Loose Fill Insulation: Should I Choose Cellulose or Fiberglass?

If you have started planning an air sealing or insulation project, it is likely you have heard countless different opinions on loose fill insulation and which is best between fiberglass and cellulose. It is important to be aware of the fact that many contractors out there will tout the benefits of the materials they sell, and their opinions will be formed based on buying decisions rather than facts. At WoW, we have installed all types of insulation materials, and our recommendations are always based on scientific and quantifiable results. In this article, we will be discussing the difference between cellulose and fiberglass insulation so you can make an informed, fact-based decision for your insulation or air sealing project. 

What is Insulation?

Insulation  is a material that acts as a barrier to heat loss and heat gain. When it comes to your home, insulation is most commonly used in roofs, ceilings, walls and floors. In most homes, insulation is one of the most practical and cost-effective ways to make a home cooler in the summer, warmer in the winter and more energy-efficient all year round. Furthermore, insulation can also reduce the amount of condensation in your home, which reduces mold, dampness and other unwanted air pollutants. There are four different types of insulation: foam, blanket, loose fill and rigid. 

What is Loose Fill Insulation 

Loose fill insulation, also known as blown insulation, is one of the most commonly used types of insulation. It can be made up of a variety of materials, such as: cellulose, fiberglass, polystyrene beads, perlite or vermiculite.

What are the advantages of loose fill insulation? 

• Versatility. Loose fill insulation can be used in new or existing homes and is very versatile due to its malleable nature.
• Sound-proof. The fiberglass material in loose fill insulation is ideal for sound-proofing.
• Affordable. It is one of the most affordable insulation materials.

What are the disadvantages of loose fill insulation? 

• Fast decay. Loose fill insulation is easily affected by convective air movement, which makes it decay quicker over time.
• Lower pest control. It does not effectively deter pests or insects when compared to foam or blanket insulation.
• Can be a fire hazard. A lot of the materials used in loose fill insulation are not fire-proof.

Choosing Cellulose Loose Fill Insulation 

When it comes to the best insulation for loose fill in attics, we recommend stabilized cellulose for several reasons. Why? 

• Unmatched performance; the R-value is much higher compared to that of loose fiberglass filled insulation.
• Cellulose is made from reclaimed/recycled materials, making it eco-friendly.
• Borates are an effective insecticide and pest deterrent.
• Cellulose is less of an inhalation hazard than fiberglass.

The only, perhaps negative, aspect of using borate cellulose is that it is more expensive than fiberglass loose fill insulation. 

Choosing Fiberglass Loose Fill Insulation

While fiberglass loose fill insulation may dominate the new construction housing market, the reality is this is because many builders face the pressure of delivering beautiful new homes, yet staying within a certain budget. This is typically why a home improvement contractor would use fiberglass loose fill insulation as fiberglass insulation does have a comparatively lower cost to cellulose per installed inch.

One of the biggest problems with fiberglass is that it is subject to convective air movement and this results in a tremendous degradation of the cumulative R-Value. What this essentially means is that while you have paid for the Energy Star recommended R-49 in your attic, for example, the actual environmental performance of loose fill fiberglass is R-25 or less when you need it most. And perhaps the biggest problem with fiberglass is that it is both skin and lung irritant, while also not an effective insecticide or pest preventive like cellulose. 

Over the years we have heard from many homeowners who have attics overblown with fiberglass that there is little to no change in temperature variation and overall comfort. Essentially, it appears the popularity of fiberglass is not due to its performance, but rather its cost. That is why we always recommend cellulose loose fill insulation for your air sealing and insulation projects. Properly applied cellulose insulation, partnered with targeted air sealing, can significantly increase the comfort of your home and greatly reduce energy bills.