How to Insulate a crawlspace

If you haven’t looked inside your home’s crawlspace in a while, it might be time to give it a thorough inspection—especially if your floors are feeling cold even when your furnace is running. While your crawlspace isn’t the most inviting place to visit, spotting damp, soggy fiberglass batts hanging from your floor joists (or no insulation at all) is a telltale sign that your crawlspace needs to be reconfigured to ensure adequate insulation and minimal moisture.

With this guide, we will walk you through the best steps to take when re-configuring your crawlspace—including the downfalls of traditional crawlspace insulation methods, as well as more modern and efficient crawlspace encapsulation processes and how you can apply them to your home.

The downfalls of traditional crawlspace insulation methods

animated graphic depicting what condensation from moist air can do to a crawlspace

For many homes with crawlspaces, it is common for builders to place fiberglass insulation in the subfloor above the crawlspace while leaving wall vents open. The thought behind this is that any moisture build-up in the crawlspace would be expelled out of the vents.

Unfortunately, this design does not live up to its intended purpose, especially in areas of the country that deal with higher humidity. Climates with high humidity levels cause moist air to find its way into crawlspaces—and as it comes into contact with the cool surfaces within these spaces, it creates condensation that could lead to insulation degradation and mold growth.

How to properly insulate a crawlspace

Rather than taking the traditional approach to crawlspace insulation, the most effective way to ensure your crawlspace stays condensation-free and insulated all year long is to enclose it entirely—no matter what climate you live in. Not only does crawlspace encapsulation reduce the chance of moisture build-up and promote better energy retention during temperature fluctuations, but it also provides a complete solution for crawlspace mold and pest prevention. Additionally, it creates an overall cleaner crawlspace in your home that you could use for additional storage.

Below, we’ve detailed four steps you can take to encapsulate your home’s crawlspace.

an infographic depicting four steps that you can take to insulate a crawlspace

1. Eliminate moisture

The first step to encapsulating your crawlspace is to eliminate sources that could be causing moisture build-up. This could include clearing a clogged gutter system, installing downspout extenders, re-grading your lawn to slope away from your foundation, or removing landscaping or garden beds that are too close to your foundation. If your crawlspace has standing water, water elimination strategies such as an interior drain system with a sump pump and an industrial-strength dehumidifier might be necessary to completely dry out the space before the encapsulation process can begin.

2. Seal crawlspace vents, airways, or access doors

Once you have eliminated potential water sources and completely dried out your crawlspace, the next step in the encapsulation process is to seal crawlspace vents, airways, or access doors. Many manufactured crawlspace vent covers help to create an airtight bond—but if you happen to create your own DIY vent covers, be sure to use non-organic materials and caulk them in place to keep moisture out. Then, using a foam sealant, seal off any gaps, airways, or cracks—including between plumbing, drain line, or wiring routes—that remain in your crawlspace. For access doors, be sure to install heavy-duty weatherstripping around their frames to keep air from flowing into your crawlspace.

3. Insulate crawlspace walls

Rather than installing batts between your subfloor’s joists (paper-backed batt insulation in a crawlspace with high humidity can become food for mold, especially if it is hanging), the encapsulation process utilizes rolled foam insulation across your crawlspace’s walls. Unlike fiberglass batts, these types of insulation resist damage caused by moisture, and deliver more thermal resistance than many other insulating materials of the same thickness.

Be sure to select insulation with the appropriate R-value (the measurement used to determine thermal resistance) for your area and climate. Before applying your insulation, read through any manufacturer specifications or installation guides, as each type of insulation features its own installation process.

4. Add a vapor barrier

With your insulation in place, it’s time to add a vapor barrier across both the floor and walls of your crawlspace. Not only does this keep moisture from being expelled from the floor in your crawlspace and add an additional layer of protection for your insulation boards, but it also makes the space healthier—which means it has the potential to become an additional usable area in your home. Vapor barriers are available in a wide range of thicknesses, but be sure to choose one that will, at minimum, withstand foot traffic or the dragging of tools or equipment—especially if your HVAC, ducting, or other appliances are housed in your crawlspace.

Professional crawlspace encapsulation services from ’58 Foundations & Waterproofing

Encapsulating your crawlspace on your own can be a time-consuming and challenging process, especially if you’re also dealing with moisture or mold problems. Fortunately, at ‘58 Foundations & Waterproofing, we can help you solve your crawlspace issues for good.

If you’re dealing with severe moisture issues or standing water in your crawlspace, our basement waterproofing solution—which includes encapsulation, dehumidifier, and sump pump options—will work to keep your crawlspace dry and free of mold. Additionally, our heavy-duty commercial crawlspace dehumidifier will work to dry out any moisture collected in your joists, subflooring, posts, and other porous materials, stopping further rot and mold growth.

After your crawlspace is dry, our comprehensive crawlspace encapsulation process includes sealing all vents to prevent moisture from finding its way in, and then sealing the floor and walls with a 20-millimeter-thick vapor barrier that is nearly impervious to rips or tears. (We mechanically fasten our liners to the walls to keep them firmly in place.) We then caulk around the top edge to prevent moisture from rising behind the vapor barrier and into the crawlspace. We will also wrap any concrete or block columns with our vapor barrier.

If you’re ready to install a permanent crawlspace solution that keeps moisture out and your home energy efficient, call ‘58 Foundations & Waterproofing today to schedule your free inspection.