Q: What is solar architecture and what are those solutions that solar architecture can solve?

A: Solar architecture, generally refers to the design of buildings that heat themselves passively -- that is, without mechanical heating systems and outside energy or with reduced reliance on such systems and fuels.

Solar buildings are heated by the low-angled winter sun, which penetrates south-facing windows. Inside, the sunlight energy is converted to heat, which warms the interior of the building during the day. At night, solar heat stored in the walls and floors continues to heat the building.

Keys to successful passive solar design are proper orientation of the house, concentration of windows on the south side, superior insulation, air tight design, overhangs to shade the building in the summer, and thermal mass to store heat gained during the day for nighttime use.

Solar architecture helps combat rising fuel prices, creates comfort at little additional cost, address air pollution issues such as global warming caused by carbon dioxide emissions, and helps reduce our consumption of declining and finite fossil fuels.

Interestingly, everything we do to heat a building in the winter passively, also helps keep it cooler in the summer.

Q: We are planning on building a log home pretty soon 2000 sq ft with 2fl + basement. and I am wanting to heat & cool it with solar energy could you tell me the best place to get supplies and also if there is a contractor here in Indiana who does solar hook ups?

A: Congratulations on your project! Heating and cooling with solar is best done passively -- rather than by active systems. Passive solar heating and cooling involves some simple, inexpensive steps such as orienting the house to the south, concentrating the windows on the house, providing proper overhang to prevent the high-angled winter sun from penetrating the windows during the summer, thermal mass to store heat, and insulation to retain heat in the structure. There are, of course, many other things you need to do to heat and cool a home passively.

You can read about them in some short articles I wrote for The Last Straw. We did an entire issue on passive solar heating and cooling. It's issue No. 36, winter 2001. You can obtain a copy by contacting the folks at the journal at www.strawhomes.com. You might also want to pick up a copy of my book, The Solar House. It contains detailed coverage of these important topics, and is written for a general, non-technical audience. I'd really recommend this over a solar hot water system that provides space heat, especially in your climate.

I don't know any passive solar designers in Indiana, but I'd suggest you call around to builders and architects and start asking who they'd suggest. Be persistent, it's very likely you will find someone with a few phone calls. If there are any large cities nearby, you can start your search there. Be sure, however, that the person is really well qualified. One way to do this would be to visit his or her homes.

Q: With Passive Solar Heating & Greenhouses, there are many older designs but I am seeking state of the art designs. If they are available please contact me.

A: (Kelly) Many of the older passive solar heating and greenhouse designs have not really been improved upon. The basic design concepts have not changed over the 25 years that I have been watching the technology. It is still a matter of allowing the sunlight into the space during the season needed, and storing that heat in thermal mass materials for the colder part of the daily cycle. There have been innovations in insulated shading devices perhaps, but even here, the basics have not changed.

Q: We live in a conventional, brick, ranch home with gas, hot water heating - we have great southern exposure - would it be possible to "retrofit" some sort of solar system and incorporate it into existing hot water heat system to heat home?

A: If you have a good solar exposure -- south-facing roof and walls -- you can retrofit for both passive or active solar. An active solar system could easily be tied into your existing heating system. I'd really have to see the house to be sure...but it sounds as if you might be able to enlist solar in retrofitting your home. By the way, I'm currently working on a new book called The Home Energy Survival Guide, which is all about this subject -- retrofitting homes for renewable energy.

The first advice I'd give, though, is to do a complete energy analysis of your home. Bring in someone to run a blower door test to test for air leakage and to assess insulation and other aspects of your home's energy performance. By sealing cracks in the building envelope, adding insulation to the ceiling and perhaps walls you can dramatically cut your fuel bills. Also, it is far cheaper to save energy than to install solar energy options. Every dollar you invest in energy efficiency will reduce the RE system cost by about 3 to 5 dollars.

Q: How would Kachadorian's solar slab work if I split it in half (E-W)with the north half about 3 feet higher than the south half? I'd put a half-wall along the split (vertical thermal mass) and figure out some way to allow flow between the "ducts" of the two slabs so I could still get flow S to N. I would have circulation not only from the warm (S) to the cold (N) part of the slab, but warm air RISING into the elevated, colder north half of the slab. Think it would work?

A: I've got no experience with this system (Kachadorian's) but think your idea would be theoretically possible. Bear in mind, however, that the warm air flows through the slab from the north side to the south side so you won't be able to promote circulation "from the warm South to the cold North part of the slab, as you noted in your e-mail.

