The economics of going solar?

Hello,

For my building [url href="http://www.livemodern.com/Members/hejiranyc/blog"]project[/url] I have been considering the various options for heating/cooling the house. And no matter how I do the math, it always boils down to installing a costly central HVAC system utilizing an oil or liquid propane furnace. I hate oil because it is just evil in every respect (environmental, political, etc.). And although propane is less harmful for the environment, it is highly unstable and is, alas, still a fossil fuel. I hadn't considered a solar photovoltaic system due to the hefty price tag involved. However, after doing some very rough math, I am beginning to wonder if it would be a viable option. Here is the rationale:

1. My first major assumption is that going with solar PV's will eliminate the need for having a conventional, centrally ducted HVAC system. This is because by going all-electric, I can meet all of my climate control needs by utilizing relatively inexpensive electric baseboard/radiant heat along with individual "mini split" heat pumps that can provide supplementary heat as well as AC. The assumption here is that the cost of this setup will be about half of what a conventional ducted HVAC system would cost. I was given a quote of $15,000 to do a conventional system, so, for the sake of argument, let's assume the non-ducted system will cost $7,500, or a savings of $7,500.

2. I will need a 5,000 watt PV setup to meet approximately 50-75% of my electric needs. This will generate approximately 6500 kWh of electricity per year. And with the sky-high cost of electricity on Long Island of $0.175 per kWh, the PV system will generate $1137.50 worth of electricity annually, or approximately $95/month average.

3. A 5,000 watt PV setup will cost $7.80 per watt and will require about 450 sf of roof space tilted at between 25 - 40 degrees facing south. This can be easily achieved on the Rapson Greenbelt 2 with the shed roof expanse over the atrium. The total cost including installation will then be $39,000, which is quite a chunk of change!

4. The Long Island Power Authority (LIPA) is currently offering an incentive on installing PV systems. In a nutshell, they will reimburse the owner of a new PV system $4 per watt. In my case, this would amount to $20,000. Additionally, New York State is offering an income tax incentive of up to 25% of the cost of the PV system to a maximum of $3750. Therefore, subtracting the $20,000 rebate plus $3,750 tax incentive from the total installation cost of $39,000, this brings the cost down to $15,250. For the sake of argument, if I also factor in the cost savings realized from an all-electric, ductless heating/cooling system, I can subtract an additional $7,500, which then brings the net cost of the PV system down to $7,750.

5. If I tack on the net $7,750 cost to the overall mortgage amount, this comes out to roughly an additional $39 per month. If I subtract this from the $95 worth of electricity generated every month by the PV system, this results in a net savings of $56 every month. Okay, this is not a ton of money being saved, but it does add up- $672 per year. Also:

-It adds tremendously to the value of the house- upwards of $25-30K.

-It saves tons and tons of CO2 gas from being emitted into the environment.

-Net metering allows you to sell excess generated electricity back into the grid, albeit at a nominal wholesale electric rate.

Does any of this sound plausible? I am interested to see whether my assumptions/calculations are on course or way off target.

Ed,

This all sounds plausible. Michelle Kaufmann had a similar experience in designing the solar solution for her Glidehouse. In her case, she has a net zero electric bill on a $22,000 system (I think she gets a pretty good rate for selling excess electricity back to the grid). She also saw instant appreciation of about $40,000. In CA, and it sounds like NY as well, it makes no economic sense at all to not include solar in a new home.

BTW, the nuclear power industry has caught onto this. Note that they are all over the news and opeds these days that they are actualy the green solution to global warming. They are spending big bucks to greenwash nuclear, now that solar is very economically viable.

Marshall

I read your original post about this with great interest. I considered PV but didn't delved into it like you have so it's been extremely informative. Looking at your figures, I just don't see how you would choose not to go PV, plus your benefit increases with time as the cost of gas/oil/elec. increases. Maybe this year it's $600+ to you, but what about ten years from now?
Our energy costs are still relatively sane here, but I do aspire to have PV somewhere down the road.

I'm totally sold on the ductless AC, regardless. It just makes so much more sense to be able to tailor cooling based on the rooms you're using and from what I understand, it's much more effective/efficient than ducted. It was our first choice and what we're going with.

Keep us posted and thanks for sharing the great info.

Can someone elaborate on the ductless AC system? How does this work?
Thanks-

Thanks splatgirl... Actually I have recently been looking into the possibility doing a hybrid PV system plus solar thermal system for hot water (for hydronic radiant, etc.). Anyway, after some preliminary explorations into thermal solar, I have drawn some impressions:

-PV contractors are a dime a dozen but solar thermal contractors are like hen's teeth. Surely there are tons of websites full of information about DIY solar setups, but I suspect it's a bit beyond my physical grasp.

