The Benefits & Drawbacks of Roll-up Sides

The main attraction of roll-up sides, as a method of ventilation, is that it is economical. There is not a significant investment and can be added to virtually any structure. Regardless of structure length, nowhere is very far from open air.

It is only by properly understanding the limitations and drawbacks that one can maximize the benefit. Just because something is inexpensive does not mean that it won’t end up being costly if it does not fulfil its purpose.

Roll-up sides should always be done in pairs (both sides). Even if you have a really high percentage of prevailing wind from one direction, there will be times when you need to ventilate into the prevailing wind.

Any time you have wind going in without opportunity of escaping,
there can be damage to the building.

The average vertical opening of roll-up sides is usually about 4’. If your greenhouse is in an extremely exposed area without any protection or wind breaks, quite often 2’ of vertical opening will be sufficient.

On the contrary, if the building is extremely sheltered, 6’ of vertical opening will be required.

One thing to remember on the height of opening is that if you have a low profile structure with a high opening, a sizeable area could get wet inside when it rains.

Regardless of the size of opening, if there is not a breeze, you will not have air movement.

It is based on this potential problem, that we recommend having end wall openings as high as possible. These openings will trigger a “chimney effect” air movement that will get rid of hot air that is trapped in the greenhouse. These openings will double as your first stage of ventilation since they would be opened when it is too cold outside to start rolling up the sides.

A drawback of roll-up sides is the amount of exposure they create for airborne weed seeds and pests. It is important to remember that when you use shade cloth to minimize this drawback, you are also significantly restricting incoming air.

The biggest drawback of roll-up sides is that there is no practical way to automate them. In other words, you have to be there to open and close them. This can be challenging on the cool, sunny days that have sporadic cloud cover. The sun goes behind a cloud and the temperature plummets and then soars when the sun reappears.

The best way to minimize this challenge is to add a small exhaust fan to the set up. This way you will have something to handle the borderline situations and then open the roll up sides once there is a more predictable need.

In the next article we will explore forced ventilation in greater detail. We also have many resources on our website, as well as videos if you want to explore the topic of roll-up sides further.

roll-up side videos

roll up side considerations

roll-up side Q&A

What is and isn’t “proper ventilation”?

Proper ventilation, in a nutshell, equals adequate air changes and movement while maintaining adequate light levels and humidity in a given area. Proper ventilation is about proper balance.

The challenging part of achieving this balance is that there is such a wide range of requirements for different plants. It is important to identify what is ideal for each variety that you are growing. It will not be feasible to have a perfect climate for each variety of plant, but you really should avoid grouping together plants with a wide difference in requirements. That would simply ensure that you are not doing very little properly.

Putting shade cloth over a greenhouse may lower the temperature to an acceptable level for your plants but that does not equal good ventilation. You may be depriving the plants of their critical light requirement plus you are not doing anything to enhance air movement.

Turning on an exhaust fan may create the required amount of air changes or movement, but with a temperature far below the plant optimum, your plants still will not achieve their potential. Fans also draw air in a straight line from intake to exhaust. This does not address “stagnant corners”.

Many times, light equals heat. They go up together and go down together. It is important to understand how and why they are controlled differently and where the overlap on that control is.

Generally speaking, proper air changes equals one air change per minute. Some plants require more and some can get by with less. For this, you will need to know what the air volume is for your building. It is a little trickier to calculate this on a gothic or quonset shaped structure. Using the length x width x 80% of peak height will give you a close enough number in either cubic feet or cubic metres.

With the next 4 posts we hope to create a more thorough understanding of how to achieve a good environment for your plants. This information will be helpful as to research options so that you can balance costs with benefits and return. Especially in the area of ventilation, many times expenses associated with proper ventilation will be offset by exponentially higher returns.

Important Notes About Hanleys & Warranties

Norm wants to caution anyone modifying their tunnel (or any structure) as this compromises the entire concept of the structure as well as voids the warranty and can start a whole host of other issues. Please call and speak directly with Norm, as well as read ALL the material on our website and installation manual before embarking on what can be economical and easy to use season extenders, or, very costly mistakes. Thank you for your interest

Hanley tunnels season extenders modified hanley

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Important Reminder – Self Sufficiency Packages

Just a quick reminder that you are still able to order the self sufficiency packages after May 31st (and any of our structures!) But it will be later delivery. As an example, when you order in June, it will likely be October delivery.

