When you're setting up your very first greenhouse for the winter, you must think about where you want to place it. Make sure the site is level and will receive a lot of winter sunshine. Think about the trees in your yard, as well as any other objects that may impede upon the sunshine reaching your greenhouse. The best place for your greenhouse is where it will receive a good amount of exposure from the southern sun.
You'll also want to make sure the greenhouse is big enough to grow your plants and for you to also have a work area (a bench for potting your plants and enough storage room for your tools and seeds). Make sure there's plenty of room to walk too.
Equally as important as your greenhouse's set up is your choice of plants. You'll want to grow cool weather plants since your greenhouse's temperatures will remain consistently under 50 degrees at night, then generally warm up as the air outside does throughout the day unless you're lucky enough to own a heated greenhouse. Fortunately, there are many different types of vegetables that you can grow in these types of temperatures. Some of the more ideal choices include garlic, celery, carrots, broccoli, spinach, parsley, kale, cauliflower, beetroot, cabbage, radishes, turnips, Swiss chard and spinach.
Although there are some greenhouses that don't need to be heated (e.g. a cool greenhouse), thus making them really easy to maintain, you should know that you can easily heat them when necessary. This is because the soil must grow out of the low 50s. With a heating mat, germination will happen, but otherwise your plants will grow really slowly.
Germination mats are definitely a way to bring some warmth into your greenhouse nonetheless. There are many other ways in which you can also heat your greenhouse without worrying about the exorbitant cost of fuel including building heat sinks.
One way to build a heat sink is by building a trench down the centre of your greenhouse, cover it with palettes and place compost on top of it. If you have a hobby-sized greenhouse, you can suffice with only a small hole built in the middle of your greenhouse. Even this will help moderate temperatures since the warm daytime temperatures will heat your compost up. Of course, you'll also have plenty of fresh compost available when you need it.
You can also build a heat sink by placing 55 gallon barrels in the corners of your greenhouse (or other practical locations throughout your greenhouse). Make sure you either buy black barrels or paint them black so they attract as much warmth from the sun as possible. While you can fill these with compost, even filling these buckets with water will make a difference of a few degrees, which is critical for your plants. There are even some people who have purchased bags of sand and wrapped them in black garbage bags.
Yet another option is to use electric room heaters. This is probably the most popular way to warm a greenhouse at night. However, you do need to use caution to follow your heater's safety instructions. You'll also want to make sure it's on a stable surface, away from anything that's flammable, and if you're running an extension cord, make sure all of your connections are snug.
There are also a lot of greenhouses that use wood (and even pellet stoves) for warmth. If you choose to install a wood stove in your greenhouse, you must check with the local authorities first since they'll typically have code regulations you must follow. Both wood and pellet stoves are easy to load and use, plus they typically come with a temperature control and some even have blowers that will circulate the heat for you.
However, you should use a great deal of caution if you choose to heat your greenhouse in this way because the stove's pipes will get really hot. This can cause the risk of melting things or even setting your entire greenhouse on fire. With careful planning or if you have a glass greenhouse you can avoid such risks fortunately.
More commonly used are electric and gas greenhouse heaters. With an electric heater you with need to have a power source either inside or close to your greenhouse. You’ll also need to make sure that the power source is safe and shielded from water getting near the plug itself. There’s a huge choice of greenhouse heaters available to buy, including gas heaters which can be run on LPG or mains gas sources safely.
Regardless of how you choose to heat your greenhouse, it's important for the heat to circulate properly. Failure to keep the heat circulating properly will cause both hot and cold spots, as well as the condensation that occurs when you heat up a cool place. Pay attention to whether your heater has a fan built into it or it needs more circulation. The best way to deal with this is with a fan. Of course, you can always invest in a ceiling fan as those are useful throughout the year.
It's also a good idea to insulate your greenhouse so you can conserve heat without expending too much fuel. One of the best types of insulation available for this is Visqueen, a durable sheet of polyethylene, but some people have used bubble wrap instead. While you may think this is crazy, when you think about the large bubbles of air inside of bubble wrap you can understand how it would preserve warmth while allowing the sun to still shine through.
There are a lot of small things you can do, and some major ones too, if you want to keep your greenhouse warm enough to still grow and cultivate plants yielding you delicious vegetables throughout the winter. While some of these ideas do cost a lot of money, others don't. It's really up to you to decide how much to invest in your greenhouse's design.