UV Stability: A 4-year UV resistant film should effectively block off at least 95% of detrimental ultraviolet radiation, reducing photodegradation and extending the film's service life. This high resistance also helps minimize yellowing and brittleness over time which could affect the greenhouses.
Tensile Strength: For me, I would consider a minimum tensile strength of 3000 psi since this will enable it to withstand strong winds as well as any possible mechanical strains without tearing apart. It is an important factor to know when it comes to extreme weather conditions.
Elongation: On average, I prefer films with elongation of at least 300% so that they can stretch to accommodate temperature fluctuations and any other structural movement within the greenhouse.
Thermal Properties: Films having low thermal conductivity; generally around 0.25 W/m·K must be chosen because they retain heat during cold periods while minimizing heat loss hence creating uniformity within crops atmosphere.