Planning on building a greenhouse or have one that just isn’t working well for you? Get tips on how to have the best greenhouse ever.
Building a greenhouse is a wise investment if you want to get serious about growing food. It allows you to grow heat-loving plants you can’t normally grow in your climate and allows you to start seeds for all crops without taking over your whole house!
Build your greenhouse bigger than you think you need or plan for expansion.
Trust me on this!
In a small backyard you’ll of course run into space limitations. That’s what happened to me. But I still regret not building my greenhouse just a bit bigger.
Or if your funds or time don’t allow you to build a large greenhouse right now, at least plan for expansion some day. A standard greenhouse can easily be added to by adding another greenhouse to the end to make a longer greenhouse.
The benefit of having two greenhouses end to end means that you can probably have a dividing door in the middle and ventilate and heat both sides differently for different types of plants.
The other alternative is simply to erect another greenhouse in a different location on your property if you have the space. However you do have then double the expense plus need to provide all the greenhouse amenities in each greenhouse that tips below will cover.
North wall of greenhouse
Build the north wall as an insulated wall as it doesn’t contribute to solar gain at all.
If you live in the Northern Hemisphere the sun “rises” in the east, “moves” to the south and then “sets” in the west.*
*I know, the sun doesn’t actually move, it’s the earth but just using common everyday language. And if you live in the Southern Hemisphere then the south wall is the one you want to have insulated.
That means that the north wall of the greenhouse doesn’t get any direct sunlight. And the main reason to have glazing (glass or plastic) on your greenhouse is for solar gain. When the sun shines into the greenhouse, it heats it up.
Therefore your north wall does very little to help solar gain and in fact can release all that heat from the day into the night, as glass or plastic does not insulate as well as a solid wall.
The north wall therefore should be build like a house wall, either out of brick or lumber.
If building from brick, the wall will heat up during the day as sun shines into the greenhouse. It helps to paint the wall inside the greenhouse a dark colour such as black to maximize capturing the sun’s heat.
If building from lumber, insulate the wall with regular house insulation. Ideally avoid using a window in this wall as you should get enough light and ventilation from the other walls.
If you’re using a kit greenhouse which usually has metal framing, you can leave off the glazing on the north wall and then build an insulated wall in place of or just outside the kit wall framing.
In my case I butted my lean-to greenhouse up to my second floor deck and build a small garden shed underneath the deck. So my greenhouse’s north wall is shared with the garden shed and I have easy access to my tools and supplies I store there, leaving more room in the greenhouse for plants!
Greenhouse knee walls
In addition to having a solid, insulated north wall, you also want to reduce glazing to the minimum you need.
If you’re growing mainly on benches and raised beds, you can build knee walls on all or most of the walls, since you don’t need sun or light at the very bottom.
Similar to the north wall, you build these as insulated walls, about knee high. In my greenhouse they are about 3 feet high (approximately 1 meter). Framed glazing then goes on top.
These are best built if you’re building a greenhouse or having one built from scratch like I did.
Or again if you’re building from a kit, you can build insulated knee walls on the outside of the kit’s walls the same height as a horizontal wall framing member.
A greenhouse without adequate ventilation will cause all kinds of problems with your plants.
You can get mildew and mold problems when plants are in a very wet environment, especially in winter when it’s cold.
But even in summer when it’s dry, having no ventilation will cook your plants and they likely will die.
So one of the top priorities when building a greenhouse from scratch or shopping for a kit is to make sure there are enough vents and windows you can open.
You ideally want windows or vents low down where there is cooler air at ground level and have it drawn out vents in the ceiling/roof.
Now you don’t want vents open at nighttime when you want to conserve all that heat gain from the day. So using some type of automatic vent opener is key to save time and avoid forgetting to either open or close them!
For more info on automatic greenhouse vent openers check out my article How To Keep Your Cool With Automatic Greenhouse Vent Openers
I also have a half door or dutch door on my greenhouse, so I open the top half in the morning and close it again in the evening. So far I haven’t found an automated way to do it!
Properly framed and glazed greenhouses are expensive and a lot of work to put up! Even my greenhouse rebuild I did myself several years ago still cost quite a bit on lumber (I used cedar) and time, even though I reused most of the windows of the old greenhouse it replaced.
A less expensive and generally easier-to-build option is a polytunnel. These use a lightweight frame made from plastic pipe (such as used in irrigation pipes in sprinkler systems) or electrical conduit and a clear or translucent greenhouse plastic sheeting.
