12 Questions to Ask Any Greenhouse Supplier

Print this. Take it to every quote you get, including ours.

The point is not that any single answer disqualifies a supplier. The point is that a supplier who can answer all twelve without hedging is engineering for your site, and one who cannot is selling you a catalog item and hoping.

About the structure

1. What snow load and wind speed is this engineered for, and how do those compare to my county’s requirement?

The most important question on the list. A structure not rated for local conditions is not a performance compromise, it is a structural risk. Ask for the numbers, then check them against your county. A supplier who does not know your county’s requirement has not looked.

2. What gauge is the steel, and what is the post spacing?

These two determine strength more than anything you can see in a photo. Wider post spacing looks cleaner and costs less and carries less. Ask, and compare across quotes, because two structures that look identical can be very different here.

3. How is it galvanized, and what happens at the cuts and connections?

Galvanizing protects steel from corrosion, and the weak points are where the steel was cut or joined. Ask what protects those. This is where a structure that lasts twenty years separates from one that has rust at the joints in year five.

4. Can this be extended later, and what does that require?

If the answer is “you would build another one,” you are buying a ceiling. Find out now, because the cheapest square footage you will ever add is to a structure designed to accept it. See the Hybrid R multi-bay tunnel for what extendable looks like.

About the covering

5. What film is included, what is its rated life, and what does it cost to replace?

Film is a consumable. You will replace it several times over the life of the frame, so its replacement cost is part of your operating budget, not a one-time item.

6. Does it include anti-drip, light diffusion and thermal properties, and do I need all three?

These do different jobs and they are not free. Anti-drip keeps condensation from falling on foliage, which is where a lot of disease starts. Diffusion spreads light more evenly. Thermal retention holds heat overnight and matters much more in the North than the South. A supplier who tells you that you need all three regardless of latitude is not thinking about your site. See greenhouse film.

About the systems

7. Is ventilation sized for my climate, and how did you calculate it?

The most common undersized component in a greenhouse. Ask how they arrived at the number. If the answer is a standard package rather than a calculation involving your climate and your span, ask again. See ventilation and cooling systems.

8. What does the irrigation system require in flow and pressure, and does my water supply meet it?

Design-stage question, and skipping it is why some systems underperform from day one. You also want to know what filtration your water needs, which requires a water test they should ask you for. See GreenDrip and BlueDrip drip tape.

9. What is included and what is not?

Get the boundary in writing. Doors, end walls, roll-up hardware, anchors, film, irrigation, ventilation, controllers. The gap between quotes is often not price, it is scope.

About the relationship

10. Who assembles it, and what does that cost?

Self-assembly, contractor, or supplier crew. Each is legitimate and they are not the same number. If self-assembly, ask what the instructions look like and how many people it takes.

11. What happens when something breaks in year three?

Parts availability is the question behind the question. A structure built to a proprietary system from a supplier who leaves the market is a structure you cannot repair. Ask what is standard and what is not.

12. Can I talk to a grower in my region who bought this?

The best question on the list, and the one that makes an evasive supplier uncomfortable. Same climate, similar crop, ideally a few seasons in. Then ask that grower what they would do differently.

Two questions you should expect them to ask you

A good supplier interrogates you at least as much as you interrogate them. If they do not ask these, they are not designing for your site.

What crop, and what county? The crop sets the climate you have to hold, the county sets how hard that is and what load rating you need. Without both, nobody can size anything.

What is your water like? Volume, pressure and quality. A supplier who quotes an irrigation system without asking is quoting a guess.

If you are applying for NRCS

Add one more: does this structure meet conservation practice standard 325? The specification is narrower than most people expect, and a structure that misses it is not eligible regardless of how good it is. We covered the requirements in what CPS 325 actually requires and the exclusions in what NRCS will not pay for.

The pattern in the answers

You are listening for one thing: does this supplier work from your site, or from their catalog?

The tell is whether the answers change when you change the inputs. Tell them you are in Vermont instead of Georgia. If the recommendation does not move, they were never engineering it in the first place.

When you are ready to compare ours against the others, the greenhouse project form takes five steps and an advisor sizes the structure from your crop and county.