hello, i'm new to this forum today, but i have been browsing around for a while now.
i have a question and was looking for some input.
i am in the planning stages of building a small passive solar home, and i was wondering if my plans for the foundation are worth the effort or not in terms of efficiency.
it would be 28'x40' with the long wall facing south, and left exposed while the other 3 sides are back filled.

off of this south wall, there would be a slab poured in the center 20' of the foundation, leaving 10' on both sides, and extending 12' out. there would then be a 3'-4' knee wall up front, with the sides extending down from the top of the main foundation down to the knee wall at about 42 degrees. the remaing 10', on the sides and across the front would now be backfilled and sloped accordingly. this section would the be framed in and covered with glass. sort of a 'walk in collector'/greenhouse.

there would be a door way located in the foundation for access from the cellar on the right, while there was a section to enter by spiral staircase from the first floor on the left. (with your back to the wall and looking south) also, there would be vents down at fllor level across the bottom, and similar vents entering thru the sill and running between the floor joist to let the heat in to the first floor thru registers in the floor like for forced hot air applications. a thermal syphon approach. both the doors could be opened for 'full on' heat transfer if this works like i think it will.

i have access to large amounts of black granite break-offs and waste chunks of all sizes. what i wanted to do here is tile the floor and walls with these pieces for their heat collection and storage capacity. plus their free and look awesome.
now assuming that the foundation is well insulated around the outside only, and the glass is of a good quality insulated type, should this foundation be a good start for the rest of my project?
i consider this to be an isolated arperture, so i can only take what heat i need without it effecting the overall comfort of the home in the event that it gets too hot. also, in the summer there would need to be a shade of some sort along with open ventilation. i look forward to any input, both positive and negative.

thanks, intransit. 

I think that you have the right idea. I see many Passive designs that use the main living area as the collection area. It'll be way too hot for comfortable living! One thing that I would add is some sort of insulation at the windows for the nighttime. Insulating drapes or blinds should do the trick, but they can be improved upon.

Good Luck!

what options are there for insulating large windows in a passive solar situation?

thanks panelcrafters.

i visited your website and noticed you have a design service. do you have  a style/design you recommend?
i see a lot of passive solar designs out there, but not many that really do the trick for me. they are either to conventional or completely ridiculous looking. 
style wise, i am leaning towards a design by habitat post and beam in deerfield mass. LINK the passive solar 1 and 2 is the direction i am leaning towards, with maybe only a loft instead of full upstairs.
problem is, i want to build myself, but not from a $90,000+ kit!
are sips a stand alone building option, or must they be used in a structural shell system like a post and beam?

thats a good question. i have not seen much for this type of application, but conventional verticle windows have lots of options.
  this may take some doing to make an effective shade for. easy enough to utilize every night during the winter, and also serve the purpose in the summer. this is why these forums are so helpful. because something like this that might otherwise be taken for granted until the project is done, can get the wheels turning so your not standing there scratching your head in january wondering why you thought in the begining it was a finishing touch and not part of the function. 
i think a scale version of one's idea's can give a better vision of how everything will come together. sounds like a winter project coming on.
thanks slenzen

Not really. Due my experience with my current house(accidental passive solar), I am focusing my efforts on active solar. And, be sure to super insulate.


Design what you like, and SIPS would be an excellent choice for your building material. They are structural, no substructure required. And, yes, you could erect them yourself.

Good Luck!

Ooopps, double post %^).

intransit, I am looking at using a more commercial type of aluminum commercial store front window wall for my south facing home because it'll be a real modern minimalist home. I'll prob use a combo of aluminum louvers or overhangs, window film, and some sort of insulative shades to keep in the night time heat in the winter.

panelcrafters, would you mind sharing your experience with 'accidental passive solar' and your choice for active? i am still open to any and all considerations.


slenzen, i too have thought about commercial store front glass. i have decided not to worry about shading (only venting) in the summer. because it is an isolated collector, i think i will be ok. if not, what the heck, it will be summer at that point so a solution will be easy enough. my intent is to heat my water during the summer with this contraption. effective insulation during the winter poses more of a challenge than i have anticipated.

Basically, it boils down to lots of South facing windows(for the view), the intensity of the Sun at 8,900' and lots of cloudless days. However, that created the perfect solar oven. In the 90's inside during the winter. Not very comfortable.

