You and I are in nearly the same climate, so my experience may be of some use to you. I have found artificial protection of mature crops through winter - by putting plastic or cold frames over them - not very succesful. It generally results in their being attacked by aphids or other insects or fungal problems. Just letting cold-hardy crops take their chances with z6 winter is more productive - and a whole lot easier! About two winters out of three we're still eating fresh greens in februrary. Starting stuff out anew in early winter inside or outside in a hotbed and then transfered to a cold-frame generally works well. Stuff grown in cold-frames is usually a lot healthier then in a hot-house. Of course, lettuce in february doesn't happen in a cold-frame. I forget about lettuce for the cold six months of the year - never heard of the stuff. In June I eat it in quantities that might seem deranged to some folks. My primary green thru late winter and early spring is walking onion. Can't recommend it enough - completely cold-hardy, reliable, effortless perennial. With that plant you could abandon the grocery store without fear of scurvy, though by May you will be tired of it! But then, you don't have to eat it again until December. Anyway, my experience has been that effort expended to "baby" plants thru winter is largely wasted effort. Expand into the now little-used former reliables like walking onion, parsnip and other crops that can be left out, put up storage crops, and enjoy the luxury of greens in mild winters when they happen.....

Since you are planning on growing these items for the fall/winter 2008, I think you would be okay placing your coldframes on the asphalt, provided you have a way to ventilate them adequately, as the temperature can get real warm in a hurry in a coldframe when the sun is shining. Drainage shouldn't be a problem, as most cold frames have no bottom on them and I'm assuming your driveway has a bit of an incline on it. The carrots and beets will need some depth, so I suggest you design/build your cold frame with sides at least a foot high if not higher, to allow the vegetative growth of carrots/beets room to grow without touching the lid of the coldframe. Also, it sounds like you would want to grow everything in either deep pots or trays within the coldframe, since this is on asphalt. Remember that pots/trays dry out quite quickly, so you might want to implement some sort of drip irrigation solution so that you are not constantly watering your plants. I read Eliot's book several years ago and went whole hog on the winter gardening idea, in fact it led me to building a hoophouse or two to indulge my need to garden year round! Remember to consult the sowing timetables in his book, those are important if you want your veggies to be mature enough once the days start getting really short and actual plant grow stops. Good luck! - Jim

Thanks Flora: very kind of you.Indeed if we were closer I would take you up on your kind offer.I need lots of glass to cover though. Thanks Gardengal: Glass is not out of question as yet.I think that the poly or fiberglass is lighter and cost effective. Its going to be a big area so I want to keep most of the light without the UV. Just need some ideas from my fellow gardeners.Thanks again.

Canokie, There are many variables that can determine whether you need a vent. If I was going to use a vent on a cold frame I would use one of the heat activated types. I will attach a link that shows what I'm talking about. Many say they work well. I have 2 that I will put in my greenhouse if I ever get it finished. On my lean to I'm installing auto operated louvers and fans thaI have never had heat issues with either of my cold frames. I keep a hi/low thermometer in each. My lean to greenhouse has way more heat issues than my cold frames ever have. On mornings where the temps have been as low as 28 degrees F I have propped the tops open 1-2 inches. This has prevented over heating along with preventing the plants from freezing. The cold frame with the tinted glass is easier to control the heat in. If I leave it closed and the temps reach 80 the max in the cold frame will be upper 90's. I have never seen the need for vents on my cold frames so far. I also dug down 6 inches deep inside the cold frame. This helps to moderate the temps also. Another thing you can do if you don't have tinted glass is to lay a shade cloth over the glass. Jay Here is a link that might be useful: Greenhouse vent