Passive solar - novice questions

We're in the market for a house (in the Denver metro area), and have just been shown a passive solar house. We have absolutely no experience with passive solar, but are by no means ruling it out. Actually, it sounds pretty appealing considering the possible energy bill savings.
Case in point, the house we've been shown is a:
- 4-bedroom ranch facing south (great room, kitchen/breakfast nook, master suite are along the long south-facing side), - there's a little 3-ft-wide sun "room/compartment/buffer zone" (not sure about the terminology here :) 'fronting' the great room; it has floor-to-ceiling glass. Then, there are two _fairly small_ windows between that and the great room, plus a door that you can open to let the warm air in from the sun room to the house. - the other 3 bedrooms, 2 baths, and mud room are along the north and west sides. No windows on the north side. - the attached garage is by the east side of the house.
Pretty much a typical passive solar design.
I've done some reading about passive solar and one thing I've learned is that how good a particular passive solar house is depends on the quality of the design, quality of materials used, and maybe some other things, too. But, being no expert, and w/o having to live in the house for a full year, how do I decide how energy efficient the house is?
Some other questions/concerns: - How do I know if the house won't be overheating in summer, and if that can't be controlled with the swamp cooler that the house has? - As I mentioned, no windows on the North side, which is what you'd expect with passive solar. But the house has a pretty decent backyard with a patio, and it backs out to open space with mountain views. So I'm not sure how we'd feel about not being able to look out the window into the backyard... I guess we'd have to find out, and if we don't like it, add a (small) window in the back :)
We'll appreciate any helpful feedback.
Regards

Is the seller unable or unwilling to show you a couple of years' worth of heat/power bills? If available, they should tell the tale pretty clearly, I'd expect.
Gordon Richmond

I lived in a passive solar house in the NC mountains for two years and it was great. We had a small propane heater for about 1300sqft and didn't even use it that much unless it was real cloudy, even in belwo zero temps. The design of the house(orientation, floorplan, materials) will make a huge difference in making passive solar effective. If the windows aren't right or the insulation isn't right, there is really not going to be much benefit. After the windows and the insulation, probably the next most important factor would be the thermal mass inside the house(we had brick flooring) to hold the heat though the night.
It sounds like this house is on the right track though. Good Luck

wrote:

- there's a little 3-ft-wide sun "room/compartment/buffer zone" (not sure about the terminology here :)

This may be a "sunspace." Is it 3' deep and the width of the great room?

it has floor-to-ceiling glass. Then, there are two _fairly small_ windows between that and the great room, plus a door that you can open to let the warm air in from the sun room to the house.

Sounds good, esp if the sunspace has very little thermal mass. You might improve performance by covering a masonry floor with a dark carpet and a masonry wall with a dark curtain.

... how do I decide how energy efficient the house is?

Ask for fuel bills. Do some calculations.

- How do I know if the house won't be overheating in summer...

Check for an overhang to shade the south glass from high summer sun, and sunspace venting to the outdoors, and maybe an outdoor curtain.
Nick

This may be a "sunspace." Is it 3' deep and the width of the great room?

Yes.

... how do I decide how energy efficient the house is?
Ask for fuel bills. Do some calculations.

I forgot to mention: my agent found some info about the energy bills (lowest gas bill: $10/mo, lowest electric: $23/mo, ave gas+electric: $106/mo). Problem is, it looks like no one has lived in the house at least for the past few months, so these figures might be artificially low.
------------------------------ Another thing: The hose has a backup PROPANE heating system. How good is propane heating compared to 'regular' natural gas (methane?) Pros and cons?

bubbabubbs@yahoo.com wrote:

Another thing: The hose has a backup PROPANE heating system. How good is propane heating compared to 'regular' natural gas (methane?) Pros and cons?

It works just the same (but it's more expensive), burners can usually just be rejetted to switch from one to the other. Usually homes only use propane if they can't _get_ natural gas, though if it's a true backup, and is rarely used, perhaps propane works out cheaper than having a minimum NG monthly bill. -- derek

... how do I decide how energy efficient the house is?
Ask for fuel bills. Do some calculations.
I forgot to mention: my agent found some info about the energy bills (lowest gas bill: $10/mo, lowest electric: $23/mo, ave gas+electric: $106/mo). Problem is, it looks like no one has lived in the house at least for the past few months, so these figures might be artificially low.

Check electric bills and fuel bills provided by the utility companies involved for extended period. Honest seller will allow access to this info.