Blown-In vs. Batt Insulation for Attics – A Comprehensive Overview of Pros & Cons

Whether you are a seasoned homeowner here in the San Francisco Bay Area or investing in your first property, there is a good chance you will come across the terms “blow-in insulation” and “batt insulation” at some point in conversational passing. Adequately insulating and rodent proofing your home is the most fundamental way to secure it from outside temperature and environmental influences and ultimately save you money. In fact, the EPA estimates that the average homeowner saves ~15% on their cooling and heating costs by simply adding quality insulation in their attic and crawl spaces. That 15% equates to approximately $200 saved each year.

So given the importance of insulating your home, which insulation is better for your attic – blow-in insulation or batt insulation?

The answer to that question is that it depends. Both blown-in insulation and batt insulation have their advantages and their disadvantages. The goal is to align what each offers with your objectives for your attic insulation replacement and optimize your home’s value.

It is important to start by determining what resistance value (“R value”) of insulation is recommended for the area you live in. In the San Francisco Bay Area, R-38 is most common for attics. The exception is Alameda County homes which still allow R-30 insulation as within code. To understand more about the R-value range for your home, you can use this Energy Star chart for reference.

Below is a comprehensive overview of the pros and cons of each leading type so you can make a well-informed choice.

Batt Insulation

First developed in the 1930s, batt insulation became popular in the 1950s and is still a common method of home insulation. Batt insulation is made up of either fiberglass, mineral wool, denim and more and comes in flat, blanket-style, pre-cut sheets, with the width being the standard center framing size between wood or metal studs. It is typically popular for its ease of use, lightness, renewability and vast range of thicknesses to support homes in all environmental locations. Batt insulation has pros and cons that you should carefully review before choosing it as an attic insulation replacement strategy.


  • Makes Future Work Easier – With batt insulation, you can easily cut around electrical wires and leave the joists and rafters visible for easy access. You can also easily take out or move sections at a time to work on other projects and place them back when you are done.
  • Do Not Need to Replace the Entire Insulation – If there is a batt insulation section that needs to be replaced, you do not have to replace the entire attic roof to accommodate it. Unlike blow-in insulation, batt insulation comes in segregated sheets that enable you to save money and time on sectional replacements without tearing apart the entire set up. Furthermore, batt insulation makes it much easier to see what is going on underneath the insulation, allowing you to catch issues like rodents nesting before it becomes an infestation that requires you to remove and replace it all.
  • Durable to Compression – In certain situations, compression can depreciate the insulation’s overall R-value. Though all types of insulation are subject to this, batt insulation is more durable and resistant to compression, enabling it to conform to your attic space without hindering the quality of the barrier.
  • Variety of Materials – The ability to choose from different batt insulation materials is advantageous. From rockwool, denim, mineral wool, plastic fibers, cellulose and fiberglass, it gives attic insulation replacement seekers more flexibility to obtain the favorable outcome they desire.


  • Expensive to Install – Unless you plan on installing the insulation yourself, batt insulation installed professionally can be more expensive than its blow-in counterpart. That is because the process involves much more manual labor, including stapling and cutting to conform to the unique traits of a given attic space.
  • Lacks Full Coverage – Batt insulation can have an excellent R-value and can seal attic cavities well. However, these sheets cannot be placed in between wood studs, which can lead to significant energy loss through the thermal bridge. Since wood studs make up a hefty portion of attic spaces, this can have a large impact in the Winter and the Summer as the air from the outside works its way indoors across the studs.
  • Mold Growth and Deterioration Risks – Thermal bridging (due to the exposed studs as discussed above) can also cause mold growth and deterioration of the insulation if the attic space is not properly vented. The heat transfer from the outside can enable the material to absorb humidity or rain water and make it a potential breeding ground for molds to form. (However, it is worth noting that this is less of a problem in the San Francisco Bay Area due to its consistently temperate climate.)

Blow-In Insulation (aka Blown-In Insulation)

Blow-in insulation, sometimes referred to as “loose-fill insulation” or “blown-in insulation,” has become a more common attic insulation replacement method in recent years for several reasons, including its radiant barrier capabilities. Blow-in insulation is developed using small fiberglass particles, rock wool or cellulose and is blown into an attic cavity to cover the entire surface. For many years, fiberglass batt was the most prominent and popular form of insulation integrated into homes to amplify heat/cooling savings. However, in the last few decades, blow-in insulation (in particular the type made of cellulose) has become popular for its ability to conform into ceiling cavities seamlessly and offer strong rodent proofing protection.

According to USI, blow-in insulation can perform up to 22% better than certain batt types of insulation with the same R-value. For this reason, Aircom only offers the highest quality batt insulation to ensure that their San Francisco Bay Area customers obtain the most favorable long-term home value, rodent proofing and savings advantages, regardless of their attic insulation replacement choice.

Blow-in insulation offers its own set of advantages and disadvantages that should be carefully reviewed before making your final attic insulation replacement verdict.


  • The Seamless Reality – Unlike batt insulation, blow-in insulation does not have seams and can conform to any cavity structure. This allows for better surface coverage and maximum energy-saving performance.
  • R-Value Flexibility – Because batt insulation is manufactured in pre-cut rolls in specific R-values, it may be difficult to find the exact R-value you are looking for at an economical price. Blow-in insulation’s R-value is determined by the amount of material sprayed into the space (the thickness of the layer). Therefore, if you are looking for a specific R-value that is less common for your area, blow-in can be a quick and affordable option.
  • Fast and Cheaper Installation/Removal – Another reason for blow-in insulation’s popularity is that it costs less to have it professionally installed or removed. This is because blow-in insulation offers a quicker and less labor-intensive integration compared to the labor intensiveness of installing batt installation.


  • Can Make Future Projects Challenging – While there are benefits to blow-in insulation fully covering attic spaces, it can also become an obstacle for those looking to perform attic projects later on. Unlike batts insulation, blow-in insulation cannot be cut or easily moved, making it hard to perform any wiring work or upgrades.
  • Cannot Be Re-Applied – Similar to the point outlined above, if blow-in insulation is removed for any reason it cannot be reinstalled. If future attic work or insulation replacement is required, it is a more expensive option than performing similar work with batts which can be easily reused following temporary removing.
  • Warm Home for Rodents (Fiberglass) – Fiberglass insulation can be a favorite for rodents to nest and tunnel in and are difficult to remove without professional help. That is why Aircom offers full rodent proofing services in conjunction with attic insulation replacement, including identifying contaminated and damaged areas, sealing rodent entry points and full-scope space inspection to minimize the risk of infestation occurring. You can find more information on Aircom’s rodent proofing services here.

Conclusion – Which Is Better?

The US Department of Energy indicates that 49% of a home’s energy bill is spent on cooling and heating. One of the largest reasons for high energy bills is the improper or outdated attic insulation. Insulation is one of the home’s greatest assets to protect value, lower energy costs and maintain high quality of living. Insulating your attic is also a great way to prevent gradual home damage caused from heat build-up that can cause shingles to swell and plywood to soften or water vapor to seep through.

So, which is better – batts or blow-in? It truly depends on the desired functionality of the attic space, future attic goals and the current attic standing. If you’re still undecided on which avenue to take with your attic insulation replacement project, the Aircom team serving the San Francisco Bay Area is on standby to ensure you gain the most favorable, long-term outcome that you deserve.


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