Oh dear, oh dear, oh dear ... the thermal conductivity, insulation value, of:
- Dry air @ 275 deg K ~ 2 deg C is 0.024 W / m K, @ 300 deg K ~ 27 deg C is 0.026
Dry Air Properties
- Polyisocyanurate foam, 'Kingspan' is 0.023 W / m K or 0.022 W / m K or 0.019 to 0.023 W / m K
Polyisocyanurate - Wikipedia, the free encyclopedia or
Celotex GA4000 Insulation Board for Floors, Walls and Roofs or
Kingspan Insulation - Kooltherm Rigid Insulation for Roof Wall & Floor Applications | Thermal Insulation - Kingspan UK
- Glassfibre 1.2 to 1.35 W / m K
Properties: E-Glass Fibre
What the manufacturers' brochures do not tell you ... the thermal properties of polyisocyanurate foam are dependent upon the gas used to 'blow' the foam. This gas can 'leak' and reduce the thermal properties of your insulation, it becomes a ~ 17 % better conductor in the first 6 months; a less effective insulator than dry air. In some other manufacturers' foams, I do not know about all, less than environmentally friendly gasses have been used as the insulating medium. The products of combustion of the foam are amongst the primary killers in house fires.
Glass fibre relies on its air content to do its insulating job ...
Air ... its problem is if heated it changes density and being a gas will rise being replaced by cooler, denser air. Its problem is heat movement by convection not conduction ... though its insulating properties are negatively affected by its moisture content.
As with all things, a little knowledge is a dangerous thing ... and you can prove anything with statistics, badly designed experiments, poorly chosen comparators or blatant withholding of the truth!
Furthermore, don't believe anything a marketing specialist tells you about the product that they are selling until you have used it and proven its capability and your need for it before buying!