Cellulose vs. Fiberglass Insulation

Insulation is necessary for everyone's home. Insulation helps keep your house cold in the summer and warm in the winter. Your central A/C unit is the system that changes the temperature inside your house, but insulation keeps that temperature in the house.

Without insulation, your A/C unit would have to work much harder to maintain the temperature you set because the heat would move outside into the cold weather, and the heat would move into your house during hot weather. Home insulation keeps the inside of your house from transferring heat with the outside temperatures. This saves you plenty of money on your heating and cooling bills and keeps the temperature in your house just the way you like it.

So, fiberglass vs. cellulose. Of these two types of insulation, which is the better pick for your home? Let's get into which has a higher R-value per inch, better resistance to air leakage, and installation methods.

Fiberglass

Fiberglass insulation is made out of small spun glass fibers. It is available in batts and can be blown-in as well. Fiberglass insulation has an above-average fire-resistance, a relatively high R-value at approximately R3 per inch, and is more commonly used today than cellulose insulation.

Fiberglass insulation is manufactured from approximately 20% recycled materials. It effectively absorbs sounds from one room to another, a commonly used in sound dampening panels in recording studios. And is usually the cheapest type of insulation per square foot you can buy.

Oftentimes, professionally installed fiberglass insulation is cheaper per square foot than you can buy it yourself, but it will cost more because of the professionals' labor costs. Fiberglass batts are a pain to install correctly by yourself, are not very effective insulators, are more susceptible to moisture and mildew, but are extremely cheap.

Blown-in fiberglass insulation is in some respects easier to install than batts, is relatively inexpensive, and significantly less susceptible to moisture, mildew, and fire.

Cellulose

Cellulose insulation is made out of recycled newspapers. Cellulose insulation is made from approximately 80% recycled materials. The recycled material is coated in a chemical solution called borates that makes it extremely fire-retardant and nearly impervious to moisture, mold, mildew, and pests. The R-value of cellulose is also higher at R3.8 per inch.

Cellulose insulation is available for installation only as loose-fill, also known as blown-in. There are, however, two types of blown-in cellulose insulation. These are wet and dry cellulose insulation. Wet is best suited for attics, while dry is best for the existing walls of your home. Wet is also suitable for wall cavities in new installs.

This insulation is more expensive than fiberglass but is more fire-resistant, better at resisting moisture, mold, and pests, better at dampening sound, more efficient at insulating, and eco-friendly. Installing cellulose insulation is a challenging DIY home project, recommended only for experienced DIYers.

R-Value

The winner of the best R-value is cellulose coming in 26% higher than fiberglass. While cellulose and fiberglass have similar numbers by the inch, remember that wall cavities can only be filled so much. Getting the most amount of insulating R-value for your depth gets the best results.

Winner: Cellulose

Air Leakage

R-Values are only a piece in the puzzle that is keeping your home conditioned. Again we have another clear winner. Cellulose allows much less air to pass through it. If you look at some cheaper air filters for an HVAC system, you'll see they are made of fiberglass. An inherent property of fiberglass is that it filters the air as it passes through. If you have existing air leaks in your house, fiberglass is not the way to go.

If you don't know if you have air leaks in your house, Sustainable InteriYours performs blower door testing to find those areas and tell you what those leaks are costing you through your energy bill. Sometimes sealing those leaks is as easy as adding a gasket to a switch cover.

Winner: Cellulose

Installation Methods

Two very different install methods between fiberglass and cellulose. Loose-fill, aka blown-in insulation from cellulose or fiberglass batts.

For the DIY homeowner, a fiberglass batt is much easier to roll into place and trim to size. The largest install problem with fiberglass batts is when they have to be trimmed to go around outlet boxes, plumbing, or other obstructions. If they're not perfect, you'll lose out on the effective insulating value of the space. An attic installation with lots of ceiling lights is a perfect example.

Loose-fill cellulose, on the other hand, drop it into the hopper and blow it all over the place. To continue with the attic as an example, an initial walkway and dam need to be created if access is needed. Sometimes HVAC equipment is installed in the attic, and you have to make sure you can get to and service that equipment in the future. There is a lot of prep work needed to install cellulose that some DIY homeowners have a difficult time with.

Winner: Fiberglass

Which one should you use?

Looking at R-values, resistance to air leaks, and ease of installation, cellulose is the clear winner to decide between cellulose vs. fiberglass insulation. Even with the increased cost that cellulose presents over fiberglass, the performance from an insulating standpoint paired with its ability to slow existing air leaks makes it a perfect choice.

Either way, increasing the insulation in your home is great for reducing your energy costs. Of all the energy-reducing projects you can do, insulation is the most DIY and can greatly impact comfort.

If you don't know what you could save by upgrading your house's insulation, let Sustainable InteriYours guide you. Check out our Online Energy Audit and get annual savings information for insulation upgrades, along with so much more.