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Why You Shouldn't Insulate Your Crawl Space with Fiberglas

Crawl Space Thermal Insulation

Among the pervasive myths about crawl space care is the belief that fiberglass insulation belongs on the ceiling, between the ground floor’s joists. Since the air in crawl spaces tends to be cold, the reasoning goes, insulation will prevent it from entering the house’s living areas. However, this idea is flawed and rests on a misunderstanding of crawl space dynamics. Installing fiberglass insulation cannot keep cold air out of your home; on the contrary, it will encourage mold and mildew growth. Instead, seek effective crawl space thermal insulation from NV Waterproofing & Foundation.


Over the past few decades, NV Waterproofing has built a reputation for reliable work, honest guidance, and outstanding customer service. Our service options include crawl space waterproofing, foundation repairs, dehumidifier installation, and more. We ensure customers’ homes rest upon a sturdy base. Indeed, our work has earned us Angi’s Super Service award multiple times in the past 10 years and selection in the Best Pick Reports for 10 years. For more information or to schedule an appointment, call us at 1-855-649-7594.


Below, we explain why you should avoid installing fiberglass insulation in your crawl space:


Does Not Keep Cold Air Out

The motivation behind installing fiberglass insulation entails a genuine problem: keeping a home warm in cold weather. And, to be fair, the traditional design of crawl spaces involved the installation of open-air vents to combat high humidity levels, which let in a steady flow of cold air.


Yet this situation calls for an amendment to that traditional design rather than adding insulation. Moreover, the “solution” worsened the problem it was designed to solve: air vents gave moisture easy access to crawl spaces. Therefore, permanently closing those vents addresses the cold air and the moisture issues.


Plus, adding insulation among the floor joists does little to keep cold air out of the house. Fiberglass insulation only works in an enclosed space, and open vents render it ineffective. Cold air can pass through insulation easily when it comes in a steady stream.


Moisture Destroys Insulation’s Ability to Retain Warmth

As mentioned above, vented crawl spaces tend to have high relative humidity, as do those with exposed dirt floors. Water vapor creates numerous problems throughout a household: odors, sagging floors, “sticking” doors and windows, and more. Yet it also prevents fiberglass from insulating a space, even in minimal amounts.


Fiberglass readily absorbs moisture, which ruins its ability to hold heat. That moisture also makes the material heavy and drags it to the floor. This process results in “nightmare” crawl space scenarios, wherein insulation litters the floor and hangs from the ceiling.

Crawl Space Thermal InsulationEncourages Mold and Mildew Growth

Finally, and most dangerous of all, fiberglass insulation spurs the growth of mold and mildew. In the waterproofing industry, this insulation is referred to as “mold candy” because of how readily the fungus grows on it. The fiberglass contains some organic material in its resin, which mold loves. Indeed, it even prefers paper-backed insulation over wood.


These fungi present several health hazards, particularly for those who suffer from respiratory illnesses. They also produce a tell-tale “musty” smell that can permeate all through a house.


So, homeowners struggling with a cold crawl space should speak with NV Waterproofing professionals rather than seek a contractor to install insulation. In addition to closing troublesome air vents and sealing out moisture, our team can install TerraBlock™ crawl space insulation. This pliable yet durable sheet material offers insulation and moisture protection, sealing your house against the elements that can undermine it.

Professional Crawl Space Thermal Insulation Installation Can Protect Your Property

Ubiquitous crawl space myths present a real danger to the average homeowner. These beliefs can lead to disastrous “solutions” for real problems, exacerbating their symptoms and hazards. Rather than rely on word of mouth, turn to NV Waterproofing & Foundation Repair. Our crawl space thermal insulation services ensure your home remains warm year-round, while our professional guidance can help you avoid further crawl space problems. For more information or a free project estimate, call us at 1-855-649-7594 or visit our website!

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12200 Livingston Rd
Manassas, VA 20109
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