Den, There are several ways to decrease the humidity in your greenhouse. I understand you already have yours, but if you are in the buying phase and using polycarbonate sheets, make sure to get the sheets with the anti condensate coating on them. This will help keep drips from forming and dropping on your plants.

Install circulating fans in your greenhouse. You can't run electricity, but there are solar powered circulating fans available. Also, if you do not have an exhaust fan and vents these are also available with solar power.

Watch your watering. Do not over water the plants. Water in the morning and water the soil rather than getting any on the leaves of your plants. This will help cut down on evaporation which will increase the humidity.

Hope this helps! Tammy

Hi Den,

We had the same problem the first year we had our greenhouse. We live in a cool hardiness zone and grow plants in containers. We realized some things (some within and some beyond our control!) were contributing to the problem, including

• a wet but warm summer
• over-watering (thinking back, we were drowning our poor plants!)
• not pruning back some of our plants' leaves (winter squash)
• not working with the automatic air vent openers to promote air circulation.

The result was that we got terrible humidity in the greenhouse and awful powdery mildew on all of the squash and cucumbers.

This year, it's been a generally cool and wet summer, and we had the same concerns as you about keeping things warm in the greenhouse. But we had to find a balance, and had to accept that we couldn't seal things up as much as we'd like. (Our outside temperatures are cool, like yours.)

Since we also do not have electricity to our greenhouse, we tried to promote air flow by

• pruning back the leaves of some of the plants, where appropriate (e.g., winter squash)
• using less water on watering day and making sure soil has had time to dry out before watering again
• adjusting the sliding window on our greenhouse's screen door to work with the automatic piston roof vent openers which helped a lot to create air movement in the greenhouse

So far, so good.

Good luck!