Does Insulation Keep Heat Out? Best Way to Insulate for a Cool Home

Saving Energy

When we talk about home comfort, most people will just be concerned with the legendary four words: Heating, Ventilation, and Air Conditioning (HVAC). Granted that these three are the giants in maintaining a comfortable temperature indoors, we can easily forget one crucial factor that silently supports all these three processes: Insulation.

What is insulation and why is it important? Does insulation keep heat out and help maintain your home’s cool and comfortable temperature? 

Let us answer these burning questions so you can keep your cool amidst the hot weather.

DP does insulation keep heat out

Does Insulation Keep Heat Out and Keep Your Home Cool?

If done properly and adequately, insulation DOES keep the heat out during the summer so your air conditioning can efficiently cool your space. During the winter, it can also keep the heat inside your home and prevent it from escaping.

Insulation refers to the act or the materials used to stop heat, sound, or electricity from escaping or entering. In terms of heating and air conditioning, insulation minimizes the chance for the cool air produced by your AC unit or heated air from the furnace or boiler to escape the space. 

Without insulation, the heating and cooling systems’ capacity to maintain the desired temperature would be undermined. If left unchecked, lack of sufficient insulation would lead to wasted energy, a feeling of discomfort indoors, and early wear-and-tear of the cooling or heating device. 

Insulation materials are designed to block or at least slow down the movement of heat either through conduction, convection, or radiation. The efficiency of these items utilized for insulation to resist heat flow is measured through R-values. Various factors determine the R-value of an insulating material such as the type of insulation, thickness, density, temperature, aging, and moisture accumulation.

How extensive your insulation or number of R-values are required for your home will largely depend on the climate where you live, which sections of the house you plan to insulate, and the type and current condition of your heating and cooling systems. Consult insulation professionals when determining the current insulation of your house and ask for advice on how much you need to add.

Better insulation often leads to improved air sealing and moisture control indoors. These will impact how you consume your energy and the resulting utility bills, your family’s health and well-being, and overall comfort.

The Vital Role of Insulation

Insulation could be the issue preventing you from fully enjoying the benefits of an air conditioner or a furnace.

The term insulation refers to the action of “covering something to stop heat, sound, or electricity from escaping or entering.” It can also be applied to the materials used to accomplish the purpose of preventing the evading or entry of heat, sound, and electricity to and from the space.

If you are familiar with how a basic AC works, you could tell that the success of the air-cooling process thrives on how insulated the space is.

The cooling process starts as the thermostat reads the current room temperature. Granted that the reading of the thermostat is correct and is not compromised by direct sunlight hitting it, a draft of cold air, or a heat-generating appliance near it, it should signal the air conditioning to initiate.

With the help of its blower, the AC draws in the warm air from the room and begins circulating it through the ductwork. Just in time for the gas-liquid refrigerant to also flow to do its job of removing the heat and excess moisture from the extracted air.

Once the heat is removed, the cold processed air will be blown back to the room as the heat separated from it is exhausted outside. 

This cycle will keep on going several more times until the thermostat temperature is reached. Given that the AC is properly sized to the room it is supposed to cool, the cooling cycle would be so smooth, you would not even notice it happening around you.

I know what you are thinking, “How does insulation get into the picture?

You see, the opposite of being insulated is exposed, penetrable, or uncovered. If in some way, outside air can infiltrate your space, it could mislead the thermostat to an erroneous reading of temperature. 

Additionally, if the processed air—whether it is chilled or heated—found a way to escape, the unit will continue running non-stop to meet the desired temperature but ultimately fail.

Imagine the amount of wasted energy if your space is not properly insulated! Not to mention the strain it will put on your air conditioner or furnace.

Understanding Heat Flow

The most obvious ways outdoor air can enter your home and the processed air to escape are the common openings around the house: doors, windows, and vents.

While they provide a natural source of ventilation to infuse your living space with an amount of fresh air and air out the buildup of bad odors and toxins, they should never be left wide open when the air conditioner is on or the furnace or boiler is running.

Keeping them shut is the best way to contain the air released by your cooling or heating systems.

