What performance standard must a product reach for it to offer a 50 year warranty, and to become CodeMark accredited? The team at Greenzone share their journey.
Any termite system installed during the construction of new buildings, extensions or renovations needs to demonstrate that it will be fit for purpose for a minimum of 50 years. In the case of chemical applications to soil, there needs to be a way to replenish the chemical in the soil; typically this is through the installation of a reticulation system. No product has carried out 50-year trials to provide real-life data, so how do suppliers demonstrate that their products will provide termite protection in the field for at least 50 years?
Greenzone has shared with us how it demonstrated to CodeMark assessors that Greenzone termite barrier would last at least 50 years in building installations.
Greenzone Termite and Insect Repellent Barrier is a patented design consisting of a compressible foam substrate impregnated with bifenthrin, allowing it to be used as both a termite barrier and expansion joint foam. When predicting how a product will perform over time, it is necessary to consider both its physical performance and the degradation of any chemical used as part of the termite protection system.
Greenzone foam is made of a closed cell, cross-linked polyethylene. The weathering and degradation of polyethylene has been studied in detail for many years. A number of studies report that so long as polyethylene has zero or limited exposure to light (UV), is not exposed to temperatures above 100°C or suffers from microbial attack, it should remain stable for many decades. Given that Greenzone is installed away from sunlight, is not exposed to temperatures anywhere near 100°C and will have generally low water contact (which would promote destructive microbe activity), Greenzone is fully expected to maintain its structural integrity for the duration of the 50-year warranty.
From an insecticide point of view, the use of bifenthrin rather than deltamethrin provides Greenzone with a more robust product with a large safety margin, to give confidence in the 50-year warranty.
As an insecticide, bifenthrin is very stable in terms of photolysis and degradation in soil (Table 1). The half-life of bifenthrin (median in soil) is 4 to 12 times longer than other synthetic pyrethroid insecticides, such as deltamethrin.
published sources
Due to its location within the Greenzone polymer matrix, which is then installed within a structure, the bifenthrin is protected from the typical degradation factors of UV light, soil, microbes and moisture. As such, the half-life of bifenthrin should be significantly longer than the half-life in soil. Indeed, in the accelerated stability studies that are required for registration, where products are stored at 54oC for two weeks (representing two years of real time), Greenzone demonstrated no drop in bifenthrin level. As such, the level of bifenthrin in Greenzone is expected to only decline very gradually over the 50-year period of the warranty.
However, even if there was a higher than expected decline in bifenthrin levels, the bifenthrin level used in Greenzone provides a significant margin of safety. The amount of bifenthrin in Greenzone is 2 g/kg, which is double the dose of bifenthrin in other pre-construction products. Furthermore, field trials carried out for registration demonstrated that even Greenzone with bifenthrin at 0.2 g/kg (10% of the normal level) still gave 100% protection. This means that the level of bifenthrin could decrease by up to 90% and Greenzone would still remain effective as a termite barrier.
This data was presented to CodeMark, along with supporting documentation from independent industry experts, providing conclusive argument that Greenzone would deliver protection from termites for at least 50 years. As such, Greenzone has been CodeMark certified and Greenzone provides a $2 million warranty on installations, subject to terms and conditions.
Further reading:
White JR, Turnbull A (1994). Weathering of polymers: mechanisms of degradation and stabilization, testing strategies and modelling. Journal of Materials Science 29, 584-613.
Restrepo-Flórez JM, Bassi A, Thompson MR (2014). Microbial degradation and deterioration of polyethylene – a review. International Biodeterioration & Biodegradation 88, 83-90.
Lyons A (2014). Polyethylene (polyethene) plastics. In, Dorin D, Carter B (eds) Construction Materials Reference Book, 2nd ed, pp 229-240. Routledge, Oxford.
