I'm weighing here only because Nathan's suggestion MIGHT work but only if you carefully consider a number of things. He is often the one to suggest low tech solutions (of which there is nothing wrong) BUT....any solution high OR low tech is a balance of a number of factors. "Cutting a bigger hole" only has a chance of working IF you also incorporate something to allow "make up air" to enter the gh through low placed intakes (shutters or vents) AND the "bigger hole" has some kind of heat sensitive device to get it to open when you need it to open. Of course, you'd also need to incorporate intakes for a "higher tech" exhaust fan as well. You should also IMHO consider what you plan to put in there. I have orchids in my gh (moderate tech at this point..moving toward higher tech)...I'm only an orchid newbie but while many can tolerate mid 90's, they sure don't thrive above the mid 80's. Finally, I'd also suggest you seriously consider(as in honest with yourself - no one else will know) how much attention you REALLY will pay to the gh day after day after day. Obviously the lowest tech solution is to go out each day (as needed) and open the door and manually open the roof vents and manually check the inside temp and then, when the sun lowers (or sets) and go back out and manually close the door and vents etc. Forget to open it up just one day when it's bright out and your orchids are steam wilted greens. Next step up would be non-electric powered vent opening devices, next above that and you are into thermostat controlled shutters and vents fans, misting systems etc. BTW, NONE of these approaches are bullet proof. I go off to work each day confident that the shutters will respond to the thermostat and the vent fan will kick in 4 degrees later. But if someone takes out a power pole and the gh sits for as little as an hour with no electricity in the mid day sun, well there is very good chane that I've got wilted greens for dinner too.

I'm curious to see what ventilation strategy for a home with no a/c, Sorry I can't be of help, we put a supply grill for a/c in closets & baths here. as far as the skylight goes there are good ones out there Vellux (I believe) has low e coatings which will filter out uv and heat and add light. the negative is that you are cutting a hole in your roof so proper install and flashing are a must. the install is the biggest problem I encounter with my clients and the installer of the skylight. even with a top notch install, it only delays the not if it will leak, but when. I would give this some thought... for less cost/worry than the skylight you could install more lights.There are qiute a few options that are energy efficient and will work well. although I'm not a fan of recessed lights..if you look at that as an option make sure that you get ICAT cans insulation contact air tight instead of the standard IC light. IC will allow hot air from attic and reduce the value of the insulation surrounding it in the attic. Buy ICAT and put cfl's if you go that route, best of luck.

I have one vent that overlaps a fan, and the room gets just as cool or warm as the others. It's a non-issue. The fan, if it's on, will just stir up the incoming air a bit sooner. For maximum comfort, if it's possible, you want the vents (outlets) near the exterior (walls) and the air return close to the center/interior). But it is often drifen by what is possible, not what is ideal.

Thanks for the advice. We had to fix up our previous house, a 1950 brick georgian, so we know these types of issues are par for the course (even if we had secretly hoped that this house was a bit better off than the last one). We used this forum a lot when working on the old place and always received good advice, so this seemed like a logical place to begin our research. You are right that natural gas is not an option- something we overlooked, due to the fact that other houses close by do have gas service (our street may be the one of the few in the area that does not have service). Insulation in attic will definitely occur. I intend to bring it up to R-50, if it is not already there (hard to tell with fiberglass on top of what appears to be cellulose). My estimate above was intended to be conservative, based on not knowing the R-value of the cellulose. There is definitely R-30 on top of that, and so the attic is fairly well insulated except for the area underneath the floor, for which we will need to have insulation blown in. We will sit tight on the windows. It is likely the most expensive option anyway, and the advice has been consistent that we are unlikely to get a high enough ROI to make it worth our while. Electric supply has been updated. Would it just be the basement overhead areas that need insulated? I ask because if walls would also be included, I think we would be precluded from going that route, at least in the traditional sense. Our walls "weep" when the temperature outside is dramatically different than what is inside. We just noticed this interesting phenomenon and apparently this is not uncommon for old stone foundation houses. Consequently, I am reluctant to put any insulation against an exterior wall due to mold concerns. As for the attic, we have vents along the peak of the roof. The fans are mounted to two windows in the attic. It seems as though they were intended to serve both roles (pure ventilation of attic and whole house). Given the recent weather I did not necessarily notice a big difference between having the fans on or off, but they did pull a lot of air. We have already had in two HVAC contractors to look at the ducts as part of an estimate to put in a heat pump to supplement our oil heat. Their take is that the ducts are in fairly good condition and sized correctly. When asked about insulating, their response was that it certainly would help, but that the costs may outweigh the intended benefits. Ballpark, do you have any idea how much it would cost to insulate the ducts(per foot of duct)? Finally, did you have any experience with shooting insulation into plaster walls. I suspect we have limited space to work with behind the wall, but any insulation is better than none. Many thanks again for the advice.