Solar Pool Cover - Installed

fuzzymotoOctober 13, 2009

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.

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eaglesgarden(6b - se PA)

That sounds great. Thanks for sharing! Don't worry about the length of the post. If you have a lot of information to share, it is going to take some extra space to share! And anyone who is not interested can just check out another thread. Most of the time, follow-ups are asked for anyway.

As far as your concerns regarding overheating, I doubt you'll need to worry about it too much, as winter approaches, the days will get shorter and you will be gaining much less solar energy during the day, and be needing to maintain the same night temps for longer periods of time! Also, during that same period, the exterior temps will be even lower, and so the temp differential will be even greater than it currently is. Meaning, if you are not overheating now, chances are you won't be overheating in the winter.

Personally, I don't see why you would mind opening the door to the interior. What are you concerned about with that? It would seem to me that it could offer some "free" heat to the HOUSE from your greenhouse, and get back a little of the heating costs of the greenhouse at night, by not needing to heat the house as much during the day. (it wouldn't make much difference, but it might be something.)

Honestly, all of your "problems" are ones I would LOVE to have! ;-) I'm still in the planning, budgeting and praying phase of greenhouses! I have unheated mini-hoophouses over a few areas of my garden, in an attempt to extend the growing season a few weeks later in the fall and to be able to start earlier in the spring (less wet and warmer soil).

    Bookmark   October 16, 2009 at 11:39AM
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Thank you. My only real concern with opening up the house door is the level of humidity it brings into the house. We fertilize with fish emulsion, so on feeding days it brings an "aroma" in but that's no big deal. As I said I just don;t like introducing that much humidity to finished home space. I'm sure our forced air heat, ceiling fans and gas fireplace will ultimately dry that out, but I'd rather not risk mold or other moisture concerns.

I did try it on Sunday. We had a warm day and with the door open the house temp went up 5 degrees just form the greenhouse....but I was able to feel the humidity (and smell the fish).

So far the pool cover has worked well. We've seen an outside low temp now of 28F and the GH dipped to 48F...but that was with the heater off. I used to turn the heat off during the day and we had a freak snowstorm (Yes in Oct) and with no sun and cold snow the GH dipped to 48F. I've now corrected that heater setup and this morning when we hit 29F the GH easily stayed at 56F. We also had a hot day (about 60F outside) and the GH only hit 73F inside. So far so good. This week we're supposed to hit 67F so we'll see...and I'm also curious to see what happens when it stays cold and when we turn on our propane heater.

We did have an interesting experiment Sat. I was able to raise the GH temps by 6-degrees simply by turning on out circulation fans and moving the warm air around (and off the ceiling). We also have 2 vent fans that I can use to push air off the ceiling, but I'm trying to leave them alone for now (and not reverse them) in case we have a warm I said earlier the vents are disabled anyway.

Time and temps will tell the full story, but so far we love this setup and can't imagine even coming close to this good with bubblewrap or any other interior insulation treatment.

    Bookmark   October 19, 2009 at 10:23AM
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eaglesgarden(6b - se PA)

Sounds pretty good. I hadn't considered the humidity factor! The 5 degree increase in house temp from the GH is pretty impressive though!

What is the humidity of the GH?

Do you have any pics of the GH before and after wrapping?

    Bookmark   October 19, 2009 at 4:50PM
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SO far the Relative Humidity has been good ranging between 50%-80% RH. As the temps drop or as I use the irrigation (or run the hose inside) it of course goes up. We have an 18-inch oscilating wall-mount fan, a small rotary heat-save fan, two 20-inch ceiling/vent fans and 2 10-inch ceiling/vent fans that I can use to move air if necessary. So far we've only been using the first two with good results.

I don't post any photos on-line so no I don't have before & after pictrues. The link below (assuming it works) is to a generic photo of the size/shape/type of GH we have.