-Solar thermal has lots of moving parts which means that there is the likelihood of failure or, at the very least, high maintenance. Since I don't know of anybody who has done this, I don't have real anecdotal data, so this is a hunch.

-Solar thermal is most effective in the summertime when you are least likely to utilize lots of hot water. Additionally, the system can overheat unless proper controls are in place to keep it cool in the summer. Again, this sounds like a lot of maintenance.

-Solar thermal is expensive, albeit, still cheaper than PV. However, there are no incentives from utility companies to build a solar thermal system since it is not hooked up to a grid.

After weighing all of my options, I am still perplexed! I am beginning to think that I should do all-PVs and hook it up to a hydronic radiant system that runs off of a ginormous electric water heater (120 gallons +). Yes, electricity is very inefficient for heat, but by utilizing a very large tank, you have better thermal mass, there is less fluctuation of water temperature and accordingly less cycling, which means less electricity per BTU output (I think?).

Anyway, I am still trying to figure out this radiant heat business- it's all about loops, manifolds, and zones. Oy! At the same time I am trying to figure out the most cost-effective way to do a suspended slab so I can have concrete floors (in which to run the radiant tubing) on the first and second floors in addition to the basement. THEN I'm going to make a decision about the solar system. How does one figure this out?? 8)

Basically a ductless AC unit, or a mini-split, is like a tiny heatpump setup. There is an interior fan unit and a separate exterior heat exchanger/dehumidifier unit that is hooked up via tubes through the exterior wall. They are typically sized for single zones- 400-500 square feet and I have seen them priced for between $500-$1000 each. They are theoretically less costly to run than a single large central AC unit and the biggest cost advantage is that there is no need for ductwork to be run throughout the house. Therefore, if you have an in-floor radiant system for heat, it probably does not make a lot of economic sense to run ductwork just for A/C. If you've got some inconspicuous spots outside of the house to conceal the exterior units, I think this is the way to go.

It sounds like you're kind of where I was in that it's relatively easy to find contractors familiar with one new/emerging/non-mainstream technology, but finding someone that's familiar with all of them together is impossible. Putting it all together requires a fairly big leap of faith on your part and the willingness to become as much of an expert as you can to assist with the interface between ingnorant parties.

Running a hydronic radiant system with an electric boiler is not at all unheard of.

What about using a tankless electric water heater for domestic hot water? And have you looked into using one of these as your heat source for a radiant system as well?

My experience has been that finding the most elegant solution to hydronic heating+domestic hot water is the biggest hurdle. There's just so many options, each with it's own pros and cons. I'm still on the fence with ours so I'd love to hear
what you're coming up with.

Solar thermal is very tricky. The first resource is

[url href=http://www.ecs-solar.com/lessons_learned.htm]Solar Tom Lane[/url]

You absolutely want a contractor who can show you 20 systems and 20 happy customers.

The house I just finished has 2 concrete floors on wood joists. Because of a lousy finish job, I had to grind it down, then I stained and polyurethaned.

You need to read a good article about concrete floors:

[url href=http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,5590,00.html]Youker System[/url]

There are companies who will quote $6/sq.ft. and it can be done for less.

At first I thought it wouldn't make sense to use a tankless water heater in a hydronic radiant wetup where hot water is being cycled constantly for many hours of the day. But after speaking with a rep yesterday, it seems to make more sense. You would basically have to make it a closed system in which the cooled water returns to the tankless unit after it has gone through its loop in the house, albeit, nominally 10-20 degrees cooler than when it left the tank. And the shorter your loops, the less temperature drop you get on the returning fluid (supposedly). So the tankless water heater only has to make up for a 10-15 degree difference vs. a 65 degree difference you would encounter by heating cold water from the main water supply line. Supposedly this approach is indeed more efficient than maintaining a large tank of hot water (only if you are going with an all-PV system).

