I built my own using a 4 X 8 sheet of 1 inch foam insulation. I found a set of plans to do this. Here is a link which has a similar plan. You can use even thicker foam insulation if you want a higher R-value. http://www.jacksonemc.com/Do-it-Yourself-Energy-Projects.43.0.html You may have to modify it a bit to fit your stairs. It was not very difficult to build. I put down weather stripping on the wooden frame. The box sits on the weather stripping which makes a tight seal. I even used the left over pieces on the sides in order to give it extra strength and weight. When I go into the attic I simply push the box so that it stands up on one of the long sides. To close I just lower the box into position onto the weather stripping. For about $25 you can build a custom fit cover. I think the key is the tight fit to stop air infiltration. I am not sure how good a job the store bought versions will do.

I'm unclear on the flooring myself - I guess there are beams going the opposite direction of the joists. Ok - I can picture it. What about your r-19 grouped with some foam? I am imaging 1 inch of foam on the plaster/drywall sprayed in to seal it. It also adds some R-value and thickness. Then if you wanted some more r-value, you could do 1 inch rigid foam (or 2 inches) on top of the joists. This would help with thermal coupling of the joists. Getting to a magical R-value is not the only concern. Sealing properly is worth a lot. That being said, you would be at r-27. Spray foam is about a dollar per sq foot at an inch thickness. So you are looking at $1500 - but you might use less because of the joists. The rigid foam is about 1/3 of that so you would need $500 for that. Not cheap but 30% tax credit would count. I think you would be fine from a vapor barrier standpoint. 1 inch of rigid foam does not count as a barrier but 3 inches would. I would want some independent confirmation on the vapor barrier question.

I need the input from some of you insulation gurus to know how to proceed with this house. Originally a ranch, it is now conisdered a cape, since part of the attic was bumped out to form two extra bedrooms and a bath. A door in the hallway leads to the unfinished part of the attic. There is ample room to stand up in most of it, and there is a crawl space over the bedroom wing. There are two air handlers (system is hydronic forced air), one in the standup part, and one in the crawl space. The old insulation, rock wool, is mostly exposed and dirty at this point, and dried out and flaking. I know we get some of the filaments coming down through high hat openings in the bathrooms, and I'm convinced, althoughthe HVAc company says "no", that a good bit of it is getting into the duct work, which explains a very dusty house, and problems breathing since we moved here three years ago. W had major ice dam issues for two years, owing to the heat in the attic,and a warm roof. We just had a second roofing job done (yes, we have done two), now bringing the ice shield down over the eaves onto the soffits, to prevent water backup from the gutters as the ice melted. This has also, I think, warmed up the attic even more. The HVAC company does not want to see the temps dropped up there, due to the equipment. I had two insulation guys here, one of whom wants to rip out everything accessible, including the insulation in the crawl space, which is stuffed between the beams . There is no actual floor in that section. I worry about the electrical and plumbing lines, and damage which might be done while they rip out and replace. They also want to insulate the ceiling, effectively making the attic part of the living space - which would aso, they say, keep the warm air from going up to the roof, and protect the equipment. Second insulation guy says it is imppossible to rip out the old insulation on the floor of the crawl space ( perhaps it is just too much work??) and wants to staple new insulation over it, but remove and replace what is accessible in the main part of the attic. He has said "no" to insulating the roof line, stating that in the summer it would be hotter than Hell!! Someone else told me it could cause the roof to rot (vapor barrier?). So now I have two different takes on this, but my major concern is getting rid of the loose stuff which is permeating the house, as much as possible, and possibly keeping the air a little cleaner. Another aspect of this might be keeping the warm air on the first floor from going up to the second floor, costing a lot more to heat the house. I just don't know which of these guys makes more sense, and whether one or the other has a valid argument. Can anyone help with this??? Thanks!

Moisture issues are very climate-specific. You don't give enough information for any meaningful advice. Where I live, for example, it is generally advisable to seal up the attic and spray foam insulate the underside of the roof.