wordwiz said:Pam,
The point I was trying to make was that I'm not sure the benefit exceeds the effort.
Obviously it would for you, but not for me.
People building solar greenhouses in both North and South America, the ones with the actual experience, think the benefit exceeds the effort. I have carefully pointed out that I recognize the limitations of the system, particularly in an uninsulated structure. I'm blonde, not stupid.
This would suggest using 50-100 bottles of water would add some heat (I don't have a clue how much) overnight, but you have to remember - the bottles will also act as an air conditioner during daytime.
Exactly! Precisely! And anytime the temperatures get above 70F on a sunny day, which is not uncommon in our winters, the water will help moderate extreme daytime heat as well as freezing nighttime temperatures. It's a twofer!
If the air is 75 degrees and the water is 70 degrees, they will give off cold air (or absorb the hot air) until they heat up. And if they are not close to a window or the plastic, it will take them quite a while to warm. Not to mention, during winter time, there are lots of days where the sun never seems to shine (SAD comes to mind).
And on the nights that follow those days, I will not be depending on the water to hold temps in the hoop house above freezing.
If it were I and I was looking at a long term solution,
Teeeeeeeeeeeeeeeeeeeeeeeeempoooooooooooooorary Hoop House.
It will be coming down in the spring, remember?
I would probably use something like an old fashioned grill or a fireplace where the heat would be diverted through an insulation-wrapped air duct into you hoop house. Then again, I used a kerosene heater for a few years and it never hurt any plants growing inside, as long as I made sure to light it outside and not bring it in for a couple of minutes. The heater I had (years ago!) 3/4 gallon of fuel every day, but it ran 24 hours at it's highest setting. You might be able to use it for just eight hours a day at a lower setting, meaning a daily cost of less than a buck.
Did you skip over the bit where Potawie kindly explained how he heats his greenhouse and we talked about the advantages and disadvantages of various heaters?
Look, nothing beats a try but a failure. The bottles are free, and the cost of the water is minimal. What have I got to lose by trying it?