Getting Started

Good Information When Shopping for a Greenhouse

When shopping for a greenhouse, it is important to recognize and understand the differences in design, When shopping for a greenhouse, it is important to recognize and understand the differences in design, quality, and price before making your decision. There are all types, styles, and qualities of greenhouses available on the market today. Each version has its purpose and market. One version is not “better” than the other, rather, “different”. An apple is not necessarily better than an orange, it’s just different. However, when comparing one apple to another apple, one may very well be better.

A greenhouse is simply an enclosed environment that can protect plants from the elements. A 10’ x 12’ greenhouse can cost anywhere from $200 up to $20,000 depending on the quality, design, aesthetics and overall purpose of the greenhouse as required by the customer. Even in larger sizes, the same is true. There are greenhouses made of plastic tubing and plastic or vinyl covering, to wood frame kits covered in polycarbonate to the prefabricated and manufactured greenhouses from extruded aluminum and glass.

The greenhouse “kit” market offers an array of low cost relatively attractive greenhouses that can be found online and in many home building supply outlets. These are quite functional and inexpensive. However, they are very lightweight in their design, and could very easily sustain considerable structural damage in a strong storm with high winds. This is because the actual thickness of the extruded parts is minimal. These typically don’t come in larger sizes because of the spans.

Then there are greenhouse structures that are a step up in durability and sizes. Heavier extruded parts allow for this. These will typically have individual vent panels at the ridge that open automatically with gas-expansion type lifters. Once again, relatively economical but still limited in overall quality and strength. Again, these are numerous and easy to find online.

Stepping up quality and design

Now we go from apples to oranges. These greenhouses are set apart from the “kit” style greenhouses in that they are designed for long term function, strength, durability, and beauty. There are fewer manufacturers of these types of structures, with only a handful of manufacturers in the US. These greenhouses are usually a long term investment. While cost is a relative thing, these greenhouses are considerably more expensive than the kit versions. The quality and degree of design are much greater.

Heavier extrusions, full-length ridge vents, taller eave height, wider and longer sizes are usually standard in these greenhouses. A major difference is that most of these incorporate a set of “sub-structures” inside the greenhouse which greatly adds to the overall support and strength of the structure. The sub-structure also plays a part in the operation of the full-length ridge vents’ operation. The height of the greenhouse, as well as the full-length ridge vents, provide better conditions for circulation, air replacement, and cooling – all important to the serious grower.

When comparing “oranges to oranges”, it is important to recognize the differences in order to determine which orange is the best. Within the same family of greenhouses – that is – same general type and structure, there are still significant differences that may set one apart from the other. This is usually reflected once again in the price. It is very difficult to see the differences in a catalog or website picture. They all look beautiful! However, a closer look will explain the differences and why two greenhouses that look identical in a picture could vary in cost. Things to look for:

1. Full-length ridge vents

Full-length ridge vents can be operated manually or automatically controlled by a thermostat.

2. Substructures

These are the channel or I-beam assemblies that are inside the greenhouse and add substantial support to the entire structure. These can be of steel or extruded aluminum. One is as good as the other in function, however, steel has to be galvanized to prevent rust, or if painted, there is a good chance of rust in the future. Aluminum has the same appearance as the rest of the greenhouse whether in mill finish (its natural color) or painted. Rust is never an issue.

Both steel and aluminum can be sized for particular load requirements.

3. Bay spacing

A bay or “row” is typically the space between the glazing bars running vertically. You may not notice it in a picture, but bay spacing varies greatly between manufacturers. The wider the space = a less number of glazing bars. The less number of glazing bars = a less number of assembly holes to be punched in the sill, purlins, eaves, and ridge vent assemblies. This reduces the cost of materials and fabrication time which reduces the final purchase price of the greenhouse. In reverse, the closer the spacing equals more glazing bars equal more material and fabrication time which equals higher purchase price. Where it may or may not matter to the buyer, the closer bay spacing equals more glazing bars equals added strength. The wider the bay spacing equals less glazing bars equals reduced strength.

4. Purlins

Purlins are the members that run horizontally down the length of the side wall, roof and across the end wall. These are attached to the sub-structures and support the vertically running glazing bars. More purlins = more attachment points to the glazing bars = added strength. The number and location of the purlins can also increase or decrease the aesthetic appearance.

