Yes, I have what is called Aluminet. I ordered it instead of the black shade cloth becasue it never made sense to me to use something black iffen I was trying to keep the heat out.

Are you talking about Aluminet?
Because it doesn't matter which side is out and it is most commonly used on the inside. Though it can be used on the outside.
I use it on the inside.

Here is a link that might be useful: Aluminet

I use mine on the outside, no reason to let the heat in to begin with...

Thanks, weebus and cactusfreak for your responses. I wish I had heard of Aluminet before I ordered my shade cloth. Mine is from Charley's -- used to be called Chill Out in their old catalog. It's woven aluminum strips with blue plastic ribbons.

Does the Aluminet help keep the temperature down? It does seem like something shiny would reflect more heat than a dark cloth. I need a shade cloth for sure. It's only in the 70's outside and the greenhouse is running over 100 with the vents fully open and a fan running.

MJ

You need an exhaust fan in there I bet. What size is your GH? Shade cloth and more ventilation...

Salads:

Weebus may be right. What is the cfm rating for your exhaust fan? What is the ventilation setup? Something is funny if you're over 100F and it is only in the 70s outside. We're sunny in the upper 80s today and my GH hasn't gotten over 95F.

Count me among the Aluminet users. I have mine suspended on a support system inside the GH which keeps it out of the wind outside and it also allows me to get the whole thing up and down in about 2 minutes.

Stressbaby and weebus, it's an attached glass 8'x12' greenhouse with two 2'x4' roof vents at the top where it meets the house, and two 2'x4' side vents at the bottom, one on the west side which has the prevailing wind and one on the south side, which is the long side of the greenhouse. There's a door on the east side and we had a two foot square house fan blowing the air out of that. I haven't found any fan that could go in the top vents.
The sun hits the house from 10AM to 4:30PM in the summer. That's when the temperature spikes. The minute the sun goes behind the tree to the west, the temps drop down right away, so that's why I'm hoping a shade cloth will help. I know it's probably stupid to get a glass greenhouse, but I want to be able to see out to the garden while I work in it. I mainly want to grow cool weather veggies for my husband and me in the fall and winter, start seedlings in the spring, and grow some early tomatoes, peppers and eggplants in the first part of the summer. If it gets too hot in the winter, we can open the door to the house to get rid of the exta heat, but I can't do that in the summer because it heats the house too much.

I like the idea of a shade cloth that can be easily put up and taken down when needed. Stressbaby, do you have a picture of your setup somewhere on this site?

Salads:

Give me a couple of days, I'll get some pics.

My GH is glass, I love glass.

Salads:

Here are some pics of the shade cloth setup.

{{gwi:300411}}
This is the lower edge where the fabric is permanently secured with plastic ties at the eave. The entire frame is built from 3/8" galvanized pipe. I looked at aluminum (too expensive) and metal conduit and PVC (too weak and flimsy). The frame is supported with conduit clamps along the eave and stainless eye bolts at the corners, attached to the GH frame with T-bolts.

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This is the side of the fabric which slides up and down. The fabric is attached with plastic ties.

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This is the top near the GH ridge. There is a 3/16" cable that spans the top edges, attached to eye bolts at the ends. I use carabiner clips to stretch the fabric taut and attach it at the top to the cable. I also have four lengths of 3/16" cable running from the ridge to the eave to help hold up the fabric so it doesn't sag.

Hope that is helpful.

SB

Wow, SB, what a beautiful greenhouse and a great setup. Thanks so much for posting the pictures and the description. That's a really clever setup. Did you design it yourself? So you have the aluminet stretched on a frame that's attached to the greenhouseand the fabric can slide up the frame when you need the shade? How do you pull it up?

We have a curved eave, with a big purlin that goes all the way across about halfway up the eave, but I think we could adapt your system to work for us. Thanks again!

MJ

MJ, I just use a wooden stick. If you had two people you could push each side up evenly at the same time. With just one person, I have to push the north end up a foot or two, then the south end up a foot, and back and forth until it's up all the way up.

I designed it myself, but this final version was perhaps the fourth or fifth revision. I tinkered with it a lot before I got a version that worked!

BTW, you can cut holes in Aluminet and the cut fabric is fairly resistant to ripping, it is fairly forgiving.

