2004-01-10 Leveraging Passive Ventilation in Greenhouse Pods

Hello Jared,

Belatedly, let me honk my own commercial horn about greenhouses.  Here at Icosa Village we have been considering the use of our Pods as greenhouses.  By manufacturing one of our double-walled Pods entirely out of translucent plastic we believe that we have a nice "hobby" greenhouse that takes advantage of passive ventilation.  We've designed opening windows (rather like three-pointed stars) for temperature control and aeration.  Here are a couple of FAQs that may be of interest from our on-line FAQ data base accessible through www.icosavillage.com and www.thepod.net.


The pressure difference across an opening is the driving force of ventilation.  This pressure difference is produced by the action of wind, temperature difference, or by the operation of mechanical ventilation systems.

Passive ventilation is ventilation provided without a mechanical means of forcing air movement. A key advantage of passive ventilation is that it is not dependent on an outside power source. A disadvantage of passive ventilation can occur in climatic areas that are subject to a combination of high heat and humidity.   The lack of a positive airflow can create conditions favoring the growth of mildew. [See PC:Humidity]

A standard for human habitation is to provide one square foot of ventilation area for every one thousand cubic feet of interior shelter space. Passive ventilation can offer appropriate greenhouse temperature control if the openings in the greenhouse are large enough to cause sufficient air exchange with the outdoors. Florida greenhouses use the general rule-of-thumb that passive ventilation totaling 40% of the floor area must be open to keep greenhouse temperatures within 10 degrees above the outside temperature. Passive ventilation works, but it is generally a manual system. Thus a greenhouse with only passive ventilation requires that the greenhouse operator is present during every day, and typically every hour, that plants are growing in the greenhouse. (www.uky.edu/Agriculture/HLA/anderson/fl_prog/ghvent_p.htm) [See PC:Ventilation & Exchange of Temperature In Hot and Humid Regions.] (Created 11/14/2003)


Icosa Village IcoPods and DecaPods have walls constructed of a high-tech sandwich of fiberboard materials and specialized films. [See MPT:Wall & Window Materials.] Only our GrowPod greenhouses have all-plastic walls.

Why aren’t the walls of all of our Pods constructed out of plastic?

The answer is that the materials used need to best suit the application.  Plastic is more expensive than Fiberboard so if one objective is to maximally reduce cost, then fiberboard is more efficient than plastic. And while plastic is impervious to water damage, it isn’t as resistant to ultra-violet (UV) degradation over time, so if longevity is a primary consideration, fiberboard walls tend to be more efficient. [See MPT:Longevity and AMT:Permanent Pod Surface Materials & Extending the Pod’s Life.] 

When used for applications like greenhouses or sauna covers, where the humidity is very high, or where translucence of the entire wall is important, plastic provides the superior characteristic and a GrowPod is the optimal choice. [See PC:Humidity and MPT:Four-Season Performance.] Finally, plastic and fiberboard also have different tactile characteristics. Fiberboard is a “warmer” material than plastic. (Posted 11/11/2003)

Regards, Markus

Jared Couey wrote:
thanks for the replys, im mainly into aquaponics systems but a pillow dome woudl be the most effective green house for it, so im just starting to get into it, i have already read alot of info on it.

i am interested in any method of making a pillow dome as cost effective to heat and maintain in a green house setup as possible. and am looking forward to the link from Rob about the solar panel setup.

i have already looked into earth wicking and geosynthetics quite indepth, even have alot of info and ideas on composting and ways of using that to help heat a building. probaby wouldnt work to well in anything but a green house but who knows till i play with it more.

i will probably be sending posts to the email group anytime i come up with more questions, right now im just tring to gather information for when im done with my aquaponics systems and designs so i can dive right into pillow dome design and construction.

i greatly aprecait ( cant spell that word and the spell checker didnt fix it :P) what these email groups do for every one involed and how well they share the knowledge thats essential to the human race and society


Markus Robinson
Icosa Village CEO
markus at icosavillage dot net
Tel: (510) 594-1174 (business)
Fax: (510) 655-1254

Visit us at www.icosavillage.com
Learn more about the Pods at www.thepod.net
Look for the '?' icon for our comprehensive
new FAQs feature www.icosavillage.com/FAQs.html

See the Pods in the January 2004 issue of the
Japanese periodical Paper Sky Magazine.
See other press reports about our Pods at

This archive was generated by a fusion of Pipermail 0.09 (Mailman edition) and MHonArc 2.6.8.