I have a 200 year old house; in the master bedroom there is a staircase up to a tiny loft above the master. I guess it was used back in the day as a nursery or some such. But you can't stand up. Anyway, I don't want to seal if off. Currently the window has a storm window so that is good. In the 50's they clad it with celotex and put 4" of rockwool behind that. I am thinking of pulling that out and adding spray foam. Cold air leaks through the old door up the the loft.
Our old house had a stairway up to the attic like that but the door was in the hallway on the other side of the master bedroom. The attic floor was exposed on all four sides of the stair case and we were able to make a foam board cover for the stairway like many do for those fold down staircases.
I want to keep it easy storage. Also there is more than one run of metal conduit routed out and around the top plate outside the frame of the second shot that would make it very difficult to get a good seal. The area is on the warm side but under insulated.
If you are just trying to stop heat from escaping into the attic I think this might be the cheapest method putting an insulation barrier. You put a couple 2x2" on both sides of the stairwell (colored in brown), and use the 2x2s to support rigid foam boards (color in blue). If you wish to access the attic you can simply remove the foam boards closest to the steps.
I agree with Lumber-Jack. By putting the barrier at the same level as your attic insulation, you're reducing the amount of surface area that is exposed to the cold air in unheated spaces. I'm getting ready to do the same thing in my walkup attic. The difference is that I'm going to use PL-300 to glue the foam board to a couple of pieces of underlayment to reduce wear on the foam board (opening and closing) and I'm going to just use a 3/4" strip around the edges for it to rest on. Going to use foam weatherstripping around the edges to create an airtight seal. I imagine it will be a little more cumbersome to move than individual pieces, but we don't access our attic often, so the added effort will be worth it. I'm still a couple of weeks away from attacking this project but will post pics when I do it.
The block off would be a nice idea but there is the problem that you are then putting that area on the cold side and there is no insulation between that space and my master bedroom which is the farthest from the stove by the way. I guess I could pull up part of the tung and groove flooring up there and blow in cellulose insulation and put it on the cold side.
Ok, so it sounds like you already have some insulation up in that attic, but does it have a vapor barrier? If not, that might be all that you'll find necessary to stop the draft. We have an upstairs area with the same sort of sloping ceiling that drops down to a vertical 4 ft wall, except that the ceiling is higher and my kids bedrooms are upstairs. The rafters had R20 insulation, and we added 2" of foam insulation on top of the roof when we redid the roof. However there was no vapor barrier inside and there was always a cold draft getting through. We eventually added a vapor barrier over the existing walls and ceiling and sheeted over that with 1" foam board and finished it with acrylic stucco. Boy what a difference! The 1" foam board doesn't really add much R value, but the vapor barrier stopped all the air leakage For less than $100 buck you could probably staple a nice thick gauge poly over that entire attic area, and tuck tape all the seems, it might be all you need, but you might want to throw some sort of sheeting over that to better support the poly so it doesn't sag and avoid using too many staples, thus creating too many holes in the poly.
You might get away with attaching some foam board to the back of the door and firring out the back side of the door frame and attaching a weather stripping that would contact the foam when the door closes. A garage door type weather stripping to span between the frame/foam backed door:
That is very similar to what I did for the new pump house I built by my pond that provides irrigation water to the yard and also now serves two livestock waterers year round. It is partly built into a hillside with a concrete pad and 3 layers of block and then framed with fiberglass insulation and 1" of blue rigid foam insulation. The seams are filled with expanding foam from a can. I put a 2' electric baseboard heater in there but it never seems to fall much under 50 inside.
Vapor barrier? Ha 200 year old house here remember. The last major upgrade to the old part of the house was 1952. Interestingly I have replaced siding in a few spots on the house and beneath that is tar impregnated Celotex sheathing and behind that the wall cavities are full of state of the art for the day rock wool insulation. The old part of the house is hand hewn post and beam construction. So the walls are not a problem and the main section of attic has had significant additions to insulation. But the insulation above the master is behind the white painted Celotex in the photo of the loft space. Then the roof is plank sheathed with gaps and a slate roof.
