When choosing a new greenhouse for your garden there are several things to bear in mind if you are going to get the most from your choice. A wrong decision can prove costly in the long run so be sure you know exactly what you need before you buy. Here are some of the most important things to consider:
What Do You Need Your Greenhouse For?
If you are looking to grow flowers or vegetables all year round then a tightly sealed, insulated greenhouse with good light transmition, ventilation and heating will be most desirable. However, if your greenhouse will only be used for germinating seedlings or wintering less hardy plants through light winters then a simple plastic frame with a polythene covering will no doubt suffice.
Free Standing or Attached?
Depending on your requirements there can be major benefits of either of these types of structures. An attached greenhouse can be a simple lean-to style greenhouse attached to the side of your house or a more expensive sunroom style construct in fitting with the rest of your building. The main advantage of either 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. The major disadvantage here however is that being attached to your home means the greenhouse will have less direct exposure to the sun which may limit the types of plants you can grow effectively and positioning to minimise this is all important. A permit may also be required as this will be seen as a building extension to your home.
A free standing greenhouse on the other hand, offers many gardeners a much welcomed retreat away from the home, somewhere to escape the madness as it were. They are typically more expensive, requiring additional heating during the winter months and cooling during the hottest periods and you will also need to plan how to get electricity and a water to your new building. Your greenhouse will however have maximum exposure to sunlight.
What Size Greenhouse Do You Need?
Before you can begin thinking about anything else you need to know what size greenhouse you require. As a rule of thumb, whatever size you think you need right now is going to be too small for you a year later. Buy bigger than you need or you'll end up looking at a costly extension or a new greenhouse before long.
However, that doesn't mean you need to go overboard. If space is an issue then a lean-to greenhouse which attaches to the side of your house or other building might be the perfect solution. Equally, a mini greenhouse or a simple cold frame might cover your needs. Whichever size you choose, be sure to check out whether you need planning permission from your local authority before you put anything anywhere or you could be told to remove it later.
Which Frame Is Best?
Wooden, Metal or PVC? Experienced hobby greenhouse owners will tell you all about the benefits of a wooden frame. If you are building your own greenhouse then wood is also the easiest to work with. Wood is also a strong frame suitable for any covering you choose and if properly maintained will last a long time. The side benefit of wood comes about when you want to drive hooks in here and there to hang tools on or otherwise affix things to the frame. This is a simple hammer job with a wooden frame but a pain with an aluminium or galvanised steel frame. Wood does however need regular maintenance to protect against the humidity of the greenhouse environment and insects.
Aluminium, galvanised steel or other metal frame requires virtually no maintenance and is also strong enough to take any covering you choose. Metal frames do conduct heat and cold however and are therefore more difficult to heat and cool. Plastic frames can only be used with lightweight plastic sheet coverings and are usually only found in small structures likes portable and mini greenhouses.
Which Greenhouse Covering?
The four basic choices of covering you will find for a home greenhouse are the traditional glass panes, polycarbonate, fibreglass or polythene plastic sheeting. There really is no 'perfect' covering or construction material for a greenhouse, and what you choose will ultimately be as much reliant upon your budget as it is upon your requirements.
Plastic sheeting is cheap and the choice of commercial growers although probably not suited to the home user as it is less than attractive to look at, tears easily and typically needs replacing within 1 to 5 years.
For the hobbyist, the choice is most likely to be between a glass, fibreglass or polycarbonate cover. Glass is the traditional choice of greenhouse covering for hobbyists and of the three, allows the most unfiltered light to penetrate through and is the most attractive if your greenhouse is going to be a feature of your garden. It does however require a strong, sturdy frame and solid foundation and if your greenhouse is going to be placed near trees, around kids playing ball or in a particularly windy area or if you just happen to be a particularly clumsy gardener, can prove to be an expensive option. A glass greenhouse can also prove difficult to keep heated in the colder months and tough to keep cool in the summer months as glass is such a good conductor, heat and cold just pass through.
The major alternative to glass is polycarbonate. Polycarbonate sheets are lighter than glass and far less prone to breakage. Sunlight penetration through polycarbonate is less than achieved with a plain glass cover however, but as light diffuses through the sheets, plants are less likely to burn under strong sunlight. Single polycarbonate is as attractive as glass but the real value in polycarbonate comes from the double or triple thickness sheets which have an in-built air space between each sheet and can save a lot of money on heating costs.
Fiberglass is a lightweight solution which allows roughly the same amount of light to pass through as glass but is less aesthetically pleasing and is prone to staining over time.
Heating, Lighting & Ventilation
Depending on what you want your greenhouse for, you should consider the associated heating, lighting and ventilation requirements. For many, the requirements of their greenhouse is driven as much by their pocketbook as it is by any other requirements. The initial outlay is easy to see but hidden costs such as heating, lighting and cooling requirements are often overlooked. By chosing the right greenhouse in the first place you can often cut down on such costs - remember - glass and metal are conductors and are therefore harder to heat during the winter months which can prove costly if you are prone to long, cold periods. A lean-to greenhouse attached to the side of a building can, with a little bit of forethought, make use of that building's heating and lighting sources potentially saving money on both initial set-up and running costs.
Mark Falco is the owner of ukgardeningsupplies.co.uk - a UK gardening shopping guide featuring cheap greenhouses and more gardening tools, equipment and supplies at low prices from UK online garden centres and nurseries.