Category: greenhouses

Home Greenhouses III: Basic Structure Types

Over the last few months I’ve had the chance to talk about the popular topic of home greenhouses.  We covered a few of the basics in my first article, then touched on some regulations that might effect the building and management of home greenhouses in some areas.  In this installment we’ll talk a bit about common structures used for home greenhouse construction so you can consider which structure(s) might be right for your situation.

Types of Structures

Greenhouse structures can range from simple to the very complex.  While home greenhouses tend to fall on the simple construction side, there are still varying degrees of complexity within structures.  Greenhouse structures can be put into a few main categories that we’ll cover below.  The key to home greenhouse success is picking the structure that works best for you, your situation, and your budget.

Lean-to structures

Lean-to structures get their name from the fact that they “lean” on something for support.  Not in a literal sense, but in a sense that another structure, usually a house or maybe a storage building, provides at least one structural wall.  A common lean-to setup would have a three-sided greenhouse structure attached to the side of a house or another building.  This could range from a structure that is a few square feet for starting seedlings in the spring up to a full-size greenhouse attached to the side of a building.  A sun-room, if equipped for starting plants, could be considered a lean-to greenhouse (at least it would at my house, since it would be primarily for plants).  This type of structure can be cost effective. You reduce the amount of greenhouse surface you have to build and cover, unless you have special issues for connecting it to your home or other structures (like foundation issues, siding that is hard to attach to, etc). You do want to make sure it is done right especially if attached to your house so you reduce the chance of damage to your home. 

A quick search finds many lean-to greenhouse kits available, from small to large and every size in-between.

One benefit to a lean-to is that it can use the wall it is attached to as a heat sink – the wall absorbs heat through the day and then slowly releases it at night when it is colder.  If you have a large lean-to greenhouse that serves almost like a sun room you also add functional space to the house where you can enjoy the sun on warm winter days.  The heat generated by an attached greenhouse can help provide warmth for your home in winter or at least provide some extra insulation. But it can also result in excessive heat gain in the summer.  Lean-to greenhouses are also protected a little more structure wise – they use the building they are attached to for structural support and can often withstand weather, like high wind, a little better than free standing structures. 

Free standing structures

Simply put, a free-standing structure is one that isn’t attached to another structure.  It stands on its own structural framework.  There are a few different options we’ll talk about here which will be further expanded in future article installments on different types of materials used. 

Hoophouse greenhouse

A hoophouse greenhouse is built out of the same structure used for a high tunnel or hoophouse.  It consists of framing made by bent metal pipes and is covered with polyethylene plastic sheeting.  A high tunnel greenhouse would have heating, ventilation, and watering equipment added and would therefore require connection to electric, gas, and water utilities (see my previous article about what this means for a greenhouse being a taxable “permanent” structure). You may also pour a concrete slab for the floor of a hoophouse-to-greenhouse conversion, but gravel or any other floor covering is fine as long as it provides a stable surface and weed control.  The “greenhouse” that I inherited from the previous homeowners was left with bare ground so they could plant it like a conservatory. 

The hoophouse greenhouse I inherited with the new house. She ain’t pretty, but she works….sorta.

While these may not be the most attractive greenhouses, they are usually a more cost-effective option for a high-quality, efficient greenhouse.  Initial construction costs will likely be lower for a comparable quality framed greenhouse though the polyethylene covering will need to be replaced every few years as it becomes more opaque and light transmission reduces.

Free-standing structures

When envisioning a greenhouse, many people envision this type of greenhouse – one with straight sides, built with a frame covered in solid material.  These are definitely more attractive than hoophouse greenhouses and can add an attractive feature to your yard.  The most common way for home gardeners to build a free-standing greenhouse is through purchasing a kit.  There are a myriad of kits available online these days, of varying prices and qualities usually depending on the materials used in the construction.  The kits can be complex but set-up is usually pretty easy to follow though you might want to factor in the cost of hiring a contractor to help with the construction on a bigger kit.  Most often these kits need to be built on a concrete foundation or pad so you’ll want to consider the cost and logistics of pouring the needed support.  And you’ll also want to think about the utility connections to the greenhouse.

