Attic Insulation: The Ultimate Guide to Weatherproofing Your Home

Cielo

Updated February 5, 2024

13 mins read

A little bit of extra attention to your attic space can go a long way. Whether you are building a new house or considering insulation for a finished home, attic insulation can serve as a great investment for making a huge difference in your cooling/heating bills. Without attic insulation, even the most energy-efficient HVAC systems will be forced to work extra hard. 

In addition to energy efficiency, most homeowners are also looking to maintain comfort all year round. If your upstairs rooms are hotter than downstairs, and the temperature is different in every room, it can affect your home’s comfortable environment. Attic insulation ensures that your home is not the direct target of the extreme outside weather and the temperature in your home remains stable at all times. 

Attic insulation is not an extensive renovation project, if you think you can handle it, take it as a DIY weekend project or call a professional and he/she can do the work for you in a few hours.

We have put together this easy guide to help you in your DIY project. Even if you are not doing it on your own, having basic knowledge can help you make an informed decision when buying attic insulation. 

Why Is Attic Insulation Important?

Attic insulation provides a barrier that inhibits energy loss from the interior of your house to the exterior. It also protects your home when the outside temperature gets to an extreme level during both summer and winter. As the majority of hot and cold air enters and exits through the roof, attic insulation is vital. 

During summers, your attic bears the brunt of the hot sun falling directly on your house, especially in the afternoon, and heat is then passed to the rest of the house. In winters, without insulation, your home could lose up to 85% of the heat through the attic. 

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You can imagine the situation of your electricity bills if you run your cooling/heating appliances without insulation. According to the EPA, you can save on average 15% on energy bills by insulating your attic. In addition to bills, fluctuating temperatures also cause your HVAC unit to work harder, increasing wear and tear. So, attic insulation greatly helps in minimizing the impact of weather fluctuations in your home.

Attic insulation also helps with your indoor air quality. Outdoor pollutants can enter your home if it is poorly insulated, which can compromise the air quality over time. Insulating your attic prevents the pollutants from spreading throughout your entire house. It also helps in avoiding moisture build-up in your home. Molds thrive in a damp environment, and water vapor can seep in and damage your walls when the humidity gets high in summers.

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Before Considering Attic Insulation

Attic insulation involves different components that you should consider when buying insulation for your attic. 

R-Value

R-value is the measure of resistance per inch of thickness. It calculates the ability of your insulation to resist heat flow. You would want to go for a higher value as it means better performance and better energy efficiency. The R-value varies depending on the type of your insulation, the recommended level for most attics is R-38.

How Much Insulated is Needed?

When deciding how much insulation your attic needs, keep in mind these factors:

• Climate: If your area faces extreme weather, you would need more insulation with higher R values.
• Age of your house: If you live in an older home, you would need more insulation.
• Size of your attic: How much insulation you require also depends on the size of your attic. Do consult an expert for professional advice. 

One thing to keep in mind is that you should aim to cover all the joists in your attic. If you easily see your joists, consider adding more insulation. Your attic insulation needs to be evenly distributed.

Types of Insulating Materials

Attic insulation is created using a wide range of materials. Before buying attic insulation, you should be aware of different materials used for insulating attics.

• Polystyrene: It has an R-value of 3.8 to 5 per inch and is mainly used in foam board insulation.
• Liquid polyurethane: The R-value of this type of insulation ranges from 3.5 per inch to 6.5 per inch. The value varies depending on whether it is being used in open cell or closed cell insulation.
• Cellulose: It is created from materials like cardboard, straw, and newspapers. It has been used for decades as an insulating material. It has an R-value of 3.8 per inch.
• Fiberglass: Fiberglass insulation is made from light woven fiber that you can easily cut. It is commonly used in blanket insulation and has an R-value of 2.7 on average.
• Denim: It is made from denim cotton. It is non-toxic, easy to install but is generally more expensive than other materials. Its R-value is 3.5 and works best for blocking airflow.
• Mineral wool: It further comes in two forms: rock wool and slag wool. Rock wool is made from natural minerals, while slag is made from waste products of molten metal. It has an R-value of 3.3. It is fire resistant but more expensive than other options.

When to Avoid Attic Insulation?

If you live in an older home, you should be cautious when going for attic insulation. Older homes were built with large spaces between walls. These spaces allow the moisture to dry without causing damage, but if they are filled with insulation, they can absorb the moisture leading to mold growth.

You also cannot do insulation on your old home’s wood-shingled roof. These older roofing materials were made to get wet and dry on their own. Stuffing insulation can cause them to accumulate moisture.  

Types of Attic Insulation: Which One Is Best Suited for Your Home

When carefully considering different types of attic insulation and determining which will best work for your home, take into account the ease of installation and R-value to get the best results.  

Here, we have outlined five commonly used options:

Foam Board Insulation

Foam boards have a high R-value with a minimum thickness, ranging from 4 to 6.5. They are created from materials such as polyurethane, polystyrene, or polyisocyanurate. They provide two times greater thermal resistance compared to other materials of the same thickness.

The foam board does not accumulate moisture, so it is ideal for areas with high humidity.

Spray Foam Insulation

As the name indicates, liquid polyurethane is sprayed in the wall’s cavities and attic surfaces where it solidifies. Its advantage is that it can fill the smallest of spaces and is effective at reducing air leakage.  This type is costly but most effective in reducing the transmission of hot and cold air. If you haven’t used spray foam before, consider calling a professional, as it is not as simple as it sounds.

