How Does Insulation Work?

Insulation is meant to stop the flow of energy.

Energy Flow

Conductors are materials that allow energy to flow freely. Energy can be moved around via electrons. The more mobile the electrons are, the more effectively energy will move through them.

Some electrons are not bound to the nucleus of an atom, so they are free to jump from one atom to the next. These are called "free electrons." A material with many free electrons will carry electricity and heat very efficiently. Because of this, copper is an excellent conductor. Not only does it conduct electricity well, but it conducts heat very well too. This is why some pots and pans are made of copper, but their handles are not.

Insulators, on the other hand, have very few free electrons. This means heat and electricity have a difficult time passing through those materials.

Free electrons are not bound in an orbit around the nucleus.

Pressure & The Path of Least Resistance

Energy naturally moves from high pressure areas to low pressure areas. A person in a cramped room tends to naturally move to a less cramped space. Likewise, hot air molecules want to move to areas that are cooler.

When moving around, nature takes the path of least resistance. When we use a wall with insulation, we are creating strong resistance to heat flow. The heat will find an easier, less resistant place to reside. In the summer, warm air molecules will find less resistance to motion by staying outside. In the winter, warm air molecules from your indoor heating will find it easier to stay inside, rather than transferring their energy through an insulated wall. This is why insulation is placed in walls, floors, attics, and crawlspaces. It effectively creates a barrier surrounding an entire living space.

Fiberglass

A great example of an insulator is glass. It's such a good insulator that it was used for many years to insulate the outside of power line transformers, preventing electricity from escaping. Naturally, fiberglass is a great solution when it comes to insulating a house. Fiberglass has the insulating properties of glass, but the flexibility of softer materials. This makes it very convenient to put in spaces of varying shapes and sizes, from walls to attics. One of its great qualities is the air pockets that are found between the threads of glass. The air pockets add to its effectiveness, because heat can become trapped, rather than passing through. This is why you don't want to compress your insulation into a more dense sheet. Doing do removes the air pockets and lessens its effectiveness.

Insulation Ratings - "R Value"

Insulation is rated by "R value." The R stands for resistance. The higher the R value, the better it can resist or block heat flow.

The value is measured by inches of depth. If you have a 1" batt (sheet) of insulation rated R13, layering it two deep would make it R26.

In a standard 2 x 4 wall, insulation usually has an R value of R13 - R15. For a thicker 2 x 6 wall, you would likely find R19 - R21.

Attic insulation requires special consideration because of its critical position in a home. Because heat travels upwards, it's important during winter time to prevent heat from escaping through the ceilings. In summertime it's important to prevent the heat from direct sun exposure from smothering a home like a hot blanket. Because of this unique importance, higher R values are required. R values of R30 to R60 are typically found in attics.

Higher R value means higher cost up front. However, it can save you money over time by making your heating and cooling more efficient. Instead of letting warm air seep through the walls during summer, or warm air to escape your home during winter, you can maintain your temperature longer before having to use electricity or natural gas to correct the temperature.

Insulation & Moisture

When windows are open, or there is significant air leakage in a home, moisture can enter into the walls. These air leaks can affect indoor air quality and temperature. They can also cause issues with your insulation.

What happens if your insulation gets wet? When moisture is trapped within the insulation, it can cause structural damage to wall boards and framing. It can also cause mold to grow.

To mitigate these issues, moisture barriers can be used to prevent water from entering the insulation. One option is a water vapor retardant. This is essentially a plastic sheet that can be attached to the framework in order to cover the insulation. Another option is faced insulation, which has a moisture barrier glued onto the insulation. Another method is to increase ventilation from walls into the attic. This allows any moisture that has been trapped to escape into the attic, where it can then be vented to the outdoors. Attic baffles are great for this.

Can Insulation Make You Sick?

With basic precautions, insulation should be safe to use. However, if there is insulation in the air, inhaling the particles can be dangerous. It can lead to irritation or infection of the lungs.

Another way that insulation can cause sickness is by accumulating mold. This is sort of an indirect cause, but improperly installed insulation may gather moisture, leading to mold buildup.

Can insulation touch wires safely?

Because wiring is insulated, you can use insulation near the wires. Something to consider is how working around the wires affects your installation. If you crunch your insulation down to fit behind wires, that insulation will have a lower R value because the air pockets are greatly reduced. If there is sufficient space, behind the wire, you can loosely fit your insulation behind it. If there is insufficient space behind the wire, you can cut your insulation so it ends on one side of the wire and begins a new batt on the other side.

Is insulation flammable?

Some insulation has a facing made of either paper or foil. Both of those materials are combustible, and must be used with caution. When using one of these flammable materials, they must be used in conjunction with fire resistant materials, like brick or wall board made from gypsum.