Please contact the office for specific pricing and delivery times. That is the most reliable way to stay up to date and accurate during these rapidly changing times

We are incredibly grateful to everyone for planning ahead, and for your patience. We love working with you on your projects and are grateful we have been able to continue that throughout the last three decades. Cheers to growing & more in 2021!

*stay tuned for our June series on ventilation! Email in your questions to multisheltersales@gmail.com to be featured in upcoming posts and videos!

What are the considerations for growing over winter?

Heating, interior tunnels, air circulation, humidity control

When someone is intending to grow in a plastic covered greenhouse over winter, the first order of business is to put a double layer of plastic with air between.

This cushion of air acts as insulation and will reduce heat loss by about 30%. A secondary benefit from this cushion of air is that it reduces condensation in the greenhouse dramatically.

Even if you are not going to heat the greenhouse, it makes sense to put the extra layer of cover with air between since it will provide a significant extra margin for cold.

The small fan which puts the air between the layers is made to work against pressure. It can not “over fill” the cavity.

When installing the second layer of plastic, it is not pulled tight. This allows the second layer to puff up to about 10 cm which is the optimum space.

It is the dead air space that creates the insulation value. If the air is moving, you will not have optimum efficiency. This is the reason it is important to be vigilant about patching any holes in the plastic when they occur.

Especially if your intention is to grow without heating, you could benefit from installing and using small interior tunnels. These tunnels would only be covered during severe weather. Since the air volume is small, even the heat from a few light bulbs will make a difference.

Interior air circulation is even more important in the winter time than it is in summer. In the winter time when things are more likely to be closed up, the probability of stagnant air is high.

It is important to monitor the humidity level in your greenhouse as well. Getting rid of excess humidity will cost you some heat, but you are creating a healthier environment for your plants.

If you are using a forced ventilation system for either humidity or heat control in the winter, it is important to have the thermostat close to the incoming air so that things will shut down quickly if the incoming air is extremely cold.

Any heating system which is used in a greenhouse should have a stainless steel heat exchanger and burner. The standard aluminized units simply will not stand up long term in the moist environment of a greenhouse.

We hope you have found value in this series of posts, helping you prepare for your new growing adventure! Reminder that the deadline is May 31st for Fall Delivery. We look forward to working with you for your projects!

What are the considerations for growing over the summer?

Ventilation, excess heat, making sure roll up sides are critter proof

One of the critically important things that each gardener/grower needs to know is the temperature threshold of each plant.

This is the temperature at which a plant will stop growing and an even higher temperature at which a plant will die.

When a plant has passed the threshold where it stops growing, it will take some time to recover and start growing again.

This is why proper ventilation is so vitally important. On a sunny day, proper ventilation is defined as one air change per minute. You must know the volume of air in your greenhouse and have your ventilation method capable of moving that much air.

A forced ventilation system is the simplest to set up and control since it is thermostatically controlled. The up front and operating cost are significant. Each exhaust fan has a cubic feet per minute (cfm) rating which must be equal or greater than the air volume of the building. A forced ventilation system also has a motorized louvre which will open each time the fan turns on.

On a shorter structure that is facing into the wind, there is the option of ventilating through the doors and windows. This is an economical system but the hardest to control.

Adding roll up sides to a structure has the capacity of moving a lot of air as long as there is air movement around the greenhouse.

This is why it is a good idea to install a window as high on each end as possible. Since warm air rises, this will create a “chimney” effect on a calm day. The down side of roll up sides is the potential for draft across the floor and the fact that you have to be there to open and close the system. You may need to put up mesh to deter uninvited guests.

In addition to changing the air in the greenhouse, it is also important to circulate the air horizontally. Stagnant air pockets invite disease problems. There is not a prescribed rate to move the air, it is just important to keep it moving.

A proper watering system would not be considered as a part of making a greenhouse more efficient but it must be remembered that a greenhouse will increase the water needs of all of the plants.

A final consideration for growing over the summer is the potential need for shade. Most vegetables are good for full sun, all the time, but it is important to remember that this does not apply to all plants.

Wishing you a productive growing season!

We hope you are finding value in this series of posts, helping you prepare for your new growing adventure! Reminder that the deadline is May 31st for Fall Delivery. We look forward to working with you for your projects!