Yes it can, and does. On a sunny clear day the temps, go thru the roof.
Then I open the roof vents and the heat goes thru the roof.
Sorry bad joke. It has been warmer than usual the past few years, but when it is sunny, snow on the ground or not, it get's hot. It got cloudy and rainy early yesterday, but before it did it hit 83f. This was about 11:00 a.m. It is cloudy and rainy today so I got a break from having to open the vents. It has been in the high 30's most of the time, and yesterday it was in the 50's and it is 60 cloudy and wet now. As soon as the high temperature is reached in the day, and it happens much earlier that I had expected, by 1:00pm. As soon as the high temp. is reached, the temps. start to drop. By 3:00
the temps are down to about 80f. At first I did not understand why the temp. in the greenhouse would rise so fast, and the drop off as soon as it peaked, even if it is getting warmer outside. Here is an example: The temps reach 100 by 12:30 and the outside temp. is 35f and sunny. By 3:00
the greenhouse temp is down to 83f, but the outside temp. is above 40f. Last year I did not have it heated or vented. I have a wireless thermometer in there and the receiver in the house, a wireless weather station. Last winter I monitored it pretty close, because I had intentions on heating it and wanted to know what to expect. I was very surprised to find these results. I remembered when I bought my telescope that the book said that the the best time to view the moon was just as it comes up. The reason for this is because it is closer to the Earth. As the moon makes it aver head it is much higher in the sky. That is why the moon looks huge when it first rises. The same principals are at work with the sun. That is why the sun looks huge when it is setting. And rising, but it is much to bright to look at when it is rising, or all day long. The only time when you can see the sun without hurting your eyes is usually when it is setting. At first it was a puzzle to me and then remembered the telescope. I am not sure if this is the reason why the high temp in the greenhouse peaks so early and then drops off even as the day gets warmer. Keep in mind, that out of sheer luck and space my greenhouse is positioned exactly the way you want it. For best sun, especially in winter, you want the peak of the GH to be aligned exactly east west. This puts one side of the roof facing directly south This fall I moved my ficus bonsai into it. I had been keeping them inside, under a fluorescent light. I hung a piece of 60% black night shade cloth up so they would not get sunburned. I was only going to leave it up for a couple of weeks tops. It is still up. Partly because I am in a wheelchair and can't take it down by myself and partly because it has been so warm. This winter we have had 0 inches of snow. Any precip. has been rain. I am not complaining cause I hate snow, being in a chair, but it has been so sunny and warm this winter. Can you say global warming. Just another reason to garden organic. I'll post a couple of picture links so you can see my greenhouse. I am very proud of it. I bought it in Feb. 2005. The greenhouse was up but far from finished in 05. Actually finished it this late summer. I did not start using it until it was complete. I have natural gas heat, year round water, (it can't freeze) and electric. All ran from the house. All up to code. All done by professionals. One great friend that did almost all the work is a plumber. Built the greenhouse, ran the gas, water, and electric. Another friend is an electrician, he wired all the outlets. And my buddy that owns his own heating and cooling business wired the exhaust fans and shutters. I have a 4 foot wide walkway out to the greenhouse and a 3 foot patio, out front. I designed the floor out of panels for chicken coops and dog kennels. Perfect. See what you think.
http://i139.photobucket.com/albums/q...e/DSCF1569.jpg
http://i139.photobucket.com/albums/q...e/DSCF1563.jpg
http://i139.photobucket.com/albums/q...0/DSCF1527.jpg http://i139.photobucket.com/albums/q...0/DSCF1530.jpg
Tom