Polyisocyanurate Ιnѕulаtіоn Materials

Polyisocyanurate (polyiso)

Polyisocyanurate (polyiso) is a type of thermosetting plastic and closed-cell foam material that has low-conductivity and a hydrochlorofluorocarbon-free gas in the cells. Because of its impressive thermal resistance, polyisocyanurate insulation yields an R-value that ranges from R-5.6 to 8 per inch.
Polyisocyanurate insulation comes both as sprayed liquid foam and as foam board. In addition, it can be used to create laminated insulation panels with different facings. Applications of polyisocyanurate using sprayed liquid is often less costly than using foam boards and they usually work better as a result of the liquid molding itself to the surface.
The R-value can drop over time as the gas is slowly released and replaced by air; this name of this phenomenon is thermal drift. There is some experimental data to indicate that most of the thermal drift takes place within two years following its manufacturing. For instance, insulation that begins with an R-value of R-9 per inch is likely to drop down to R-7 and remain so unless the foam somehow becomes damaged.
The R-value can be stabilized somewhat with plastic facings and foil on rigid polyisocyanurate foam panels. Some testing has suggested that the R-value of rigid foam stabilized with foil facings can be maintained for over 10 years. When correctly installed and faced by the open air, reflective foil can also double into a radiant barrier. This could provide another R-2 to the total thermal resistance depending on the orientation and size of the air space. A stabilized R-value of up to 7.1 to 8.7 per inch can be achieved with panels that have foil facings.
Polyisocyanurate is used as insulation by some manufacturers in structural insulated panels (SIPs). A SIP can be manufactured using either liquid foam or foam board. The liquid foam is injected under considerable pressure between wood skins that, when hardened, creates a strong binding between the skins and the foam. Polyisocyanurate wall panels are usually 3.5 inches thick and ceiling panels can be around 7.5. Although more costly, these panels are more fire-resistant than EPS. In addition, they insulate better per given thickness by about 30% to 40%.

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