looking for a porous fabric to cover a greenhouse

I'd like to use a row cover type spun-bond fabric to cover a hoop house instead of the usual plastic sheeting material. The reason for this is that fabrics have more shading and venting ability during the day, while still keeping things warmer at night. My plastic covered greenhouse just got way too hot during the day, even with vents and the door open. Also, there was a rainforest humidity effect in the plastic tunnel which seemed to promote bugs and disease.

The problem is that I've yet to find a fabric that would be strong enough and come in large enough sizes.

Does anyone have any ideas?

Would geotextile fabric for roads work? You can buy it in big lengths, quite wide and at reasonable cost.

Around here we get a fabric used by the paper mills that we use in place of geotextile for roads.

I'm not sure. Would geotextile let in enough light for the plants? I've never handled the stuff and don't know what it is like.

Thats a tall order to find something like row cover that would be large enough and strong enough to cover a GH.  Instead why not look into shade cloth for your GH.  I've bought shade cloth from here: http://www.shadeclothstore.com/default.aspx and was pleased with the service and product.  Shade cloth can be had in several percentages of shade and will definately help keep your GH cooler.

ETA:  If you do buy shade cloth get the knitted and not the woven.  Knitted is a stronger product.

Would a hoop house covered with just shade cloth be any warmer at night? The main cooling force on my field during spring and fall nights is radiant cooling to the sky. Would shade cloth interrupt radiant cooling? I'm assuming it would slow down the wind.

I could of course spread the shade cloth over plastic mesh, but that is one more layer to deal with and would reduce the breathability of the structure.

Tyvek house wrap will hold up. While not porous, it let's water vapors thru.

While not 100% sure, I would say that shade cloth would not be much help in holding heat in at night. Too porous.  It would be used over the top of your plastic covering, you could drape it over, which is the most common way or build a frame that sits above your current GH and support it from there, kinda like a tent rain fly that doesn't touch the tent.

A place I worked at many years ago had several glass greenhouses.  We were located in middle GA in probably zone 9.  We always "whitewashed" the glass greenhouses each spring.  Mixed it up and applied with a garden sprayer.  They make a special coating that goes on and over the course of the season slowly washes off the glass.  It definitely kept the GH cooler than the bare, clear glass.  I don't know where to source that any more or if it would be compatible with plastic covering on a GH.

I hear you on the radiant cooling at night.  That is my biggest obstacle as well.

Walt Chase wrote:A place I worked at many years ago had several glass greenhouses.  We were located in middle GA in probably zone 9.  We always "whitewashed" the glass greenhouses each spring.  Mixed it up and applied with a garden sprayer.  They make a special coating that goes on and over the course of the season slowly washes off the glass.  It definitely kept the GH cooler than the bare, clear glass.  I don't know where to source that any more or if it would be compatible with plastic covering on a GH.

We used to use a product called "Glass Wax" for this - it was a glass cleaner.  It came in a small can and you diluted with water before spraying it on.  Anything that didn't slowly wear off could be rubbed off the glass at the end of the season with a towel. I don't know if the brand is still available, but that might give you more info to go on.

Any way you could do a design modification to your greenhouse to allow for a window overhang, and therefore a permanent solution?  I love this design by Bill Mollison in his permaculture book,

Saved on my pinterest page

Sherri

We use housewrap for a lot of things. Plants will grow under it. Its moisture permeable, and not as transparent as plastic. I'd try it over a small area and see if you like it.

Last Summer I tacked two king size flat sheets end to end and covered my greenhouse with it. The difference it made was surprising (to me anyhoo). When it was really scorching outside I was ducking in to the greenhouse to cool off.

Gilbert, what dimensions would you need to cover your greenhouse? Johnny's Selected Seeds has Agribon AG-19 row cover, which lets in a lot of light (85%) while protecting plants down to 27F overnight. If it's left on during the day it keeps things 5-10F warmer than outside. They have a 30 foot by 100 foot dimension cut of it on sale right now for $89, and shipping would add another $20 or so (the illustrative picture at the link isn't a representation of the 30x100 dimension product, FYI):

http://www.johnnyseeds.com/tools-supplies/row-covers-and-accessories/row-cover/agribon%2B-ag-19-row-cover---30-x-100-9054.html

Gilbert, You might check with the folks over at repurposed materials , they have a couple of different types of fabric that might work .  http://www.repurposedmaterialsinc.com/polyester-fabric-in-rolls/den-polyester-rolls/

This may be a little late, but I am currently testing agribon AG-19 for my pvc conduit hoop house(8' high, 20' wide) for the following reasons:
1) It is comparable to the price of 4 mil construction sheeting at "big box" stores.
2) I was able to find the width I wanted Of 30 feet. Comparable price plastics came in 10'-12' widths, so I would have to find some way to splice the plastic.
3) Assuming it lasts me a full year, it will cost about the same per year as what I've found for actual greenhouse film.
4) I expect it will allow sufficient water(rain/humidity) to pass through, reducing/eliminating the need to water and preventing excessive humidity.
5) It will retain heat and reduce the possibility of excessive frost(zone 7b), but I also hypothesize that it since it is breathable, it will reduce or eliminate the need for venting during warmer days.

I do not expect to grow tomato's in mid-winter, but my goal is to achieve a space to grow cold weather crops through most if not all of the winter in my climate, be able to use the space to transition spring transplants to the outdoors, with minimal daily upkeep such as watering or adjusting venting. Without the higher costs of other alternatives such as automatic venting, irrigation lines.

I just recently completed the install, and it is warmer inside, but I haven't tested the temperature difference other than with frost on the ground outside during early/mid morning, I am not unbearabley cold inside with just a T-shirt on.(that may be attributable partially to an increase in the wind chill temperature and not the actual temperature as the fabric reduces wind speed.)

During install, I did notice that it snagged and ripped easier than a plastic would have, but overall it seemed like it would be at least as durable to wind as plastic would be. Snow is minimal in my area, but In areas with snow I believe, because it isn't as slippery as plastic, it would not shed snow, and because it snags easily brushing off the snow would not be an option.

I will try to remember to follow up with the success or failure of the system. I would also be interested in knowing if you found something that worked.

Hello Joey,

Thanks so much, and welcome to permies!

I haven't found anything, but will definitely look into AG-19.

Keep us updated!

I know this an old thread but what I've done with some of my tunnels is to cover the hoops and one end with plastic greenhouse film and then the other end with agribon. Generally very low maintenance as the snow usually slides off and the agribon is enough to keep it warm at night and cool enough during the day. During the extended deep cold I'll cover the agribon end with either plastic or an old sheet.

Gregory, that is a great idea!

Welcome to Permies!