A Brief Guide On The Various Types Of Attic Insulation

November 17, 2020 | By Pamela Vargas-Touchard |
Types Of Attic Insulation: Mineral Wool Insulation

When you’re ready to replace the insulation in your home, you’ll need to choose the best types of attic insulation for your budget and your overall goals. Some insulation works better than others, some types are more expensive (and, typically, more energy efficient), and some are more eco-friendly than others. 

Which Of These Types Of Attic Insulation Is Best For Your Building? 

This guide is dedicated to helping home and business owners choose the best types of attic insulation for their building, after weighing the pros and cons. 

Understanding R-Value 

Attic insulation is one part of your home’s comfort and energy-efficiency systems. In addition to keeping you warmer in the winter and cooler in the summer, reducing your demand on the HVAC system, your attic insulation also protects your home from moisture issues when paired with a good roof and ventilation system. 

The key to all of the above is to install insulation with the right R-value for your geographical location.  

The Department of Energy (energy.gov) explains: 

An insulating material’s resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value -- the higher the R-value, the greater the insulating effectiveness. The R-value depends on the type of insulation, its thickness, and its density. The R-value of some insulations also depends on temperature, aging, and moisture accumulation. When calculating the R-value of a multilayered installation, add the R-values of the individual layers. 

Here in the Bay Area, professional insulation contractors use the energy.gov R-value map as our guide. We are in Zone 3, so we use the following R-value guidelines. 

 Add Insulation to Attic   
Zone Uninsulated Attic Existing 3-4 Inches of Insulation Floor 
    
3 R30 to R60 R25 to R38 R19 to R25 

Today, we’re going to discuss the four most commonly used insulation types. 

Fiberglass (batts or rolls) 

Fiberglass insulation is by far the most widely used insulation in today’s homes. This is because it’s cheap, effective, and it’s easy to install on your own if you know what you’re doing. Fiberglass insulation comes in loose batts or rolls, and these come faced or unfaced. Faced means the batts are lined with a paper layer for ease of application and to minimize contact with the thin fiberglass particles. Un-faced batts or rolls leave the fiberglass exposed on both sides. 

It is an ideal option for attic insulation, especially if you have an attic with standard-spaced joists and beams and minimal obstructions. It can be cut to size/fit, but will still leave marginal gaps here and there. To maintain its R-value around vents, you need to cut it very accurately. 

Fiberglass batts are not considered eco-friendly because the fiberglass particles can loosen over time, especially if they are chewed up by pests, dampened by leaks/moisture, or manipulated over time via subcontractors (HVAC, plumbers, electricians, cable, internet, etc.) working up in the attic space. The particles irritate the skin, respiratory passages, and stomach/g.i. tracts so always wear full protection, including mask and safety goggles when working with fiberglass. 

COSTTypically, fiberglass batts cost between 20¢ and 60¢ cents per square foot. 

Loose-Fill Insulation 

Loose-fill insulation options are starting to take over where the fiberglass batts are leaving off. This is because many options include eco-friendly alternatives made from recycled paper and scraps. Because the particles are loose, loose-fill insulation is also a wise choice for older homes with flatter roofs (less headroom), unique shapes, or multiple obstructions such as pipes, vents, and crossbeams.  

NOTE: Loose-fill insulation should not be used around recessed cans as it can be a fire hazard. Click Here to read about the safest insulation to use around recessed can lighting. 

While it can be spread manually, contractors always use machines to blow loose-fill particles into place, and these can be rented for around $100/day. Loose-blown cellulose is considered one of the most effective insulation options out there because it easily fills spaces and surrounds pipes, vents, ducts, etc. That said, it is very sensitive to moisture and gets moldy when wet for too long. If you choose loose-fill, we recommend having your roof inspected and ensuring your roofing system, attic vents, etc. are in top shape so moisture isn’t a concern. 

COSTLoose-fill insulation runs around $1 per square foot. 

Spray Foam Insulation 

Spray foam insulation has one of the highest R-values of all (3.5 per inch for open-cell, 6.5 per inch for closed cell). As a result, it’s often advertised as the most eco-friendly option. This is not necessarily the case. While spray foam insulation is one of the most energy-efficient options, the chemicals (mostly polyurethane) used to make it are by no means eco-friendly. Keep that in mind so you can weigh which side of the eco-friendly coin matters more to you. 

This is not a DIY material, and it should always be sprayed in place by professionals. 

That stated, contractors and homeowners love sprayed foam insulation because it seals all those gaps, hard-to-reach places, and crevices that are often impossible to get to with any other product.  If a vapor barrier is neededclosed-cell insulation is the better choice.  

COST: Open-cell spray foam runs around $1.25 per square foot, closed-cell costs around $1.50 per square foot. 

Rock Wool (Mineral Wool) 

If eco-friendly insulation is the goal, rock wool batts are probably the best option for you. They are made from mineral wool and recycled products. Although they come in blanket or batt form, like fiberglass insulation, they are heavier and firmer, which makes them easier to work with. Rock wool batts/blankets can be cut to size and shape more accurately, allowing for more precise installation around obstructions, vents, and outlets/penetrations. 

Rock wool is both moisture and heat resistant, which is also appealing to homeowners. In fact, they’re so heat resistant that rock wool batts can be used to create one hour, fire-rated assemblies, and also help to slow the spread of flames. This is one of the reasons they are rapidly increasing in popularity, proportional to California’s fire season threats. And, if the blankets get wet, they are just as good as new once they dry – which is not the case for fiberglass or loose-fill options. 

COST: Rock wool batts are roughly 80¢ per square foot (only 20¢ more than fiberglass).

Let Us Do The Hard Work For You

Are you interested in consulting with a Bay Area insulation contractor as you determine which of the various types of attic insulation is best for your project? Contact us here at Attic Solutions for a free, no-obligation consultation. 

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