It is so warm in our area right now that I dont think the vents would be closing until 1am or 2am lol. It is already past 10:00PM and it is still 80F outside. The vents are still open almost completely. With this warm weather we are having, I am not even sure if my vents close completely at night. When I wake up in the morning the vents are already open a few inches. It did take me a few tries to tweak the pistons to get them to open and close near the desired temperatures. Then when summer arrived, I had to make adjustments again. I am sure I will need to adjust them again once winter hits.

If you are worried about critters install chicken wire barried around foundation about 8" deep. The top edge of the wire should be covered by the floor. I would lay down weed barrier first, no matter what the floor covering. No weeds! If you are worried about too much heat in the summer the best and cheapest bet is to make your poly easily removable. The less poly the more air circulation. Without knowing how your structure is configured I can't tell you if seasonal poly removal will be easy for you or not. It does beat paying fot electricity for fans. The panels can be replaced with framed screens. Pretty easty to make yourself to size.

Great Information! I have been here for years, and have only had a small greenhouse once, and only for a short time, but I'm finally building my home, with a GREENHOUSE ATTACHED TO IT! I have waited years for this, and your suggestions will help me a lot. Following this forum for so long, you notice how things changed over the years, and topics that were so important years ago, sometimes are a given now. So keeping up with what is important to people today, is a really great thing to share with everyone. I know it helped me to make new decisions on what I need. 1. Leave room to expand (a must) 2. More AMPS (this was always a great issue) 3. Placement of water source 3' up, not on the floor 4. Place water source in the center of the GH 5. Place for hanging more plants, not just shelving And this is just the start. I knew a lot of these, but think of them differently these days, some, like hanging plants, never really considered it! The water issues are wonderful, and exactly what I needed to see. AMPS is one issue that has been constant, never enough from what I remember. Now for my greenhouse. It will be part of my home, it's 12' wide by 40' long, faces east and south on my lot, will have huge drains in it, will have a special tile floor, will be 1/2 open to my living room/dining room/ kitchen area, but stops at the kitchen, which is a full wall with a window to the greenhouse, it will also contain my office, if I can figure out how to keep it separate from all the water that will be used in it. On the outer wall, it will have windows on 3 sides, about 3' up from the floor all the way around it, and of course, a glass ceiling. The heat and venting is being worked out by our landscaper, an old and dear friend of ours, and that's about it. Now you can see, why reading this was so important. Time to rehash years old information, that I needed to consider again. Thank you all for your information and thoughts. Keep it up, I can use a lot more!

I'm piggy backing on the OP's original post because I am in a similar situation. I have an empty vented attic (no HVAC equipment or duct work) with blown cellulose on its floor between & covering joists (@ least to code if not exceeding) This attic sits over our master bedroom, master bath & master closet. Air in those room always seems to be 2-5 degrees colder or hotter depending on season. Have had HVAC equipment & airflow checked - all in line along with original blower door test which had us 50% tighter than the comps. So I think somehow air is still leaking down over this part of my house. The only reason is that the attic roof area is open to the air infiltration via a passive ventilation combination of eaves, ridges, & side gables & leaking air below to the master space. Foam would be at least 3x the costs of additional cellulose but beneficially make the attic temp closer to whatever below however, may require additional mechanical ventilation. Additional topping of blown cellulose would be no problem in an unused space but would it compact in the future & possibly get ineffective in a vented environment & have to be redone? What is the most effective but cost conscious way to insulate the attic if HVAC equipment is not up there to get my temps back in line with the other spaces in my house?