Where Does Passive Solar Work?
Ken Haggard, formerly an architecture professor at California Polytechnic, is an architect and principal in the San Luis Sustainability Group. Since the late sixties, Ken has designed more than 200 solar buildings, from homes to large commercial and institutional buildings—as well as the first permitted straw bale building in California. An active member of the American and International Solar Energy Societies, he received the Passive Pioneer Award from ASES in 1999 and was made a fellow of ASES in 2000. His office and home—in Santa Margarita, California—are passive solar, off grid, and straw bale. With David Bainbridge, Ken wrote Passive Solar Architecture: Heating, Cooling, Ventilation, Daylighting and More Using Natural Flows, published by Chelsea Green in 2011.
Questions and Answers
Q: We are planning on building a 40' geodesic dome house in the future. In our energy research, we are considering solar (as the dome shape is very efficient). But, we live in the Pacific NW (WA state-near Portland, OR). I have never seen a home that uses solar energy here. Am I correct in thinking that this energy source would not be the right choice for our area, because of the lack of sunshine? A bio-mass reactor type system like Nature's Furnace is our next possibility at this point.
A: (Daniel Chiras) I've actually helped to design a couple passive solar homes in the Pacific Northwest, one in the state of Washington and the other in Oregon. Here's the scoop on passive solar design in the PNW or other less- than-sunny locations: Unfortunately, the sun only shines about 33 percent of the time in November, December, January and February, but the way I figure it is you might as well capture that sunlight and use it for free heat! You'll need to insulate your home very well -- exceeding the model energy code specifications by 30 percent or so -- and you'll need to pay very close attention to your orientation and how well you seal the home, but it can be done! I've heard of people getting half of the energy from sunlight in the PNW and also around Buffalo, NY which is also a bit lacking in sunlight during the winter months. (Buffalo is in what we designers call the gloom belt!)
Q: I live in Ireland, where the weather is mostly wet, cold and cloudy. I have a lovely south-facing hill, on which I'd like to build an earth-sheltered passive solar home, but most of the books I've been reading seem to be based on experience in drier climates. How suitable is earth sheltering and passive heating for my needs, do you think?
A: (Daniel Chiras) Earth sheltering is quite feasible in wetter climates, though, you must take special precautions to drain water away from the house, to keep water from accumulating around the walls, and to waterproof the sections of the house that are underground. Passive solar is feasible in any climate, though performance varies with the available sunlight. Architects are able to supply about half of a home's annual heating demand in some of the least sunny areas in the United States like Seattle, Washington and Buffalo, New York through passive solar. The greatest heat gain often occurs during the swing season -- the fall and spring -- when the weather is a sunnier.
Q: I am living on the Island of Corfu in Greece. I have just bought a piece of land with a south-facing sea view about 400 meters high. I would really like to build a passive solar house (as far as the Greek architects will let me!!. They make a face when I mention passive solar) How can I keep the place cool in the summer if I have big windows on the south. ( I am very cold in the winter as it is really damp here.)
A: (Daniel Chiras) The key to passive solar heating and cooling is to orient the long axis of the house east and west, so you achieve the greatest solar exposure during the winter when the sun is low in the sky. A good overhang will protect those windows in the summer when the sun is much higher in the sky. You may want to get a copy of my book, The Solar House, and even send one to your architect. This will help them understand why a passive solar home, if properly built, will stay cool in the summer and warm in the winter.
Q: I read somewhere about a system that makes the windows darker in the summer (with a push of a button?); would you know anything about that?
A (Daniel Chiras) I don't know a lot about the windows that darken. I believe it is fairly new and is probably very costly. When you read my book, you will see why you don't need such a thing. You can incorporate all of the ideas for passive solar heating and cooling to stay warm in the winter and cool in the summer and you don't even have to draw attention to what you are doing. Just design your house using the ideas in my book, The Solar House, and you'll have a marvelously comfortable home with very low energy bills.
Q: We plan to build on some acreage with few building restrictions on the panhandle of Florida - where the weather is fairly mild. Is is possible to build something that is efficient, using passive solar and perhaps a geothermal cooling system that can address both the heating and cooling issues we will face?
A:(Daniel Chiras) Yes, you can use passive solar to gain a little heat during the cold part of the year, the short cold period, I should say. Interestingly, almost everything you do to passively heat a home will result in substantial savings in cooling and greater summertime comfort. You might want to get a copy of my book, The Solar House: Passive Heating and Cooling to study this subject more. I am doubtful that a geothermal cooling system is the way to go where you are, but you might want to call some local contractors who specialize in such systems, if there are any. You might consider an air-source heat pump for cooling, though.
Q: We plan to build our new project using green materials and passive solar design, etc. The home owner would like the house to be hurricane resilient and on stilts. The location is on a small lot on St. Pete Beach, on a small bay off the Gulf. I am worried that with an expanse of windows on the South wall (facing the water) the house will boil. I've done some research, but I just haven't found any direct mentioning of passive solar design in Florida. We plan on integrating solar panels and the like for electric bill relief, but is there a way to keep the house cool using passive solar? Are awnings and overhangs the only way? Do you know of any Green house plan databases that could give me an idea of the proper architectural characteristics for this particular environment?
A:(Daniel Chiras) Passive solar is really quite suitable for southern Florida, but the amount of south-facing glass is considerably reduced, compared to a house in a colder climate. Good overhangs also protect the home from solar gain during the rest of the year. Interestingly, almost everything you do to passively heat a home also contribute to passive cooling. Not to sound too commercial, but you may want to read my book, The Solar House. It's highly readable and will help you design a home that will work in your area. My book contains an entire chapter on passive cooling and describes a whole host of design features that contribute to this all important goal.
