. Online book dealers will likely have them, too, but it also usually costs more that way.

Bedwarmers -- anything from a long handled fancy metal basket which opened to put coals in to a simple covered pan filled with coals, were also regularly used at bedtime. Bedrooms were very often not heated, or were less warm than other parts of the house, so before anyone retired for the night, a bedwarmer was slipped between the covers and run over the sheet to warm it. (Who likes to climb into a cold bed?) Either that method was used, or the foot warmer, or both combined. We may have electric blankets nowadays, but our ancestors were no fools about having a warm bed to climb into either! Good luck to you, I hope this at least gave you some ideas.

-- Bonnie Camp (, April 27, 1999.

Basically--no. By the time you haul sufficient blocks or rocks in and out every day it's better to buy extra longies instead. Space heating with solar costs.

-- Carlos (, April 27, 1999.

I suggest a varation on an idea we used while hunting in the desert. As you know the temps vary greatly in the wide open desert region. In the day it may be 100*+ F and drop to 30* to 40* F at night. We used the water filled black barrel idea for showers after a long day climbing through the rimrock. Felt great I'll tell you! OT, I propose setting up a stand about 8' tall, perhaps 2 step ladders, nailing a piece of 5/8" plywood between just large enough to provide a roost for a 55 gal. barrel. Since heat loss is directly effected by aspiration from the wind, I would use 1 mil. plastic, possibly in a pyramid to provide a transparent wind break for your shower. One of the things I can't imagine losing is the ability to get clean, even if a little less frequently. It is a marker of civilization I don't intend to give up. By the by, if one had some hot water bottles around, the soapy water could be taken 'inside' for a while, till, the sand man comes near.

-- spun@lright (, April 28, 1999.

Hi, P, Real Goods ( sells a type of attic-insulating foil which is said to keep heat out in summer, in in winter. I believe there is also a reflective paint does the same thing. Maybe a search on the web would produce other sources/more info for the foil. I remember reading about this stuff when it was first introduced some years ago and insulation experts were raving about it.

My grandmother used to heat bricks in an oven of her coal stove, wrap them in soft flannel and put them in the beds for warmth. You ain't seen nuthin' until you've seen those beautiful ferns made by the frost on the INSIDE of your windows! We had hot water bottles too (in rabbit and lamb shapes!) in flannel covers. The bottles were rubber and more comforting but the bricks held the heat longer. In even older days pottery hot water bottles were used, probably more effective but not as comforting and easily broken.

The Hungarian talks about stoves covered in ceramic tiles which retained heat(common in other European countries, I believe, but not in Britain). The coal stove my grandmother had was similar to the one my family had until we moved and left it in the house. Huge black iron thing, not only with a fire area, hotplates and ovens but also with a boiler connected to the tap for hot water. The fire was "banked up" for the night, using complicated maneuvers with dampers and such, and smouldered until morning when it was fine-tuned to leap into life again.

We're counting on the solar panels to run our water bed heaters on really cold nights. If the gas stays on, we'll have gas logs. If not, we'll go to bed early.

-- Old Git (, April 28, 1999.

May I suggest black ABS pipe that is used for drains on sinks and toilets. One could put a grid of pipe on the sunward side of the house, insulate around the pipe and possibly put tenplast - coroplast that is translucent over it. Have a barrel rather high in the house and connect the ABS pipe to the barrel.

-- Brian (, April 28, 1999.

--OLD GIT-- As always you come through with an excellant 'stitch', drawing the patchwork of community awareness into a more useful and wonderful safety blanket. Thankyou! How does the old addage go..? An ounce of prevention is worth a pound of cure!! Treating the living space is far more effective than fighting the cold or heat. Combinations that would hardly have been thought of by the most clever of us, sometimes just fall together by accident. ie; It was reported in one genre or other yesterday, the TV I believe, that a fireman noticed that the only article in a recent house fire, that was not burned beyond recognitation, was a baby diaper. Unable to account for this he began to investigate, and lo and behold it turned out that the gel used to treat the diaper has superior resistance to fire. They gave the name of the substance but I will have to track it down. (unless someone here happens to know it). Combine this with the superior insulating quality of cardboard, and I think I can increase the attic's R-rating substantialy, very economically, and quite safely by using this fire resistant gel between a layer or two of cardboard. An old acquaintence of mine used cardboard extensively for insulating, but I reguarded the risk to great concerning fire hazzard. This addition to the equation may just tip the scales in favor reconsideration. In the past we have torn down some very old houses and found newsprint dating back to the early 1900's stuffed in the walls for insulation. Neat reading, but I wouldn't think of using it as insulation. The attic would be ideal for some upR rating. I'll get the name of this gel and get back to ya with a cost/benefit summary.