Now there are also holes, cracks, and crevices on the wall that you should look out for. The thickness of your walls, ceilings, and floors also plays a factor. How so?

To understand this, we need to understand a basic natural phenomenon that is happening daily in your house: Heat flow.

Simply put, heat flow or heat transfer is the predictable movement of heat from a warmer place to a cooler one. 

For example, in summer the heat attempts to travel from outside where it is scorching hot to the inside of your house where it is cooler because of the shade or a fully-operated air conditioner. While in winter, the hot air you manufacture through a broiler tries to escape to the chiller outdoors.

This exchange of heat will continue until there is no longer a temperature difference.

Heat moves in three ways: via conduction, convection, and radiation. Let us take a quick science detour based on an outline provided by the Department of Energy (DOE), Office of Energy Efficiency & Renewable Energy (EERE).


“Conduction is the way heat moves through materials,” says the DOE. As mentioned, the inevitable movement of heat is from the warmer material to the cooler. One way the heat can travel is when two solid surfaces are in direct contact.


Convection currents or convective loops occur when warm air moves upward because it is lighter, while colder air descends because it is much denser.


“Radiant heat travels in a straight line and heats anything solid in its path that absorbs its energy,” the agency focused on energy continues to enlighten. This emission of heat commonly comes in waves and it is received by objects that have a lower temperature.

The main goal of insulation materials is to stop these three natural heat flow mechanisms from overtaking your heating or cooling system.

So, if you think about it, insulation is kind of like a left tackle to your quarterback of an AC or furnace! The key now is to find a qualified left tackle strong enough to resist harsh weather conditions.

Types of Insulation that Suit Your Home

The way to pick quality insulation for your home is to know its R-value: the higher the figure is, the better its resistance to heat flow. 

Various factors determine the R-value of an insulating material such as the type of insulation, thickness, density, temperature, aging, and moisture accumulation.

The Department of Energy once again offered some reliable guidance on understanding the efficacy of insulation materials. To summarize 

1. “Installing more insulation in your home increases the R-value and the resistance to heat flow.”

The goal behind more insulation is to reduce to the least possible the risk of the indoor processed air escaping, and to the outdoor air penetrating your home. Adding more insulation material to one section of the home automatically increases its total R-value, except for loose-fill insulation. 

2. “The effectiveness of an insulation material’s resistance to heat flow also depends on how and where the insulation is installed.”

Which part of the house you intend to insulate will determine the type of insulation material you should choose. For example, in insulating a wall or the ceiling, you should consider the studs, joists, and other building materials where heat could easily pass through. 

IMPORTANT: “Thickness must not be used as the sole factor in determining the R-value of loose-fill insulation, particularly for attic insulation,” DOE warns.

3. “The amount of insulation or R-value you’ll need depends on your climate.”

Each state or zone, not to mention building codes, requires minimum insulation or R-values. On their page dedicated to insulation, the Department of Energy provided the list of recommended insulation for attics, floors, and how much additional filling you should add to your existing insulation.

4. “Consult a local insulation contractor,” “a qualified home energy auditor”, or “a team of local building professionals familiar with energy-efficient home construction.”

If in doubt about measuring the current insulation and heat flow resistance of your home and knowing how much more you should add, there are several professionals you could tap into for help. 

Insulation contractors are the most specialized in installing thermal insulation. Meanwhile, a home energy auditor will examine first your existing insulation as a routine checkup before a whole-house energy assessment.

The Perks of Proper Insulation

Two major aspects of our home life are impacted by quality insulation: our energy consumption and overall comfort.

Considering how heating and cooling systems function, it makes sense that the better your home resists heat flow or heat transfer, the better performing your AC and furnace will be. You will get the maximum benefits of these devices since your environment is sealed and not invaded by outdoor temperature.

No energy is wasted as your AC unit or furnace does not have to work twice as hard to cool or warm up space because of leaks, drafts, and poorly insulated surfaces. You may probably save your unit from early wear-and-tear and possible repairs because of overuse.

Consequently, better insulation often leads to improved air sealing and moisture control indoors. As a result, you will have the peace of mind that your family will get its deserved comfort, health, and well-being.

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