The grow space
Get the grow space right and everything after it gets easier — a sealed, dark, air-managed box beats any spare room.
A good grow space is a controlled environment, not a room with a plant in it. Light-tight, air-managed, temperature-stable and contained — set it up once, test it, and the rest of the grow is maintenance instead of firefighting.
What good looks like
What a good space is made of
- The tent
A sealed, reflective box
A tent zips light-tight, reflects 90-95% of your light back at the canopy, and gives you ducting ports for extraction. A basic 80x80cm runs about €60-80 and does everything a converted spare room can’t.
- Footprint
Match the tent to the grow
Size the tent to the number of plants, not your ambition. One or two plants want an 80x80cm; four to six want a 120x120cm. An oversized tent with one plant in the middle is impossible to heat and humidify evenly.
- Siting
Where it lives matters
The tent inherits the room’s temperature, so put it somewhere you can hold above 15°C in winter and below 30°C in summer. Mind the carpet, the door, the noise, and whether you can carry water to it without doing yoga.
- Airflow
In at the bottom, out at the top
Air comes in through passive intake vents low down, warms, rises, and leaves through a carbon filter and inline fan at the top. That pull creates negative pressure — the walls suck inward and the smell stays in.
- Light hangers
Centred and adjustable
Hang the light dead centre on the top crossbars using ratchet hangers you can raise with one hand. Start it higher than you think, because the plant can double or triple in the first weeks of flower and will come for it.
- Access
Plan for water and reach
The tent floor is not waterproof. Lay floor protection first, put a drip tray under every pot, and arrange pots so you can reach the back ones from the opening.
The numbers that matter
The numbers that matter
Do this
The the grow space checklist
- Lay floor protection — builder’s tray or pond liner — before the tent goes up
- Match the tent size to your plant count, and leave 30cm above it for ducting
- Hang the light centred on the top crossbars with ratchet hangers, higher than you think
- Mount the carbon filter at the top, fan sealed to it, ducting short with gentle bends
- Open the passive intake vents at the bottom and leave 10-15cm clearance from walls
- Add two clip fans — one above the canopy, one below — aimed across the tent
- Keep the timer and power strip outside the tent, with a drip loop on every cable
- Run the dark-room test: everything off, room black, tent zipped — fix any light you see
Watch for
Catch these early
The early sign, what it means, and the fix. The full stories are in the book.
Tent walls balloon outward instead of sucking in
Positive pressure — your intake is stronger than your exhaust, so air and smell push out through every gap.
Fix: Check for kinked ducting, a clogged filter, or an undersized fan. Size the fan to tent volume plus 20-30% for the filter.
📖 In the book, “The Sauna” seals every vent and watches the tent puff up like a balloon. The full story →
A glow around the zips or seams in a dark room
Light leaks in during the dark period, which can confuse the plant in flower and trigger male flowers across the crop.
Fix: Tape the seam, tuck the zip flap, adjust the Velcro. A two-minute job that saves three months of work.
📖 The book opens on a crop pollinated by a two-centimetre gap under a hallway door. The full story →
The smell comes back a few months in
The carbon filter is saturated — Irish humidity makes it absorb moisture as well as odour, so it tires early.
Fix: Replace the filter. Your nose adjusts to the smell; your neighbours’ won’t.
📖 “The Chimney” learns that stealth is consideration, not paranoia. The full story →
A damp patch appearing on the ceiling below
Runoff is wicking through the tent floor into the carpet and fabric — the floor was never waterproof.
Fix: Drip tray under every pot, builder’s tray under the tent, pond liner under that. Empty saucers so roots don’t sit in old water.
📖 “The Flood” doesn’t notice for a week, then has the landlord conversation. The full story →
Questions
The grow space FAQ
Do I really need a tent, or will a spare room do?
A spare room holds a plant; it doesn’t control an environment. It leaks light, has no exit route for humidity, reflects far less light, and can’t mount a carbon filter. A basic €60-80 tent gives you a sealed, reflective, ducted box, and pays for itself the first time it prevents mould or a light-leak disaster.
What size tent for my first grow?
An 80x80cm. It fits one or two plants, gives room to work, and the 1.8m version has headroom for a moderate stretch. One plant in a huge tent is impossible to heat and humidify evenly.
Where in the house should the tent go?
Somewhere you can hold above 15°C in winter and below 30°C in summer, since the tent inherits the room’s temperature. Mind the carpet and the door. Garages are cold, attics cook, sheds are damp — and make sure you can actually reach it with a watering can.
How big a fan do I need?
Tent volume in m³ × 60 for m³/h, then add 20-30% for the filter. An 80x80x180cm tent needs about 85-90 m³/h; a 120x120cm needs around 220-250 m³/h — a 150mm fan.
How do I keep the smell from getting out?
Run an inline fan pulling air through a carbon filter at the top of the tent, intake vents open at the bottom. That negative pressure pulls all the air, smell included, toward the filter instead of leaking out the seams.
The whole story is in the book
The spare-room grower in Grow Good Bud didn’t fail at growing — he failed at building the room, and the chapter walks the whole Saturday-afternoon build.
The web gives you the lesson; Grow Good Bud keeps the scars. The kit to grow it is at Dublin Indoor Gardening.