The Foundational Science Backing SlabTECK
At Hygrothermix, science comes first. Before creating our first product, we spent two years in dedicated R&D, focusing on the physics of heat and moisture transport in concrete slabs. We don’t rely on buzzwords or repurpose existing technology — we engineer purpose-built solutions based on measurable, real-world outcomes.
We aren’t marketers. We are building scientists, engineers, product developers, manufacturers, and installation experts with decades of hands-on experience. We used this experience and research to bring you the best possible system of valuel-engineered products. