Ecscuba said:So far I am pleased with my HFGH except I wish I had gone 8 x 10 instead of 6 x 8. It's kinda crowded in there already.
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Am planning to add some raised bed planting area along the south side of the GH building with cement blocks, ...

Great potting bench!

If you mean "cinder blocks", their thickness takes up a lot of floor space inside a crowded greenhouse.

I make raised beds outdoors by using concrete paving stones stood up on end and leaning inwards slightly. Since they are only 3/4" thick or 1" thick, they take up much less space than cinder blocks.

However, the tallest wall I make with them is only 16" tall, and I should straighten out their leaning angle every few years.

8" x 16" x 3/4" : make an 8" wall or a 16" wall
12" x 12" x 1" : make a 12" wall

8 x 16 pavers:



12" x 12" in foreground, 8x16 in the background. You can see how the 12x12 pavers are thicker.

Carol, a 'heat sink' of some sort inside the greenhouse will be cheap and easy through the winter. A friend of mine in Utah used to keep his greenhouse warm and also humidified by placing tubs of water inside. Daytime sun would heat the water up, then at night the density of the water helps it cool off slower, and it also evaporates somewhat to hold humidity up.

In the coldest weather or when there was a run of cold cloudy days, he used a waterbed heater to keep the water warm at night. He had very low power output to keep his large greenhouse a stable temperature. You are much further south and have stronger sun plus not as cold temps in winter so possibly just a tub or two (plastic storage tubs, @ 15gal size from Target or Wal-Mart work great) might keep the greenhouse temp up pretty well for you.

Right now, you're probably benefitting from the heat rising from the warm ground, and being trapped inside the greenhouse but as the ground cools off that will diminish.

I love the idea of using large containers of water as a heat sink. If you can paint them black, they'll absorb more heat.

I wonder whether leaving them open is a good idea? If you need the humidity more than the heat, then yes.

Considerable heat energy will be used up by evaporation, converting liquid water to vapor and chilling the rest of the tub. That heat will be released (partly wasted) when it re-condenses on the greenhouse walls.

It will also transport heat out of the tubs much faster than radiation and conduction would have carried it away. If the heat reservoir is so large and so warm that it lasts through the night and through cold spells anyway, then no problem.

In Utah, certainly the humidifying effect was needed. In cold, sunny weather in the high desert the humidity can drop below 10%, crackling dry.

I know this because I just got back from visiting my kids and grandkids there . . . my lips crack as I'm walking off the airplane when I arrive. I hang wet towels around my bed at night when I visit so I won't dry up and blow away . . . you git the picture.

I'm pretty sure I saw on the Greenhouse forum that @Dave has a large fish tank in his greenhouse, both as a heat sink and to raise the fish. Is there a lid on that fish tank?

Maybe a large garbage can full of water would be even better. Big and deep, with not too much surface area on top. It would take up less floor area, too, but might not fit under the shelves to get it out of the way.

Ahh, I understand. I was picturing a greenhouse with water running down the walls and making the floor much too damp.

Not many pieces of garden advice apply both to coastal PNW and a desert!

A black 55 gallon drum would be great if you can find them free.

I don't keep a lid on the fish tank. The thread "Aquaponics" in Permaculture forum

My 6 x 8 is so full I couldn't get 15 gal container in there. I wish more and more that I had a bigger GH. I must not have a full understanding of using the water because I painted milk jugs and filled them with water, put the caps on and hoped the sun would warm them. I have them around the plants but I don't think they are doing much. Maybe I should remove the caps?

That side of the GH will get a lot more sun once the leaves drop from the elms. Maybe that will make a difference. Or am I fooling myself and I should just ditch those milk jugs??

I am now thinking about putting another layer of solar blanket material over most of my two GH's. I have excess material to do this. I just need some warmer weather to proceed with the project. I don't know whether that second layer will give me any added insulation value, but there is only one way to tell.

My (outside) 20 gal. tub of plant water was frozen for the second morning in a row.

RICK Yes cinder block. My bench is outside the GH in what will be my fenced garden area eventually, right next to the GH. My 6 x 8 GH really has no room for a potting bench, unfortunately. But I have those brick pavers in the floor so with the bench outside I just brush the dirt off. Guess that's an advantage. I have a tall set of shelving in there and I can use a tray and do a little seed potting now and then. Our winter in central Texas is short so I will get by and sometimes we get some nice warm days even in winter. Until I bite the bullet and decide to expand the GH. Hubby already suggesting this!!

I did see a wonderful potting bench in utube that had a large pan that slides in the top to catch the dirt. Nice for in the GH if you have room.

Carol, once the elm leaves fall that will make a huge difference. Go out and shake that tree, girl!

A heat sink only works if the sun heats it up during the day. Once the greenhouse heats up more in the daytime, the milk jugs will heat up more and hold heat through the night. Have faith, even if they are only holding a little heat, it all helps. A true 'passive solar' system but you can make it more 'active'.

If you take the jugs out and set them somewhere the sun will hit them all day, you'll be surprised how warm they get. Just remember to whisk them into the greenhouse as soon as they are no longer in the sun. That way their accumulated heat will stay in the greenhouse and not be lost to the outside air.

I do this with mine in the winter, my husband calls it my exercise program. Schlepping jugs of water around the yard to keep them in the sun, then into the covered areas in the evening keeps my arms toned, I'll admit.

Nice potting bench here with the undermounted bin for potting:

And nice and sturdy looking, Arlene!

DYZZY you made me laugh. It's night here. Guess I will wait until morning to shake the elm trees. They are taller than the house. Haha
I did read something on Daves garden. Row up those water bottles along the sunny side and then put the pots of plants on top. Maybe a shelf in between if needed for support. I'm envisioning 8 feet of bottles down one side getting the sun from those barren elm trees! They suggested not using milk jugs as they scrunch down too much from the weight but those heavier ozarka large water bottles or half gallon juice bottles might work. And wouldn't take up too much of my height space in the little greenhouse. I also ordered a 14 x 28 clear solar pool cover. Can't wait to get that installed.

