Insulation 101

On this page, we will explain how Insulation works. This area is designed to help our customers learn not only the benefits of properly insulating their homes, but answer any questions you have about the process.

  • Reduces heat transfer from radiative heat sources
  • Reduces heat transfer from conductive sources
  • Divides the air space to reduce convection current

This combined reduction in the types of heat transfer allows you to keep your conditioned air where it belongs, regardless of the season or outdoor weather conditions. Installing your insulation correctly is the key to having it work for you instead of against you – a poor installation can result in a loss of 25-30% of your R-value. Combining insulation with other R-value rated products increases what they call your Effective R-value, and can help you increase your heat retention benefits.

How Insulation Works

R-value and Heat Transfer are the two main factors that determine how well insulation works. Your HVAC system must replace the heat gained in the summer and the heat lost in the winter to keep your space comfortable. Heat resistance is created by properly insulating a space, which reduces heat flow and allows your space to maintain a comfortable, even temperature.

What is R-Value?

The ability of a material to resist temperature changes can be measured by its R-value, just as we can measure the level of energy (heat) in an object by determining its temperature. Thermal Resistance is the source of the term. Commercial insulating materials such as cellulose, fiberglass, and spray foam are tested and given an R-value rating that indicates how well they keep heat out. The better the material insulates, the higher the R-value.

R-value is a measure of thermal resistance per inch that can be used to compare materials “apples to apples.” A one-inch cube of R-7 material will be twice as effective as a one-inch cube of R-3.5 material at insulating. A material with a high R-value can add up quickly. For example, a six-inch thick layer of R-4 material would be rated R-24.

The R-value of a building’s insulation is important, but doubling the R-value won’t double its resistance to heat loss or gain. Doors, windows, studs, and air leakage are among the complicating factors. Temperature change (and moisture with it, but that’s a different topic) occurs through conduction in studs, windows, doors, and other building elements, as well as through air movement, regardless of the R-value rating of your insulation. The R-value is only one part of the overall picture. We’ll talk about how much of a difference sealing can make in a building’s energy efficiency later.

Heat Transfer, Why is that important?

Heat transfer, is the great balancing act of energy. It all comes down to nature’s tendency to balance and normalize different energy levels.

When it comes to heat loss in our homes, there are a few basic rules to follow. Heat flows from hot to cold; it can never be stopped, only slowed; it can flow by convection, conduction, or radiation; insulation prevents heat loss by resisting heat flow, as measured by R-value (RSI).

A difference in air temperature is the primary cause of heat transfer. Convection, conduction, and radiation are the three methods by which heat is transferred from your home to the outside.

The natural movement of air caused by temperature differences is referred to as convection. You’ve probably noticed that the upper level of your home is warmer than the lower level during the winter or summer as heat rises.

Another common method of heat transfer is conduction. When you pour hot coffee into a new mug in the morning, the mug’s surface temperature changes from cool to hot as heat transfers from one thing (coffee) to the other (your mug). This is different in your home because each material has a different ability to resist conductive heat flow. By trapping air, which is a poor heat conductor, insulation prevents heat loss.

Finally, heat transfer by radiation is the electromagnetic transfer of energy from one location to another. This can range from the warmth a fire radiates as it burns in the grate to the sun shining in through your windows and warming your home.

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