Comparison To Conventional Insulation
The thermal resistance of VIPs per unit thickness compares very favourably to conventional insulation. For instance, standard mineral wool has a thermal conductivity of 0.044 W/(m·K), and rigid polyurethane foam panels about 0.024 W/(m·K). This means that VIPs have about one-fifth the thermal conductivity of conventional insulation, and therefore about five times the thermal resistance (R-value) per unit thickness. Based on a typical k-value of 0.007 W/(m·K), the R-value of a typical 25 mm-thick VIP would be 3.5 m2·K/W (20 h·ft²·°F/BTU). To provide the same R-value, 154 mm of rockwool or 84 mm of rigid polyurethane foam panel would be required.
However, thermal resistance per unit price is much less than conventional materials. Aerogels are more difficult to manufacture than polyurethane foams or mineral wools, and strict quality control of manufacture of the membranes and sealing joins is important if a panel is to maintain its vacuum over a long period of time. Air will gradually enter the panel, and as the pressure of the panel normalizes with its surrounding air its R-value deteriorates. Conventional insulation does not depend on the evacuation of air for its thermal performance, and is therefore not susceptible to this form of deterioration.
In addition, VIP products cannot be cut to fit as with conventional insulation, as this would destroy the vacuum, and VIPs in non-standard sizes must be made to order, which also increases the cost. So far this high cost has generally kept VIPs out of traditional housing situations, However, their very low thermal conductivity makes them useful in situations where either strict insulation requirements or space constraints make traditional insulation impractical.
Read more about this topic: Vacuum Insulated Panel
Famous quotes containing the words comparison to, comparison and/or conventional:
“In comparison to the French Revolution, the American Revolution has come to seem a parochial and rather dull event. This, despite the fact that the American Revolution was successful—realizing the purposes of the revolutionaries and establishing a durable political regime—while the French Revolution was a resounding failure, devouring its own children and leading to an imperial despotism, followed by an eventual restoration of the monarchy.”
—Irving Kristol (b. 1920)
“Most parents aren’t even aware of how often they compare their children. . . . Comparisons carry the suggestion that specific conditions exist for parental love and acceptance. Thus, even when one child comes out on top in a comparison she is left feeling uneasy about the tenuousness of her position and the possibility of faring less well in the next comparison.”
—Marianne E. Neifert (20th century)
“The line that I am urging as today’s conventional wisdom is not a denial of consciousness. It is often called, with more reason, a repudiation of mind. It is indeed a repudiation of mind as a second substance, over and above body. It can be described less harshly as an identification of mind with some of the faculties, states, and activities of the body. Mental states and events are a special subclass of the states and events of the human or animal body.”
—Willard Van Orman Quine (b. 1908)