Actually thought i'd try and explain my system a little better. I know there has been some differences in how i do mine in a greenhouse and Dawns indoor.

First let me say i have no formal education on seed starting or horticulture. This was something i started as a hobby and it grew into a job.

My greenhouse is the typical hoop style, not because i think they are better. I just happened to come across the frame at a reasonable price.So i had to learn as i went to put it together.

let me back up for a minute. My very first greenhouse was a little shelf unit with a clear cover with the zipper front door. I had zero experience with starting seeds except for a few i managed to start in a south facing window. Then i carried them to a west window to get afternoon sun.

Hense the little shelf unit came about. dummy me, decided to put it on the back porch in full sun with the zipper zipped(since the wind was blowing) with very tender tomato seedlings inside. They were cooked in no time. Remember we were all newbies at one time.

My second greenhouse came many years later, a harbor freight 10x12. Lets just say they will work for a hobby/backyard set up.

then i came across my 16x48 frame, which was once used to house baby ostrich. No they wer'nt mine.

It was only a frame with some shade cloth when i took it apart and hauled it home.

Ok,I'm multi tasking in my greenhouse. i have some plants that i over winter and i have new seedlings and ready to plant veggies all at the same time in the spring.trying to regulate the temperature can be frustrating at times. especially while i'm away during the day. I usually set the exaust fan to come on when it reaches about 75 degrees. my greenhouse runs east to west because that was the best location i had to use.

Now back to why and how i use the domes and mats. I normally set them on the north side out of direct sunlight. I have the foilback insulation on the north wall to try and keep the north wind from zapping the heat out of the GH.

normally i'll use the dome at night to keep the seed tray at an even temp and humidity. If it going to be a sunny day where the temp in the Gh will be warm, i'll remove the dome. Gh will get hot on sunny days even with the exaust fan going full blast. My center height is only about 7', so the heat cannot rise above the plants very much.So with a dome and warm temp in the GH, the tray can get pretty warm and humid under cover.

Once i see the first sprouts i remove the dome, even if it is just a few braking the surface. Why? with the high humidity inside the dome you get condesation, which difusses(sp) the available light even more. So the first seedlings to emerge are trying to find the light and getting leggy while the other seeds are still trying to break free.

Once the plants start germinating and coming through i move the tray to the south side of the GH. There the plants get all the sun they need and dont have to stretch to get the much need light.

My experience has been to have better and more success with keeping the seedling roots on a warmer side as opposed to a cool damp side. thats were the fine line comes in as to having the roots too wet.(also this ties in a little farther down with the cold air that might be introduced)

Because i am gone during the day i tend to overwater a little so they dont dry completely out.I have to do it the best way i can with my equipment.

beleive it or not most of the time you are trying to bring the temps down in a GH, except for cloudy cool days and of course cold nights.

I have a regular box type fan suspended in the middle of the GH above my blue flame heater and 3 osilating fans situated throughout the Gh to keep the air moving. Heating is expensive. it is nothing to use 150 gallons of propane in a month. Especially if it is down in the 20's, cloudy for days and north wind howling.

Sunny days, even if it is 20 degrees outside that GH will get warm. exaust will kick on, bringing a blast of cold air through, which can damage sensitive plants, sapping any heat stored up.(this is where the cold artic blast comes from)

It can be a challange with a home made set up.Hopefully i have explained why i do some things the way i do. It's just the best way i know how, with what i have to work with.At times the temperature swings can be 30+ degrees or more.

It's not just a challenge with our weather outside, it's also a challenge in a greenhouse when your trying guess what the weather might be like while your gone.

Do you leave the heat set a little warmer , wondering if the the clouds will remain or do you turn it down, so when the exhaust kicks in, it is'nt burning up your propane for nothing.(remember that cold air is being pulled across the heater thermostat, calling for heat also).

I probably made it sound much worse than it actually is. Hopefully others on here with Gh's will tell their experiences and the challanges they have faced.

If i have confused you even more, just ask and i'll try to explain. I tend to leave out stuff that i dont think about.