They are not as durable as a real greenhouse as the plastic will eventually need to be replaced, but they can serve as a temporary greenhouse until you can build your dream greenhouse.
And they are somewhat portable and can be dismantled to be used elsewhere.
You can either buy the raw materials from a home centre and the greenhouse plastic from a greenhouse supplier or buy a whole kit that includes everything.
Water source in greenhouse
A running source of water for watering your plants and cleaning right in your greenhouse or just outside the door will go a long way to save you time and effort.
It may involve running some buried pipes to your greenhouse from the nearest hose bib on the outside of your house. Or you could do it the simple way and have a long hose temporarily connected in summer and put it away in winter to avoid it bursting from freezing temperatures.
In my case my greenhouse is a lean-to style and I have a hose bib connected to the house water system right on the east wall. I went one step further though and also had a plumber run a hot and cold water line run from my laundry room on the other side of the wall to a laundry sink that I build a simple cabinet for.
So I can wash my hands with warm water and use hot water to clean pots and tools! Definitely welcome on a cool fall day.
Tools and supplies storage in your greenhouse
In order to avoid the walk to and from a garden shed (and then forgetting something and having to go back!), have at least the most used tools and supplies stored in your greenhouse.
Usually you’ll have some space underneath benches or maybe against the north wall where you can build some shelves for various supplies and pegboard to hang your tools.
In my case I have some storage in the greenhouse but I also have my garden shed attached, so I can just go in there steps away from where I’m working.
If you want to see how I organized my tools and supplies in both locations, check out this video tour:
If you’re wondering what supplies and tools you need, check out these buying guides for some ideas:
- 10 MUST HAVE GARDENING TOOLS THAT YOU NEED TO START GARDENING
- 15 SPECIAL GARDENING TOOLS THAT YOU WILL FIND HELPFUL
- 21 BEST GARDENING SUPPLIES TO KEEP IN STOCK
Greenhouse rainwater collection
Warning: In some areas it is illegal to collect rainwater because of water rights. Check first to ensure you’re not breaking any rules.
Greenhouses have roofs made of smooth materials such as glass or plastic and are perfect for collecting rainwater from. Plus controlling water runoff from a large surface is always desirable as erosion and flooding can occur if you don’t handle the water falling on your greenhouse roof.
Putting on gutters (or some kit greenhouses come with gutters) and then funnelling the water into one or more water barrels is not only good for the surrounding area but you can use the rainwater to water your plants in the greenhouse.
Even better is if you can move the water barrels inside the greenhouse and put the drain hose of your gutters through a hole in a wall or framing member to drain into the barrel(s).
Once the barrels are full they act as a mass that will heat up from the sun during the day and release the stored solar energy at nighttime when temperatures drop. In fact some commercial greenhouses will use a whole wall of water-filled black-painted barrels on the north wall to collect heat energy.
Greenhouse temperature monitoring
Greenhouse temperature is very important.
Obviously if the temperature drops too low you run the risk of losing plants in winter.
But just as dangerous is if the temperature soars too high in summertime. You can lose plants that way too, especially if your ventilation is not adequate.
So having a way to monitor the min and max temperatures during the day is important. And of course remember to check!
You can do it the manual way and simply have a thermometer in the greenhouse. But it only is useful if you remember to go into the greenhouse to check the temperature. And it only gives you the current temperature.
Or you can get a relatively inexpensive min/max thermometer that uses resettable indicators to show you how low and how high the temperature went in a day. You do have to manually reset the indicators and also check it once a day.
Here is one that is available on Amazon.com (bonus is that it also measure humidity – more on that in the next tip):
Or you can monitor the current temperature remotely. There are relatively inexpensive wireless transmitter and receiver combos that do this.
Or you can go with more sophisticated (and expensive) sensors that connect to your home’s wireless network and then you can check on your phone or computer and even get graphs showing the minimum and maximum temperatures over time. And get alerts if temperature goes below or above a certain set point.
More info on sensors plus links to purchase on Amazon.com in my article on 7 Best Greenhouse Accessories And Features For The Perfect Greenhouse
Greenhouse humidity monitoring
Humidity is just as important as temperature in a greenhouse.
I’ve already covered some of the ways to monitor temperature above, so the same options generally apply to monitoring and recording humidity. There are lots of options, some handling both temperature and humidity.
Usually you don’t want humidity levels to go above 80%. And depending on what you are growing, you also don’t want humidity levels to drop too low, under 50% can result in problems for your plants.