Anyway, after searching high and low for someone who can help me with my solar issues, I just found someone in my backyard. Literally two blocks away from me in the West Village: http://www.quixotic-systems.com/index.html . They do HVAC (including radiant), plumbing, and electrical work, as well as PV solar and solar hot water systems! For hot water they use these evacuated [url href=http://www.sssolar.com/collectors.asp]tubes[/url] versus the standard flat panels- I have never seen these before so I am not sure if they are better/cheaper/more efficient, etc. They say that they have never come across someone doing a hybrid thermal-electric system incorporating radiant heat and a swimming pool (an ideal heat dump in the summer), so they seemed really enthusiastic about my project. Or perhaps they were enthusiastic about the potential $$$$$!! :zz:

Great that you were able to find what sounds to be a competent contractor that gets what you're going for. Maybe if they're excited about your project you can work out a comp deal in exchange for being a marketing venue for them.

With regard to tankless WH for radiant:
As I understand it, one of the issues with this set up is that because they're designed for cold water coming in, not hot/warm, the relatively high temperature of the water returning from the floor can be problematic to the unit.
I'm not positive, but I think I've read about a means to overcome this and/or units that are designed to deal with it.
I also recall reading that it's more efficient to circulate faster, lower temp water vs. a slower circulation and higher temp water. Can't remember enough to say why in twenty words or less, however.

Have you researched the boiler+indirect water heater avenue at all? Not sure if that's a viable option for electric or not??

As I said, I'm still on the fence about a heat source for our system and I'm about to have to revisit all of this stuff. We'll have to continue to compare notes and it's nice to know you'll have PV and solar figured out by the time I can fork over the $$ for it

I don't have personal experience, but from my research I think you'll do much better, especially in terms of efficiency, by using a boiler specifically designed for hydronic heat, such as the [url href=http://www.houseneeds.com/shop/HeatingProducts/boilers/monitor/monitorboilersmainpage.htm]Monitor series[/url]. Coupled with a [url href=http://www.houseneeds.com/shop/HeatingProducts/boilers/monitor/monitorindirecttanks.htm]superinsulated indirect storage tank[/url], you can get hot water, too.

It costs quite a bit more than a tankless water heater, but you'll have some peace of mind knowing that you're using equipment that was designed (and, more important, warranted) for the purpose, rather than something that might sorta kinda work.

-Steve

For a good perspective on using water heaters as boilers Click here and download the "Water heater vs Boiler Debate."

For one mans perspective on the "exceptions to the norm" Click here and download "Financing the Fringe."

We are in the same boat. We are starting construction in August and trying to figure out what the best combination of equipment is. We have a large, flat roof that sits North/South on the lot and gets lots of sun (we are in Los Angeles)

Half of our house will be on a slab with radiant heat. I am trying to figure out what the smartest configuration and combination of PV, solar thermal, and water heater will be for us.

Add to the mix that we would like to put a pool in a few years down the road and would like to have that heated with solar thermal as well.

I went on a tour of solar homes in Philly a couple of weeks ago. One house had an evacuated tube hydronic system. I was really impressed with their performance, and besides that they looked really cool in a futuristic, chem-lab sort of way. The owner was an installer so he had demo pieces to show us. In one 10-tube section he'd pour water and steam would come out in less than a minute. It was a hot sunny day, but he said he typically has enough to hot water the 5,000 sf home. To keep from needing a heat dump he used a low-tech solution: existing deciduous trees shade the panels in the afternoon. In the winter they are bare, of course.

I have an indirect hot water tank that is coupled to a Buderus boiler. Its already quite efficient (I saved nearly $1000 this past winter) but I've been wondering how much solar could jack that up.

I am at wit's end with the issue of green energy. None of the contractors I have spoken with are returning my phone calls or following up on promises to provide estimates, etc. Even if cost was not an issue, going into the solar arena is prohibitively difficult just from the perspective of dealing with passive-aggressive contractors. Is this part of the solar contractor's written code of conduct? Everyone claims they are so busy. I have a hard time believing this since I have hardly seen any solar installations anywhere. Adding insult to injury is the House's wide adoption of the president's so-called energy bill that gives the biggest kickbacks to his buddies in the oil, gas and coal industries while throwing out a pittance to the development of renewable solar and wind energy technologies. And ZERO incentives for industrial and residential use of solar and wind. :zz:

Anyway, besides growing increasingly embittered, I am also rethinking my strategy. I believe there is a reason why there are so few people involved with solar hot water. It's dated technology that is not very cost effective even over the long haul. And it does have lots of mechanical components that need to be maintained. And in a northern climate, you get the least amount of hot water when you really need it the most, i.e., the winter. Accordingly, you have overheating issues in the summer to deal with.

