How Much Insulation Do I Need in My Attic?

While a majority of homes have some insulation, have you ever thought about whether or not your home has enough insulation? It creates an important layer of protection between you and the harsher conditions outdoors. Without enough insulation, you may be missing out on energy savings or a better sense of comfort. Putting in new insulation can be a great investment, especially when you know where it will have the largest impact. 

For many homes, that includes their attic. Unfinished attics in particular can be much cooler than the rest of your home, even though heat rises. It can quickly escape through small cracks or other flaws. Adding more attic insulation to your attic can help your home retain more heating and cooling, and help you save more money as a result. But how much insulation do you need in your attic? 

Calculating How Much Insulation You Need 

You’ll need to head up to the attic to determine how much insulation is already installed. Measuring is an easy process and can be accomplished with a measuring tape. Simply check the depth of the existing insulation against the closest joists. A good rule of thumb is that the insulation should measure several inches past the joists, but ultimately you’ll need the measurement itself. 

Your local climate affects how much insulation is considered adequate. Colder climates need a few more inches of insulation compared to climates further south. This additional insulation helps protect against the bitter cold and longer winters more common in the northern part of the country. 

While a strong layer of insulation is beneficial, the total efficiency is also affected by the materials used. Some materials are more insulating than others, making them better at resisting heat loss. This resistance to heat flow is known as the R-Value. 

Make Sure Your Insulation has the Correct R-Value 

Even if your insulation stretches past the floor joists, a small R-Value means it’s not trapping as much heat as you might hope. Cooler climates typically want an R-Value of 38 or above, which roughly means 12-14 inches of insulation. You may need more or less depending on the material used for insulation. 

What Type of Attic Insulation Is Best? 

There are a number of materials used to create home insulation. Each of these materials has a different R-Value, and you’ll want to understand them before deciding one insulator is better than another. We’ll review the 4 most common types and what their R-Values can range between. Don’t forget that the climate changes what R-Value is considered as enough insulation for your attic. 


Fiberglass insulation can be found in both loose fibers as well as standardized batts. Between these two types of fiberglass insulation, you can expect an R-Value of 2.2 to 3.8 per inch. 


Shredded denim or paper fibers from old newspapers forms the bulk of cellulose-based insulation. It’s one of the oldest types of insulation and can offer an R-Value between 3.1 to 3.8 per inch. 

Mineral Wool

Even rocks and minerals can be shredded into soft insulation for your attic. Mineral wool, also called stone wool, is made from minerals like basalt. It can also be made from industrial slag or even glass. Mineral wool insulation offers a range of R-Values from 2.2 to 4.2 per inch. 

Spray Foam 

Instead of rolls or batts, spray foam insulation is sprayed directly onto the surface for insulation. This foam is made from numerous composite materials and conforms to the shape around it. Spray foam insulation can offer some of the highest R-Values, averaging 3.5 to 8 per inch. 

Can You Have Too Much Insulation? 

While it seems correct to assume that more insulation means higher energy efficiency, there’s such a thing as too much insulation. Excessive insulation can encourage mold growth and trap other airborne particles within the fibers. Unless you’re experienced with evaluating and installing home insulation, it’s best to leave the job to a professional. 

Professional installation ensures an even distribution throughout your attic, from the center of the floor to the spots closest to the roof. This consistent layer will give your home the best layer of protection. If you’re considering installing more attic insulation in the U.S., look for technicians that can evaluate your existing insulation. They’ll be able to justify why your home needs however many additional inches of insulation.