If you have too high humidity you’ll need to improve ventilation, lower watering or fix leaks in your greenhouse roof.
Store summer flowers in the greenhouse
In the busy growing season in summer my greenhouse serves as a growing house for warm-season crops such as tomatoes, peppers and melons.
In winter, I store all my summer flower baskets and containers as well as my banana plant (still in a container as it’s young) to keep them frost-free. If the temperature stays warm enough, they continue to flower!
I have several clothes rods hanging from my greenhouse roof to hang my baskets from to reclaim floor and shelf space.
I also store some of my more tender herbs in the greenhouse in winter.
It helps to have the tender plants in containers of course otherwise you’d have to dig them out, plant them in a container and do the reverse in spring.
Greenhouse potting bench
The greenhouse will normally be your go-to place to do some repotting or washing of tools and pots as well as a place to start seeds in spring. It will generally be warmer than outside, even if the sun isn’t shining as you’ll be protected from the wind and rain/snow.
So having a potting bench or all purpose bench for doing some of those tasks on is essential. Your potting bench can also double as a seed starting bench.
In my case I build a few tables/shelves at a comfortable height when standing. They are slotted so that any excess water runs down (and I’m sure to store anything underneath in watertight containers or bags) in case I overfill pots.
You can also construct a free-standing potting bench or purchase one. Here is a versatile one on Amazon.com:
The nice thing about a free-standing potting bench is that you can move it outdoors when the weather warms up as the greenhouse may become too hot to comfortably work in.
Greenhouse electric power
Next to having a good supply of water is a good supply of safe electrical power.
You’ll need to power heating mats and grow lights for seed starting, power heaters and ventilation fans, power a vacuum (see next tip) and other such electric devices.
It pays to hire an electrician if you need to run an electrical cable to your greenhouse. You definitely want to make sure it is buried correctly so that you don’t slice through it with a spade! And the connections at each end need to be made in accordance with the electrical code in your area.
You also need to keep in mind a greenhouse can potentially be a wet area, so all outlets should be GFCI (Ground Fault Circuit Interrupter) or protected by a GFCI circuit breaker.
And as the example photo shows, try and get outlets that have covers over them that you can close. Even better are ones you can close while something is plugged in. Here is an example on Amazon.com:
Vacuuming the greenhouse
Yes, you read that right: vacuuming the greenhouse!
I find vacuuming works much better and faster than using a broom or brush and dustpan. You can be a lot more thorough and you avoid putting clouds of dust into the greenhouse air.
However before you even think of using the household vacuum to clean up the mess in your greenhouse, think again. You might have some resistance from other members of your household!
Instead get yourself a wet-dry vacuum that is usually used in workshops to clean up – you might already have one for that purpose. These vacuums are designed to deal with things such as spilt soil, dead leaves from plants, spider webs (although try to keep some spiders as they do eat pests), and other debris that tends to collect. You can even vacuum up puddles of water.
Make sure to have a safe outlet to plug in the vacuum or use an appropriately rated long extension cord to the nearest outlet on your house/garage.
Cleaning greenhouse windows
Getting enough light into the greenhouse is critical. Especially in winter when the sun is weaker in the northern latitudes or if you live in a climate with lots of grey winter days (that’s the west coast of Canada where I live).
So it’s important that you clean your greenhouse windows and roof panels regularly especially in fall for maximum light transmission.
Do a quick vacuum (see previous tip) to get rid of any spiderwebs and major dust.
Then grab a bucket and a squeegee used for cleaning windows and start cleaning from the top down.
If possible only use fresh water with no added chemicals as you don’t want it dripping on your plants. Or if you find some stubborn spots you can use a biodegradable dish soap, just try and catch any drips in a cloth or move plants out of the way if you can.
Use an extension pole to reach the roof panels. This is much safer than using ladders and stretching over panels to reach the farthest corners.
Greenhouse backup heat source
If you’re using your greenhouse in winter to store tender plants and don’t want to lose them in cold climates, you’ll likely have to add some sort of heat source. It will act as a backup in case the temperatures plummet too low.
There are many options for heat sources including electric heaters, propane or natural gas heaters and wood stoves, including rocket stoves.
Each one has it’s advantages and disadvantages, so best to do some research into the different types and see what works best for you.
Above all else, make sure to heat your greenhouse safely! If using electric heat, make sure your electric supply is protected with a GFCI circuit (mentioned in a tip above) and if using any extension cords, make sure they are rated for the heater’s load.
