Does your home get swelteringly hot in the summer?
How about drafty and freeze-your-toes-off cold in the winter?
Do your heating and cooling costs jump around like a stock ticker during the hottest and coldest months of the year?
Well, these are all signs that you might be under-insulated, and surprisingly floor insulation could be the culprit.
In this guide, we’ll discuss how you can insulate your floors and make your home more energy efficient in the process.
Should You Insulate Your Floors?
Insulation is one of the best ways to reduce your utility bills, better manage your energy consumption, and keep the temperature in your home stable year round.
However, insulation isn’t just for walls and attics.
Do I really need it?
Underfloor insulation may seem like a waste of time, especially if you’ve taken care to insulate the exterior walls and the attic.
However, that allows the third surface of your room – the floors – to be vulnerable to outdoor elements.
The end result is flooring that is always cold, which may not be a big problem in the warmer months, but can definitely feel uncomfortable come fall.
The Benefits of Floor Insulation
You can and should add floor insulation to prevent the outside temperatures from coming in. This is especially true if your home was built on a pier and beam, or post, foundation.
Aside from cold feet, not insulating your floors can dramatically increase utility costs.
Your cooling and heating systems will need to work harder to keep the room at your desired temperature, which will definitely translate to higher energy consumption.When you have cold floors, the very first thing you should consider is insulation. Here's why: Click To Tweet
If you have the ability to insulate your floors, take the time to do it. Your budget and your toes will thank you because insulation resists the transfer of heat from warmer areas to colder areas.
Insulation is even more important if your home has wood flooring. Insulating your wood floors will also protect them from water damage.
Older homes are less likely to have floor insulation. This is why these homes often feel drafty and cold in the winter.
How to Select The Best Floor Insulation for Your Home
Insulation is key to an air-tight solution, and the type of insulation you choose will make the biggest impact on your energy conservation.
Here are some considerations for choosing the best floor insulation for your application.
Floor Insulation R Value: What to Consider
It’s also key that your material has the correct floor insulation R value for your home’s location.
The R-value is short for thermal resistance. This term is used to determine how well the insulating material can resist heat flow (the transfer of heat).
The higher the R-value of an insulating material, the more effective it is at insulating a home from the elements.
Simply by insulating your floor, you’ll improve your home’s R-value and energy efficiency. However, it’s often a good idea to go with the highest R-value that you can afford.
Higher R-values are most costly, but they do an even better job at air-sealing your home.
Here in the U.S., the Department of Energy recommends a minimum R-value for different surfaces of your home based on your climate zone.
There are seven climate zones in the U.S., ranging from 1 at the southernmost tip of Florida to 7 in the highest and northernmost areas of North Dakota, Minnesota, and Alaska.
If you live in zone 1, the minimum required R-value for an attic space is R30 to R49. Both floors and crawl spaces require a minimum R13.
However, if you live in zone 7, the minimum required R-value for an attic space is R49 to R60. For floors and crawl spaces in zone 7, the minimum R-value is between R25 to R30.
See the resource map below:
To get county-specific information on your climate zone (along with recommended R-value rating), check out the IECC recommendations here.
Remember that the R-value is the minimum suggestion, and you can also go to a higher rating if your budget allows.
It’s also important to note that R-values are monitored by the Federal Trade Commission. This eliminates or at least sharply reduces the incidence of false advertisement.
You can trust the R-value rating on any insulation material sold in the US, instead of relying on price as an indicator of quality or performance.
Floor Insulation Options: Fiberglass vs. Rigid Foam
There are two common types of insulation available in the marketplace. They are fiberglass batting and rigid foam board.
Of the two, fiberglass is the most popular. However, the type of insulation you use will greatly depend on its location within your home.
Fiberglass insulation is popular in attics, where they will need to bend and conform around different structures.
However, in basements where moisture is more of a concern, rigid foam seems to save the day. These styrofoam boards resist moisture better than fiberglass.
Here’s a closer look at both:
Fiberglass consists of spun fiberglass and is often sold in long rolls or single, unrolled pieces.
It’s flexible and able to fit around awkward spaces. Fiberglass tends to be easier to use for novice DIYers, but this shouldn’t be the only consideration when deciding which insulation to choose.
As mentioned above, fiberglass doesn’t do as well at resisting moisture.
In fact, the very reason why fiberglass is a great insulator is the same reason why it’s not the right choice for floors that are subject to moisture or mold.
Fiberglass contains air pockets that, while providing a strong thermal barrier, are also prone to trapping moisture.
Rigid Foam Insulation
In contrast to fiberglass, rigid foam is the right choice when protecting your floors from moisture.
These styrofoam boards, made from either polyisocyanurate or polystyrene (extruded or expanded), won’t warp or crack.
If you plan to use radiant heat floors, you should definitely opt for rigid foam as your insulation choice.
Rigid foam is also the go-to insulation for basements where moisture is almost certainly an issue.
Fiberglass is more popular because it’s less expensive than rigid foam – almost 50% less in a head-to-head competition.
When it comes to installation, fiberglass is easier to handle because of its flexibility.
However, fiberglass can become a serious skin, eye, and respiratory irritant.
You’re basically dealing with millions of individual glass fibers, and it can lead to itchiness (at the very least).
Protect yourself by covering up with long sleeves, long pants, long gloves, safety goggles, and a respirator.
How to Install Floor Insulation: Step-by-Step
Although the best time to install insulation to your floor is during a home remodel, you can install insulation any time.
Floor Joist Insulation and Sizing
The insulation material that you choose must be the correct width so that it can fit within the floor joists as snugly as possible. The correct thickness is another concern.
Choose insulation material that will completely fill in the joist bay whenever possible.
Otherwise, thin insulation can fall from the subfloor and rest on the OSB or plywood that’s used to encapsulate the insulation.
If and when this happens, the floor loses its insulation benefits entirely.
How to Install Fiberglass Insulation in Your Floor
Trim and place:
- Trim fiberglass to fit within the joist bays of the floor. Use a utility knife for the fastest and most exact cut.
- Place the cut insulation into the joist bay. Be careful not to compress the insulation, because its loft contributes to its R-value, or ability to block the transfer of heat.
Create the moisture barrier:
- If you’re using a kraft or paper-faced batt, install it so that the paper is facing upward, toward the living space.
- The paper should face the space that is intended to be warmer in the colder months. This creates a moisture barrier.
Secure the insulation:
- Although the paper should touch the subfloor, don’t excessively push the fiberglass against it so that you maintain all of the insulation’s R-value.
- At an interval of 6 inches from the rim joist and then every 24 inches down the length of the joist, hammer in nails on opposite sides.
- Then, loop wire from one nail to the opposite nail. Twist the wire around both nails to keep the insulation in place. Make sure that the wire is taut without compressing the insulation.
How to Install Rigid Foam Board Insulation in Your Floor
- Cut the rigid foam board to the exact size of the space needed.
- Use the appropriate adhesive glue for your floor material (plywood or cement). Look for an adhesive that bonds to foam specifically.
- Create a zigzag pattern on the back of the rigid foam board insulation (stopping short at 1 inch on either side). Then, press the foam insulation against the underfloor.
Final Thoughts on Insulating Your Floors
When you have cold floors, the very first thing you should consider is insulation. Insulation can reduce your energy bill and also help you feel more comfortable in your home during those frigid winter months.
The next step after insulation is installing radiant heat flooring. If you’d like to learn more about radiant heat flooring, give our DIY floor heating guide a read.
And then go ahead and click the link below to download the 1-page floor insulation cheat sheet to get a quick summary of the recommendations covered in this post.