How To Insulate A Crawl Space

As part of overall home air sealing and insulation, Crawl space insulation helps the energy efficiency of your entire home.

Heat is easily lost through the floor without crawl space insulation, and cold air covers your lower ground floor.

Insulation also helps in the preservation of air quality and the reduction of energy expenses.

Crawl spaces are divided into two types: ventilated and unventilated, and each requires its own sort of insulation. The purpose, though, is the same: to create a thermal envelope around your space.

crawl space

In our guide, you can learn all the ways you can deal with your crawl space walls and exactly what a local contractor or what you need to do yourself in any home repair of these areas.

By the end, you’ll see what to do to stop frozen pipes and moisture buildup, reduce heat loss and keep your floors warmer by reducing energy costs with proper insulation. (Read What Heaters Are Safe To Leave On Overnight)

How Should a Crawl Space Be Insulated?

Fiberglass insulation can be installed under the subfloor between the floor joists if the crawl space is ventilated, which is good because it aids in the elimination of moisture. An air barrier is vital to avoid moisture and mold; it’s critical to seal insulation and cover it with a vapor barrier.

If your crawl space isn’t ventilated, insulate the crawl space’s walls rather than the room’s subfloor. This leads to less insulation require and also eliminating any need to insulate ducts and pipes.

For added protection, a polyurethane vapor barrier might be installed over the dirt floor. To protect the barrier from harm, it might be covered with sand.

While a capable person could install crawl space insulation, hire a professional. They’ll clean up and dispose of old insulation correctly, and they’ll frequently spray the space with bacteria- and fungicides.

You’re in luck if your winter temps rarely drop below freezing. Installing six-inch-thick R-19 fiberglass batt insulation between floor joists, as well as meticulous moisture control and mold avoidance, is installed. The best part is that it is inexpensive, costing around $1 per square foot.

Here is the way to do the job right and put a stop to that cold air seeping up the floors of your split-level home.  (Read Basement Heating Options)

Support: Unfaced fiberglass batts should be installed to touch the living space subfloor’s underside. The best fiberglass batts support is wooden lathes placed every 18 inches or a crisscross webbing of wire.

Ventilate: An contractor for your insulation will easily calculate the ventilation of your crawl space requirements and cut in new crawl space vents as needed.

Seal your subfloor: If there are any holes for electrical wires and plumbing pipes, these need to be sealed with spray foam insulation.

Insulate your plumbing pipes and HVAC ducts as this reduces heat loss and freezing.

Closed-cell spray foam can add thermal, and moisture protection yet is more expensive at around $5 per square foot. However, it could be the only solution for filling between truss-type joists.

Avoid using any open-cell spray crawlspace insulation, as this would soak up moisture in damp crawl spaces.

Here you can see an overview of how to deal with your crawl space in a cold climate.

In a cold region, the best technique is to insulate the walls of your crawl space and cover all air leaks so they are sealed off from the weather. As a way, plumbing pipes and HVAC ducts are shielded from freezing temps, saving energy.

The ideal option is to use rigid foam insulation to insulate crawlspace walls. It comes at roughly $5 per square foot for skilled installation, but it is a long-term solution.

A thorough job also covers the following:

Closing the vents: Closing vents in your foundations doesn’t solve the issues. Holes need to be sealed and the vents eliminated.

Insulating the rim joist that sits on top of your foundation walls needs doing with closed-cell spray foam.

Insulating the foundation: Using waterproof construction adhesive, you need to glue rigid foam insulation board to the inside of your foundation walls and seal the seams using waterproof tape.

It can cost around $26 for a 4-by-8-foot sheet of 2-inch-thick expanded polystyrene insulation that offers an R-value of 7.7. Two layers of said insulation are recommended.

Vapor barrier: Whether your crawl space’s floor is, be it dirt, gravel, or concrete, it absorbs moisture. You can protect the ground by using a 6-mil polyethylene plastic vapor barrier.

