A question like this is difficult to answer without evaluating your space in person, but there are a few guidelines to help give you an idea of which type of insulation will work best in your space:

• What kind of insulation do you have now, and what condition is it in? If your attic currently has fiberglass or cellulose in good condition, your most efficient option is probably to add more of the same product. Because the thermal performance of fiberglass and cellulose is slightly different, we do not usually recommend layering fiberglass on top of cellulose or vice versa.
• What is your primary goal? Comfort, efficiency, and health are important to all of us, but some of us place more emphasis on one or the other. If comfort is the most important (and you have the resources), you might want to consider spray foam. If efficiency and short-term return on investment are most important, a combination of loose-fill and proper ventilation will be a more cost effective option for you.
• How long do you intend to remain in your space? If you’re planning to stay in your current space for 20 years or more, spray foam is a great solution! While the upfront cost is higher, you install it once and never have to think about it again. However, if you expect to move in the next few years, you’re probably better off with loose-fill and proper ventilation.
• How open is your attic space? If your attic is very tight and difficult to move around in, filled with lots of ductwork and other obstacles, loose-fill may be the only reasonable option for you. Spray foam requires a fairly open space to apply correctly, so it’s not a great solution for tight attics.
• How old is your house and neighborhood? The older your house (and the trees around it), the more likely it is that critters such as mice and squirrels can find their way into your attic. Rodents love to nest in fiberglass insulation! You can discourage critter intrusion with spray foam, which seals their entry points, or cellulose, which smells bad to them.
• What are your personal preferences? If you’ve decided on loose-fill, it then comes down to personal preference. Cellulose is slightly cheaper and is considered “greener” because it’s made of recycled materials and provides a slightly higher R-value per inch. It needs to be replaced every 15 years or so. Fiberglass, on the other hand, is a little more durable, and should last around 20 years.

Asking yourself these questions should give you a good idea what kind of insulation to consider. We are always happy to come look at your space and help you determine the best solution for your needs!