Discover How Below-Slab Moisture Control May Play a Quiet but Critical Role in Reducing HVAC Load and Improving Energy Performance 
When it comes to building energy-efficient homes, insulation, air sealing, and right-sized mechanical systems often steal the spotlight. But there’s a lesser-known opportunity to cut energy costs that starts much deeper—literally—beneath your feet. Beneath every slab is an often-overlooked source of unwanted and uncontrolled moisture from the ground.
At Stego®, we’ve long known that a strong foundation starts with better below-slab moisture and vapor protection. And now, we can put real numbers behind it: choosing the right vapor barrier doesn’t just protect the building envelope and occupants, it also can help contribute to meaningful energy performance gains and long-term cost savings—giving you the data to make an informed choice from the start.
In this article, we’ll explore how a below-slab vapor barrier works, the measurable energy savings it provides, and why it’s a smart investment for builders and homeowners alike in terms of building performance and long-term value.
The Problem: Moisture Moves Through Concrete — and Costs You Energy
Even in dry climates, there’s always moisture in the soil beneath a new home. In vapor form, this moisture naturally migrates upward from areas of high concentration (the subgrade) to lower concentration (the conditioned interior of a home). This process is known as vapor diffusion—and without the proper below-slab protection, it can wreak havoc on both flooring systems and energy efficiency.
Concrete Is Porous — And That Matters
Despite its strength, concrete is not impermeable. Water vapor can pass through it relatively easily. Once a home is built and the HVAC system is running, the pressure differential drives that vapor to move up through the slab and into the home. If left unmitigated, this movement of water vapor can lead to an increase in relative humidity within the home interior (if not interrupted by a resilient flooring material – which is an even worse scenario). This added potential moisture load increases the demand on dehumidifiers and HVAC systems—contributing to increased energy use and higher utility bills. Thus, in any new home build, taking the ground out of play with an effective vapor barrier is critical.
Not All Vapor Barriers Are Created Equal
When it comes to below-slab moisture protection, builders are faced with several options: high-performance vapor barriers like StegoHome® Wrap 15-Mil, lower-grade generic poly sheeting, or, in some unfortunate cases, nothing at all. Ultimately, the material’s water vapor permeance (and, tied closely, its ability to maintain a low permeance over time) is the key to reducing moisture movement into the home from the ground. The differences are staggering:
Let that last figure sink in, 54+ gallons of moisture entering the home annually through a 1,500 sq. ft. slab without any below-slab vapor barrier. That’s over 100x more moisture than StegoHome Wrap 15-Mil allows.
Real-World Impact: Energy Cost Savings That Add Up
Moisture doesn’t just affect flooring—it also impacts how hard your mechanical systems need to work to keep the home comfortable.
Using a conservative analysis model, we evaluated a 1,500 sq. ft. home with an active dehumidifier and no vapor barrier. Factoring in the additional water vapor load, we calculated the energy demand required to remove that moisture and the resulting cost over time.
The Results:
- $17 per year in average energy savings by using StegoHome Wrap 15-Mil instead of nothing.
- Full material cost payback in 16–22 years (well within the service life of the home).
- Stego’s Life of the Building™ Warranty ensures performance well beyond the breakeven point.
💡 This isn’t a “nice to have”—it’s a measurable, mechanical load reduction that saves money year after year.
Why Builders Choose Stego: Peace of Mind, Performance, and Payback
StegoHome Wrap isn’t just about stopping vapor—it helps deliver long-term value.
- Durability: Stego barriers resist tears and punctures during install and placement.
- Low Permeance: Designed to exceed ASTM E1745 requirements beneath the slab over time.
- Unrivaled Support: From submittals to on-site advice, Stego is here to help.
- Life of the Building™ Warranty: Protection that lasts decades—not just the first few years.
Go Green (and Save Green): Exceeding Residential Energy Standards
Stego barrier solutions can help your projects qualify for—and even exceed—today’s most recognized green building programs:
✔ ENERGY STAR® Certified Homes (v3.1) StegoHome® satisfies the capillary break requirement beneath concrete slabs.
✔ EPA Indoor airPLUS (Version 2) Our vapor barriers support moisture control and radon-resistant construction and meet the new performance requirements.
✔ NGBS Green Certified® Products directly contribute toward Resource Efficiency and Indoor Environmental Quality credits.
By reducing below-slab moisture intrusion, Stego barriers help to improve indoor air quality, enhance energy performance, and support sustainable building practices. It’s a powerful combination for builders looking to stay competitive in a market increasingly focused on health, wellness, and environmental impact.
FAQs: What Homeowners and Builders Want to Know
How does a vapor barrier help with energy savings?
By preventing water vapor from entering the home, you reduce the need for dehumidification and temperature control, which in turn can lower HVAC system usage and energy bills.
What’s the difference between a vapor retarder and a vapor barrier?
It comes down to water vapor permeance. StegoHome Wrap 15-Mil is considered a vapor barrier with a <0.01 perm rating, while StegoHome Wrap 10-Mil is considered a vapor retarder with a permeance below 0.1 perms. Higher permeance = more moisture vapor passing through.
Can I use a generic poly liner instead?
Generic 6-Mil poly sheeting does not provide even the minimum benchmark for permeance in this below-slab application over time and is no longer considered an acceptable option. Generic poly lacks the performance, warranty, and installation durability of StegoHome Wrap. It can tear easily and may break down over time — leading to more moisture, more energy use, and potential long-term damage.
Is the payback really worth it?
Absolutely. While the estimated energy cost savings average about $17 per year, StegoHome Wrap Vapor Barriers are built to perform for the entire life of the home—far beyond the breakeven point. And when you factor in the added benefits of improved indoor air quality, reduced risk of flooring issues, and support for green building certifications, the long-term value extends well beyond simple cost recovery.
Build Better from the Ground Up
Builders who specify and choose StegoHome Wrap aren’t just making a smart technical decision—they’re making a smart business one too. By aligning with industry-established flooring and concrete requirements and providing increased Radon Resistance compared to generic poly sheeting, StegoHome Wrap addresses client demands for improved safety, health, and lower ownership costs, while reducing builder liability. And with only a negligible bump in upfront material costs, StegoHome represents a high-performance solution with tremendous value.
Moisture may be invisible, but the damage it causes is real. Trust StegoHome Wrap to protect what truly matters—now and for decades to come.
Post Comments