Get rid of moisture: Because of the humid air, condensation in the crawl space is usually unavoidable. In addition, the slightest plumbing leak can build up. Mold hates moisture, so a dehumidifier or sump pump will help you get rid of it. (Learn How Long Does Vinyl Siding Last)

Once your crawl space has been shut off from the outside, it can be connected to your home’s HVAC system via vents. As a way, warm air circulates beneath your cold floors to warm them and keeping you warm. In the summer, though, there’s no need to cool your crawl space; close the vents while your air conditioner is running.

crawl space with dirt

What is the Best Way to Insulate a Crawl Space With a Dirt Floor?

You can begin installing the insulation, protecting your crawl space, and improving your home’s energy efficiency now that you know what kind of insulation you need to buy.

Step 1

Clearing the crawl space is the first step. This is to ensure you have enough space to work comfortably and move around. Remove any sharp rocks or debris to avoid injuries and damage to the insulation.

You may need a professional to tenure there is no asbestos or radon gas in the area.

Step 2

Consider whether you’ll have issues with bulk water accumulation. Even if your crawl space has never flooded, that doesn’t mean it won’t. For added security, consider installing a sump pump at the lowest point.

Step 3

The next step is to deal with any moisture in the crawl space and find and fix the source of the moisture. So, keep an eye out for leaking fixtures.

Water heaters and air conditioner condensation drain pipes are examples. Apply a waterproof membrane to the walls to prevent future moisture issues. This waterproof membrane works well to seal porous concrete and other surfaces.

Step 4

Now consider the vapor barrier. It may sound difficult, but all you need to do is cover the crawl space floor with 6-mil plastic.

Step 5

When insulating a ventilated crawl space, avoid covering any vents. Instead, fill the ‘joist bays’ with fiberglass batting. In material to maximize insulation, do not squash the fiberglass.

Step 6

If you’re insulating unventilated crawl spaces, begin running non-faced batting from the floor to the sill plate and following the concrete foundations. This type of batting helps to keep moisture out of the crawl space.

Next, extend the insulation by seven inches over the newly installed vapor barrier. Finish the job by inserting insulation into the joist bays to meet the rim joist.

Crawl space inside

What Type of Insulation is Best for Crawl Spaces?

The best way to insulate a crawlspace is think of it as your basement and insulate from the ground up.

Spray foam is quick, has a high R-value, seals out moisture and air, and fills all the tiny holes. Not cheap, but effective, and best of all, someone else will slither around in your crawlspace instead of you. No need to lay down poly beforehand because it will act as a vapor barrier.

There are two ways to insulate the walls–If your crawlspace is over 5 feet high, you can frame a 2×4 or 2×6 – 1 inch away from the concrete wall, sitting it on small chunks of foam to keep it from touching the ground and absorbing moisture. Then spray foam is applied behind the studs and into the cavities, leaving enough room for wiring if needed.

To protect the foam from fire, drywall can be attached to the stud wall. Spray foam is the only vapor barrier required.

You can also apply EPS rigid insulation foam boards directly to concrete using either strapping and tap con screws or a foam board adhesive, but only on walls. XPS foam can be substituted for EPS but has higher greenhouse gas emissions.

XPS is a vapor barrier at 1 inch, and EPS foam is a vapor barrier at 2 inches or thicker.

Rock wool (mineral wool) boards (similar to fiberglass batts) are an alternative product that is made from recycled stone dust and does not burn. However, mineral wool is not a vapor barrier, so a poly membrane should be applied first.

How Do You Insulate a Low Crawl Space?

Experts advise a professional installation to convert crawl spaces into a conditioned spaces to save energy. Condensation is eliminated, reducing the chance of mold and mites.

Air ducts lose less energy, and first-floor rooms get warmer in the winter as there are no cold floors. Removing water sources from the crawl space becomes a priority.

Downspouts and sidewalks, patios, and garden beds are regarded to slope away from the house, and a sump pump or basement waterproofing system is fitted.

Close all vents and ensure hatchways are caulked to stop draughts. Seal rim joists and sills and fill joist bays using a rigid insulation wall insulation board for insulating crawl space areas and cut energy loss.

Seal joints with a foam sealant or appropriate adhesive and seal between the crawl space wall and the sill with caulk or foam sealant.

How To Insulate A Crawl Space (2)

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