So, it became obvious that your 'collection area' should not be a living area. That's why I'm sold on active solar and super insulating. With a storage tank full of hot water, you can set the temperature to your liking w/o living in an oven. It's just that simple.

Good passive solar design really isn't that difficult. Check out http://www.ourcoolhouse.com
I designed and built myself a very similar house but with a basement. Absolutely love it.

Passive houses do have a temperature swing, but it's not a real problem. During typical winter weather, my house is 69F in the evenings, 65 in the morning. You'd be amazed how comfortable 65 is with good windows and superinsulated (SIP) walls. We never turn on the heat until it gets down to 63F inside.

The reason you want to build passive solar for new construction is that it is almost free. To pay someone to install an equivalent active system would be almost $20k. It's the only choice for retrofit, however.

Panelcrafters, There is a very well designed house in CO that uses the whole basement as a passive collector:
http://strike.colorado.edu/~sjg/land/building_seminar.pdf

Direct gain has been shown time and again to be the most cost effective, however.

What if you never had to 'turn on the heat'?

What are people paying for GeoThermal systems? And, they are electricity hogs. What if I spent that $20k, and never had to pay a penny for heat for the life of the structure?

I've seen the project. And, also notice the amount of living area given up for heat collection. They did a very good job, and they also realized that the 'Heat Collection' area would not be suitable for most indoor activities. Cost Effective? How much do you think that the 'Collection Area' cost to build?

I guess that my point is that there is more than one way to provide free, or nearly free heat for a house. I just prefer that the indoor temps are human controlled not decided by the weather.

Bingo! ORNL recommends exposed thermal mass. Makes sense doesn't it?

yeah, it makes sense in hindsight, but i like other points of view, both positive and negative.
helps work out the bugs. :-)
 
the cost of my colection area will be under $5000 with glass, and near maintenance free. no moving parts and uneffected by power outage's. thats a lifetime of free heat after the return on invesment kicks in.
an active solar home is still at the mercy of the weather in prolonged outages. if you wanted to go totaly off grid, thats quite an increase in power consumption. with the correct thermal syphon design, you can move the air quite efficiently. 
actually, for an extra $1000 on top of the $20,000 investment, a whisper windmill would probably be more than adequate. with your location, you must have a tremendous amount of wind in the winter.

they both have pros and cons, thats for sure. 
maybe a hybrid 50/50 approach would be something to consider?

That's why you design your storage(Water, Rock or Salt) to last as long as you estimate that you could be w/o sunshine. And that is definitely location dependent. I am lucky enough to live in an area that gets lots of sunshine and has a high solar isolation value.

Yes, there is wind, but a 100-200w PV panel would easily power the pump for the collector to storage loop.

Possibly. But in my location, I'm going to go with(and recommend) a Super Insulated structure and active solar. I will have a direct vent pellet stove for backup %^).

i will look a little closer at active solar. do you have a source for reference to link to?

salt? you mean like what water softeners or whatever use?

i have a direct vent pellet stove and it does an awesome job of heating our log home. how would they run on solar? between the igniter, auger and fans, they seem like they must consume a fair amount of power. that same question goes for an outdoor woodstove. pellets were fairly economical when they first came out, but they are getting pretty high around here.

For storage info check this out: Purdue University - Solar Energy Heat Storage. It explains Glauber's salt. But I will be sticking with water for storage!

For a working example of a Net Zero home(using active solar for heating) see: Solar Harvest. Look at the Brochures and Technical Documents.

The Pellet stove would just be a backup source of heat, with no connection to Solar(Unless you are using PV to power it!)

thanks panelcrafters.

that got me looking a little further and i came upon this link. LINK, it compares both active and passive solar design pros and cons.
i like the fact that active solar can be retrofitted and installed in incremental steps, not one huge cash investment all at once. kind of like adding more pv panels as they are needed.

I think you need to think about the entire design. One should not end up with an oven when building passively. There are many books out there that will help in deciding how much glazing you can get along with. Myself, we are building in NM with adobe. Using the walls and concrete flooring for the heatsinks, solar supported radiant floor heating as backup. Still in the planning stages, but this is the direction.

Bill