How To Insulate a Concrete Basement Floor and Why You Should
You should insulate a concrete basement floor to improve comfort, stop condensation and prevent heat loss. Depending on the height of your basement ceiling and your budget you have three concrete insulation options to choose from.
In a Hurry? If you’re looking for concrete insulation product options then click here for the Home Flooring Pros recommendations. Read on for the full story.
In this post you’ll learn whether you need to insulate your basement, what your options are, what products to use, how to install them and how much i is all likely to cost you. Please feel free to use our quick links to zip to the information you need and please leave a comment or question at the bottom of this page. We always love hearing from you.
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Do You Need to Insulate Your Concrete?
There are three reasons to insulate a concrete basement floor – Comfort, stopping condensation and preventing heat loss.
Comfort – The ground beneath the concrete is a cool 50F to 60F, and heat rises. The resulting lack of heat near the floor produces cold feet for sure, or an entire basement area that is cooler than desired.
Condensation Prevention – Cold surfaces like an uninsulated concrete basement floor condense moisture, as you know, and that moisture is just what mold spores need to reproduce and grow.
Cutting Costs – Heat transferring through a bare concrete floor means higher heating bills. Insulation cuts heat loss significantly, and your basement floor insulation will pay for itself in a few years.
What Are Your Options?
What is the best basement floor insulation? We recommend you consider three types based on the height of your basement ceiling and the cost you’re willing to pay. They are
- A fully insulated basement subfloor for a full-height basement
- Pre-fab subfloor panels where height is limited
- Electric underfloor heating systems when you want the coziest basement floor
But first – make sure the concrete is properly sealed. Strange but true, concrete is porous, and water migrates through it from below. Get a quality concrete sealer from your local home improvement store. Clean the floor, follow directions on the can, and take this very important first step in a healthy, warm basement floor. If you don’t, moisture will get trapped beneath your floor, and you will end up with mold issues in most basements.
A Note on Basement Ceiling Height – Most basement ceilings are 8 foot or higher. But some older homes have lower ceilings, and current universal building code allows for 7-foot ceilings, which limits the amount of height you can give up for an insulted basement floor.
When You Have Plenty of Height
A fully insulated basement subfloor system gives you a better insulation R-value, but is only a good fit when the basement ceiling is at least 8 feet high.
An insulated subfloor starts with a vapor barrier over the sealed concrete. Yes, the sealer will prevent most moisture issues, but a vapor barrier is a cheap step in doubling your protection against moisture and mold.
From there, you have a couple of options using rigid foam, considered the best practice.
Option #1: Install foam insulation boards (panels) as the foundation, OSB on top, finished with your choice of appropriate flooring. This is the most common approach.
Polystyrene 1” foam boards offer an R-4 to R-5 insulation value, about the minimum you’d like to have to make a basement floor warm. Choose 2” boards for improved insulation.
Alternative to Option #1: Choose a rigid board insulation that is strong enough to use directly under your flooring without OSB or plywood. Specific product recommendations and how-to’s are found below. This is also a great choice where ceiling height is limited.
When Height is Limited
Where height is tight, you have a couple of different options. Here’s an overview of them:
Option #2: Pre-fab Insulated Basement Floor Panels: These panels have a thin insulation bottom layer and an OSB top layer. Most fit together tongue-and-groove or in similar fashion. The R-value of most insulated floor panels is around 2, but where height is limited, there’s only so much you can do. This R-value will certainly help take the chill off the floor.
Option #3: Electric Underfloor Heating Mats or Cable: The mats are mesh with wiring attached. Mats start at about 12”x48” and can be as large as 16”x720” for basement floor use. The mats plug together to cover the concrete subfloor. A hard material like OSB is used to form the floor above the mats. As electricity flows through the wiring, electric resistance heat is produced, which radiates up through the flooring. The wiring connects to a thermostat, typically mounted on the wall, that controls the heat.
Electric resistance cables and fasteners or underlay are an alternative.
Some hardwood, laminate, carpet and luxury vinyl flooring are suitable for use over electric underfloor heating systems. Check the manufacturer’s information to be sure it’s okay for this application.
Product Options for Concrete Floor Insulation
Here are the systems described above with product recommendations.
Option #1: Insulated subfloors – EPS foam insulation boards are made by Kingspan, Johns Manville, Dow, Owens Corning, Lowes and many other brands. You’ll find several options at any home improvement store. You can see some of them here on the Home Depot website.