You may want to use some energy software like Energy-10 or Builder Guide for Windows to analyze your design early on to determine how it will work for you. If you don't want to mess with it, I will do energy analyses for selected clients and could give you some feedback on the design process from beginning to end. We can do an initial analysis to see how the home will perform (with respect to winter heat and summer cooling) and then tweak the design to achieve your client's goals.
Q: I will be moving to Paros island in the Cyclades island complex in Greece. I would like to build a home that will be totally self sustained, from power and water. Also I don't want to spent more then $150,000. Where do you recommend I start from?
A: (Daniel Chiras) I don't know what construction costs are in Greece, and I imagine that heating and cooling aren't a challenge. I also don't know what natural building materials are there...and I don't know the purpose of this house. Is it for you or for a family? I'm not a whole lot of help. It's hard to offer any concrete advice with so little information to go on. However, that said, I'd start small. Overestimate costs. If houses are being built for $150 per square foot, I'd build a small, 800 square-foot home. That will give you some money to install a solar electric and solar hot water system. Personally, I'd build a passively heated and cooled building that's appropriate to the climate. I'd use all natural materials and set up a rain catchment system for drinking water. I'd recycle all waste water (black water and gray water) and use it to nourish plants that supply much of my food. You might want to read my books The Solar House and The Natural House to get started on the project.
Q: Is Solar Water and Space heating effective in Ireland, as we do not get much of the sun all over the year?
A: (Kelly) Even in locations with less annual sunshine, both solar water and space heating can be effective, since whenever the sun does shine you will notice the benefits. A house designed for passive solar heating doesn't cost anything after it is built, and once a solar water heating system is installed, the energy is free, so there are real advantages.
Q: I am a true building novice but considering buying a lot in HMB Ca. about half block from the beach and building a totally green home. Do you have any recommendations for a foggy, rainy environment that can get windy and has about 25 fairly warm days per year. I would guess salt air would be a big concern, and the front of the house would face North, Northwest. I am sure there are lots of people in No. Cal to talk to but thought I would take a chance and see what you might have to say.
A: (Kelly) I lived in coastal northern California for a number of years, and very much enjoyed it, although the wind did get to be a drag after awhile. Even in such foggy environments, passive solar homes still work...you just won't get as much heat as you would in a sunnier climate. But then on the coast you don't need as much heat either. In order to take advantage of the sun that you do get, it is best to face the major windows toward the south. I take it that your major view is toward the north/northwest, so this might be a disadvantage in terms of good solar design. Perhaps you can make some compromises that will give you both a decent view and passive solar...
Practically any of the building technologies discussed on this website can be employed in a coastal environment, if good design and construction techniques are followed.
Q: Is it even feesible to think of building a solar home in Alaska...We are thinking of purchasing about 17 acres and would like the home to be pretty much self sufficient... Winters are Oct 1st til about April 1st. We do not wish to be reliant on heating fuel for winters, cutting trees for fuel, etc...I was also thinking of wind power for electric and using Electric for a back up sourse as well as a generator... What are your thoughts...
A: (Kelly) In Alaska where the sun shines for only a few hours in the dead of winter it would be virtually impossible to expect solar energy to passively heat your home during this time, so the idea of being completely self-sufficient energy-wise is difficult to accomplish. On the other hand, any warmth that you can get from the sun during the winter would be a welcome addition. Standard passive solar home designs will store the sun's heat for a few days, but not for several months.
There are some long-term heat-storage strategies that might be worth investigating. The Earthship designs (such as shown at http://dreamgreenhomes.com/plans/earthship.htm ) do pretty well at storing heat for a long period.
As for back-up heat, it would take a very large (and expesnive) wind generator to provide much electric heat...and it would only do so when the wind is blowing (batteries wouldn't do very well for this). Obviously a generator can provide back-up electricity, but this would be ineficient for heating and is not a "green" option. With 17 acres of land you may well have enough firewood that could be culled to provide backup heat...that would probably be my first choice.
Q: We are wondering if we should be okay considering an earth sheltered home facing North (fantastic view or we'd face it the other way)? We are in Idaho and have purchased a dream piece of land that we are hoping to build our home. Could it be considered if there are plenty of sky lights or an atrium built into the design?
A: (Kelly) Idaho generally has a climate that favors passive solar designs, which unfortunately means facing most windows toward the south to be able to collect the winter sunlight. For energy efficiency I would certainly advise that you do this.
Q: I'm living in Quito, Ecuador. We are at 9,000+ft in the Andes and 20 minutes south of the equator. This unique location means that any day of the year can have a low of 40f and a high of 80f, but we tend to hang between 50f and 75f, though being in the sun can feel much hotter. We also get 12 hours of dark and light. I have a family friend who is very poor and she's planning for old age and scared of being in true poverty when she can no longer work. I've been thinking an Earthship might be the answer to her problems. I'm wondering if the new design (non slanted windows would work here). Do you think this design would work? I worry about the angle of the windows, if the house should face north or that is irrelevant, and if the mass of the tires would really ever managed to heat up given the nightly drop in temp (or just even overcast days). What are your thoughts?
A (Kelly): From what you say, the rear-round average temperature would be about 63 degrees F. So you don't really need to increase that very much to have a comfortable temperature for a house. This means that passive solar heating would likely be all you need to keep things comfy. I would say that the Earthship design with vertical glass, facing north in your hemisphere, would supply all the heat needed. In fact it might be too much at times, so some means to limiting the solar gain through the glass would be a good idea, such as insulated curtains. The inherent thermal mass in the Earthship design should be very beneficial in your climate.
