This value and the calculated Psi Values detailed in this latest data sheet means that according to the 2-box model, Thermobar Warm Edge Spacer can be substituted into any current Window Energy Rating (WER) Simulation, including all rigid tubes and foam spacer systems.
Thermoseal Group proposes that substitution of spacer systems should take place when sightlines (including spacer height and accepted simulation measurement for sealant depth) are the same measurement or smaller AND the total box value (including thermal value of spacer and sealant) is equal or better. This will ensure that substitution can only positively affect the overall WER value.
Thermoseal Group’s Sales Director Mark Hickox, said: “WER calculations are derived from figures based on the 2-box model figures detailed on BF Data Sheet – including the spacer and the sealant. This makes sense as it gives an overall value for the whole sightline of the unit.
“We are manufacturers of both rigid and foam spacer systems so have no bias as to which option customers choose. However, if you look at the information as detailed below you can see the figures associated with Thermobar and those of a current foam spacer system. Note that foam systems require a larger simulated sealant depth which negatively affects the 2-box model total. Resultantly, even if the 2-box model figure is re-calculated using lower spacer W/mK values than Thermobar, the 2-box value is likely to still be less thermally efficient than a comparable Thermobar sightline.
“On this basis, we propose that the BFRC adopt the 2-box model method of substitution and give manufacturers the opportunity to substitute the whole sightline of the unit as long as the overall 2-box value is the same or lower. Thermobar with hot melt sealant currently offers the best 2-box value available.”