Insulation in Walls

Wall Insulation


Walls don’t bear the same “heat load” as  a ceiling does, so they don’t require the same amount of insulation depth. There’s often much more wall exposed to the outside than ceiling, however, in a home.

That makes walls just as important to the comfort and efficiency of a home. Lack of wall insulation inevitably leads to discomfort. Since we spend our resting hours at home, comfort can have a big impact on quality of life.

Architecture, framing, age, and even the habits of people living there create a unique environment within each building. Additionally, the construction industry’s understanding of the impacts of insulation has come along way over the years. 

Most general contractors understand how to pass insulation building codes. The difference between passing code and the situationally correct insulation, however, is like getting a car with 15 miles per gallon when 30mpg cars only cost a couple hundred dollars more. It very little time for that slightly higher initial cost to pay for itself.

Please keep in mind that the information below is true in most cases, but nothing replaces an expert insulation contractor’s inspection.

The Best Wall Insulation

Most Effective: Blown in cellulose (R14 or R21)
Notes and Exceptions

Heavy wind, strange framing, and many other somewhat common scenarios may warrant more total insulation or a combination of spray foam and cellulose.

Air sealing is crucial for the same reason that blown-in insulation is better than batts. Air carries heat and sneaks through wall penetrations (for pipes, wires, around doors, etc.). In some areas, lack of air sealing causes more problems than not enough insulation.

Cellulose blocks air, but additional sealing around door frames and window jams may be advised.

The Most Recommended Option

R14 or R21 Cellulose

Walls with 2×4 framing will only fit R14, and 2×6 walls fit R21 (excluding closed cell spray foam, which can achieve R21 in a 2×4 wall). Blown in insulation has better coverage. Cellulose outperforms fiberglass and is less expensive when factoring in heating bills.

Can you Insulate Walls Without Removing Drywall?


We use a method called dense pack cellulose to blow in the insulation behind existing walls. Rather than removing the drywall, we drill an access hole in each wall cavity and pump in insulation though flexible tubing. This results in full insulation, sound dampening, and air-blocking coverage and only requires drywall patching after–a far easier task than replacing entire sheets of drywall.

The process is shown in the video at the top of this web page, and you can learn more about the remarkable qualities of cellulose insulation here.

Dense Pack Cellulose

We are one of the few insulation contractors in the greater Madison, WI area that can dense pack cellulose by blowing cellulose insulation into existing walls. By drilling a hole every 1 – 2 feet and then blowing insulation into walls, our technicians can insulate without removing drywall. 

This process can be done from either side of the wall, so insulating exterior walls from inside or outside the building may be possible depending on siding and wall type.

Why Blown In Insulation

Full Coverage

Blown in wall insulation performs better than batts, boards, or rolls of insulation because it can’t have gaps. Heat takes the easiest path, so even limited gaps covering 2-5% of the surface reduces total attic insulation quality by up to 33%. 

Blown cellulose insulation prevents mold growth and condensation, in part, because it can’t have gaps.

Why Cellulose Insulation

Similar Cost, Far Better Results

Cellulose wall insulation costs slightly more upfront than fiberglass but much less overall. That’s because it’s so much better at insulating. You’ll generally get back the difference in cost within 1-2 winters through lower heating bills. After that, those lower bills are money in your pocket. 

The financial benefits of cellulose doesn’t even consider the numerous other benefits of cellulose.

Why R14 or R21

The Modern Day Standard

R21 is the modern recommended R Value for walls. Walls with 2×4 framing only have room for R14 worth of insulation. That R Value makes the most of the situation without drastically increasing the project price by using spray foam or converting to 2×6 walls.

R Value only tells part of the picture. That’s why the actual performance of R21 cellulose outperforms R21 fiberglass and is similar to R14 closed cell spray foam (explained here).

Types of Insulation

A Big Difference

No matter the location, insulation type plays a big role in results. We go into detail about the 3 common insulation types in this article.

Insulation Types at a Glance

Fiberglass is the least expensive upfront, the least effective, and the most expensive over time.

Cellulose is slightly more expensive upfront, a great insulator, and offers the biggest “bang for your buck.”

Close cell spray foam (polyurethane 2-part foam) is the most expensive, offers unmatched insulation value, and generally gets the job done when other insulations won’t.


State Rebates & Incentives

Many (though not all) Wisconsin insulation projects are eligible for hundreds of dollars in rebates through the state’s Department of Energy. We typically are able to help at least one client capture a rebate each week.

We are certified to implement these rebates and complete nearly all the paperwork for you. We even instantly discount the rebate from your invoice, so you’re not left waiting for the rebate check to arrive.

Know YOUR Numbers

Planning with general numbers often leads to inaccurate estimations and budgets. That’s one of the many reasons we offer free estimates. Whether you need a quick fix or are planning for work next year, work with actual numbers specific to you.