This is the single decision that separates our two models, so it's worth understanding properly rather than assuming more expensive means better for you.
Poly film
A tensioned plastic film over the frame. It's what most commercial growers use, and it works.
In its favour: lower cost, high light transmission, lightweight. If the priority is getting growing without spending more than you need to, film is not a compromise on the growing itself.
Against: it's the component with a service life. Film degrades under UV and eventually needs replacing. It transmits light directly rather than diffusing it, which in a hot Okanagan July can mean leaf scorch on the plants sitting under the brightest patch.
Polycarbonate
Twin-wall rigid panels. More expensive, and the reason the Harvest costs what it does.
In its favour: the air gap between the walls insulates, which matters in a climate with cold nights well into spring. It diffuses light rather than transmitting it directly, so growth is more even and scorch is less likely. It's rigid, so it handles snow load and hail in a way film doesn't. Ours carries a 15-year manufacturer warranty.
Against: cost, and slightly lower total light transmission than clear film — though diffusion usually more than compensates.
Which one for BC
Honestly: either works. The frame and base are identical between our models, so this isn't a build-quality decision.
Polycarbonate earns its price if you're somewhere with heavy snow (Sicamous, Revelstoke, the Shuswap generally), if you want to push the season hard at both ends, or if you'd rather never think about re-covering it.
Film is the sensible choice if you're in a milder spot, if budget is the deciding factor, or if you're new to greenhouse growing and want to find out how much you'll use it before committing more.
Compare the Harvest and Sprout — same frame, same base, different roof.