We'll be getting another good test this week on the opposite side of things, as temps are supposed to hit 70F on Thu. We're continueing to test cold nights, but I'll be curious how hot it gets on a hot day with the cover on and the GH sealed tight.

    Bookmark   October 20, 2009 at 10:26AM
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Just an update...we irrigated for the first time followed by two cloudy days and one hot sunny day. So far our humidity is a little higher than I'd like it and we saw a 90F plus high temp, but the circulation fans seemed to take care of both with no visible problems. I was able to drop the humidity a little by leaving the door to the house open and opening some windows in that room, but this isn't a process I'd like to use much especially if it is cold outside. We're monitoring the humidity abd being careful with water in the greenhouse (all irrigation & misting is off), but I'm not sure there's much I can do beyond that. I'm sure a de-humidifier would bring down the levels but I'd rather not go that route if I can avoid it. Short of cutting an opening in the pool cover, any other suggestions? We're also thinking that when we fire up the propane heater, it will naturally dry the GH a little also.

    Bookmark   October 23, 2009 at 10:20AM
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Hi Fuzzymoto,
I just ordered a 12 mil pool cover- I'll keep you posted how it works.

    Bookmark   October 26, 2009 at 7:58AM
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eaglesgarden(6b - se PA)


At the risk of hijacking this thread, can you give me some more information about the compost heater?


1) Did you insulate the underside of your greenhouse? How deep did you go? What thickness and material?

2) What did you use to line the compost heater?

3) Are there any extra vents to allow airflow to the pile other than the top vent?

4) What are the dimensions of the compost heater?

5) Are you adding any compost activation organisms, since theoretically, there would be very few organisms in the pile to start?

6) Any additional information you could add would be great!!!

    Bookmark   October 27, 2009 at 10:20AM
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At the risk getting too far off topic, here is a link that I think answers most of the compost furnace questions:
Also, here is more info:
Let me know if you have more questions- I'm happy to help, maybe comment on my blog so we avoid further hijacking...

    Bookmark   October 27, 2009 at 12:47PM
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At the risk of UN-Hijacking this thread:

We had 55MPH winds and a heavy rain last weekend....and while we did see some rain penetration, the cover didn't budge. We do occasionally get higher wind gusts but this is a good sign so far.

As far as the water penetration, it was raining sideways and even a new weathersealed steel door in our basement had water blown under the door. Nasty day but a good test for how well the cover is attached.

    Bookmark   October 28, 2009 at 11:13AM
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eaglesgarden(6b - se PA)

Sorry fuzzy!

Thanks for the update!

    Bookmark   October 29, 2009 at 5:36PM
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I finally installed a solar pool cover on the roof glazing of my greenhouse. I went with the 12 mil diamond clear, as a compromise between insulation and light transmission. As far as attaching it, I ended up cutting the pool cover into panels, and streching them over frames- essentally making storm windows from the pieces. You can see more about this on my blog...

    Bookmark   November 18, 2009 at 10:50AM
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Did you install the panels on the inside or outside?

    Bookmark   November 19, 2009 at 9:23AM
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I installed them on the inside. They are held in place with 2 screws with a small gap (1/2") at the top to let out moisure (between the glazing and the solar pool cover storm windows).

    Bookmark   November 19, 2009 at 10:43AM
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Interesting. We did our sharecloth on the inside (and it works great) and out solar pool cover on the outside. We wanted to minimize the seams and seal the GH as tightly as possible to conserve heat/fuel/$$$. So far we haven;t even turned on the propane heater...just the electric has been sufficient...BUT our weather has been VERY mild for Nov.

    Bookmark   November 20, 2009 at 11:15AM
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Just a further update...

We've now hit December, and although our weather has been fairly mild we are seeing nigh time lows in the 20's and daytime highes in the 40F range AND we are still only using our little 5K BTU electric heater. We've monitored the temps and we haven't seen anything lower than 50F even on the coldest nights with most nights in the mid-50's or low 60s. I suspect when the really cold Zone 4/5 stuff hits the propane heat will have to come on, but so far so good. Definitely worth the time and money to install a solar pool cover if you can.