I am now beginning to think that I could get the greatest energy savings by coupling a larger array of solar photovoltaic panels with a geothermal heat pump system. This does involve going back to using forced air, which is less than ideal. But the energy savings (supposedly) is phenomenal. Assuming a constant year-round ground water temperature of 50-55 degrees F, heating and cooling requires little more than the electricity needed to run the pumps, the fans and the heat exchanger. There is already a well in my back yard through which I can run the ground loop. And the Long Island Power Authority is providing incentives: a rebate of $800 per ton as well as a $0.02 reduction in the kWh rate of electricity (which is still a whopping $0.155! :mad: ). I am hoping that ultimately the PV array will spin my meter backwards during the spring and fall months, while greatly supplementing my electricity use in the summer and winter. I don't think this will necessarily result in a net electricity usage of zero, but perhaps it can come pretty close?? :zz:

I think that sounds like a good plan. The winter performance may surprise you.

You can get geothermal heat pump systems (and conventional air heat pump systems, too) that will work with hydronic heat, so you may want to consider that. You can also get a heat pump water heater as part of the package. You'll still need ducting for the VAC part of HVAC, of course.

How deep is your well? When I was talking to the local geothermal contractor (being in rural southeastern Ohio, there's only one), he suggested that for my 2000 sq ft design, I'd probably need to have three 100 ft wells, spaced at least 10 ft apart, if I went the vertical well route. Roughly in the neighborhood of one well per ton of heating/cooling. They'd be smaller in diameter than ordinary water wells, so they would cost less to drill (and around here it's all soft sandstone and shale anyway).

I think solar hot water is, in many scenarios, a good way to supplement DHW production. But here in the temperate zone, it's never going to be enough, and if you're going to go geothermal anyway, the added cost probably doesn't make sense.

-Steve

steve,

To be honest I haven't really explored the well yet. Currently it is being used as the potable water source for my rear neighbor even though the well is technically located on my side of the property line. However, she acknowledges that she will need to switch over to the municipal water supply over the next few months for health reasons. I wouldn't give this well water to my dog, she declared. Eastern Long Island actually sits on top of a big ginormous aquafir that is fairly close to the surface. Plus my lot is nothing but fine, beachy sand, so even if an additional well or two is needed, it shouldn't be an enormous expense.

As far as sizing is concerned, I am inclined to think it will require a 5 to 6 ton system for nominally 2500sf of conditioned space. This is purely a guesstimate based upon the high ceilings, the greenbelt atrium that soars over two stories in height and the abundance of glazing. It is likely going to incur lots of heat loss and heat gain, hence the large system. Hopefully the abundance of concrete in the floors and the walls will help to moderate this somewhat.

Regarding radiant heat, as efficient as it is, it is still not as efficient as a forced air geothermal heat pump (again, supposedly). And although I am sure it is quite comfy, my primary objective here is to use as little external energy as possible. Plus, if I am having the ductwork put in for the AC, the tubing and manifolds and boiler for a radiant system adds an astronomical cost to the system.

Some good solar contractors can be found at the Wall at [url href=http://www.heatinghelp.com]HeatingHelp[/url]

Solar hot water is still many times faster payback than Photovoltaic solar.

Hi folks
This is my first post so bear with me. I love solar but I think there are a few factors you left out.
1. you won't be producing some of the electricity when you need it most so you may be selling it at wholesale and buying it back at retail. that could reduce your annual savings.
2. If you only produce 50-75% of your needs you may be paying another $1100 for the rest of your electricity, which could be inefficiently produced with the same oil you're trying to save.
3. That oil might be more efficiently used in a good furnace at your house.

Of course, if it does make 75% of your electricity it is somewhat better. A larger system could solve the green issue but then the economics get worse. Inflation affects both energy sources, and definitely helps with the long term costs, especially for the mini split air conditioners, I just don't know if it cancels out the inefficiencies of using electricity for heat.
Andy

Andy,

By law, the utility has to buy your surplus electricity at retail. The program is called net-metering.

In some areas of the country, electric resistance heat is getting more competitive with other fuels. Those elec costs have been 6-8 cents per kwh for 30 years and still not moving.

Kevin

That's true with my system in Oakland, Ca. but I don't know if it is a national law. Hejiranyc said in the original post that the utility company buys back the surplus at a nominal wholesale rate. In Oakland we have tiered rates for residential electricity that go up drastically (sp?) when you go above the lifeline rates.
Andy

The terms vary from jurisdiction to jurisdiction. In Ohio (where I live), the terms are not all that favorable to the consumer: You get the retail rate until you've dumped enough power back into the system that your net consumption for the billing period is zero. Anything you send back beyond that is priced at the utility's cost, which is generally only 1/4 or so of the retail rate.

