Retrofit, expand or build new? A commercial greenhouse decision hub

Step 1 — Measure the constraint before pricing the solution

Every route below is only defensible if you can name the binding constraint in numbers. Collect these before any supplier conversation.

• Current yield per m² per year versus the realistic band for your crop, climate and technology level
• Rejection and quality-loss rate, and the months in which it occurs
• Climate log: hours per year outside target temperature, humidity and VPD ranges
• Energy and water use per kg produced, and the tariff trend behind them
• Structural condition: gutter height, span, foundations, corrosion, glazing or film age, wind and snow rating versus current code
• Site headroom: spare land, water volume and quality, grid capacity, labour availability, road and cold-chain access
• Market pull: contracted or credible demand for the additional volume, with the price it clears at

Route A — Retrofit the existing greenhouse

A retrofit raises output or lowers cost per kg inside the footprint you already own. It is usually the fastest route to a measurable result, and the one most exposed to hidden interface work between old and new systems.

• Typical scope: climate computer and sensors, screens, heating or cooling upgrade, dehumidification, fertigation unit, drain recirculation and disinfection, irrigation network, LED or supplementary lighting, insect screening, gutters and glazing replacement
• Strengths: no new permits in most jurisdictions, no new land, shortest path from decision to production effect, capital concentrated on the actual constraint
• Risks: structural or electrical capacity may not support the new load; existing controls may not integrate; work often happens around a live crop
• Non-negotiable pre-work: as-built drawings, electrical load study, structural verification and a written interface list stating who connects to what
• Downtime is part of the price — quantify lost production weeks and require the supplier to state the installation window and crop-cycle constraints in the bid

Route B — Expand the existing site

An expansion replicates a production model that already works, next to the team, utilities and logistics that already support it. Its economics stand or fall on whether the shared infrastructure can carry the extra load.

• Typical scope: additional bays or compartments, extension of climate, irrigation and fertigation capacity, added buffer storage and pump capacity, packhouse and cold-store extension, electrical upgrade
• Strengths: proven agronomy, shared overhead, one management team, incremental phasing possible
• Risks: shared systems reaching their ceiling — water volume, pump station, boiler or chiller capacity, transformer rating, packhouse throughput, labour supply and housing
• Compatibility question to settle first: does the extension match the existing structure, or is it a different generation of greenhouse operated as its own compartment? Both are valid, but they price and control differently
• Require every bidder to state which existing systems they assume are adequate, and to price the upgrade separately if they are not

Route C — Build a new facility

A new build is chosen when the current asset or site caps the business rather than slows it. It carries the longest lead time and the widest scope, and it is the route where an undefined RFQ does the most damage.

• Typical triggers: gutter height or span unsuitable for the target crop, obsolete or unsafe structure, insufficient water or power at the site, unsuitable orientation or drainage, market or logistics reasons to produce elsewhere
• Typical scope: land preparation and civil works, structure, climate system, growing system, irrigation and fertigation, water treatment and storage, energy supply, packhouse and cold chain, automation, commissioning and training
• Strengths: full freedom on crop, height, technology level and phasing; a single coherent design instead of a patchwork of generations
• Risks: permitting and grid connection timelines, civil-works variation, labour recruitment, and a ramp-up curve that is often underestimated in the business case
• Phase the tender: many buyers award design and site works before the full technology package so the schedule is not held hostage to one negotiation

Step 2 — Compare the routes on the same basis

Compare cost per additional kg of marketable production per year and cost per usable m² over a defined horizon — not headline CAPEX. A cheap retrofit that lifts yield 8% can be worse value than an expansion that adds a full compartment, or better value than both alternatives; only normalised figures show which.

• Use the same evaluation horizon (typically 10 years) and the same energy, water and labour tariffs for all three routes
• Include downtime and ramp-up: lost or reduced production during works is a real cost of retrofit and expansion
• Include replacement timing: film, screens, glazing, pumps and controls do not have the same life
• Include the do-nothing case as a baseline, so the decision is measured against continuing as-is

Step 3 — RFQ scope checklist (all three routes)

Whichever route is chosen, every bidder must receive the same defined scope. These lines belong in the RFQ regardless of route.

• Chosen route stated explicitly, with the constraint it is intended to remove
• Crop, production target, cycle plan and quality standard
• Site data: coordinates, climate data set, wind and snow design loads, water analysis, power capacity and tariff
• Areas: gross, usable growing, and service or packhouse area — stated separately
• Scope boundary: exactly where the supplier's responsibility starts and ends, per system
• Interfaces with existing assets (retrofit and expansion): controls protocol, electrical tie-in points, hydraulic tie-in points, data integration
• Civil works, foundations, drainage and site access — included or excluded, stated per line
• Installation window, permitted downtime, working hours and live-crop constraints
• Utilities during construction and who provides them
• Commissioning at defined conditions, functional testing, and the acceptance criteria used to sign off
• Training, documentation, as-built drawings, spare-parts list and service response times
• Warranty terms per system, with start date defined by acceptance rather than delivery
• Delivery terms, currency, price validity, payment milestones and liquidated-damages position
• Explicit exclusions list — bids without one are not comparable

Common mistakes in this decision

• Retrofitting a structure whose gutter height or span cannot support the target crop — the money is spent and the ceiling stays
• Expanding without re-sizing the pump station, water storage, transformer or packhouse, then discovering the ceiling after commissioning
• Building new because the existing site is frustrating, rather than because it is measurably limiting
• Comparing a retrofit bid against a new-build bid on total price rather than on cost per additional kg per year
• Letting the first supplier who visits define the route, and the RFQ, in their own image
• Leaving interface work unassigned so it appears later as variation orders on both sides

Questions buyers ask before selecting a greenhouse company