I found this info on a website. I hope it answers your question.

"Most people are unaware that, according to the US Department of Energy about 25-30% of their homes energy is lost through their windows", Lee added. "Installing custom drapes with a heavy-weight (6oz) cotton flannel interlining can reduce the loss of heat by 25% in the winter and also reduce heat gain in the summer by up to 33%" Lee said. When choosing an interlining material you should use a 100% cotton flannel material which will provide great insulation plus an added sound barrier.

For those who live in a frigid climate, you may also want to consider using an English Bump Interlining which is about twice the thickness of flannel interlining. As the name implys, English Bump is a tradtional material that was used in the cold damp winters of England to keep homes warm. "You really have to know what your doing with Bump", said Lee, "It is very heavy and difficult to properly sew but the results are amazing, it's like wrapping a blanket around your house".

The Bump interlining sounds like a great idea! I'm an avid sewer and have never heard of it. We have cold winters too. Thanks!

Here is a link that might be useful: Drapery Lining Guide

Great info! Thank you so much!!
Hmmm I wonder if 2 layers of flannel would be like 1 bump cloth. Seems like it would be easier to work with. The bump cloth I sampled was really heavy!

I think 2 layers of flannel would work. I would just look for the 6 oz that they suggested.

Also, shop around on the internet for good pricing. It definitely varies!

I've seen your other posts about your dining room. So pretty!

I always love to see it when someone sews!

Here's a link to one fabric website

Here is a link that might be useful: Drapery Lining

Have you found a source for bump? I've looked off and on and gave up some time ago, but I have a large project that I'd like to begin soon. I'm dreading restarting the search.

I have several wholesale resource for drapery supplies. Try this:

Here is a link that might be useful: Read Window

Dawnp: Thanks for the compliment! And the link. I have some great sources for interlinings, such as the one I linked to above. I found a 7oz flannel interlining that may fit the bill. I'm wondering if I'm going overboard with the bump or 2 layers of flannel? I know bump is 12oz. I need a full bolt of it. I am also an avid sewer but don't have any "hands-on" experience with bump cloth. I just read somewhere on another sewing forum that some are using light weight polar fleece as interlining. I'm going to research that option a little more before I make any big purchase.

Here is a link that might be useful: Another source for interlining

I can't see why the polar fleece wouldn't work! I know how warm my fleece PJ's are. Good idea. Is it wide enough? It would be a real pain to have to piece it.

What room are you making draperies for?

Thanks for the links!

You're welcome! The fleece is about 60"w. My mom has many bolts in storage that I may be able check out this weekend. It would be so great if I found something that worked!
I make all of my drapes. We've been in this house for almost 4 years now & this is the first winter that seemed really brutal with the drafts. I want to interline ALL of my drapes now. I'll tackle the DR first since those are the ones that are unfinished still.

I've never used interlined drapes until recently, and they're amazing! I knew it would help more than just a lining layer, but WOW. The difference in drafts and noise is really noticable.

I'm still not 100% pleased with my new guest room drapes...the side seams will not lay flat and straight, but the color, price, and interlining make them worth keeping.

I've never sewn drapes with any kind of interlining, but please let us know what you choose, and what it was like to sew with. I'd think that the fleece would be a nice alternative.

franksmom: I will let you all know what I end up with. Just curious, do you know what kind of fabric is the interlining in your guest room drapes?
I can think of a number of reasons why the side seams won't lay flat. Unfortunately if the fabric wasn't cut right to begin with, nothing will help but redoing them.

Hanes makes a classic napped lining which is a really nice lining that is essentially flannel on one side and sateen on the other. You can use it alone or the Hanes site recommends using it with an interling. The flannel side "grabs" the interlining (I assume flannel) and is easier to sew. That might be easier and cheaper than tracking down bump.

Yes, I am familiar with the napped lining. But all of my drapes are already lined. I plan on adding the interlining to my existing lined panels. Just torn on if I should use flannel, bump, or fleece. :)

Thanks! I didn't have those sources before.

I checked that interling last night, and it looks like a thin fleece. Huh! It's just serged at the bottom.

I've washed and pressed those drapes twice, added weights, and even redid some of the side seams. I could totally redo all of the side seams, but I'm worried that it will leave marks from the original stitching. Or I could just shut the door...

Was wondering what OP chose . . .
I'm fixing up a drafty 73"w window with a lined and interlined hobbled Roman shade and lined drapery panels in 100% polyester (probably Romo Sirente). I've heard a lot about English bump cloth, but I'm a little afraid that the thickly interlined panels will be too heavy, and cover the window area too much. I guess tiebacks would help with that, but I'm wonder if the bump cloth will be "overkill" and I should just use flannel. Will be very grateful for any thoughts, recommendations.

I first used bump to interline curtains 32 years ago. At that time, I brought it back from a trip to London - not available in my part of the country and no internet.

Fast forward, and it is now readily available online, even if not locally. The last few times I've bought it, I've gotten it from Angel's <http://draperylining.com>;. They have a huge selection, great prices and couldn't be easier or nicer to work with.

@Anglophilia--thanks for the comment about Angel's! I was just checking out their site, about an hour ago, and wondering if I wanted to bother signing up to download their prices: thanks to you, I just did--and you're right! Their prices are excellent!!!

I am pleased to see this thread active again - great info here!

I am toying with the idea of making some lined and interlined drapes, using a high quality muslin fabric for the front. I like the natural look and color of the muslin.

Does anyone know if it will work with a 6 oz flannel interlining and the napped sateen lining, or will I have trouble with the weight differences of the fabric, such that they would not hang well? (No pleats - just rings with clips on a rod.)

Can someone suggest to me a good insulated magnetic curtain pattern to fit in two open doorways.   I want to DIY, and save money.  Perhaps buy from Op shops,  but I cannot decide whether to use a doona insert, as it's padded and very insulated then back it with preloved curtains to match my living room. Or to purchase flannel or Bumpf.  Please assist, as I want to do this before winter ends.  An easy peasy and quick weekend sewing job suggestion would be great from someone.   Please!  Ann from Qld Australia.