Looking ahead to summer heat in a greenhouse

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stillwood Madison, AL Feb 22, 2007

I live in Granville County, NC (near Wake Forest and Raleigh) and have a 10 X 20 greenhouse. This is the first full year cycle I have had it operating. This winter I have managed so far to keep the inside temps above freezing - usually at least in the 40s - in spite of an abnormally large number of nights going down to the teens - even to 11 degrees ( global warming is not helping my greenhouse - more like global freezing). So the electric bill is bigger than I like - but I love the blooming impatiens, hibiscus, princess flowers, primroses, roses, and geraniums. So I am just rationalizing away the higher electric bill (it's a hobby and other hobbies like golf and movies cost money too - I just use electricity instead).

But summer will come and heat seems to be the bigger problem. Here is my question: I have an exhaust fan up high and 2 vents - last summer the fan ran a lot (most) of the time and the inside temps still got up pretty high - like 110+. Would it help any to run a regular floor fan (on a pedestal) as well or does that just stir around the hot air? I realize the plants probably don't think "boy, that fan feels good" like we do when it's hot. But would it actually help to cool the air more for the plants?

I will be moving outside to the porches most plants and leaving in only the succulents and generaniums- probably.


Post #3215704
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Eggs_Zachtly Washington, MO(Zone 6a) Feb 22, 2007

Quoting:
I realize the plants probably don't think "boy, that fan feels good" like we do when it's hot.

Oh, but they do. ;-)

Air circulation is quite an important factor, when creating the environment inside your greenhouse. Actually, a couple fans, one at each end will help tremendously. Ideally, as far as I've ever been told, you want the air inside the greenhouse to flow in a "circle". This will help keep the temperature even, throughout.

HTH,
Eggs

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stressbaby Fulton, MO Feb 23, 2007

"Would it help any to run a regular floor fan (on a pedestal) as well or does that just stir around the hot air?" My answer is no.

I will give you a different point of view. The fans you describe sound like they are for horizontal air flow (HAF). That air flow is important in a number of ways (disease reduction, reduction of internodal stretch, etc). But HAF is much less important if you have an properly placed, adequately sized exhaust fan running. The air movement with the exhaust fan on is adequate if, again, it is proper sized and placed. You can achieve energy savings, in fact, by turning off your HAF fans when your exhaust fan comes on. My climate controller has a setting, in fact, for that very purpose.

Consider other methods of cooling...shade cloth, misters, foggers...also, your exhaust fan may work better if you close any ridge vents in the summer.

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StonoRiver Johns Island, SC Feb 24, 2007

That last comment has been my experience, stressbaby. I theorize that with my 4 ridge vents open, most of the replacement air coming in came in through the ridge vents, so it kept the top of the greenhouse (where no plants live!) relatively cool, but the benches sweltered. Even with the side vents open. Ridge vents work great in the winter months, but they're counterproductive when you need them the most.

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