Green Attic Insulation: How to Insure A Cozy & Energy Efficient Home

by ‐ Tags: green living, alternative energy, building science

Colder temperatures are creeping in! In Boston, harsh winter weather is a serious consideration for homeowners when thinking about insulating their homes for the upcoming season. Attics are one of the most important areas of a home to insulate to reduce heat loss and thereby decrease energy consumption. Understanding and improving aged or inadequate attic insulation is an important step to insure a comfortable and energy efficient home.

What specifically makes the attic the most important part of your home to insulate? The heat in your home rises and can escape through a poorly insulated attic, significantly increasing your utility bills. As long as your attic is not being used as a dwelling space, less energy can be used year round with well-insulated attic floors. By reducing the total space needing to be conditioned, you subsequently reduce your energy usage. Attic insulation improvements are so effective that the return on investment time can be as short as a couple of years. Savings from insulation retrofits are estimated to be 15-30% annually!

For homes located in areas with consistent winter snowfall, taking action to prevent ice dams on the roof of your home can save you thousands of dollars in potential damage repair. Damage to your home from ice dams can be avoided through a) manually removing the snow off your roof, or b) (a more appealing and better long-term solution) improving your attic insulation to cut down the heat loss causing the formation of the ice dam.

So what are the best types of attic insulation materials? First, let’s understand the basics:

Before insulation installation, locating and sealing air leaks is vital since air leakage can cause up to half of your home’s energy loss. Once that process is complete, choosing the proper insulation material should be based off of several factors. The required metric by which all insulation material types are specified is called the R-value, which is a measure of an insulation type’s ability to resist heat flow. The R-value is the product of both the R-factor of the material and the inches of insulation installed. A basic guideline to follow is that the higher the R-value the better. However, proper attic insulation varies across the US due to various climate zones. To identify your ideal R-value range, use this R-value calculator or follow the map and table provided by ENERGY STAR®: 

insulation map resized 600

R value table

While reducing your energy usage is an important component of creating a greener home, the materials you use should also be a high priority. Here are some types of sustainable insulation products for your attic:


Insulating your attic with cellulose is one of the most sustainable and effective solutions to your insulation needs. Usually made from approximately 80% recycled newspapers, the material is treated with nontoxic borate flame retardant and can be installed either as a loose-fill or spray-on product. According to this study, cellulose can perform better than fiberglass (described below) as temperatures become more extreme, because the R-value of the cellulose insulation stays the same, while the fiberglass insulation R-value drops.

Recycled Fiberglass

Alongside cellulose, fiberglass is one of the most common attic insulation materials. Fiberglass insulation products are made from spun glass fibers and can be composed of up to 40% recycled glass. However, in general this is the least sustainable option. There are several downsides during the installation process, including health concerns such as respiratory problems and exposed skin irritation. For a comprehensive comparison between cellulose and fiberglass insulation materials, read this article.


Similar to cellulose, cotton insulation products can be made from up to 85% textile scrap and are treated with nontoxic flame-retardants. A major benefit of this insulation material that is most often made from recycled denim is the absence of health hazards associated with other insulation products. However, a homeowner can expect to pay more for a similar R-value achieved by cellulose or fiberglass due to cotton’s less efficient insulating properties.

Soybean-Based Spray Foam

While the purely petrochemical form of this insulation type may be one of the least sustainable insulation option, soybean-based, water blown spray foam is an extremely effective insulator. This is another insulation material that is on the expensive side, however it can truly be a superior air sealer in comparison. The sustainability factor is up for debate due to varying degrees of petroleum replacement by soybean in different products.

Each home is unique in its attic insulation needs, however an educated investment into creating a sustainable and energy efficient home is one that will pay off not only through your finances, but also for the environment.

Feeling like your attic could use an upgrade? Start out with this helpful Attic Insulation DIY Guide from ENERGY STAR®!

Getting Started with Water and Energy Management Our free guide walks you through the basics. Get started today!