5. Fasteners

Screws, bolts, and nuts – all needed to assemble the greenhouse. Greenhouse companies use a variety of stainless, zinc plated or aluminum. Stainless is the most ideal, as it won’t rust and is stronger than aluminum.

6. Built-in and free-standing benches and shelves

Benches are offered in a variety of materials; wood, aluminum, galvanized metal, composite and /or a combination of all. Built-in benches use the interior greenhouse frame as the back supporting portion of the bench or shelf. This makes for very stable construction. Compare the materials the benches are made of when comparing prices. The size of the material in the framework as well as the bench top material. Aluminum is ideal since it does not rust or decay. An aluminum grid or expanded panel is ideal because it will not rust, and it allows for good air flow and drainage to potted plants. Galvanized materials are good as well. Lighter weight construction is offered also. Smaller or lighter framework with hardware cloth tops (wire mesh). This works effectively, however may have some limitations as to the size and weight of potted plants.

Aluminum framed benches and shelves can easily be constructed from similar extrusions used in the greenhouse and can easily be painted to match the greenhouse finish. The tops are typically left in mill finish.

7. Evaporative cooling

Evaporative cooling is an essential part of the greenhouse function for the more serious grower. This, along with heating for the colder months, will enable you to use your greenhouse year-round. An evaporative cooler is simply an enclosed fan unit which draws air through wet pads and blows the cooled air into the greenhouse. The bottom of the cooler holds water which is pumped up and dispersed to the pads on three sides of the unit. The water trickles down through the pads, cooling the air slightly. As the cooler air is introduced into the greenhouse at roughly bench level, the warmer or hot air is displaced upward (hot air rises). The most efficient place to remove the hot air or allow it to escape is through the ridge vents; the highest point of the greenhouse. This “air replacement” with cooler air is what keeps the greenhouse from being a hot box. This along with some type of roof shading make for a very comfortable working and growing environment inside the greenhouse; even on a 100-degree day with high humidity. Some may disagree, but it’s true.

The control panel of the cooler is usually framed into the glass greenhouse end wall – opposite the door on typical back yard greenhouses. The quality of a cooler installation can vary from good to bad. Frame kits and installation kits are essential for a proper installation. This allows the cooler to be easily removed or replaced if need be. Stands are optional depending on the distance between the ground and bottom of the cooler. The cooler should be up and off the ground by at least 3-4 inches. This allows for draining the cooler. The drain is located in the bottom of the cooler.

8. Overall design

There are several factors that go into the design of a greenhouse that can make a significant difference in the final product.

Ease of assembly: If doing the installation yourself, this can be a big factor.
Aesthetics: How the purlins line up with the glass junctures or the benches will affect the final appearance? Thought out clean lines of the design.
Ease in custom modifications: How does the factory look at custom sizes or designs? Are you getting exactly what you want from your salesman?

9. Labor and installation

As in most cases, dealing with hired labor can vary from being a terrible to a great experience. It is no different in the greenhouse industry. The quality of the greenhouse, the installation and the customer satisfaction is only as good as the quality of people you hire to do the work. This can also be reflected in the price being charged for the labor or in this case, the installation of your greenhouse. Price for labor is a relative thing. It can vary greatly. Sometimes with good reason, sometimes not. It is good to question your dealer or salesperson as to the qualifications of the installers. The ideal installers would be those who work full time in the greenhouse business, either in sales, manufacturing or a combination of both. Age and experience at least in the leadership role of the installation crew is also a plus. The crew will vary in size according to the size of greenhouse being installed. It can vary from 2 to 4 to 6 men.

Again, experience and knowledge trumps number of workers.

Everything else being equal, the installation is what will impact you the most in the overall experience of fulfilling a dream to own a quality greenhouse. Price should be an important factor, but not necessarily the deciding factor.

It is good to know some detail about what you may be purchasing. Ask more questions of your dealer or salesman. If he or she says “Ours is better”, ask for an explanation. Why is it better? The better question is, “All things being equal, what sets yours apart from others?”. Any good salesman should be happy and able to quickly provide an honest answer. Ask first, before offering your knowledge. This will be a good indication of what the greenhouse company is used to doing.

There are even more expensive greenhouses on the market, usually much higher in cost, mainly because of ornate design for luxury and elegance.

I hope this information has been helpful. Please call with any questions you may have. Thank you.

Steve Reno
Southern Greenhouses
www.southerngreenhouses.com
281-381-2435