Spray foam insulation has two types:

• Closed-cell: In this type, the cells are filled with gas that helps the foam expand to fill the spaces around it. It has the highest R-value – 6.2/inch.
• Open-cell: The cells are filled with air, which gives them a spongy texture. This one has an R-value of 3.7.

Note: Avoid urea-formaldehyde spray foam insulation because it emits dangerous vapors.  

Blanket Insulation

One of the popular insulations for attic spaces, blanket insulation, mainly consists of fiberglass. It is also constructed using cotton, mineral wool, and plastic fibers. Also, it comes in the form of batts and rolls. It is quite inexpensive but is not as effective as foam insulation. Typical batts and rolls have an R-value between R-2.9 and R-3.8 per inch of thickness. Medium-density and high-density blankets have R-values between R-3.7 and R-4.3. You can cut the batts and rolls to fit in gaps. Make sure to wear a mask and gloves as fiberglass is a lung and skin irritant.

Blown-In Attic Insulation or Loose Fill Insulation

As the name suggests, you blow in a paper-like material to the space that needs to be insulated. This insulation type comprises of fiberglass, cellulose material, or rock wool designed to fit any area. For fiberglass, the R-value is 2.2, while for cellulose, the value is 3.8. It is quite suitable for areas where you cannot install any other type of insulation.

Radiant and Reflective Insulation

Radiant and reflective insulation is different from other insulation types as it works by reflecting away the heat and is used in areas with hot summers. Most other insulation types work to reduce heat flow in a place instead of reflecting.

This insulation is created using a reflective barrier such as aluminum foil placed over material like polyethylene. This creates a pocket of air between two substances, which minimizes heat transfer. The attic’s roof gets direct sun and gains most of the heat energy. Radiant insulation reduces the transfer of heat from the roof to the other surfaces in the attic.

They are the best insulation for attics in hot climates and can lower 5% to 10% of your cooling costs.

How to Insulate an Attic?

When installing attic insulation on your own, you should opt for a blanket or loose-fill insulation as they are the most DIY-friendly types.

When installing blanket insulation, begin from the walls and work towards the center of the floor. Be sure to place the insulation in the joists carefully. For more protection, you can go a little overboard and install insulation across the tops of the joists.

With a loose-fill or blown-in insulation, begin by completing the gap between joists, starting from the walls. Furthermore, it’s best to have a helper around so one can hold the hose and the other can control the flow from the blower. Fill every space; just make sure to leave the air vents uninsulated. 

Moreover, with a finished attic you won’t be able to fill every nook and cranny, so contact a professional and let them decide the best insulation for your attic.

Pros & Cons of Different Types of Attic Insulation

Some insulating materials are DIY friendly while some are not; some emit dangerous vapors while others do not pose any health hazard. Each insulation type comes with its own pros and cons.

Attic Insulation Cost

Depending on the type of material you are using, attic insulation cost ranges from $1,500 to $3,500 or $1 to $ 7 per square foot.

To calculate the cost according to the type attic of insulation, refer to this table by Home Advisor:

Tips for Maintaining Attic Insulation

To properly insulate your attic and maintain it in optimal condition, try to incorporate the tips and best practices listed down below:

• Cover the ceiling joists so that your insulation stays in the place firmly and reaches its target R-value. 
• Always measure the area where you need insulation before cutting the product.
• Never compress the insulation to fit it in a place as it causes it to lose its R-value, especially blanket insulation loses its effectiveness when it is forcefully compacted.
• When installing insulation, do not block the airflow at the eaves. This comprises the insulation’s effectiveness in winter.
• Avoid installation insulation over electrical wiring systems as it can be a fire hazard.
• Don’t place blanket insulation over air vents as it can cause dangerous particles to circulate your home.
• Do not cover the air vents in your attic as they are needed for adequate airflow.

Attic vs. Roof Insulation

For homeowners, it can be ambiguous to distinguish between attic and roof/ceiling insulation. At first glance, both may look the same, but that is not the case.

You install attic insulation on the attic ceiling and floors, while roof insulation installs on the roof slope, above, and below the rafters.

Just like attic insulation, roof insulation also comes with a set of advantages. For homes with air conditioning ducts installed within the attic, roof insulation can provide a more relaxed environment in summers. Furthermore, roof insulation protects against moisture damage when snow piles up on the roof in winters. 

Maintain the Best Temperature Settings in Your Attic 

After getting done with the insulation, you would want to maintain ideal temperature and humidity levels in your attic throughout the year. However, frequently managing the settings can be a big hassle. You can opt for a smart thermostat or a smart AC controller that works with ductless mini-split, window, or portable AC. These smart climate control devices learn about your heating/cooling needs and adjust temperature and humidity levels according to your preferences, so you don’t have to micromanage the climate in your attic. By connecting the device to your smartphone, you can easily cool your attic in summers and make it extra cozy in winters with just a click.

Moreover, they also help with energy savings. The smart AC controller, for instance, sends you monthly reports about your energy usage and can help you save up to 25% on your bills!

Now that you know all about attic insulation, gear up to make your home more comfortable. After insulating your attic, you will see the benefits in no time!