For propane, gas and wood heaters, make sure their flue gases are properly routed out of the greenhouse to avoid carbon monoxide poisoning.
And with any type of heat, keep all flammable materials away from the heater.
Polycarbonate greenhouse roof
Traditionally glass has been used in greenhouses, mainly because of its property of letting the most amount of light into the greenhouse.
However using glass has some downsides, especially when using it for roof panels.
It is heavy, so getting it on the roof requires help. It also is breakable, regardless of how the glass is treated. Even tempered safety glass will break if you hit it hard enough on the edge and then it explodes into tiny pieces of glass (don’t ask me how I know that firsthand!)
And glass is hard to cut unless you have the right tools and even then you run the risk of breaking the glass. Tempered glass can only be cut by a glass shop with specialized equipment.
If you frequently get hailstorms or have trees close by that could drop large branches, the safer alternative is using a plastic sheet such as polycarbonate. It also is much lighter and can be easily cut with the right tools.
You’ll give up some light transmission but twin wall or multi-wall polycarbonate has a better insulation value than glass, so you may actually retain more heat at nighttime. It works better in summer by filtering the sunlight when the high sun can be too hot. Whereas in winter with the sun lower, light normally doesn’t come in through the roof anyways.
You can also glaze the walls with polycarbonate but then you do give up quite a bit of light transmission. Therefore in my greenhouse I reused the existing glass windows from my old greenhouse above the knee walls.
Greenhouse drip irrigation system
If you have a lot of plants in the greenhouse in different spots, it can take a bit of time to water everything!
So you can add a drip irrigation system for more carefree watering. This also works well if you go away on vacation and don’t have anyone that can take care of your plants.
Most systems are easy to install. And you can put them on a timer so that they really are “set it and forget it”.
However do check to make sure they are working properly and that your plants are getting enough water. You may have to adjust the drippers for individual plants that either need more water or less than other plants.
Here is a kit available on Amazon.com that has everything you need to setup drip irrigation in a small greenhouse. It’s designed mainly for containers and hanging baskets. You can also buy individual parts to extend this system or just buy parts separately for a more custom system, especially if you also have in-ground or raised beds:
Green energy for the greenhouse
A few summers ago I setup a solar panel close to the greenhouse. At first I was going to use it for a pump to pump water from my rain barrels into a watering can or hose.
But then at work we were getting rid of some old computers and I realized the power supply fans could be used for something.
So I came up with a system of these fans hooked up to the solar panel for free ventilation!
For more info on how I set this up, see my article Free Greenhouse Ventilation Via Solar Panel
I currently don’t have a battery or inverter attached to my system, so I can’t run grow lights or heating mats at nighttime, but that is an upgrade I’m considering. As well as adding more panels!
Instead of solar panels, you can also setup a small wind turbine. Make sure to check local regulations as there are restrictions in most urban areas on size and location. Or if you live in a rural area and happen to have a stream nearby, you can also look into micro-hydro and setup a water turbine to create power. Lots of different options to save money and be more self-sufficient.
Greenhouse watering cautions
Your plants will dry out fast in the greenhouse in summer, especially on hot sunny days. Even if you overwater, water will evaporate and so long as you have good ventilation the humidity levels in your greenhouse should stay low enough.
However it’s really important that you avoid excessive watering in winter as too much dampness can lead to mold, mildew and fungus problems. Even just standing water in drip trays can cause issues.
And where possible use rainwater. Rainwater is not as cold as tap water, has less impurities and minerals. When harvesting the rainwater, make sure to only use roofs that are either tile, metal, glass or polycarbonate/fibreglass. With a cedar shake or asphalt tile roof, there is some concern that the rainwater will contain toxins, which you don’t want on your food plants.
Greenhouse seating area
Finally consider setting up a cozy seating area in the greenhouse to enjoy a sunny winter’s day. You don’t need to only work in a greenhouse!
Some greenhouses are big enough to even use as a conservatory, where you could have your meals in.
But even the smallest greenhouse may have room for a folding chair that you can set in a corner for a nice cup of hot coffee or tea after puttering around in your greenhouse!
Just don’t sacrifice your plants to the great outdoors so that you can be comfortable!
Greenhouses are a great investment. With these tips you can make your greenhouse the best one on the block! While you might not be able to take advantage of all of these tips, pick and choose which ones work best for you.
If you enjoyed this article, have something to add or have any questions, please leave a comment below.
Wishing you all the best!
Tranquil Urban Homestead, Victoria, BC