-Steve

what about reselling excess energy to the next door neighbors? I'm surprised more people havent tried to get their neighborhoods interested in linking together to share energy at a variety of levels based on how much each homeowner is able to spend on their system.

I have actually been trying to put together a business model that makes enough sense to get whole neighborhoods or small cities to all go solar at the same time to save money, increase the value of their homes, and improve the environment.

In theory the concept of truly being off the grid, i.e., community solar collective, would be a beautiful thing. However, the reality is that you lose all of the incentives provided by the electric company, which can be substantial; you must feed your additional power directly into the grid (no battery backup allowed). I know that at the current going rate of $7-8 per watt, I would find installing a PV system to be cost prohibitive; the $4/watt incentive being kicked in by LIPA is makes it feasible.

Now that gas is over $3 per gallon in much of the country, I hope people are waking up to the reality that energy conservation must become a way of life. Accordingly, we collectively need to communicate to our elected officials that we will no longer tolerate energy policies that are geared towards rewarding the old buddies in the gas and automotive industries while giving the developers/manufacturers of renewable energy technology shortshrift. It sickens me that green energy technology exists today, but is prohibitively expensive/underfunded/underutilized, while Exxon is making RECORD profits, and terrorist-supporting regimes are continuing to manipulate the world with their oil output.

:mad:

I am surprised that it has taken such a long time for someone to suggest using geo-thermal to heat your home and domestic hot water. It is by far the best heating system, and most sensible system currently available. Just a few thoughts from our own projects that we are working on up here in Edmonton, Alberta using geothermal:

- a 5-6 ton system for a 2500sf house sounds about right. I would go with a heat exchanger-to-forced air duct system for the simple reason that you can also use the duct work in the summer for air conditioning. Otherwise if you do infloor heating, you will still need the duct work for the air conditioning, which will cost you more. (note: geothermal provides AC as well as geothermal, the pumps are just run in reverse!)

- including solar panels for domestic hot water should (in most locations) provide you with about 75% of your domestic hot water needs. Even if you do not put them in now, you should have your plumber provide plumbing to the roof for future use. I am quite certain that in the not-too-distant future, building code may require these panels, as they do in South Korea, Spain, and a few other places already (by law).

- Currently, 37 states and several Canadian provinces net meter for electricity so you can sell it back. It is a state or provincial juristiction, but probably 5-10 years from now most of North America will have net metering.

- PV is still the most expensive choice for power. Considering you are also doing geothermal for heating, average power consumption is increased by approximately 30% (but you have no gas bills). If you live out of town on a acrage or farm, wind power is probably your only other viable option. For commercial and industrial applications, leasing fuel cells (from GE Money for example) is now becoming a mainstream, realistic option. It might not be cost effective yet for the average residential consumer.

- Because of the current interest in geo-thermal technology, make sure to use a reputable geothermal company, preferably with a certified geothermal engineer on hand. There are many fly-by-night operations out there that think they know what they're doing and don't. You don't want to spend thousands of dollars on a system, and find it freezes up in the winter, or isn't large enough for your needs. An professional will always design the system most suitable for your climate, location, and house design.

- OH YA...and the number one way to keep your heating costs down is to SUPER INSULATE. No one in their right minds should be considering anything less than atleast an R-rating of 40 for walls and 60 for the roof. Also, cheap windows means bad insulating value...go for quality and r-value. Generous roof overhangs to protect from summer sun, and south window exposure for winter sun mean that you may not have to heat your home much at all!

Hope this information helps...with the rising cost of natural gas and heating oil, I feel even more compelled to get off the grid. :grin:

Hi, I thought I would put in my two cents worth. We are in the process of planning a home to be built in the spring. Here is what I hope to accomplish:

1. Super insulate the house. Energy costs will go up quite a bit this winter and there will be higher costs in the future. Money spent now on insulation will reap rewards later. Also, install a heat recovery ventilator to bring in fresh air. Better insulation will also allow you to purchase a smaller and cheaper HVAC system.

2. Use as little energy as possible by the use of efficient appliances and HVAC system.

3. Use radiant floor heating. As I understand it, radiant floor heating actually saves money because you can maintain a lower temperature in the home still be comfortable. This is because radiant heating, heats the objects in the room and not the air itself.

4. Use a heat pump for heating and cooling. In colder climates, an air source heat pump may not be efficient. A geothermal heat pump is very efficient, but they cost $5 to $7 thousand dollars more. An AC system using high velocity ducting seems a reasonable option.