Option #1 alternative: Rigid foam boards ready for flooring – If you want to skip the layer of plywood or OSB, consider a hardened foam strong enough to support flooring immediately on top of it. DRIcore Insul-Armor is the most popular.
Option #2: Insulated basement floor panels with an integrated OSB top layer – DRIcore subfloor panels (not Insul-Armor) and Amdry are the best known. Panels are available in 3/4″ and 1” squares, each 2’x2’ from Home Depot and other retailers. Here’s a selection of DRIcore panels available at Home Depot.
InSoFast panels with R-10 insulation and ThermalDry decking with a tough magnesium oxide underlayment layer above the insulation are pricier options sold by online retailers.
Option #3: Electric Underfloor Heating – The best-known brands include LuxHeat, Danfoss, SunTouch, HeatTech and QuietWarmth. Find options locally at home improvement stores or online from many retailers.
How to Install Your Insulation
Let’s describe the best practice for an insulated basement floor. There are two or four parts to this design depending on the materials used.
4-part installation: First, a vapor barrier like sheet polyethylene is laid over the concrete floor and wrapped up the walls about 3 inches – excess can be trimmed later. The seams should be secured with a heavy-duty tape made for the purpose. Secondly, EPS rigid foam panels cover the vapor barrier. Boards from .75” to 2” are commonly used. Seams should also be securely taped.
The third layer consists of ¾” or 1” thick treated strips laid 16” on center across the rigid foam. These planks, often called “sleepers,” should be secured through the rigid foam to the concrete beneath using masonry screws or nails. Finally, 5/8” or 3/4″ plywood or oriented strand board (OSB) can be fitted over the treated strips and secured to them with wood screws.
Can you skip the sleepers? Yes. Their main advantage is to create an air gap beneath the OSB that can improve the insulation value of the floor, much the way a second pane of window glass improves insulation.
2-part installation: This method includes a vapor barrier covered with one of the super-strong foam insulating floor boards like Insul-Armor designed to have flooring laid on top of them – they won’t crush.
Either way, you’re done – and your basement floor is insulated and protected from condensation.
Basement Insulation Cost
Upfront and ongoing costs should be considered for the most common basement floor insulation practices.
Insulated Basement Subfloors
The standard method of vapor barrier, EPS foam with an OSB overlay costs $2.25 – $3.85 per square foot for the materials. Anticipate estimates of $1.00 – $1.50 per square foot for installation.
Insulated Basement Floor Panels
All-in-one insulation and OSB panels like DRIcore and Amdry cost $3.00 – $4.00 per sq/ft. Installation goes quickly, so you’ll get estimates of about $1.00 per square foot, maybe a little less, for the labor.
The best-known option is DRIcore Insul-Armor with 3,000+ pounds psi strength and an R-value of 4.1. The cost is $2.25 to $3.00 per square foot depending on the quantity you purchase.
Electric underfloor heating
The cost for the mats is $7.00 – $30.00 per square foot based on mat size and what’s included such as integrated padding or vapor barrier. Average pricing is in the $10-$15 range per square foot. Cables and fixing materials cost an average of $8-$10 per square foot, and up to $20 per square foot if you include the purchase of a membrane that is laid on the concrete floor and designed to securely hold the cabling in place.
Installation estimates will run $1.50 – $2.50 per square foot when everything is included – laying out and securing the mats, connecting them together and to your electric panel and installing the thermostat. You’ll need an electrician, or at least should hire an electrician, for the panel hookup. It will take about an hour or less with a minimum first-hour fee of $65 to $150.
Energy cost: And then, of course, you have the cost of running electric radiant floor heating. Electric heat is the most expensive type of heat. Hang onto your seat…Depending on the size of your basement floor and the months you use the system, expect additional electric costs between $1,000 and $2,500 per year in most homes! That’s according to the calculator provided by Warmly Yours, an online retailer of electric underfloor heating systems, for a 1,000 square foot basement.
Home Flooring Pros Conclusion
Before you start dreaming of a beautifully fully finished basement you need to budget for some form of insulation for your concrete floor. If you don’t you will compromise all your other renovation efforts. This isn’t necessarily a concern if you only intend to use your basement for storage, utilities or a workout space. It’s pretty essential if you plan to install more expensive flooring like cork or carpet and want your basement to be dry, warm and comfortable.