    Bookmark   December 3, 2009 at 9:52AM
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We've been in the single digits the last few nights with daytime highs in the 20's. Our greenhouse has not gotten below freezing (our goal is to stay above freezing), and we have not had to use any heat source (apart from our compost).

    Bookmark   December 3, 2009 at 3:56PM
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Interesting. We're aiming a little higher for our lowest temp (55F+) so I'm not sure that method would work for us but if it's working for you and free that's great.

    Bookmark   December 4, 2009 at 2:53PM
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Having said all that in my last post, the temnps are forcated to get to -16 to -20 with highs in the single digits for the next few days. So, I'll be putting an oil filled electric radiator out there so our water barrels don't freeze!

    Bookmark   December 5, 2009 at 8:40AM
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We're dropping into the single digits this weekend too. I have a feeling it won't be longe before our propane heater has to be fired up. Still we've been very pleased that a simple solar pool cover and 5K BTU oil-filled electric heater have been able to keep the GH above 50F even with outside temps in th teens and 20's. This time last year (with no solar pool cover and colder temps) we were just getting ready to fill out 2nd big tank of propane.

    Bookmark   December 7, 2009 at 10:01AM
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After a few nights in the low teens and single digits (F) we saw the GH drop into the high 40's so we decided to finally activate our 30K BTU propane heater. We have the thermostat set just about as low as it can go and with mild outside temps (of course it warms up as soon as we light the propane heater), the greenhouse has been easily staying in the high 50's to low 70's. We also activated our circulation fans (to push the heat off the ceiling) but I'd swear at this point the electric heater and the pilot light of the propane heater are keeping the GH warm without the heater even coming on. How odd it felt to go out at 9PM and find the GH temps at 70F...especially since our living room was only 63F!

    Bookmark   December 15, 2009 at 10:20AM
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eaglesgarden(6b - se PA)

That's awesome!

If I were you, I would probably spend more time in my GH than my living room!

What are you estimated heating costs, thus far? (Fuel only, not equipment).

    Bookmark   December 17, 2009 at 8:23AM
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We do plan to spend more time in the greenhouse. Only trouble now is that by the time we get home from work, it's dark out :(

As far as costs it's easy to see our heating costs are drastically down, but not easy to calculate exactly how much. The GH shares a propane source with our garage & studio which we are heating about the same as last year. Just a rough estimate but we have two 100-gallon tanks that cost about $500 to fill. By this time last year they had been filled once and were about 50% full. As of Sunday, both tanks are 60% full and have not been filled yet this heating season. I don;t know this years propane rates but I'm hearing they are pretty close to last year. I'd say that's a significan savings. Keep in mind we did see an increase in our electric bill by about $20 per month for late Oct & Nov when we were only heating the GH with electric. Even so I'd say the savings in just a few weeks in propane have already paid for the solar pool cover.

As an added bonus, we're seeing much more reliable GH temps so we can start to us ethe GH more. In fact we're planning to start some salad greens from seed this weekend. Our tomatoes are starting to fade and our cukes are fading also. Any other suggestions for winter vegetables? We don;t plan to add supplemental light so I know we;re limited by that but I'm betting there are crops that will grow even now.

    Bookmark   December 17, 2009 at 10:06AM
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This message is for wildlifegardenermt 5.
Hello; you talked about using diamond clear 12 Mil solar pool and made screen window out it and used it inside the greenhouse. Is the 12 Mil flexible enough to make the screen?
By mistake I bought the 16Mil and I am having hard time making the screen because it is so rigid.
Can I order 12Mil and make my screen with it for winter. I live in Chicago and it is zone 5. My green house is 12'x10' and it is detached.

    Bookmark   June 23, 2011 at 1:12PM
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