Is my husband right or wrong?

[franfleur]

We are having a greenhouse/sunroom built which will be attached to the side of our house. It unfortunately will face north and catch the light going across east to west. The main use of this greenhouse will be to winter our many houseplants that sit out on balconies and decks through the warmer parts of the year.

Everything I have ever read says that we should have a roof vent. My husband says it is not necessary as we will have side windows and a big patio door.

Can we get away without a roof vent during the hot summer months when the sun will be beating down on a clear acrylic roof? Will opening the side windows and the patio door give enough air movement and bring down the temperature to a comfortable level?

[Ralph Walton]

Even with a roof vent you may find the sunroom uncomfortably hot in the summer; a skylight can cook a small room. The light (and heat) needs to be intercepted before it gets into the house.

Check with your supplier or builder about sun screen hardware. There are woven screen products that will stop up to 80% of the heat/light, and also some relatively inexpensive paint on products (think "whitewash") that will wash off with the fall rains. Look under "nursery supplies" or "greenhouse supplies".

By the way, the answer to your first question is "yes".

Ralph

[growest]

Fran--I've worked around many patio covers/solariums and agree with others that roof vents are seldom used. They would be a problem to waterproof for one thing. I think the windows/patio door will be practical for ventilation of your sunroom for much of the year.

One setup where roofvents do work is on the tomato greenhouses, but notice that they are about 12-15 feet high at the ridges where the vents open...this allows the hot air to collect at the top and exit the vents well above the "living space" in these structures.

As Ralph mentions, it will be impossible to keep your room cool without shading in the hot summer weather. Even the insides of our houses get stifling at times, and the sun coming into an acrylic structure will be much worse in midsummer. Either some type of shading, or just avoiding the "sunroom" during the hot weather will be necessary. I do know that a greenhouse with rolled up sides and shadecloth is cooler than being outside on a sunny hot day, so shading is certainly effective.

This sounds like a great addition to your home, should be very enjoyable for you, and your plants. Windowsills just can't provide enough light for most plants in the winter!

[Ron B]

Freestanding greenhouse used by retired gardeners I knew for overwintering marginally hardy plants was emptied out each summer, as it was too hot to keep going then.