Solar Pool Cover - Installed
After quite a few people were nice enough to help with many of my Greenhouse questions, I thought I'd give back by detailing my recent solar pool cover installation experience. Please keep in mind these are early days. The cover has been on for about 3 days and we still haven't hit winter. Here are the detail...
GH: My greenhouse is a 16' x 10' home attached all glass aluminum frame, south facing; with our home as the north wall. We have a 5K BTU electric oil filled radiator heater and a 30K BTU propane direct-vent wall-mounted heater. We have automatic roof & wall vents (4) equipped with thermostatic vent fans and thermostatic circulation fans. We also have an automatic misting, irrigation & fertilization system. We are zone 4-5 in PA on an exposed hill with LOTS of wind. We have a concrete epoxy-coated floor with 2 built in floor drains and an insulated full foundation.
Last winter: Last winter we used no insulation and just ran the heaters. Our experience was ok, but inconsistent and somewhat expensive to feed the propane and electricity necessary to attempt to keep a 55F minimum with outside temps reaching -19F a few nights and teens on other nights. We were able to maintain temps, but not consistently enough to trust it with our expensive plants.
Choices: We decided to check out bubble-wrap and solar pool covers. For us the bubble-wrap was just too labor intensive, trying to get it to attach correctly and work around all of our obstacles (vents, fans, doors...) and plants not to mention dealing with 12-foot ceilings. We also didn't feel it would be a good weather seal so we opted for a solar pool cover. We purchased a 44' x 22' clear solar pool cover in the 16ml thickness.
Installation: Before starting we disabled all roof & wall vents...these were REALLY hard to reach even from the ladders. First off let me say my main worry was weight...and I was right. This sucker is HEAVY! Rolled up it's the size of a fat hot-water-heater and other than rolling it, we needed a hand-truck to move it. Once unrolled in the yard we found it to be rigid and stiff and not easy to work with. We knew the challenge would be getting it up on the roof, and we were right. We had two people and three ladders and it was VERY hard getting it up, but do-able in the end. I would recommend at least 3 or 4 people, one on each ladder at the top of the roof and one or two pushing the cover up to clear the sharp corners. Believe it or not the cover is stiff enough that you CAN push it up.
Plan of Attach: Since our greenhouse has wooden sleepers all around that attach the aluminum frame to the concrete floor and to our house, we opted to get small strips of wood and sandwich the cover between the sleepers and the wooden strips with screws. This was relatively easy EXCEPT for the first few. Keeping the cover on the roof from moving and screwing in at the same time was tricky. Once we had a few in place it was easy. We were also lucky enough to have a window in our house that opens just above the center of the greenhouse roof. We used this window to not only help pull the cover up, but we also found a way to add some wood strips up there for additional support in the center of the roof. Given the shape of our GH (not square with a sloping roof), and the stiffness of the solar pool cover, the folding/wrapping of the GH was tricky. I had hoped to get nice tidy gift-wrapped package corners (or hospital corners as my mom would say), but the cover is way to difficult to move around that easily. After the fatigue of a few hours of pulling the cover up...we opted for somewhat messy corners that we secured with a few strips of clear duct tape. We also opted to NOT cut the excess cover off to tidy up corners. In my opinion it offers more insulation (less air infiltration) where the folds are and the excess cover extends beyond our greenhouse frame, beyond our concrete foundation and down to the grass. We used some extra concrete blocks to secure the slack cover edges that were left beyond our wooden strips and the slack mess at the two corners. It's not pretty, but I'll bet it will be warmer and in the end it's not terrible looking either. We completed the attachment with some bungee cords stretched from side to side over the roof and from top to bottom coming down the roof. We also added some extra tape on some of the folds just for extra security from wind and cut out our propane heater vent & taped it. This entire process with setup and cleanup, with 2 people took about 5-hours.
Experience so far: When all was said and done, while we are anxious to see how it stands the test of time in cold weather and/or high winds, we are pleased at how well it is attached. Other than the very top edge where we can't reach, the entire perimeter is secured with wooden strips & screws...not to mention bungee, tape and concrete blocks. I'm sure we'll have to watch out for some minor flapping, but there doesn't seem to be any way for wind to get in. Of course time will tell. As far as temperatures, we are REALLY pleased. Once finished we sat inside to monitor temps and with no heaters and just some minimal sun the temps were in the 70F range with outside temps in the 50F range. That first night we saw an outside low of 31F and with only our tiny little electric space heater, our interior low temp was 58F, and that heater only comes on and off intermittently all night. This is also without our big propane heater. Our experience with the last two nights has been the same...with the solar pool cover and just the small heater, we are maintaining a temperature differential of between 15 and 27 degrees!!! Now yes I realize it is early fall and once we hit the deep freeze it will be harder to maintain that, but also keep in mind I have another 30K BTU propane heater that isn't even on yet. SO far it seems to be working REAL WELL!
Concerns: At this point we're concerned about a few minor things. First, how will it stand up to winter snow and winds. We are debating climbing back up on some of the ladders to tape the top edges of the roof that we can reach that don't have wooden strips. We'd be taping the solar pool cover top edge to our vinyl siding just to prevent wind from getting in. I'm not sure if it is worth the time and effort and I'm not sure how much I can reach anyway. Tape & time are cheap so I suspect we'll do that if for nothing else but to perhaps seal in a little more heat and airflow. We did bring in our 60-gallon black rain barrel just for giggles....maybe it will give us a little solar/passive heat, maybe it won't...either way it's free. Our main concerns, especially right now, are heat & humidity. We sealed everything. This includes our vents and our door. We did this to prevent any air leaks, but we are concerned that we can't vent heat or humidity. to the outside, so we are carefully monitoring relative humidity and high temps. The nice thing is that with the cover on and our interior 30% aluminet in place, we have reduced some of the solar heating. We also have 6 circulation fans in place to keep air moving and all are thermostatically controlled. W ehave also turned off our misting and irrigation for now. As a final fix or emergency vent, the door to our greenhouse opens to our house into a room that has 25-foot ceilings and 4 large ceiling fans. If it gets too hot we can vent into our house. I'd rather not have to do that, but it probably beats cutting the cover for emergency venting. Our final concern is that our two kitties arent crazy about the cover blocking their bird and squirrel viewing pleasure. They both love watching the chipmunk-channel and now it's all blurry.
Sorry for the long write-up, but hopefully it helps someone decide if or how to install such a cover. Of course I'm happy to answer any questions anyone may have.