5. Use solar and wind energy where possible. I plan to install an active solar hot water heating system a year after we move in. I will use this for space and domestic hot water heating.

6. Install an efficient stove in the basement, either wood pellet or corn. This could be used for space heating or to supplement the hot water heating system.

I know all this sounds ambitious, but I am committed to reducing my energy usage where I can. I also have the mechanical skills to install the solar system myself.

I see I'm not the only one confused as heck about this.

For me:
1) Solar is a fantasy. MI does NOT have any such rebates or any reverse metering... nor is there any notion of doing so in the future. IF your state has it and sun is fairly plentiful... then by all means, go for it. From everything I see about it, it seems fairly simple to DIY... as many retailers sell kits.

2) I want radiant as I will have slab on grade and that would be rather cold in winter without it. My original notions of it heating the whole house were dashed when I discovered how expensive WARMBOARD (subfloor radiant hose-ready product) was for my second floor - $15k for ~1500sf. Now radiant is more just a luxury of substantial cost.

3) Most everyone here is building with efficiency in mind and the idea of no ductwork seems counter-intuitive to me as was mentiond earlier. The V in the HVAC, I have read many places, is SUPER important in a tight house. Otherwise, one risks stale air and mold - health issues that normal leaky homes don't fear, because they leak all over.

I, too, was trying to get around a ducted home, but have yet to get around how I would VENTILATE the house (fresh air, recycling old air). Even the hi-velocity AC systems seem wierd - they never mention how the RETURN air system works. They never show any hi-velocity SUCTION/RETURN line(s). How does that work?

4) As nice as geothermal sounds, I've only ever heard bad things about their maintenance (pumps, leaks, etc.). I cannot fathom the cost of digging up the buried lines to find a leak in a closed system. Mechanically, they seem more complex than traditional systems... and lack the contractor availability/size/base.



Trying to do the economic math on the various systems available and variables per region and needs is a HEADACHE. I, too, wish SOMEONE would write a book that advises on this topic.... based on cost.

A completly solar powered house is a fantasy for me.

I have a grasp of what it would take to do though.

My house would be a fairly conventional two story thing with a basement and a green house covering the elongated southern exposure. I would super insulate this house untill i got the heat loss down to 10,000 btu or less. Mysunspace would have a insulated wall on the house side. I would run duct work in this house so that i could easily air condition it and run air through a well insulated thermal storage to heat the house. I would have just a window or two on the east and west exposures. Possibly another sunspace on the east.

I would put my solar collector inside the sunspace to avoid problems with freezing. The storage for hot water would be on the other side of the wall from the sunpace and would have a heatexchanger that works by convection of the hot water.

I would have a thermostat in the sunspace that would turn on a blower(possibly a ecm blower in a air handler) and this blower would only circulate air through ducts embeded in dirt used as thermal mass in the basement. This thermal mass would basically be a insulated room filled with dirt or something else.

There would be another set of ducts going through the dirt, conected to a secondairhandlerthat would supply the house with warm air when the sun was not shining. This thermal mass would be sized to hold three to four days of heat.

I would drill a hole in the basement floor during construction forthe smallestwater to water geothermal heatpump. This would run cold water up to a water fall in the house for cooling and to the air handler for heating.

Pretty boring, uh?

Out of all those post that took a while to read i did not see anyone mention doing detailed load calcultions on solar houses. That would be step two after you come up with a floor plan. Then if you have created a house that has unreasonable heating and cooling needs you could go back and redo the house plans untill you have a house that can feasably be conditioned. Solar enthusiasts get carried away with the windows. If you keep them to a min then the house gets easier to heat and cool plus mabey less expensive. If you can seperate the solar collector from the living space then it will not be a heat loss when the sun is not shining and your controled thermal mass will heat the house for longer.

Hey on that radiant thing.

There is some debate about wheather it is more efficient that a ducted heating system.

If you have to air condition it really makes no sense at all. It could be more comfortable but keep in mind that these are superinsulated houses so there is not going to be so many cold surfaces anyway unless you go nuts with the window in which case your radiant floor is going to be radiating heat outside also.

The other issue is that if you are burning gas then the forced air furnaces generally more efficient at burning gas than the boilers that tend to get installed.

A forced air furnace if installed right, so that it is sized very close to the house(ie for less than the few coldest days of the year) will be as comfortable and more efficient that a boiler. I hear someone screaming right now.

The only way that a radiant floor makes sense to me is if your solar collector is water based. IMHO