Tag Archives: season extension for greenhouses

Season Extension: Ventilation & Heating

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To make your greenhouse more of a year round functioning entity, there are two main areas in which you have to make the structure more efficient-Heating and Ventilation.

1. Heating is your biggest expense for the winter so retaining heat is a priority.

The easiest way to retain heat in your greenhouse is to install a double poly cover with air in between. A small squirrel cage blower attached to the inside layer of plastic aids in maintaining air between layers.

The more dead air space between these layers you can create, the closer you will be to achieving a 30% reduction in heat loss. Holes will result in air movement and therefore less efficiency. 3″-5″ consistent space is ideal. It is a given that you would have less than that around the edges and over the ridge.

Double plastic will have a considerably longer life span. It is important to realize that as plastic gets older, the light transmission will be reduced which will reduce production.

Infrared plastic (IR poly) does further reduce heat loss and increase light diffusion so it can also be a consideration when looking for ways to reduce heating costs.

2. Ventilation is also one of your biggest considerations for the warmer times of the year. Ventilation can be done through forced or mechanical methods or passive through vents or roll up sides.

Vents are extremely effective since they can be placed higher up where the heat needs to be expelled. Mechanical ventilation is more costly both up front and to operate but it is easier to control since it is attached to a thermostat. For mechanical ventilation to be effective, it needs to be sized and located properly.

Roll up sides are less costly and simpler to install but are restricted by the fact that you have to be there to open and to close.

Climate control is especially challenging in the spring and the fall since most days you will have the need for both ventilating and heating.

One area that you need to be especially aware of is stagnant air. Without proper air movement, circulation and exchanging, stagnant air can cause many different types of diseases. It is important to understand what your plants require

Season Extension: Moving Your Structure

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A significant part of season extension involves moving an intact structure.

This basically allows you to get two (or possibly three) plots of production from one investment.

The idea is to start a relatively cold tolerant crop very early in the season (the timing will be different in different locations).

  1. Once the crop is firmly established in location A, (and it has warmed up) you will move the structure to location B and start another crop.
  2. You will harvest the crop in location A and then after working the soil, plant another crop in location A which is intended for fall harvesting.
  3. After location B is harvested and before frost you will move the structure back to A.
  4. Instead of doing twice in location A you could also choose location C.

A structure can be equipped with wheels which will run over the soil. There is quite a bit of flexibility where you go and the terrain you navigate.

The structure can be equipped with rollers on a track. This will determine where you go and this is usually intended for moving a bigger structure with fewer people.

The most common method of moving is sliding the structure on the soil. The base rail can be wood or steel.

It is critically import to understand the logistics of moving on a structure before you start. It is not hard to move a structure but it is also not hard to do damage.

Having a plan for proper anchoring is very important for a movable structure. Your structure is at a vulnerable state when you release the anchors. Once you start, the job must be completed quickly. You have to be aware that the anchors may not come out or go back in easily so you may need to give yourself some extra time.

One other area of consideration on a movable structure is the ends. There must be some sort of a flap or vent along the bottom so that when a structure is being moved, the ends will not uproot plant material. Generally speaking to have this ability in the ends takes away from the structural integrity, so some extra anchoring may be required.

You can see more information and photos on our movable information page. Please don’t hesitate to call us with ANY questions you may have. This can be a very useful addition to your structure, but must be understood correctly.

Season Extension: Hanley Caterpillar Tunnels

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The first area to discuss regarding season extension are those structures that are simple enough to disassemble and relocate to another spot-primarily referring to Hanley Caterpillar Tunnels.

The real lure of these buildings is their low cost and simplicity to move. Generally the area is prepared in advance and then the tunnel is moved over the area when the planting is to be done.

Since the original design specified 6′ hoop spacing, the intent was always to remove the cover before risk of heavier snow fall. More often now, growers are going to 5′ spacing (and sometimes 4′) to allow the covers to remain on longer or even permanently.

By having a smaller hoop spacing, it allows the cover to stay on permanently, which allows for a much earlier start in the spring.

The key to the concept of the Hanley working is in the rope.

  • The back and forth pattern of the rope resembles the way a person would lace up a boot.
  • Typically there is a spring loaded clip at the base where the rope passes through.
  • Once the rope is fully installed, it is important to tighten it through three passes from end to end.
  • If the rope is not tight enough, the wind will create wiggle and movement sideways.
  • When the plastic is tight enough, it also allows the grower to slide the plastic up the hoop to allow ventilation.

Generally the plastic is about 25′ longer then the tunnel.
This allows the installer to bunch up (pig tail style) the extra poly at both ends between a pair of posts.
It is important to get the plastic as tight as possible lengthwise first.
There must also be a rope from the top of the last hoop to the tie off post.