You'd also probably have to provide an assist with a fan. Don't rely on natural convection. That seems to be the case with many of his successful applications of this idea. Bends in the "ducts" in the system would reduce air flow even more, making a good circulating fan vital. 

I talked with a gentleman in New York State (Bruce Brownell) who has installed hundreds of these slabs; however, he uses metal ducts in poured concrete rather than relying on the cavities in the cinder blocks like Kachadorian. I think this might be a wiser way to go.

Q: Regarding Kachadorian's solar slab concept, are there any issues with regard to bacteria build up in the blocks or pipes placed in the slab? If so, any recommended methods of eliminating them?

A: Yes, moisture is a concern. I talk about this a little in my book The Solar House. Kachadorian talks about it in the newest edition of his book. He says he's never had a problem with mold build up but could imagine that it might be a problem in moist climates. I recommend, if you are going to use this technique, that you embed plastic pipe in the floor to transport hot air beneath the slab rather than concrete block. It's a cheaper strategy and would not present the myriad of irregular surfaces on which mold could grow. You could also clean the pipe by pulling a rag through it...

C: Someone had suggested plastic pipe, but I was concerned that the lower thermal conductivity might make the system less efficient. However, the air flow is quite slow so I'll take it that using plastic is not much of an issue.

Q: We have your book "The Solar House" which I feel is the best resource on the subject. We are planning to build a new home near Minneapolis, MN. The house will be oriented southeast facing a pond (true south is not an option) therefore potential solar heat gain will be limited. Do you feel a radiant floor heating system could be justified since we could circulate water continuously during the day and theoretically increase the effectiveness of the thermal mass of the 4" concrete floor?

A: I'm not sure I understand your question fully. If you are interested in installing a solar hot water system and using that system to provide hot water for a radiant floor heating system that's imminently doable in most locations so long as the panels are in the sun from 9 to 3 PM each day. You may also want to consider a design that allows a good view of the pond (part of the house is oriented in that direction) while also capturing solar heat through south-facing windows (part of the house is oriented to the south). Sometimes an L-shaped building will allow a person to capture a view and capture solar heat...Just a thought.

C: The proposed solar energy gain in the house will be in the form of passive light entering the house through approximately 70 sq.ft. of glazing from the SE facing windows. We plan to have a concrete or tile floor with embedded radiant heat coils. Thanks but an L shaped house is not possible in our situation. My question is this: If the fluid in the radiant coils in the floor is circulated continuously, thus drawing heat away from the area actually receiving direct sunlight from the SE windows, would this effectively increase the thermal mass of the floor alone and increase the efficiency of the system?

A: Thanks for the clarification. I see what you are saying. I'd have to see the floor design and study the orientation of the house to answer this question fully and accurately. In general, however, your idea seems sound. Fluid in radiant coils in the floor would draw heat away from the mass and distribute it elsewhere, effectively increasing thermal mass and moving heat to locations where it is needed. However, the efficacy of this design depends on the angle. That is, if the wall containing the solar glazing is pointed too much to the east, you're just not going to get that much solar gain. You would probably be better off mounting some solar hot air panels on the roof of the house or on the ground nearby (and orienting them properly) or mounting some solar hot water panels and using that heat to charge the floor mass in your house (through an in-floor heating system). Again, though, I hate to give this kind of advice without studying the site plan and a floor plan of the house.

C: Here is a solar hot air system concept:. A 2 inch space is created between a sub roof and the metal roof using 2x2's running both horizontal and vertical. The horizontals are made to allow hot air flow toward the peak by drilling holes in the 2x2's in increasingly larger diameters in the horizontals closest to the peak to encourage a stronger flow. The peak has connecting duct that uses a photovoltaic connected to a fan that forces the hot air down into the thermal mass buried in the foundation. To encourage heating of the mass exit ducting recirculates the cooled air on the opposite side of the mass back into the roof.

I have heard that there is a great example of this system here in the valley that I am trying to locate and visit. The owner has stated that the mass reaches temps of 150F in the late summer and works well into the early spring.

Another avenue that has been mentioned is to build a integral trombe wall foundation that vents up into the modular/manufactured home. I can visualize vertical piping embedded in to middle of the trombe wall mass that connects to duct work and a fan.

Q: Could you, please, tell me more about active solar heating systems suitable for Ireland.

