I am working on a design for a seed starting chamber. I spend way too much time babysitting my starts in the spring. They are too cold, too hot, too wet or too dry. This will be a natural light setup attached to the widow from house to GH. Here is a pic of the window from inside.
From outside
Here is a basic sketch of what I have in mind.
The heat tape is Flexwatt. It comes in 11 in rolls sold by the ft. There is a +/- clamp with teeth that go to each side of the tape. It is plugged into a thermostat with a soil temp prob to set temp range. Regular 1020's trays with saran wrap or clear domes for germination. This is what reptile breeders use on their breeding racks under tanks.
The 2 troughs will be 1/4 luan bottom with 1x2 sides lined with EPDM. I have most of the scraps for this but it only allows 1 1/2 in of water until over flow. I am figuring a 1/2 to 1 in of water flow. Water will pump up from a container inside through window opening to the bucket with siphon outside. I want to drain everything back inside at night to keep water warm.
The GH will keep it warm during the day. At night I can open the windows to regulate heat. The sides of the box will be foam for insulating. The front will have a plastic curtain to hold in humidity.
Things I need to figure out.
1) Will a 1 1/2 side be enough to get good watering at 1/2 to 1 in deep.
2) Media...rock wool, coarse sand, foam, sand/penlite/peat mix. Starts will go into AP and dirt.
3) Getting too hot. Possibly a fan/thermostat blowing inside the house to draw cool air through box