-- spun@lright (, April 28, 1999.

Soapstone retains 5 times as much as the next heat retaining material. The Inuit heated the igloos with soapstone "lamps" that were actually long narrow bowls. In the bowls they would burn animal fat. Apparently a real art to making a good lamp fire. There are woodstoves that are made from soapstone but they are not cheap and I want one. Actually it would not be hard to make a small "charcoal stove" from soapstone and use an aluminum downspout as a chimney and stick it out a window. Be good for one room. Soapstone can also be cut with just a bow saw. Goes through just great. (Use brazilian stone) use pins to join pieces and one would have a toastly little stove :o)

-- Brian (, April 28, 1999.

Brian--re tenplast coroplast

Haven't heard of these before. Could you give a general description of the material and some common uses?

-- spun@lright (, April 28, 1999.

Well I am in Canada so it could be called something differant somewhere else but tenplast - koroplast is a plastic cardboard that is sold in 4* 8, 4*10 and 4*12. It comes translucent or differant colors. Tenplast has excelent insulation values as compared to glass and is tough, lasts a long time and easy to work with. I would seriously consider this stuff for windows as the light will come in yet there will be significate heat retention. An this stuff is reletively cheap compared to heating cost saved. It is good for greenhouses also. Sunroom?

Tenpast is used mainly for signs.

-- Brian (, April 28, 1999.

I worry about people in apartments in cold weather. Some of the best methods of passive power is not loosing the heat. Start of course with your body. Have good warm clothing. Choose one room in the apartment as your bug out pad in case of power failure (even not Y2K related and do this in a house to). A very important principal to apply in such a situation is that you do not need alot of room to be comfortable most of the time. Choose a room and be able to open your window for fresh air. I myself thought about the soapstone thing a bit and if one was to put in a bit of effort a soapstone propane stove would not be to hard to manage. Get a good size chunk of soapstone say 1' by 1' (whatever eh!). Cut it with a bow saw so there is a flat bottom and top. You can drill this stuff pretty easy so the idea is to put a common propane torch nozzle in a hole you drilled in the side of the stone attach a 1LB propane tank or 20 - 100 LB with hose and adaptor. Propane tanks should be kept outside. Drill holes from the top to meet the one with the torch nozzle. actually the more vents side and top the better, one may wish to vent it outside but propane is pretty clean stuff. The main thing is to have the window open a bit. Put the "stove" near the window. One could then place a frying pan or pot on top for cooking. As the soapstone retains heat the propane doesn't have to be on all the time. One can maximize the cooking - heating then. A pressure cooker would be good for heating water and then using a stainless steel thermos one can "cook" a meal of stew, rice, oatmeal what ever. Don't forget the differance in even having that little water for keeping clean is invaluble.

Next one would want to elevate a living area so your chairs are above the floor. 3/4 inch plywood would do the trick. Just a couple of sheets on concrete blocks and a pach of carpet will give you an elevation from the drafts. Have VERY comfy foot gear. Actually to inject something for those that have been there and done that, it is my opinion that the body particularly the hands and feet are capible of withstanding alot of cold. There can be something to be said for "toughing it out" as a ligit basis. The body definitely supplys us with a "second wind" in relation to the cold and the hands and feet. People seem to have their strengths and weakness. My strengh is hands. Weakness is feet.

The rest of the apartment should be left cold. All food of course should be delt with. If it is freezing, get ice from outside and put it in the fridge - freezer. Your water should be in your warm room, put it higher on a shelf if possible. Only keep what you need in the warm room to keep you comfortable. Remove the furniture if it is of no use. The less stuff in the room the less to heat up. Hang your blankets along the wall to dry and help insulate your room. Have a tent and some foam for sleeping at night. Pattern your sleep around the sun. Northern Canada ignore that last comment. No sun :o)

Well there are a few ideas.

-- Brian (, April 28, 1999.

