I had my crew build a small greenhouse attached to the back of my garage, southern exposure, sheltered from wind, with a chick run under the big table, and nice big horizontal windows for cross ventilation east to west and southern windows that tip outward and open at the bottom. It has done a great job of keeping my rescued Lowes ornamentals alive all winter, starting some purple water lilies over the winter, and keeping a few bog plants green..
I want to start my seedlings in there.
I have a bunch of heritage seeds from Annie's - any special instructions? Like potting mix vs top soil? I usually just put my seeds in the ground but we are having a bumpy weather year - drought hot, drought cold, pour rain. I lost my first round of broccoli and chard seeds to the one and only really hard freeze we had - in November.
There is bottom ventilation facing east but in a very protected corner, under the door, and the greenhouse door is an old screen door with a screen in the window.
You may need some bottom heat to start seed, heat pads. I use what ever soil I have, may mix some worm poo in. Worms are a great addition to your GH.
A 2'x3' tub, little care and great byproduct .
But bottom heat and little water is my main idea.
Show us a pic of your set up.
The heating pads sold for starting seed are water prof and have no temp control. They are 110 watts and keep temp 10 dig above air temp.
I started a thread as how I constructed a one from an old heating pad, I'll try and find it.
A water bed heater should work.