Insulation provides resistance to heat flow. Heat flow is the movement of warm or hot air to cooler air. The flow continues until there is a balance of temperatures. For example, hot air will continue to flow into your home on a hot day until the inside temperature is equal to the outside. On a pleasant spring or fall day, you might open up the windows to take advantage of the ideal temperature. When the weather is more extreme, however, you need to manage the heat flow.

When you buy a new home, insulation is installed to slow down the movement of heat. Now, heat flow moves in three ways:

• Conduction: Heat moves through a material, like a metal pot absorbing heat.
• Convection: Heat circulates through liquids and gases, and since hot air is lighter, it rises above cold air.
• Radiation: Heat travels along a straight path and absorbs energy from anything along that route.

So, your home insulation is installed in any place with exposure to heat flow: exterior walls, around the foundation, and in the roof, to name a few. Without insulation, the heat will move through the walls, floors, and ceilings—up from the basement, down from the attic, and in through the walls, doors, and windows. The goal of insulation is to produce resistant to the natural flow of heat.

R-value: The resistance factor

Home insulation products are rated for their thermal resistance factor, commonly known as R-value. This measurement is determined by the insulation type, thickness, and density. To determine how much home insulation you need, refer to a map that shows the R-value zones, rated on a scale from 1 to 7, with colder climates on the high end. Southern Florida and Hawaii score a 1 rating, while Alaska and northern Minnesota earn a 7.

You probably hear about radiant barriers. This reflective material doesn’t absorb heat, like insulation does. Instead, it reflects the heat. Radiant barriers are commonly installed on roofs to deflect the heat away from the roof (where it can be absorbed and potentially pass into the main part of the home). According to the U.S. Department of Energy, a radiant barrier on a home in a sunny climate (e.g., Zones 1-3) can reduce cooling costs by 5% to 10%.

Retrofitting an existing home with the correct amount of insulation could require a professional, depending on where and what type of insulation you need. New homes incorporate the standards for home insulation. They also improve the comfort and energy efficiency in a new home by installing moisture control and air sealing.

Spend a little time learning about your home’s insulation and you’ll spend much less later on the energy costs.