Glazing thermal performance

The thermal performance of glazing is characterised by the U factor (the heat transfer coefficient or heat loss factor) the lower the U value of a glazing the lower the heat loss, and it is important that the U value is given for each type of glazing... 

Besides durability, premium sealants are judged by special properties as shown in Table 4. The ability to take on greater elongation and compression is measured by movement capability in terms of joint width. The stability to UV exposure is important for those glazing and insulation compounds used in modern high-rise structures. Thermal stability is in demand for solar collectors, or for other structural materials. On the basis of these evaluations, we can foresee future trends of sealants as shown in Table 4. Silicones appear to out-perform others. In the meantime, technical advances will provide low-modulus polysulfides, and better movement ability for both polysulfides and polyurethanes. Their cure time will be decreased and the UV stability will be improved to match or compete with silicones. All three will be developed for better adhesion under the un-primed conditions. 

Vacuum glazing performance (in terms of equivalent thermal conductivity) determined from potrai-tial U-values on the order of 0.5-0.3 W m and a thickness of the evacuated gap d—0.3... 1.0 mm) without taking into account the thickness of the glass panes. 

Cotana, F., A.L. Pisello, E. Moretti, and C. Buratti. 2014. Multipurpose eharacterization of glazing systems with silica aerogel In-field experimental analysis of thermal-energy, lighting and acoustic performance. Building and Environment 81 92-102. 

The selection of a particular adhesive type is for reasons other than modulus and associated stress distrihution. This might be for example, specific adhesion, chemical resistance, setting speed, gap fill capability, durability, heat resistance, fire performance, electrical properties, thermal conductivity, colour, toxicity or price. Low modulus adhesives are used very successfully in low stress applications to accommodate differential thermal expansion in applications like bonding glass to aluminium in double glazing assembly. 

Thermal expansion = 115 X 10 7°C Articles can be strengthened with a compressive glaze Applications include high-performance institutional tableware (latest version of Pyroceram ) and cups for the Corelle line of tableware... 

---