A frame built greenhouse. You can buy kits to build structures like this yourself, or you may want to hire a contractor to help if you aren’t handy. I saw this one at a community urban farm in Trenton, NJ.

Ridge and furrow greenhouses are framed greenhouses that are built together in tandem. These structures are usually used only in large-scale commercial production, so I’ll skip those for home greenhouses.

Geothermal greenhouses

Geothermal greenhouses are gaining in popularity, mainly because people are excited about reducing the need for using electricity or gas to control the temperature.  And I say reducing, because in extremely cold weather there will likely still need to be supplemental heat.  These structures are definitely different than your standard greenhouse.  These structures are usually sunken into the ground to take advantage of insulation by the soil and also the constant geothermal temperatures.  There is also usually a high solid wall on the north side of the structure, with a slanted roof made of light-passing material that faces to the south.  This allows maximum light to enter the structure and allows that light to heat the solid wall to hold and release it during the night when it is colder.  There is also usually an air intake in the ground a few hundred feet away that allows for the pulling of air through a tubing system to warm or cool the air with geothermal temperatures, depending on if it is cold or hot outside. 

This geothermal greenhouse project is run by the North Platte Natural Resource District in Scottsbluff, NE. Note that there is a solid wall to the right (with trees growing against it) and that the ramp leads UP to the ground level. The floor I’m standing on in this picture is about 6-8 feet below the ground surface. In addition to standard fare, this greenhouse grows citrus, pomegranates, and figs in one of the coldest parts of Nebraska.

A walpini greenhouse is a specialized/rudimentary style geothermal greenhouse that is sometimes referred to as a pit greenhouse.  Instead of building a structure, it is constructed of a pit dug into the ground and covered with a transparent roof.  While they sound simple, there are several drawbacks to these structures.  One – they don’t do well in wet areas or areas with high water tables, for obvious reasons.  Secondly, they were initially designed for use in areas near the equator with the sun almost directly overhead.  To function in latitudes far north or south you almost always have to build up a wall on one side to slant the roof cover toward the sun.  And even then it is unlikely that light will reach the floor of the structure where plants are growing. 

Summary

There’s a lot to consider when picking the type of greenhouse structure for your home greenhouse.  There’s often a trade-off between cost, quality, and aesthetics.  Options range from the simple to the complex in terms of size, structure, and function. So think about the goals you have for your greenhouse and consider the many different options available to you. 

Sources

https://aggie-horticulture.tamu.edu/ornamental/greenhouse-management/greenhouse-structures/

https://extension.uga.edu/publications/detail.html?number=B910&title=hobby-greenhouses

Home Greenhouses Pt. 2: Regulations & Restrictions

Last month I dipped into some of the considerations of owning or building a home greenhouse, having just “inherited” a greenhouse with my new house.  The questions and comments were numerous, so I decided to continue on discussing considerations for home greenhouse ownership and operation.  There will likely be a few more articles down the line….so strap in. 

This time around, I thought I’d talk about something that we hate to talk about, but is important to understand: rules and restrictions around what you can and can’t do, especially if you live in an urban area or municipality. 

I know, I know.  We all just wish we could do whatever we want, but when we live in close proximity to others there are usually some sort of rules we have to follow to keep the peace.  I have a little better understanding of how it works, now that I helped write an urban ag ordinance with our city planning department (fingers crossed is passes city council next month!) that will “decriminalize” urban farming, including controlled environment ag structures like greenhouses.  Of course, aside from what you can and can’t do there are tax implications that you should be aware of, no matter where you live (more on that in a bit).

Zoning, Ordinances, and Planning Commissions – oh my!

Most agricultural activity, which includes greenhouses, is likely regulated to some extent if you live within a municipality.  Even if you don’t live in a town or city, there could be certain building codes or ordinances on county or state levels that you’ll want to check into. 