There are a couple of challenges to consider with the hanley tunnels.

  1. One of these challenges is to create a proper entrance. Typically entrance is achieved by slightly lifting the plastic and ducking underneath.
  2. The other are of challenge is the low shoulder height of the structure. This restricts the use to a couple rows of taller items in the middle and a couple rows of shorter plants along the side. The width of the tunnel does lend itself to three regular size beds.

Once you have learned about the nuances of the hanley tunnels, and asked any questions that come up, you will be better prepared to have these efficient season extenders work for you and your application.

Feel free to look at our Hanley Application page for more information and photos, and give us a call with anything else you require.

We are pleased to have many happy customers these structures are working for, and look forward to you being next!

Check out our book if you want to know more “So You Want to Buy a Greenhouse…Your Guide to Planning a Greenhouse Purchase”

Organic Greenhouses/Shelters-uses and benefits

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There are many benefits to having a greenhouse structure for organic growing and housing. They are often used a season extender for protecting crops from the elements, blight, and fungus. Since Organic growers and farmers do not use pesticides, this type of protection is often required for some of the more sensitive crops.

The structures are easy to move to allow the expansion of the growing area.These structures can easily help to give you the opportunity to grow more crops in a limited area. What many of our customers also do, particularly with Hanley Caterpillar structures, is start growing the early crops under the protection of the structure, and as the crop is stable enough, they move the structure to be able to start the next planting.

Knight Hanley Structure

Our structures are also used for organic livestock raising to ensure the animals have a healthy, safe and protected environment out of the elements. They are versatile structures, and only require the changing of clear to white plastic for the various uses. The environment allows the animals to have sunlight, but still get the shade they require.

Goats5

The combination of the double layer of plastic, roll up sides, and inflator fan, on both the greenhouse and livestock shelters, helps to reduce condensation and keep the structure ventilated. We are excited to be working on a solar powered fan option for those off grid customers or if the structure is out in the field away from electricity as we know many of our organic growers and farmers are in these situations.

Modified Hanley Tunnel

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One of our most popular structures is the Hanley tunnel because it is the cheapest way of covering an area for season extension.

As a way of addressing some of the challenges and limiting factors with the tunnels, we have come up with a modified Hanley.

The two areas where it significantly improves on the regular tunnel are the side clearance and the peak for snow shedding. Instead of using 24’ of steel to make 17’ wide and 7’6” high, we are using 26’ of material to make 16’ wide and 9’ high. It still uses 28’ wide plastic with extra at the ends to make the same kind of “tails”.

Sliding the plastic up on the sides is still the way that the tunnel is ventilated and you will still have the same challenges as far as creating access.

The re-bar anchors, base plates, clasps and rope are the same on the modified Hanley as they are for the regular tunnel. We supply 5’ more of extra plastic for the tails since the building is taller.

The peak on the end hoops are very hard on the plastic, so we have designed a more rounded hoop at each end. It is strongly recommended to have 3 guides ropes at each end to brace back to the anchoring posts of the plastic.

Any structure with ends is not considered a Hanley Tunnel. We are more than willing to discuss the differences and benefits/drawbacks between tunnels and cold frames should you wish to know more.

The main thing which is critical to understand before going with a modified Hanley is the extra wind load which the structure will be subjected to. Going from 7’6” to 9’ high, results in a 40% increase in the wind load. This issue is what makes the correct tightness of the ropes an even more critical consideration.

It is also the reason why we strongly urge customers who
do not have any tunnel experience to start with a regular tunnel.

Why Wait Until Spring?

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In an ideal world, we would have nothing to do in the summer but have time to build the extra space we need for growing, storage or livestock housing requirements.

The reality is, that is seldom how things work, but many of the people that we talk to are intimidated by the possibility of building either in winter or when times are less then ideal.

When your Plan A won’t work there are actually many other options when it comes to scheduling putting up your building.

During late fall, winter or early spring, you will need to be a bit more selective as to the days you will be working, but it can be accommodated. It will not be as convenient, but that does not mean you have to do without that extra required space for the upcoming year.

The first thing we need from you is a bit of information to have a good understanding of the area you are working with. This will allow us to advise you on how to get a proper foundation in.

The phrase “there is no such thing as too many anchors” is even more applicable during inclement weather.

After that, you simply pick your days when you work outside or you simply work shorter days.

Unless you hit it very lucky with an abnormally perfect cover day, the reality is, is that the cover will not go on perfectly. This is ok since there are ways of overcoming this as well.

We have additional information on our website to work with temporarily securing a loose cover and the process of retightening a cover once warmer weather comes. We will have short videos explaining this process up shortly. Any possible inconvenience of having to do this retightening will be more than offset by the convenience of having that extra space now, rather then trying to accommodate building later.

We look forward to working though your challenges with you