3 Ways Heat Transfers And The Importance Of Insulation
October 29, 2011
Not so long ago, the only kind of insulation available for ceilings and walls was "rockwool." Fiberglass and cellulose joined the list, and they are generally the offerings of standard building material suppliers. You might be surprised to learn of many other different materials that currently are used as insulation.
Selecting a type of insulation is often based on price and availability more than on the material's impact on the environment, performance, human health, and building science.
Some of the other products and variations used for insulation include cementitious foam, vacuum panels, cellular glass, recycled cotton, polyester, wool, polystyrene, polyisocyanurate, and gas-filled panels.
Understanding how heat flow works may offer some insight into the types of insulation for consideration. There are three ways that heat transfers from one place to another; radiation, convection, and conduction.
Radiation
The spread of electromagnetic waves can occur from one surface to another across a vacuum. Heat from the sun warms our faces without the sun actually touching us, and there is the void of space, which is a vacuum. Similarly, sitting in front of a roaring fire, we feel the heat without making contact.
Convection
The physical movement of liquids or gases by way of their molecules is convection. It is natural in the act of heat rising and drawing cooler air beneath.
The molecules of the air increase in size and become more buoyant from heat; this is why they are lighter than the cooler molecules. Liquids also have natural convection due to heating.
Thermal Conduction
The more prominent way that heat transfers in most people's minds is through contact. Molecules in one object are transferred when some source heats them. Their energy transfers to something they touch. This is what happens to your hand when you grab something that is hot.
Whatever type of insulation we use, we have to be concerned with all three ways that heat moves from one place to another. The insulation in the wall protects against thermal conduction because it keeps the heat or cold from affecting things on the inside by touching them. This is because the insulation absorbs and lessens the heat transfer.
Low E glass is one way to lessen heat transfer by way of radiation. The thermal foil in the attic rejects radiant heat from the roof. To retard convection heat transfer requires sealing and caulking so cool air or drafts do not make interior spaces uncomfortable.
Insulation must be chosen because of how well it addresses each of the heat transfer methods. Determining the type of insulation that is best for your particular situation is best discussed with someone knowledgeable in the industry.