One thing I've been trying to do, is to make better use of natural heating sources in the house. One very obvious place for this, is keeping warm in bed.
Now blankets are an obvious answer here, but traditional blankets aren't as effective as you might expect, and actually let a lot of body heat escape. Furthermore, the bed (mattress, etc) itself can actually get cold, and quite simply pull body heat away from you. So I've been looking for ways to better give that "toasty feel" in bed, without resorting to a lot of room heating and/or "electric blankets" (which not only use electricity, but also directly subject your body to their magnetic fields). And it's surprisingly hard to find technologies to do this very simple task.
However, two strategies I've found (which work well together) are to use "Reflectix" ( a reflective "isolation", that looks like silver coated bouble-wrap of all things) between the mattress and the box-springs, and then to use "emergency thermal blankets" on the top of the bed. Both of these strategies work, by effectively reflecting your own body heat back to you, vs having that heat escape into the room. While neither approachwill make the bed warm when you first get in it, either (or both) approaches (and they can be used together very effectively) will cause a gradual warming effect, that is very similar to having an electric blanket turned on (low), except it uses zero electricity, and doesn't subject your body to the (sometimes slightly annoying) electrical/magnetic fields of a real electric blanket. Instead you just get the warmth without any of the baggage that otherwise would come with it.
In the case of the Reflectix (silver bouble-wrap type "isolation"), you can pick up rolls of the stuff for a few dollars at many hardware stores (which is where I picked up my last roles of the stuff). Just cut it to size, and tape smaller pieces together (if your bed is bigger than what you can cut from your role), and just put it as a "pad" between your box-springs and your mattress. By doing it this way, someone won't even notice that they are sleeping on a pad made out of insulation. And anyone seeing the bed won't see anything different (as the mattress will cover up any evidence you have anything different. But the mattress will just feel a little "warmer" when you lay on it, as body heat that would otherwise escape through the bed will be reflected back at you. That does a great job of saving against heat loss down through the bed (1/2 of the problem).
However, for heat loss up through the covers, blankets have been the traditional approach. And while they help, traditional blankets still let a lot of body heat escape. Which is why I was looking for a better approach in this area. Now, there are those "emergency thermal blankets" (basically reflective mylar) that you can get from various places, but it seems like virtually all of them are made so flimsy, they should tear almost immediately (i.e. clearly NOT made to last). Which is why I've been looking around for an alternative that provides the advantages (for body heat retention), with some ability to last. And I finally found a product (so far, I've only found ONE) that seems to provide the heat reflective advantages of those "emergency thermal blankets" with a design that might actually hold up to some use. It's the so-called "Liberty Mountain Thermal Emergency Blanket" ( http://www.libertymountain.com/catal...product&id=550 ) and seems to be a cross between a tarp (for strength) and a traditional "emergency blanket" (for heat retention). They are a little more expensive than traditional "emergency blankets" (about $13 + shipping each), and I could really go with a better tarp color (the red is a bit tacky). However, they are available from multiple retailers (I picked up 3 of them from: http://outdoorcooking.com/catalog/it...l+Blanket.html ), and they do seem to work as expected. I found that the combo of tarp and emergency blanket is very effective at both providing strength and retaining body heat. In our case, since they don't come in "king size", I just put two of them on our king sized bed, over our traditional blanket (one as a "foot warmer" of sorts, and a 2nd "thermal blanket" for keeping the upper body warm). So far, we've only used it for one night, but the extra retained warmth (over the warmth already retained due to the Reflectix under our mattress) was very noticeable and appreciated). So at this point, the experiment seems like a success. In fact, if the other family members like the results (after trying it out for themselves), we might get some more of these for the other beds in the house.
Aerogel is the new thing to watch out for. It was an original idea from the 30's that didn't really get into development until finally recently. Aspen Aerogels is the company that is going to be the company that markets the product. Basically, it's an insulator that is almost all air. It's refered to as "liquid smoke" because that's how the fibers look.
Since it's mostly air, it has almost no weight. The applications are very limited. Coats made from it are around $500 right now, but the users of them have complained...they have complained that they are hot.
I ran into some shoe insoles that I found in a Christmas outdoor catalog that claimed to have Aspen Aerogel. I did some research, and it was the same Aspen Aerogel. I found the same insoles at Walmart for $11, about half price. I've been using them for about three weeks right now, and they leave my traditionally cold feet very warm.
Expect more Aerogel stuff to come...building insulation, automotive applications, clothing, etc.
Only problem is the thermal blankets tend to trap moisture so you can end up with damp blankets and sheets and work up a good sweat if you are too warm. I have some pieces of worn out thermal blanket from Harbor Freight at $3 each that are the mylar 0.0005 thick and it is amazing how much warmer you feel with that over all the blankets or in between them. I keep one in the car during the winter in case of emergencies. WHen folded up they fit in the palm of my hand and unfold to about 4x7 feet.
JanGeo makes a great point. One key factor in keeping warm (as any winter sports person will confirm) is keeping dry. You can be wearing all the layers in the world, but if they trap the moisture from your sweat, then you will end up cold. I personally use a thick (very thick and full compared to anything you can get in the states) blanket made of acrylic as my first layer, and then I keep a down comforter at my waist down. Works really well, even with my room temperature hovering at around 10 C.
If I were to use a thermal blanket... which I have considered, it would be for underneath me.
Yeah definately want something below you - I have a floor that is always 50 degrees when the room is 70 - insulated floor in the basement ceiling but it is cold down there so I put the thermal blanket pieces under my 8" thick sleeping pad. When I use the thermal blanket on top it actually forms condensation on the inside.
The window quilts in our house use a product that I belive is under the name Warm Windows, and it is basicly a layer of cloth, synthetic quilt batting, space blanket, quilt batting, cloth, these work great on windows, and could work for what you are talking about, but it must be noted that they might drive you crazy, as when you move them they sound like a plastic bag rustling, this might wake some people.