I don't know why, since there seems to be an awful lot of people who do the "jug" thing, but I just can't see how the sun heating black plastic jugs of water can be of any help at all in the fall/winter months. Some of you who do this will have to explain to me how this works "effectively". Let me give you an example and then y'all can explain it to this dummy. Next Wednesday, the low that morning is going to be around 20 F with a wind chill in the mid to lower teens. The high will be 41 F! It will be sunny and cloudless the entire day. How will the sun heat those black jugs during that day? And IF the water is indeed warmed, what will the temperature by of this "heated" water. Lastly, how long would that warmth last when the low Wednesday night to Thursday morning will again be around 20 F?

Carol, I think you will love the affects that the solar blanket material affords you. I have posted numerous comments on what the solar blanket material has done for my greenhouses and will soon add another layer for (hopefully) far greater heat retention in those greenhouses.

Ken, the basic premise of 'passive solar'; you let the sun heat up a heat sink that has a lot of density. Like water. Bricks work well too, and a greenhouse built with a dark brick wall on the north side stays very warm because the wall is a big, dense heat sink. The bigger the greenhouse, the bigger heat sink you would need, of course.

Say on your 41deg. sunny day your greenhouse gets up to what? 75 or 80deg. or so for several hours while the sun shines on it? Everything in the greenhouse will be that warm by the time the sun goes. Less dense materials like the soil in the pots will cool off faster, but the water cools very slowly and also supplies humidity if you leave the top off the water container.

It's true, jugs are not as effective as a larger mass of water like a plastic storage bin, but if you group them together, they maintain a goodly amount of heat. I use big 2gal. water jugs that we buy our hurricane supply of water in. We drink the expensive water after hurricane season, then fill the jugs with well water and put in used coffee grounds to make the water a dark color. Then I set the jugs in the full sun all day if the night is forecast to be cold. They get very warm, and 2 or 3 jugs on the bottom shelf of my little greenhouse shelf units keep them above 60deg. all night. Not to mention the weight keeps the shelf units from blowing over, which is an added benefit.

I got it and understand all that, Elaine. With an outside temperature of 40 F, and the sun being low in the sky (relative to summer), there simply won't be much heat generated in my greenhouses. And the further north one goes, the greater the angle of the sun and thus the heat generation will be even more limited.

Keep in mind that my greenhouses are also covered with solar blanket material, and though that material is supposed to transmit the infrared but not the UV range of light, there still is just not that much heating going on. My greenhouses will never see 80 F with 40 F outside. I have followed this for many years. But let's say those jugs do heat up to 80 F (which they won't). How long is that heat retained/radiated? Will that temperature be even 50 F at midnight? There will be at least six more hours of sub-freezing temperature outside. Heck, there might be twice that time of sub-freezing temperatures.

I guess what I am saying is that when push comes to shove, the little heat I would get from all those heat-sinks is far outweighed by the space I would lose. That space is at critical mass during the fall winter months, with my hundreds of tropical plants (600+).

That's odd, Ken. My greenhouse will definitely get up in the 80's if the sun is shining, regardless of the outdoor temps, and they get MUCH lower than 40 here in the frozen northland! However, the long side of my GH faces directly south, and in the summer, it gets way too hot to use at all. The cheap plastic clock I had in there melted one summer!

Like you, other than some "baby orchids", jade/aloe vera, and rooting plumeria cuttings, by greenhouses are emptied in the spring and will remain empty until the fall. My greenhouses do get some shading from large oak trees that are east and south of the greenhouses and those oak trees are still pretty much fully leafed. The free-standing GH probably only gets about 4 hrs. of sun and the other greenhouse is a lean-to and gets full shading (in the fall/winter) from 2:00 PM on. the Perhaps the trees/house shading is the reason my GH's don't get as hot in the fall and winter months. Heck, they will get 110 F in the summer with fans going and door/vents fully open.

I gladly take what little sun we get with my gh exposure. I think once the leaves drop off the nearby trees it might get sunnier, at least on sunny days. I love the idea of large water masses heating the GH. AND the waterbed heater that you can pick up used for $10. I don't have hot water access but I could fill up my sink with buckets of hot water from the house. To use the waterbed heater, I would have to use a container with thin walls. First, I will wait til the leaves all drop to see what heat I can harvest from the sun. With the recent cool temps, I think that will be very soon.

And lets not forget the tin can solar heater posted by Anne.
The thread "Start Saving Your Soda/Beer Cans! Soda/Beer Can Heater for A Greenhouse" in Greenhouses forum

Ken, I'm also surprised that your GH doesn't heat up more than that in the winter; yesterday we had 28F outside and inside my hoophouse -- which is only covered with a layer of 3-mil plastic - it was up to 55F. Inside my Rion, which has the twin-wall poly, it was nearly 70; and the sun wasn't out for that long during the day. I've never actually tried using the water jugs -- I'd like to in the hoophouse, but there isn't room because the plants are growing in the ground and I only have about a 1-1/2-foot wide path down the center. (I obviously need a larger hoophouse!) After warming up yesterday, it was still 24F this morning, when it was 15F outside. Even in the middle of the winter, when the high outside might be 15F or so, if the sun is shining all day my GH will easily get over 80F.

Also, water actually gives off heat as it cools, and even as it freezes... that's how the "wall of water" things that you put around plants to protect them from freezing work.

Is it possible that the solar cover on your GH is actually preventing it from warming up more? That doesn't really seem logical to me, but maybe it's actually blocking enough of the sun to have that effect