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Quick answer
A mushroom farm needs four climate-controlled rooms: spawn storage at 2–4°C, incubation at 22–25°C, cropping at 14–18°C with 88–95% RH and CO₂ below 1,000 ppm, and post-harvest storage at 0–2°C. A 4-stage 500 kg/day facility needs about 415 m², costs ₹90 lakh–₹1.36 crore before subsidy and takes 13 weeks to build.
Key takeaways
- The cropping room is the hardest to engineer because it must hold 14–18°C, 88–95% RH and 4–8 air changes per hour at the same time.
- Mushrooms produce 3–4 kW of biological heat on top of the envelope load, so undersized cropping-room cooling is a common engineering mistake.
- During incubation, compost temperature must not exceed 30°C, and it can run 4–6°C above room ambient.
- Each room needs independent humidity control, with ultrasonic humidifiers of 8–12 kg/hour mounted in the duct, never inside the room.
- A correctly filed NHB application can return ₹30–45 lakh against a ₹90 lakh build.
The Four Rooms Every Mushroom Farm Needs
Room 1 — Spawn Storage (2–4°C, 70–85% RH): Hold mother spawn until use. Standard 100mm PUF cold room with single Daikin split.
Room 2 — Incubation (22–25°C, 80–90% RH): Allow mycelium to colonise substrate. CO₂ 1,500–5,000 ppm. Duration: 14–21 days. Critical: compost temperature must NOT exceed 30°C — internal temperature can climb 4–6°C above room ambient.
Room 3 — Cropping (14–18°C, 88–95% RH): Trigger pinning and produce flushes. CO₂ below 1,000 ppm. 4–8 air changes per hour. The hardest room to engineer — you're holding low temperature AND high humidity AND high fresh air simultaneously.
Room 4 — Post-Harvest Storage (0–2°C, 90–95% RH): Hold harvested mushrooms before dispatch. Fresh mushrooms lose 1–2% mass per day to respiration.
Sizing the Rooms
For a 500 kg/day fresh mushroom production target (~180 MT/year):
| Room | Floor area | Capacity |
|---|---|---|
| Spawn storage | 8 m² | 4–6 weeks of spawn |
| Incubation room | 80–100 m² | 18–24 racks |
| Cropping rooms (3 in rotation) | 100 m² each | One ready at any time |
| Post-harvest storage | 12–15 m² | 3 days buffer |
| Total | ~415 m² | 180 MT/year |
Smaller commercial farms (50–100 kg/day) can compress to 2 cropping rooms.
Cropping Room Equipment Specification
Refrigeration: Daikin scroll ODU 8–10 TR, matched IDU with EC fans, R32/R410A, EEV, hot gas defrost.
Humidification: Ultrasonic 8–12 kg/hour, mounted in duct, never inside room directly.
Fresh air: Filtered intake with motorised damper, 4–8 air changes/hour modulated by CO₂ sensor. Heat recovery exchanger in premium builds.
Sensors: 3 temperature sensors at different heights, 2 humidity, 1 CO₂, BMS controller with 5-minute datalog, remote alarm.
Construction: 100mm PUF (150mm in hot zones), floor with drainage gradient, insulated sliding door, 3.5m minimum ceiling height.
Common Engineering Mistakes
- Undersizing cropping room cooling — mushrooms produce 3–4 kW of biological heat on top of envelope load
- Single shared humidifier across rooms — each room needs independent humidity control
- Steam humidifier near electrical panels — corrodes contactors
- No CO₂ sensor — mushrooms grow long stems and small caps when CO₂ is high
- Ignoring drainage — at 92% RH, condensation is inevitable; without drains you have a pool by week two
- Aluminium racks — high humidity corrodes aluminium; use stainless or polypropylene
- No spore exhaust filter — occupational health hazard for workers
Capex by Stage (2026 Prices)
For a 4-stage 500 kg/day facility:
| Component | Cost (₹L) |
|---|---|
| Spawn cold room (8 m²) | 4–6 |
| Incubation room (100 m²) | 14–22 |
| Cropping rooms × 3 (300 m² total) | 38–55 |
| Post-harvest storage (15 m²) | 5–8 |
| Air handling, humidification, controls | 12–18 |
| Civil + drainage + electrical | 14–22 |
| Commissioning, validation, training | 3–5 |
| Total | ₹90 lakh – ₹1.36 crore |
Lower budgets (₹35–60 lakh) can build a 100–200 kg/day operation with shared infrastructure, but lifecycle yield will be 30–40% lower.
Subsidy Eligibility
Mushroom cold rooms qualify under:
- NHB scheme — capital subsidy up to 35% (50% for NE states)
- MIDH — horticulture cluster development assistance
- State horticulture missions — additional state-level support in UP, Punjab, HP, J&K
- PMFME — 35% capital subsidy up to ₹10 lakh for smaller operations
A correctly filed NHB application can return ₹30–45 lakh against the ₹90 lakh build.
Construction Timeline
Week 0–1: Site survey, civil drawings, HT power feasibility
Week 2–4: Civil works (foundation, drainage, sub-floor)
Week 5–7: PUF panel installation, refrigeration piping
Week 8–9: Refrigeration commissioning, pressure test, gas charge
Week 10–11: Humidification, ventilation, controls
Week 12: Validation runs, thermal mapping, training
Week 13: Handover
Total: 13 weeks. Allow 16 weeks in your business plan.
FAQ
Frequently asked questions
What temperature should a mushroom growing room be?
Button mushrooms: 14–18°C cropping. Oyster: 16–22°C. Milky: 28–32°C. Each species has different needs.
How much does a mushroom cold room cost in India in 2026?
A small single-room setup runs ₹6–10 lakh. A 4-stage commercial 500 kg/day facility runs ₹90 lakh to ₹1.36 crore before subsidy.
Can I use the same cold room for incubation and cropping?
Technically possible for very small operations, but expect 30–40% lower yield because you can't optimise either stage.
What humidity is best for mushroom storage?
Fresh mushroom storage needs 90–95% RH at 0–2°C. Lower humidity causes cap shrinkage and browning.
Do mushroom cold rooms qualify for NHB subsidy?
Yes. Mushroom cultivation is eligible for NHB capital subsidy up to 35% (50% for North East states), credit-linked and back-ended.
Written by
HyperCold Engineering Team
Cold room and cold storage engineers at HyperCold™, a Daikin equipment partner founded in 2020 and headquartered in Sirsaganj, Firozabad (UP). We design, manufacture PUF panels for, install and maintain cold rooms across India.