Greenhouse Buying Guide: Basics of Choosing a Greenhouse

Greenhouse Buying Guide: Basics of Choosing a Greenhouse

When choosing a new greenhouse for your garden, there are several things to consider if you are going to make the most of your choice. A wrong decision can be costly in the long run, so make sure you know exactly what you need before you buy.

What do you need your greenhouse for?

If you are looking to grow flowers or vegetables throughout the year, a hermetically closed and insulated greenhouse with good light transmission, ventilation and heating will be the most convenient. However, if your greenhouse will only be used to germinate seedlings or to overwinter less hardy plants in mild winters, a simple plastic frame with a polyethylene cover will certainly suffice.

Independent or attached?

        Depending on your requirements, there can be great benefits from any of these types of structures. An attached greenhouse can be a simple shed-style greenhouse attached to the side of your home or a more expensive sunroom-style construction that fits in with the rest of your building. The main advantage of any of them is in terms of maintenance and running costs, as an attached greenhouse will benefit from being very simple to adapt to your existing lighting, heating and water sources. However, the main downside here is that being attached to your home means that the greenhouse will have less direct sun exposure, which can limit the types of plants you can effectively grow, and the location to minimize this is very important. A permit may also be required as this will look like an extension of your home building.

A freestanding greenhouse, on the other hand, offers many gardeners a very welcome retreat away from home, a place to escape the madness, so to speak. They are generally more expensive, require additional heating during the winter months and cooling during the hottest periods, and you will also need to plan how to bring electricity and water into your new building. However, your greenhouse will have the maximum exposure to sunlight.

What size greenhouse do you need?

        Before you can start thinking about anything else, you need to know what size greenhouse you need. As a general rule of thumb, whatever size you think you need right now will be too small for you a year later. Buy larger than you need or you'll end up looking for an expensive extension or new greenhouse in no time.

However, that doesn't mean you should overdo it. If space is an issue, then a semi-detached greenhouse that clings to the side of your home or other building could be the perfect solution. Similarly, a mini greenhouse or a simple cold frame can meet your needs. Whatever size you choose, be sure to check if you need planning permission from your local authority before putting something anywhere or you might be told to remove it later.

What frame should I use?

        Wood, metal or PVC? Experienced hobbyist greenhouse owners will tell you all about the benefits of a wooden frame. If you are building your own greenhouse, wood is also the easiest to work with. Wood also makes a sturdy frame suitable for whatever siding you choose, and if properly maintained it will last a long time. The secondary benefit of wood comes when you want to insert hooks here and there to hang tools or attach things to the frame. This is a simple hammer job with a wooden frame but a pain with an aluminum or galvanized steel frame. However, wood needs regular maintenance to protect against humidity in the greenhouse environment and insects.

The aluminum, galvanized steel, or other metal frame requires virtually no maintenance and is also strong enough to support whatever deck you choose. However, metal frames conduct heat and cold and are therefore more difficult to heat and cool. Plastic frames can only be used with lightweight plastic sheet covers and are typically only found in small structures such as portable and mini greenhouses.

What greenhouse cover?

        The four basic coverage options you will find for a home greenhouse are traditional glass panels, polycarbonate, fiberglass, or polyethylene plastic sheeting. There really is no "perfect" coating or building material for a greenhouse, and what you choose will ultimately depend on both your budget and your needs.

Plastic sheeting is inexpensive and the choice of commercial growers, although probably not suitable for the home user as they are not attractive to the eye, break easily, and usually need to be replaced in 1 to 5 years.

For the hobbyist, the choice will most likely be between a glass, fiberglass or polycarbonate cover. Glass is the traditional greenhouse cover option for hobbyists, and of the three, it allows the least filtered light to penetrate and is the most attractive if your greenhouse. However, it requires a strong and sturdy frame and a solid base and if your greenhouse is going to be placed near trees, around children playing ball or in a particularly windy area or if you are just a particularly clumsy gardener, it can prove to be an expensive option. A glass greenhouse can also be difficult to keep warm in the colder months and difficult to keep cool in the summer months, as glass is a good conductor, heat and cold just pass.

The main alternative to glass is polycarbonate. Polycarbonate sheets are lighter than glass and much less prone to breakage. However, the penetration of sunlight through the polycarbonate is less than that achieved with a simple glass cover, but as the light diffuses through the sheets, the plants are less likely to burn under strong sunlight. Plain polycarbonate is just as attractive as glass, but the real value of polycarbonate comes from double- or triple-thick sheets that have a built-in air gap between each sheet and can save a lot of money on heating costs.

Fiberglass is a lightweight solution that allows roughly the same amount of light to pass through as glass, but is less aesthetically pleasing and tends to stain over time.

Heating, lighting and ventilation

Depending on what you want your greenhouse for, you need to consider the associated heating, lighting and ventilation requirements. For many, the requirements of your greenhouse depend as much on your pocket as on any other requirement. The initial outlay is easy to see, but hidden costs, such as heating, lighting, and cooling requirements, are often overlooked. By choosing the right greenhouse in the first place, you can often cut these costs; Remember, glass and metal are conductive and therefore more difficult to heat up during the winter months, which can be expensive if you are prone to long, cold periods. A greenhouse attached to the side of a building can, with a little foresight, make use of that building's lighting and heating sources, which could save money on both initial installation and running costs.