Semipro, thinking about this situation:
The house to which we hope to retire is in a place that gets some remarkable wind and weather in the winter. There is a sliding glass door on the back of that house, thankfully facing the one (1) wind break that we have on one (1) side of the house- not facing the back directly, on which we get prevailing winds.
When we first looked at the house, I eyed that sliding glass door with trepidation. I guess I automatically assumed that all sliding glass doors are leaky and transfer heat and cold.
Much to my surprise and delight, I cannot detect any air flow, nor even a lot of conduction of heat or cold, from that sliding glass door. Of course there is some conduction- if you touch the glass it is warm or cool, depending on the time of day, sun exposure, time of year- but it's not as dramatic as I thought it would be.
It's a new construction house built by a man who has lived in this geographic area for his entire life, as did generations before him. One of the things that convinced us to buy this house is that while it has many nice features (we like the floor plan, the finishing work on the trim, etc. is superb because it is so well done, this guy takes pride in his work) the bulk of the expense of the house was in meat and potatoes construction and materials rather than amenities, lipstick and mascara. We don't have miles of stone counter top but we do have good windows and doors. We don't have a jetted tub but we have sturdy, weather resistant finishes and materials. Etc.
So it shouldn't be a surprise that the sliding glass door isn't the leaky sieve of a sliding glass door like we had when I was growing up, but it did surprise me.
I noticed on your profile that you are in the process of renovating a "fixer upper." (BTDT x 2, still doing it, as a matter of fact, with the house in which we currently live in town, gotta love older houses- and we do!) Have you gotten to replacing that door yet? If so, is it sealed around the edges where the door fits into the side of the house?
In our first fixer upper, we had an ant issue that was not to be believed. We sprayed. We sprayed. We went under the house looking for rot. Couldn't find any. It took a couple of *years,* I kid you not, and some other problems, to figure out what was happening. When the house was constructed, proper flashing wasn't placed in between the band board and the back stoop, nor was flashing put between the band board and the deck on the back. Moisture ran into that space, rotted the band board (I think I have my terms right) and ants set up multi-generational condos. We ended up ripping the brick back stoop and the deck off of that house in the process of tracking down our ant problem. Once we got the rotted band board off of the house and replaced with new board, voila! No more ants- ever. I don't think we ever had another ant in that house.
Years later, when looking at real estate during another transaction, our realtor and I visited a beautiful home that was well-situated and nicely done, but I noticed immediately that the lot was heavily wooded and that the entire back of the property just seemed, damp. The deck was growing mold. The yard was growing moss. The brick foundation was growing moss. And a repair guy was there, removing the sliding glass doors (there were multiples) from the large open living/dining area to the deck. The view from the back of the house through those sliders was gorgeous but my older, more mature real estate eye just saw moisture. It was obvious that the repair guy was going to have to repair the floor in front of the sliding glass doors as well. It was at least wet- there was staining- and I'd bet there were other issues as well.
That house was built at about the same time as the house in which we had the band rot where ever another structure touched the back of the house.
Whoops. I would have bet a tidy sum of money that there was no flashing in between that deck and the band board of that house.
That's a little off topic but your leaky sliding door reminds me of that. Have you checked the seals around the door? Is there a chance that the leaky air could also be a problem with leaky water?
If the door itself is leaking air, maybe the most expedient thing to do is to replace it, and to make sure that the framing around it is dry, sound and appropriately sealed.
If the door is OK, perhaps a trip outside with a caulk gun could help the most.
Otherwise, if everything is dry, in good shape, and as sealed as it's going to get, DUDE, CURTAINS TO THE FLOOR. LET THEM PUDDLE IF NECESSARY. Look on the Pottery Barn web site. Puddling is an acceptable home fashion statement! Washable is the corollary to puddling, especially with dogs, see avatar.
<:3~
Medieval people were not fools. The whole concept of heavy, puddling draperies and wall tapestries hails back to medieval times and drafty castles. I'm serious- go look it up.