A: (Kelly) The main difference between active and passive solar heating systems is that active ones employ some more complex moving parts, such as fans, that help move air or fluid from one place to another. I like the passive ones because they are generally simpler and less prone to mechanical failure. Active systems can be used in situations where the house does not have adequate solar exposure (to the south) for passive systems to work. In these cases solar panels that either heat fluids or air are placed where they do get lots of sunshine, and then this is transported into the house to heat tubes in the floor, bins of stones (or other thermal mass materials), or radiators. A simpler active system might just use a fan between two rooms to help move hot air from one room to the other.

Q: We are looking building a completely "off-grid" home. We are looking at earth sheltering due to the simple fact of it's insulating properties and we would be building it in West-central Minnesota which is quite hilly. But I have questions regarding using solar for passive heating and cooling. I've found two methods that I think would really work for us. One is Passive Annual Heating Storage (PAHS). The other is Annualized Geo-Solar (AGS). Both seem very similar. So what is the big difference? And would they truly work in such an environment as Minnesota's below zero winters?  And in and earth sheltered house using the hybrid heating method as described above, is the whole house insulated on the outside of the concrete?

A: Passive Annual Heat Storage and Annualized Geo-Solar are two very similar techniques. Both rely on a layer of subterranean insulation (an insulation apron) that extends quite a distance from the foundation. As you probably know by know, this insulation extends all the way around the house and serves to trap and retain heat. This reduces the temperature difference between the foundation and the ground and thus reduces heat loss. In the winter heat is transferred into the house, helping to maintain comfortable interior temperatures.

In PAHS, the first system, however, heat under the insulation builds up naturally from the ground and to a lesser extent from the house. In the second, heat is pumped into the storage area beneath the insulation by using a solar hot air or solar hot water system that operates all year round, especially in the summer.  Unfortunately, there's very little information on either system and very little data to back up claims of their effectiveness. I've looked for it and so far haven't found much at all other than some anecdotal information. If you decided to attempt either one, as I've been contemplating, you'd be a pioneer. Hopefully, you could collect some real data on the performance of the system by burying temperature sensors in the walls and around the house and monitoring heat flow and household performance.

I personally would try the Annualized Geo-Solar technique using a solar hot air panel with a solar electric module to pump air through pipes around the house (beneath the insulation).

Q: I also find the Seabird Island Project very interesting using more of an active approach to solar space and water heating. Would that also be an option for us? I realize some back up for water heating would be needed. Could you combine the ideas of using the "active" solar heating from the Seabird project and the storage systems of the other two by piping the hot air to under the ground to be used later?

A (Kelly): About the applicability of the Seabird Project approach, I would say that it would likely be effective in Minnesota. One aspect of the Seabird project includes geo-coupled air tubes, so I would think that the two systems could be combined in some way.

There are different schools of thought about whether it is best to insulate the interior mass from the ground or not in general (with conventional passive solar heating). I am inclined toward using the insulation (on the outside) since I think it gives you more control over temperatures during all seasons. But I don't have direct experience with PAHS or AGS systems, so it might be better to follow the advice of the designers of these systems.

Q: We are building a passive solar in the mountains of West Virginia at latitude 39 degree North on a south-facing slope. We have loads of thermal mass and will be super insulated. Will wood stoves as backup heat be sufficient? We hate to have to put other expensive systems in when we love wood. But do we need a backup for times when we are away?

A: I can't really say if wood will be sufficient without specific details of your home construction -- its airtightness, levels of insulation, solar glazing, level of insulation, earth sheltering, climate, etc. How cold does it get in the winter? How sunny is it?

If you are building a truly superinsulated earth-sheltered home with ceiling insulation of R50 or better and wall insulation of R30 and you have a good solar resource and plenty of mass you probably would not need a backup heat source except to satisfy local building code. If that's the case, I'd install a couple of thermostatically controlled electric baseboard heaters to pass inspection. You may never need them, but you'll have to determine that as you live in the home.

You should be able to get by with wood as your sole source of heat but I don't want to make any guarantees based on the tiny amount of information I have at hand. You should have someone perform an Energy-10 analysis or a Builder Guide for Window's energy analysis to get a better handle on the thermal performance of your home.

You do want to guard against too much thermal mass. My experience has been that too much mass actually works against you. Be sure to insulate between the ground and the foundation and any earth-sheltered portions of your home...and insulate well...to reduce heat loss through these structures.

I know I haven't given you a very definitive answer, but I hope I've helped in some small way.