In considering shade for plants there are many considerations besides the % of shade factor. Many greenhouse growers use a white wash on their existing greenhouse cover.

What type of plants are in the house?

Plants do not feel the heat the way we do. Some plants that require shade, require shade for protection of the intensity of the sun. A shade cloth of black coloration can trap and collect heat, it is important to ventilate with black shade cloth.

White shade cloth will reflect heat, light and have less heat build up with the advantage of interior light reflection.

Any shade cloth will provide more shade with age and will have less ventilation properties. The small knit that lets light through will collect debris and thus will allow less light through with years of collecting debris.

Some of the most innovative shading available today are not shade fabric but white transparent strips that allow ventilation and work like a venetian blind. They are designed to open on cloudy days allowing the maximum light in but on bright sunny days they close to shade the plants in the house.

If you do not wish to use a white wash, do not want to go for a major expense in shade strips and have plants that like full sun, I would look for a white 30% shade cloth.

Just a few thoughts...
Bruce

Bruce,

On the Greenhouse thread there was a discussion about dark shade cloth sitting directly on top of the greenhouse actually raising the temp in the greenhouse. I find that hard to believe, but I really have no experience. When you say, "A shade cloth of black coloration can trap and collect heat, it is important to ventilate with black shade cloth." are you referring to the regular ventilation system of the greenhouse or something in addition? Is the shade cloth you're talking about placed on top of the greenhouse? Is there any air space between it and the greenhouse glazing?

I have always planned to use a removable, black shade cloth that is just sitting on top of the greenhouse.

Thanks,
jb

I appreciate the interesting responses.
Especially the " many considerations besides the % of shade factor." Available _types_ of shade hadn't entered my mind when I posted the first question. And the point about "
small knit that lets light through will collect debris" is another example of all the info I'd neglected to mention. We currently _have_ such in use at the moment, and which we remove and store for the "debris" seasons - but is proving inadequate for year round use.

So let me regroup to clarify..."
-first a reminder the core of my first question
- - "off season use for the greenhouse"
&
- - "still having enough light for 'pleasant'. "
We are _not_ going to be growing in it in the summer. The salient space use dynamic is 'pleasant'.
We were thinking that some strong amount of shade would make it a nicer off season work space, that if persistent cloudy condistions warrented, we could pull the darkness back to one end for a while - or otherwise adjust some other way.
-- I like the reference to venetian blind types and would welcome any leads or opinion on them.

But I still have to return to the basic question of a percentage that will yield a combination of 'pleasant' while keeping the "exhaust" need to a minimum.

As you can, Thanx again.

jb,

Two articles in the "American Nurseryman", January 15 and February 15, 2002 publication, by Sven E. Svenson, professor at the North Willamette Research & Education Center, Oregon State University, Aurora has some very valuable information on shade. The articles are titled "Shady Business" and "Shady Business Part II". Part II is very good. You may be able to order reprints at (312)782-5505, Extension 305.

Most interesting comments in the articles is the discussion of distinguishing the difference between shade and temperature. To use shade for shading plants and using shade to cool plants are two different subjects. When you shade for light intensity is one thing and when you shade for temperature is another thing. The articles mentioned above go into great detail on materials and color of shade cloth.

Black shade cloth absorbs radiation and provides the most shade while white shade cloth allows more light (diffused light) and provides a cooler environment.

If you are using shade cloth for cooling, the shade cloth should be suspended outside and above your house so heat can escape through the cloth. Mr. Svenson suggest two layers of shade cloth with four to twelve inches of space between layers of 30% woven black shade cloth and this would provide light reduction of a single layer of 50% shade cloth.

It is very difficult to cool a house in the summer. I use fifty by seventeen foot hoop house's that are run east to west with 60% black shade cloth for shade plants. No plastic, the cloth is stretched over the frame with a five foot opening running the length on the north side and one foot opening running the south faced length. The openings allow ventilation. These shade houses use 2/3 less water and stay cool with good air movement. Hosta's love it!

I have read of other studies that show an enclosed structure of shade cloth, no plastic on the structure, but just black shade fabric will accumulate heat.

Hope thats a help,
Bruce

We have a tunnel with a removable reinforced PVC cover. This means that in the summer months I can remove the ends and replace the cover with a 50% green shade net.

This provides an environment which is 'pleasant' for both humans and seedlings when the thermometer skirts around 100 degrees as it has today. In addition there are no ventilation problems and watering requirements are reduced drastically.

I keep one small portion of the tunnel covered so I can work when it's raining, which isn't very often!

I am building a shade house for my daylilies in containers. I live in Texas where the heat and the amount of sunlight are extensive in the summer months. It is my understanding that red shade cloth does well for some flowering plants, but I have never seen it used. My question is: what color of shade cloth is the best for growing daylilies and what density of shade cloth should I use? ( I am trying to reduce the excessive heat that is here in the summer months)
Thank You for the help.