We used to experiment with various passive heat transfer devices at work to reduce electric power consumption.

Attaching a large, dark colored vertical duct type enclosure on the outside of a south facing wall permits heat buildup within the space. Openings to and from the interior of the home, at the top and bottom of a room, allows cool air to enter at the bottom and heated air to exit at the top. These openings should be able to be closed at night or cloudy days when the direction of convection will stop or reverse.

Dark green is supposed to be better than black for collecting heat.

Another trick that intriqued me was the "heat pipe". A long copper tube, sealed at both ends and holding a small amount of alcohol and a vaccuum. This was done using a valve and tubing attached to a suction pump. Before creating the vaccuum and sealing up, a small amount of alcohol was placed inside.

A match was held at one end where the alcohol collected. It would boil and the "steam" would rise in the tube, greatly heating its entire length, until it condensed back to liquid and ran back to the pool at the bottom. The tube would quickly become too hot to touch.

We didn't put this contraption to any great use but I can visualize sunlight being focused on a small pot containing alcohol with a radiator or other heat dispensing device attached and located where it would do some good. A solar cooker for example, when not doing chickens, could help heat the house.

One other thing we learned when trying to reduce the power bills is that electric utility companies have what they call peak rates. The rates go higher according to your peak usage. The more appliances and other electrical devices that are on at one given time, even for a short period, sets the peak consumption rate that will be applied to your usage for the entire months billing. We built a solid state circuit to monitor a group of heaters and other high current devices which allowed only one to operate at a time. The individual duty cycles were small enough to allow this and it saved a bundle.

As for newspaper insulation, we bought a Sears prefab years ago in which the attic had been insulated with newspaper. It apparently works very well but besides the fire danger, it provided food for lots of silverfish. Nasty buggers.


-- Floyd Baker (, April 28, 1999.

Puddintame, the posh name of the stuff I was talking about is "radiant barrier." If you plug this term into Alta Vista it'll give you tons of sites. A bit of info appears below, but before that I want to mention something I forgot: Real Goods also has relatively inexpensive solar-powered roof vent fans.

"Attic and wall radiant barriers and reflective insulations made of aluminum foil are becoming a popular way for homeowners to save energy and money, while substantially increasing the comfort levels of their homes and offices. This increasing popularity, in addition to the increased exposure of the last several years, is due to two other reasons. First, tests by the Florida Solar Energy Center, Oak Ridge National Laboratory, Tennessee Valley Authority, Texas A&M University, and other institutions have proven how well radiant barriers and reflective insulations work. Second, manufacturers are improving the quality of radiant barrier and reflective insulation materials, especially the barrier bubble products."

James Dulley, the handyperson type who has a weekend newspaper column, says that radiant barriers can reflect up to 95% of an attic's heat.

We've planted our west-facing front yard with fast-growing Leyland cypresses and a paulownia tree, plus lots of medium-height shrubs since we moved in six years ago and these plantings have drastically reduced the heat gain in the living and dining rooms. Had we needed to I would have situated a trellis in front of the south-facing windows and planted deciduous vines. Luckily, we have a very wide overhang which shades most of those windows; solar film takes care of the rest.

-- Old Git (, April 29, 1999.

One source I read suggested pitching a tent inside for sleeping and making a "nest" of blankets, etc. Pile couch cushions on outside and anything else that will insulate. You keep warm by retaining your communal body heat. Three dog nite?

I lived in Iceland for a couple of years. Their stoves were lined with volcanic rock. (the denser kind - not pumice.) This type of rock may be obtained in the Pacific Northwest and the Islands. Wonder if one could fashion something similar to the soapstone affair. Did read that you should never heat a wet rock and I know you aren't supposed to use river rock for firplaces because it shatters.

The local Karuk Indians are renowned for their basketry. They can weave pine needle baskets so tight that they hold water. They never did develop pottery. They would heat a rock and drop it in the water in the basket to heat it and then pull the rock out. Gives a whole new dimension to "stone soup."

I have a one burner (electric) that is only 600 watts - which isn't bad wattage for something that heats. My biggest concern is hot water when the woodstove isn't in use and it isn't warm enough for solar. Any suggestions that a non-engineer might use? I can see us hauling hot water around and getting scalded from spills.

-- marsh (, April 29, 1999.

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