Is there anything dreamier than the thought of soaking in a hot tub, looking up at the moon and stars, with all your beloved plants surrounding you? Many people have created a private paradise in their back garden by installing a hot tub inside a greenhouse. Besides the relaxing benefits it has for the user, it is also brilliant for creating warm, humid growing conditions that tropical plants love.
You can have a hot tub in a greenhouse. It is a great way to keep a hot tub sheltered from the elements and harness the heat retentive properties of water to warm the greenhouse. Ventilation, temperature, and accessibility are important to consider when planning to build a hot tub in a greenhouse.
If the idea of having a hot tub inside your greenhouse excites you, you will need to keep a few things in mind to make this dream a reality. There are some practical factors to consider, like the size and accessibility of the greenhouse and hot tub, how to adequately ventilate the greenhouse and prevent damage from condensation. This article is a guide to everything you need to know before you build a hot tub inside a greenhouse.
Heating a Greenhouse with a Hot Tub
A body of water retains heat for much longer than air. This is the reason many people keep black water-filled barrels in their greenhouse – to act as a heat sink. During the day, the water heats up by absorbing solar radiation. At night, the water remains warm and radiates heat into the greenhouse.
While there are cheaper, more efficient ways of heating a greenhouse, putting a hot tub inside is definitely a viable way to add warmth to your greenhouse.
In terms of efficient energy use, having a hot tub in a greenhouse is a great idea. You would be using electricity to heat the hot tub anyway, and instead of just losing that heat to the environment, one can capture it and use it to warm the air in a space.
Sinking the hot tub into the ground, rather than having it standing above ground, will maximize the heat retention, as the soil around the tub will further insulate it.
Practical Considerations for a Hot Tub in a Greenhouse
As one can imagine, there are quite a few factors to consider and plan for before you build a hot tub greenhouse. By taking these practical measures into consideration, you will avoid running into trouble during the installation of the hot tub greenhouse or later when you are using it.
- Size and accessibility. The first and most obvious issue is to find a greenhouse that is large enough for the hot tub you have or to get a hot tub that is small enough to fit inside the greenhouse you have. There is no particular order in which things must be done but ensure that there is enough space in the greenhouse around the hot tub and that the door opening of the greenhouse is large enough to fit a hot tub. It is easier to install a hot tub and then build a greenhouse around it.
- Ventilation. Hot tubs release lots of steam. Without adequate ventilation, the water vapor will condense on the greenhouse material. Include plenty of air vents in your greenhouse design and consider installing extractor fans. Place a cover over the hot tub when it is not in use to prevent water vapor from escaping into the air. Using an insulated hot tub cover is energy efficient because it keeps the water warm without needing to use electricity.
- Location. Unless your hot tub is wood-fired, you will need to install it somewhere close to an electrical socket—plan for this when siting your greenhouse and deciding where to place the hot tub inside the greenhouse. By considering the power supply, you avoid having to spend extra time and money digging a trench to run and bury an electrical cable.
- Temperature. Plastic greenhouse panels magnify solar UV rays and retain heat much better than glass. This can lead to the problem of overheating the greenhouse. Plastic hot tub covers can warp and melt!
Here’s a quick short video showing a monastery that has a hot tub in their greenhouse:
Advantages of Having a Hot Tub in a Greenhouse
There are many fantastic advantages to having a hot tub inside a greenhouse:
- Creates a unique, luxurious space to relax in.
- Enjoy your hot tub all year round, no matter the weather.
- The hot tub water retains heat, warming the greenhouse.
- Reduces the cost of heating the greenhouse.
- Protects the hot tub from weather damage.
- Great for plants that thrive in hot, humid conditions.
Disadvantages of a Hot Tub in a Greenhouse
Consider the following downsides to putting a hot tub in a greenhouse:
- The temperature inside the greenhouse may get too hot, especially if it has plastic panels.
- Condensation caused by the hot tub will lead to wood inside the greenhouse rotting or metal becoming rusted.
- Hot tub covers are often made from vinyl material that can form cracks from heat and cold stress.
- Very hot and very cold conditions will cause the pH level in the hot tub to change. Frequent water testing is necessary.
Hot Tub Chemicals and Plants
Hot tubs do not heat up enough to kill microorganisms. Therefore, to prevent harmful bacteria and algae from growing in the hot tub, one needs to add chemicals to the water regularly.
The most popular chemicals used to sanitize hot tub water are chlorine and bromine. Unfortunately, these chemicals are released into the air, causing an unpleasant odor, eye- and skin irritation, and coughing. They can also be absorbed by plants.
While chlorine is a micronutrient that plants require to photosynthesize, too much chlorine can be toxic to plants. If too much chlorine accumulates in a plant, the leaves will turn yellow and brown.
Because chlorine and bromine kill microorganisms, they will also kill millions of beneficial soil microbes if greywater from a hot tub is used to water plants.
It is crucial never to use hot tub water on any vegetables that you are growing!
Here’s a video showing how to build a hot tub enclosure to see what’s involved, with more info below:
Greenhouses Made for Enclosing a Hot Tub
The idea of having a hot tub inside a greenhouse is gaining popularity, and there is now a company that manufactures greenhouses specifically designed to enclose a hot tub!
Solardome® is a UK-based company that creates glass geodesic dome greenhouses that are designed to enclose a hot tub or swimming pool. Their greenhouses are architecturally stunning and are built with enough ventilation to overcome the issue of condensation.
Putting a hot tub in a greenhouse is a great idea for many reasons. Besides creating a tranquil space to relax amongst your plants, you will benefit from the lower cost of heating your greenhouse. The plants will love the heat and humidity that the hot tub creates.
Building a hot tub enclosed in a greenhouse is not a straightforward DIY project. It is important to consider a range of factors when planning a project of this kind:
- Size, space, and accessibility. The hot tub needs to fit inside with ample space around it, and the greenhouse must have doors large enough to accommodate the tub.
- Temperature. Over-heating can be an issue.
- Ventilation. The greenhouse needs more air vents than usual.
- Condensation. Steam will escape from the tub and condense in water drops on the greenhouse material. This moisture can cause problems in wooden structures or lead to rust.
- Proximity to a power source. Hot tubs need electricity, so the greenhouse needs to be built near the mains power supply.
You can buy greenhouses that are specially designed to enclose a hot tub. Of course these are very expensive, but one can take inspiration from them when planning your own greenhouse build.