How Much Insulation Do I Need in My Attic?

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

For many homes, that includes their attic. Unfinished attics in particular can be much colder than the rest of your home, even though heat rises. It can easily escape through small cracks or other flaws. Installing more attic insulation to your attic can help your home retain more heating and cooling, and help you save more money as well. 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 find out how much insulation is already in place. Measuring is an easy process and can be done with a measuring tape. Simply check the depth of the existing insulation against the adjacent 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 impacts how much insulation is considered adequate. Northern climates need a few more inches of insulation compared to climates further south. This added insulation helps protect against the bitter cold and long winters more common in the northern part of the country. 

While a thick layer of insulation is beneficial, the overall efficiency is also affected by the materials used. Some materials are more insulating than others, making them more efficient at reducing 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 reaches past the floor joists, a small R-Value means it’s not trapping as much heat as you might think. Cooler climates generally need an R-Value of 38 or higher, which roughly ends up at 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 several materials used to manufacture 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 go over 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’ll find 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 turned into soft insulation for your attic. Mineral wool, also known as 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 

Unlike rolls or batts, spray foam insulation is sprayed directly onto the surface for insulation. This foam is made from multiple 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 equals higher energy efficiency, there’s such a thing as too much insulation. Excessive insulation can increase mold growth and trap other airborne particles between the fibers. Unless you’re experienced with evaluating and installing home insulation, it’s best to leave the job to a pro. 

Professional installation ensures an even coating throughout your attic, from the center of the floor to the spots closest to the roof. This consistent seal 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.