You’ll want to look up your municipal code online, or call your municipal administration (like city hall, mayor’s office, planning office, etc.-whatever you have) to see if there are specific allowances or restriction for or against greenhouses.  There are a few scenarios that could play out here, so you’ll want to be prepared on how to proceed.  In general, you might find that greenhouses are:

  • Permitted, but only in certain zoning areas (more on that later)
  • Permitted, but requiring a permit of some sorts
  • Restricted altogether
  • Not mentioned at all

If you fall in that last category, then anything you do will exist in a gray area, where it isn’t strictly legal or illegal but the fate of your greenhouse (or any fines you might incur) would be up to interpretation by whoever is in charge of compliance (and what side of the bed they woke up on that day).  And your greenhouse could be made legal or illegal at any time in the future if some sort of ordinance or decision is made. In the case of our new ordinance here in Omaha, greenhouses and structures like high tunnels will be allowed, but only in certain zoning areas.  People who already have structures (and have for years) will now find that those structures are either allowed or banned (or will require a permit).  Of course, enforcement of issues like this are often complaint-based, meaning that the municipality probably isn’t driving around looking for your greenhouse but if you and your neighbor aren’t on good terms they can call and turn you in. 

As for zoning, there are several different categories and sub categories.  The ones you’re most likely to encounter are residential, commercial, industrial, and agricultural (there are others as well).  And then there are usually numeric (or named) sub-zones within those zones denoting the density or intensity of use on those zones. 

For example R-1 (Residential 1), might be for a single-family dwelling whereas R-3 would be for a small apartment building.  C-1 (Commercial-1) might be for a single-use building like a stand-alone fast-food restaurant and C-8 might be for a skyscraper office headquarters.  Municipalities use these codes to denote what is and what is not allowed in certain places.  For example, the code we worked on for Omaha allows certain types of farming on all residential zones with a conditional use permit and on commercial zones without a permit.  (Home gardens and even community gardens are not considered farms and are allowed on all residential zones without a permit.)  Many municipalities may also have agricultural zoning on properties around the periphery but still within the city/town limits.  On lots like this, most agricultural practices are allowed. 

Three things you can do with NYC's new zoning and land use map - Curbed NY
Your municipality may or may not have a map available showing lot zoning, like this small area of NYC.

Since a greenhouse is a structure, there may or may not be a requirement for a permit for the structure, even if it is allowed.  This could be dependent on a number of factors, including whether it is considered a permanent or temporary structure, whether there are utilities going to it (which is usually the case for a greenhouse), or even how the structure is constructed.  In some areas, it comes down to how pretty or ugly the city and your neighbors think the structure might be.  In discussions for our ordinance, there was talk of not requiring a permit for a greenhouse but requiring permits for structures like high tunnels/hoophouses because there’s an (incorrect) assumption that greenhouses are prettier than high tunnels.  But many people make greenhouses out of those structures (the greenhouse I inherited is just a high tunnel with a space heater). There was also an assumption that a greenhouse wouldn’t have loud, flapping plastic but a greenhouse would (I kid you not). 

The tax man cometh….for your permanent agricultural structure.

One other thing you’ll want to consider about a greenhouse has to do with the tax bill.  Since greenhouses are considered permanent structures, many places consider them a permanent improvement to your property and will add them to the tax bill like they might do an out building or garage.  The municipality will definitely know about it if you have to apply for a permit or if you get a visit from the assessor.  But this could also be dependent on how your structure is built.  If you build a solid sided greenhouse (one of the nice looking ones) with a concrete slab floor, permanent utilities, etc then it will definitely considered permanent.  But if your structure is more like a high tunnel/hoophouse like mine (a high tunnel in a trench coat pretending to be a greenhouse) then it could be considered a temporary structure and not taxable. 

My high tunnel parading around like a greenhouse

High tunnels are considered temporary since you could really take them down at a moment’s notice (and some planning department officials think this means that you take them down and put them up each season, despite how much an extension educator tries to convince them otherwise….but I digress). So your mileage may vary depending on your local rules and how your structure is constructed. 

So what home greenhouse topic should we cover next?  I’m sure there’s plenty of questions out there – be sure to leave them in the comments.  Also – would you like to have your greenhouse featured in a future article (this means I don’t have enough home greenhouse pictures)- feel free to send them to me at john dot porter at unl.edu.