SB, I wish I had heard about Aluminet before ordering Chill-Out from Charley's. The Chill-Out is only for use outside the greenhouse. We'll give it a try, but if it doesn't lower the temps considerably, I'm going to send it back and get Aluminet to set up like yours. The order won't get here until Thursday, so we tried fastening a blue tarp over the greenhouse and my husband rigged a large fan right under one of the roof vents to exhaust hot air. It was still hard to keep the temps under 100 even though it was in the seventies outside. Then this morning it was 56 outside and 49 in the greenhouse.

I'm glad to hear that you have glass and have made it work for you. Do you use any insulation besides the Aluminet in the winter?

MJ

You will need more venting, what you have is not enough. I would install some circulation fans, that will help. Overall just remember the samll the space, the more difficult it is to regulate the temperatures.

Salads,

The funny thing is that with a GH at about 1000 cu ft, a box fan (rated at 1500-2000cfm, I think) ought to be enough. I wouldn't expect such a large temperature differential.

Is the fan big enough? Is it drawing air efficiently across the room? Any screens or obstructions to air flow?

My Aluminet will come down sometime next month. I'll add a solar pool cover this year for extra insulation.

The GH isn't that large. That temp differential is something I would definitely expect.

Here is a link (credit to Cactusfreak) that describes temperature gradients in relation to cooling systems. With natural ventilation, you should be able to get down to a 20F differential. With adequate exhaust you should get down to a 10F differential. Your system must be able to turn the air over every 60 seconds or so.

I agree with Weebus, you need more ventilation. That temperature differential is expected only if the ventilation is not adequate.

In the end, I think, most people end up with a combination of fans, shutters, natural ventilation, and shade fabric.

Keep us posted, Salads.

Here is a link that might be useful: Cooling info link

Thank you for saying so well, what I have been unable to.

That cooling link is great. Thanks! I only have about 800 cubic feet of greenhouse space, so controlling the heat is a challenge. I can open the door to the house which helps drain off some of the heat, but it's not practical when the greenhouse is over 100. It would be great if we could have this kind of greenhouse heat generated in the winter when we could use it for supplemental heating, but it's usually cloudy in winter.

The shade cloth is supposed to arrive today. I'll let you know if it has any effect. I can't open any more vent space without prying off the glass and I'd rather avoid that if I can, so I hope the shade cloth will lower the temp enough to allow me to have the greenhouse open to the house.

MJ

We put the new shade cloth up yesterday. It's called Chill Out and has foil strips alternating with an open weave of a clear fiber. The day before yesterday we had outside temps in the mid-70's and the greenhouse got to 114 with all of the vents open and the exhaust fan going. Yesterday it was hotter outside, mid 80's, but the greenhouse peaked out at 104. This is still too hot for plants, but it's an improvement. I'm annoyed that the greenhouse company didn't tell us what kinds of problems we would be having with a small attached glass greenhouse. They "designed" the greenhouse with what they said was plenty of venting, but they were obviously wrong.

Now that we're going into fall, our outside temps should be dropping into the 60's for day and 50's at night. I have a feeling we'll have to keep the greenhouse empty in August and September, but my main reason for wanting it was to grow greens all winter and start seedlings in the spring, so I still think it was worth building it. I thought our main problem would be keeping the greenhouse warm enough not to freeze lettuce in the winter, but now I see that cooling is a bigger challenge.

MJ

I think we may have the heat problem under control. We moved the shade cloth down so it clears the top vents. The cloth must have been blocking some of the exhaust from the fan. The highest it has gotten in the past two days is 87. The outside temps have been in the high 70's and sunny. With these greenhouse temps I can keep the door from the greenhouse to the house open.

MJ

There you go, that's more like it.

OK We have that prolbem solved. Who's next?! I'm gald you will be able to enjoy your GH more.

Well, I am GLAD also.

I have always read that with PROPER ventilation (enough shutters and a fan with the right CFM rating to exchange air at least once per minute) you shouldn't have greenhouse temps more than 8-10 degrees over outside. However, the problem is worse in smaller houses.

I finally found someone in my area with a REAL greenhouse-it's a glass 20' X 44' homemade-this guy has his ventilation system down pat-with no shade cloth or evaporative cooling-his house never got over 101 this summer and that was on the hottest day we had (outside high temp about 94). He heats with gas in winter and says be prepared to spend $$$$!!!

I have propeer ventilation in my GH, but If I can get the same effect without having my exhasut system kick on and off on a regualr basis, would n't that be better? Also, not all plants want the amount of light offered on a July day at high noon... My house never gets over 95* on the hottest day of the year...

stressbaby's system is excellent, want to make this handy for spring planning.