Insulation projects are often focused on exterior walls and attics. While insulating these areas is important, homeowners can also save money on their heating (and cooling) costs if they insulate the space under their floors.

Underfloor insulation can take a variety of forms. For homes without basements and those with unheated cellars, adding insulation can bring heating costs down. Owners might also consider insulating basements, foundations, or even the space between the basement and first floor.

The type of underfloor insulation that is right for a given home depends on its design and climate control needs. However, most houses can benefit from added insulation under the floors of the main living space. Some underfloor insulation projects could fall into the do-it-yourself realm, but many will require the special skills of a contractor who knows how to deal with moisture, ventilation, and air sealing.

Here are six reasons why underfloor insulation may be right for you:

1. It Eliminates Drafts

Underfloor insulation will help eliminate drafts in homes that are raised above the ground (those that have a crawlspace or are set on piers). Insulating under the floor will prevent drafts from entering via the gap between the floor and the ground.

One tactic is to place rigid insulation panels between the floor joists. The contractor would need to cut the panels to fit tightly, and caulk the spaces in between the insulation and joists. The caulking is necessary because the wood expands and contracts based on temperature and moisture. If the floor joists are enclosed, the contractor can spray foam insulation into the space.

Other options are also available. Because a homeowner needs to prevent moisture buildup, some forms of insulation, such as batts, may do more harm than good in this given situation. A qualified contractor will be able to recommend the right material for the job.

2. It Will Prevent Heat Loss

According to the experts at This Old House, underfloor insulation will help the house retain heat, but it will not necessarily make the floor warmer by itself. Homeowners expecting to have a heated-floor effect after they insulate beneath the surface will be disappointed. Hot air rises, therefore, the cold air outside the house will actually make the insulation colder than the interior. This natural phenomenon will not make the floor colder, nor will it create a warming sensation.

Underfloor insulation will, however, prevent heat loss. Insulation impedes temperature change, meaning less energy is needed to maintain your chosen temperature.

More than 10 percent of an average home’s heat is lost through the floor. This percentage can be much higher in older homes with hardwood floors—or floors made of other materials that conduct heat and cold. By preventing this heat loss with underfloor insulation, homeowners will see an energy bill savings of at least 10 percent.

3. It Will Create a Vapor Barrier and Reduce Moisture

Wood floors are especially vulnerable to moisture. A layer of insulation between the floor and crawl space helps create a vapor barrier, preventing moisture from creeping in and soaking the wood floor (which could eventually stain or warp the wood). Panels or insulation with rigid corners is the best option for creating a complete barrier.

In some houses, drainage and ventilation in the crawlspace can also play a role in combating moisture. Homeowners should consider hiring a professional to check this space for other moisture problems before investing in underfloor insulation.

A vapor barrier could also benefit homes with damp basements. Homeowners left to rely on sump pumps or dehumidifiers to keep their basements dry should consider installing a layer of insulation under the first floor.

4. It Will Help Keep Pipes From Freezing

In homes with piping beneath the floor, insulation provides extra protection. In climates with freezing winters, pipes are prone to cracking and bursting if the water inside of them freezes.

Since pipes often run near the floor, they are placed in areas that residents do not usually inspect. Sections of pipe could be located in incredibly cold areas near or under the floor, and the homeowner would never recognize the risk of pipes freezing.

A layer of insulation between the pipes and a home’s exterior could lower the risk of wintertime pipe bursts.

In colder climates, another option (if feasible), is to seal off the crawl space and insulate the exterior walls rather than the floor. This technique protects the under the main floor of the house. However, sealing off this space or installing closeable vents requires a proper plan for reducing moisture beneath the home.

5. It’s Cheaper Than Insulating Uninsulated Spaces

For residences with an unheated basement or a room above an unheated garage, underfloor insulation could be cheaper than installing insulating and ductwork.

When opting for this type of insulation, homeowners must be sure to air-seal the space—caulk in between joists and insulation and fill any cracks between the heated and unheated rooms. In both a garage and basement, air sealing helps keep contaminants like car exhaust or moist, musty air from permeating the living space.

6. It Will Help in the Summer, Too

Aside from controlling the moisture in your main living spaces, insulating beneath raised floors and between the first floor and basement can help control interior temperatures in warm months.

This echoes scientific concept that “hot air rises.” Especially in homes with a ventilated crawlspace, the floor can conduct hot air from outside into the conditioned interior. If it seems like your air conditioner is constantly running—this may be why.

As with other insulation projects, the contractor needs to ensure that the insulation used can withstand moisture and that a complete barrier exists between the interior and exterior.

How to Fund an Underfloor Insulation Upgrade This Year

As colder weather approaches, homeowners might think that adding underfloor insulation is a project best suited for next year. However, property assessed clean energy (PACE) financing can help homeowners make energy-saving improvements with no money down. By leveraging their home equity, a property owner can immediately finance eligible upgrades, such as underfloor insulation, and then pay for their improvement on their annual property tax bill.

If planned correctly, some energy efficiency improvements can even pay for themselves, using any utility bill savings to make payments over the long-term.


PACE can help you finance underfloor insulation, making your home more comfortable and energy efficient. Contact YgreneWorks at (855) 901 3999; info@ygreneworks.com to see if PACE is available in your area.