Converting an Old Wine Cellar into an Indoor Garden

Our new house has an old wine cellar—but I can’t keep the stuff around long enough to warrant storage on this scale! Instead, I’m going to build an underground indoor garden or “grow room”. I hope you will follow my progress, from design, build, maintenance and hopefully expansion over the coming months.

So here it is. The cellar of my dreams! 18 feet long, 8.8 feet wide with a ceiling 9.5 feet high. I can’t wait to get growing in here but there’s a lot of work to be done first. 

The arched ceiling, comprised of flakey rock, needs some attention.

My plan is to create a “room within a room” – I want a nice rectangular grow space with 90 degree angles and a ceiling that can easily support grow lights, ventilation and air-filtration equipment. I also need to install a bunch of electrical sockets on their own ring main, as well as a lighting controller.

A 1000W high intensity discharge (HID) grow light can cover between 16 and 25 square feet of growing area. Once the grow room is built, I will have room for up to eight 1000W grow lights, although I’m going to start off with just two, dial it in, and only then look to expand. I’ve seen a few indoor gardening projects fail because growers took on too much, too soon—I don’t intend to add another entry to that catalog!

Looks like someone already tried to plaster the ceiling, and it was either chipped away or it fell off.

Here are five important things I need to consider:

1) Location and Insulation

The better insulated your indoor garden, the easier and more efficient it will be to maintain a healthy environment. A sun-facing bedroom with a large window in a poorly-insulated wooden house in California will cost you a fortune to keep cool in the summer and heat in the winter.

I’m fortunate to have this cellar. It benefits from the natural insulation of the surrounding rock and earth. Subterranean grow rooms can suffer from issues relating to high humidity though—especially when full of transpiring plants. I will need to ensure proper ventilation and maybe invest in a dehumidifier too at some point.

2) Air Intake

Indoor gardens tend to be either ventilated or air-conditioned with supplemental carbon dioxide. I’m opting for the former. (Although I don’t rule out the AC route further down the line.) Whichever path you choose, your goal remains the same: keep temperatures moderate and maintain carbon dioxide levels so your plants can photosynthesize.

  Check out the thickness of my walls! Yes, they’re solid!

I like to draw incoming air from an adjacent room rather than the outdoors. I find the temperature and humidity of the incoming air is more stable and there’s reduced risk of sucking in bugs into your indoor garden.

However, my house is old (It was built over 300 years ago) and the walls are incredibly thick! Whereas, in the past, I might have simply busted a hole through to an adjacent room and fitted a fan and a flange, it’s simply not possible here without some heavy duty equipment. There has to be an easier way!

You can see the door to the cellar in the photo above. It’s one of two double-doors. I could take one of the doors out of action and cut a hole in the lower panel—but I like having both doors available for bringing large equipment in and out. Fortunately there’s a small ‘oubliette’ (mini-cellar) just off the main cellar that shares a thin wall the adjacent room so I’ll install a vent and use my ‘oubliette’ as a sort of ‘lung room’ for the main garden. I’ll talk about this in more detail in a future post.

3) Air Extraction

 This old servants’ staircase up to the kitchen is no longer in use (damn, where did all my servants go?) but it does provide some awesome air extraction possibilities!

So—I need to bring cool, fresh air in from an adjacent room—and I need to expel hot air from the air-cooled Magnum XXL 6” reflectors and from the garden itself. These two processes are commonly referred to as “air exchange” – it’s all about letting your garden (or, rather, your plants) to breathe! 

This disused, old servants’ staircase at the far end of the wine cellar really is a godsend. It leads up to a boxed in cupboard behind a cloakroom next to my kitchen. Even better, there’s a window up there—so I can extract all my garden’s hot air directly to the outside world. Alternatively, with a few more holes, I can extract the hot air into the living quarters of my house above during the colder months to help with heating it. If I go this way I’ll also use a carbon filter to purify the extracted air from my indoor garden so that my house is filled with warmth but no garden odors.

4) Water and Drainage

Having a water supply near or in your indoor garden is highly recommended. I’m going to be growing using a mixture of hydroponic and soil-based, organic techniques. I love growing in recirculating hydroponics systems as it uses around 80-90% less water than conventional growing techniques. Even so, I will need to change-out the reservoirs from time to time so drainage points will be useful too.

I’m going to install a mixer tap so that I can use both hot and cold water to create a tepid nutrient solution—around 66 ˚F or 19 ˚C—this is the ideal temperature for a hydroponic nutrient solution—it’s warm enough to foster a healthy root metabolism and cool enough for sufficient dissolved oxygen levels in the water.

5) Electricity

Depending on their size and application, indoor gardens can use varying amounts of electricity. If I reach my goal of filling this cellar with plants, I’ll be using upwards of 8 Kilowatts of power, just for the grow lights! I called a professional electrician in to help install a dedicated electrical panel for the garden, 18 sockets—six each per ring main—and a Helios 7 lighting controller by Titan Controls (wired directly into the panel) to safely control my grow lights. The Helios 7 can power up to eight 1000W lights so it’s the perfect fit for my needs.

I’m running both 240v and 120v power. My pumps will be on 120v, my lights and fans will be on 240v. I prefer 240v for lights and fans because it’s more efficient and less heat is produced.

The metal frame work will support the damp resistant plasterboards to create my ‘room within a room’.

The metal frame is drilled into the floor and strengthened with metal and wooden cross beams.

Plasterboard in place! I hung some Magnum XXLs up too so I could get a better feel of the garden space.

Check out the electrical sockets high up on the walls and on the ceiling! These will be really handy for powering extraction fans and environmental controllers without electrical wires dangling all over the place.

So, the plasterboard is in place. The gaps have been grouted. What’s next?

Well, I need to paint the boards. Then I need to consider what reflective materials I’m going to use to line the walls. Indoors, every photon counts! I also need to line the floor with something waterproof in case of the inevitable spills!

Air-exchange needs to be calculated and the correct fans and filters installed. There’s still a ton of work to do but I think I’ll save that for my next post! Thanks for tuning in. 


Converting a wine cellar into a year-round indoor garden

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