Greenhouse: Building our Harbor Freight 10' by 12' Greenhouse, 1 by oldmudhouse

oldmudhouse wrote:
I’ll use this year round for my cacti and succulents. They need protection from the cold about 5 months of the year (figure 45° minimum.) The rest of the year they need protection from scorching sun and the wicked-beaked Thrasher birds that poke holes in my plants.

This greenhouse sits in full desert sun! To help, I thought we’d build some screen panels to replace some of the polycarbonate panels during the summer. (I don’t know how many, or which ones, so any suggestions are welcome.) The poly panels will be affixed with clips and screws, so I should be able to remove them at will. Also, we’re planning to build some simple screen doors that will slide on a track inside the greenhouse, so I can keep the poly doors open, the screen doors closed, and the dratted birds out.

It will get hot inside when the panels go on, so first we want to work on the electrical, water, and floor. Time to face the thing that scares me the most about having my first greenhouse… heating and cooling.

I’d love to keep things simple, but because of our summer heat, I’m thinking I’ll need screens for ventilation, shade cloth, AND an exhaust fan (16”). This greenhouse has four roof vent windows as well. My plants will take temps up to 100°, but that’s the max. Our normal summer temps can sometimes reach 100°, so I can only imagine what it would be inside a poorly ventilated greenhouse in full sun.

If you can read my scribbles, I’ve made a drawing with my plan for bench location. I’m thinking 12” concrete pavers for the walk areas, and gravel under the benches. I’d really appreciate ANY comments, since this is all new to me. Specifically, though, I need to figure out the following so we can size and locate the electrical:

1. Using online heating calculators, it looks like we’ll need about 10,000 BTU. I guess that’s two 1500 watt heaters, or one larger heater. Do I just sit the electric heater(s) on the ground? Does location matter?

2. Where’s the best location for the exhaust fan? If I put an exhaust fan high in the back (east) wall, would it work to just use my screen doors as a vent on the west side?

3. I understand I also need a simple fan to keep the air circulating 24-7. How big should it be for a 10x12, and where’s the best place to mount this fan?

Thanks so much for any help!
Sheri