There are all sorts of heating alternatives, many discussed here in previous posts if you need details, that will work better than floor vents. Unless you furnace runs constantly the heat would be very intermittent and as you said, dry out everything quickly.

The goal in germination is consistent soil temps even if not the ideal temp. So even a sunny window, while far from ideal, would work better than the heat vent. look around your home for heat generators - a sat/cable TV box, the top of an old fridge, an incandescent light that can be left on 24 hours a day, many use a box lined with foil with a light bulb in it, a string of Christmas lights the tray can sit on, all sorts of things.

None of them will work as well as a temp controlled germination mat and germination will take longer but care and attention they can work.

Alpine strawberries are difficult to germinate under ideal circumstances (see post below) but tomatoes and basil will do okay with 75-80 degree soil (use a thermometer) IF you can keep it consistent.

Hope this helps.

Dave

Here is a link that might be useful: one of many discussions here about alpine strawberries

Thanks so much dig dirt... also for the alpine strawberries link.

An incandescent light converts most of it's energy to heat. With a little care for safety, you can set up a heat box and put the seed containers on top of it. A thermometer is necessary to check soil temperature. Temperature can be regulated by moving the seed containers up or down, or use a light dimmer to regulate the heat.

I know that fluorescents dont put out much heat....... but I just put the seed trays on top of my fluorescent fixtures as a heating "pad". My fixtures are hung from shelves that have a back and sides and I hang a mylar curtain over the front. So the heat from 12, 2 bulb fixtures does add up. The top shelf can get up to 90 degrees (measuring air temp not soil) in a room that is kept closer to 60-65.

I realize this is not the recommended way to do it, but it has been working very well for me for the past 3 years.

If you are starting tomatoes and basil you don't need a heating mat. What you need is a fluorescent light set up. Buy a shop light that has chains and 2 regular fluorescent tubes. You can get both at walmart for less than $50. Set it up in your basement with the light no more than an inch away from your pots or plants--when they grow. I guarantee you will have beautiful plants to set out.

Both my son and I grow our tomato plants this way. I do have a heat mat and use it for other plants like petunias that like bottom heat but I never use it under tomatoes or basil. The temperature in my basement is not as high as it is upstairs yet the tomatoes grow beautifully

Thank you all for your advice... this is very helpful.

As a market farmer [small] I/we are always out to 'jump start' and really use heating mats for many [re:most] seed types. My old source went out of business and I'm looking for new online outlet with but two criteria: least expensive and dependability. Any knowledge would be greatly appreciated. Anybody with ideas? ps, I've built light boxes, converted heating mats, etc. and just buying the product made for bottom heat works best..thanks

About ten years ago I was faced with the same problem. From a salvage yard I bought a 3x6 foot 10 gauge aluminum plate. From Charlies Greenhouse supply I bought a bulb type adjustable thermometer,and a 300 watt cable used to prevent rain gutters from freezing. A sheet of 1/2 inch foam board from a building supply. I fiber glassed the heating cable to the foam board and secured the aluminum plate on top, with the thermostat bulb fastened to top of the plate. I now have head adjustable bottom heater, water proof and easy to clean when needed. Al

google/utube "homemade heating mats". We made our out of outdoor lighting ropes between 2 pieces of wood. Good luck. Mine works great.
Penny

I agree with mandolls....fluorescents don't put out much heat compared to incandescent, but it still puts out noticeable heat which surprised me. I am also a newbie and need to invest in a soil thermometer, but I can tell by experience so far that the shelf I added immediately above my top tier 4' 2 bulb fluorescent light fixtures stays a nice comfortable "warm" and has been perfect for germinating all manner of vegetables so far. You could even box in (or just tent it with plastic) the area above the light and it would become even warmer but that's not necessary for my setup inside the house where the air temp is usually 70-75 anyway. With a cooler basement setup you may want to build a sort of grow box to trap more of the heat rising from the light fixture as your germination station.

Now I've just planted daylily seeds on the rack to germinate so we'll see how they do but I expect good results.

Good luck with your seed starting!

One never knows what to expect at garage sales. About 5 years ago I was able to find an incubator as used for premature hospital births. With small modifications I am able to use it for those seeds preferring temperatures over 75 degrees. I keep it on the bench in the greenhouse and only plug it in as I need it. Al