This comment is clearly too late for the last poster...but I thought I'd add it for anyone else who, like myself, stumbles across this thread, searching for info on bumph vs flannel...
I can't speak for bumph, having never used it--but I used to live in a scary drafty loft in Boston--where the single outside facing wall was brick and badly in need of repointing...and the two windows were very drafty. I covered the windows with plastic, after first resealing and winterizing them as much as possible--and there was STILL so much draft left, that it would blow out candles. I even covered that entire WALL with plastic, and then fabric (to make it look like wallpaper--it was a rental)--and my heating bills were STILL over $300 a month (year, 2007, total footage in loft, 850 sq ft)--and it was never, ever warm. (The draft was so bad when I was covering the walls with plastic--that after fastening the top of the plastic--the bottom billowed out 3 ft from the wall!!!)
So I decided to take a page from drafty old castles...knowing they used tapestries, to cut down on drafts--and I made heavy, floor to ceiling, pinch pleated curtains, out of an upholstery weight chenille (with a really soft hand), and lined them with a heavy flannel interlining and a napped sateen...and for good measure, I puddled the heck out of the bottoms of the curtains.
The end result was HEAVY curtains: 0ver 40 pounds each! (11 ft ceilings)--but within an hour of putting them up, I had a toasty warm loft...which stayed evenly heated all day and all night--and my winter heating bills dropped to a little over $100 a month.
As an unexpected bonus, the curtains were SUMPTUOUS looking--big, and fat, with AMAZING drape. They looked like a million bucks...and yet, making them was a piece of cake. (This, from someone who doesn't sew, and can't measure worth darn. No, for reals. I can't tell you how it happened, but one curtain wound up being like 9" longer than the rest. Didn't matter though, since they all puddled like mad. I also can't be bothered with basting, or anything like that--I just stuck fabric together with pins, and started sewing. The hardest part was the header, with the pinch pleating tape--since I was sewing through like six layers of heavy fabric AND the pleating tape, on a non-industrial sewing machine. ;))
The bottom line is--my heating bills dropped $200 a month with the addition of my heavy drapes...my indoor temperatures were much more even...the drapes definitely acted as blackout drapes and sound deadening (although those weren't objectives of mine)--AND they looked much more expensive than any off the rack curtains would ever look.
Heavy flannel lining and a napped sateen lining, combined with a heavy fabric should be plenty for all but the very coldest spots in the US. (Depending, of course, on how you hang them!)
Q