Cold Frames- Seeking advice

So I have a few small cold frames that my housemate built. I am wondering if any of you could relay effective methods of prepping the ground for them in order to create a hotbed effect, without the use of electricity. (eg. manure)

I do plan to sink the frame into the ground a bit,  and to bank some earth around the sides of the frames but from there I would purely be guessing as to how to optimize the situation in order to create heat. Any suggestions are welcome.

I just had a half-brained idea about using old gutters to line the edges of the frame, or the edges of the earth bank, and filling the gutters with water which I understand has a greater R value than earth. What do you think...

If I remember the stories correctly, my grandfather used to dig a trench, put in raw horse manure, then fill the trench, and plant above... he used it for tomato starts.  I don't know how much or how deep.  I was having some ambitions around this... maybe next year. 

http://www.holon.se/garden/howto/hotbed_en.shtml

if you can tilt them slightly to the south, not sure what the angle is in your area..but enough to capture more sunlight..also you can line the back wall of the frame with either reflective material that will reflect onto the plants or with black to soak up heat..

you can basically build a compost pile in the soil under your cold frame..in the past people made HOT frames with horse manure buried in the ground as it heats up a lot when it decomposes..but you gotta make sure it is deep enough to not burn the roots of your plants

I might trench down a bit, put in a short wall built of straw, then scatter straw, manure, and the soil from the trench. That way, the soil the plants are in is fairly well-insulated from the soil beneath, and even that has some insulation from the cold air outside. You'd have to make the straw wall sturdy enough to support the cold frame: depending on how big we're talking, it could be flakes broken from a bale, or whole bales of straw.

In the illustration, gray is the cold frame, light brown is soil, dark brown is manure, yellow is straw, black is the initial ground level.

Paul: I've been leaning towards that idea as well but have yet to track down specific measurements for the depth and I don't want to guess on this at the expense of the plants.

Brenda: The walls are short but tilting them southward sounds like a great idea. And there's a hydroponics store selling reflective wall coverings that I could use. There's also reflective insulation at home depot that may be worth a look, though its pretty expensive and you have to buy massive rolls of it.

Any idea how deep the compost pile should be for say...leeks or onions? their root depth is pretty shallow if I recall.

Joel: Thanks for the diagram. I do have some straw and hay bales I could use for this. Wouldn't it be more well insulated if the bed was sunk into the ground some, still keeping the same idea you've presented otherwise?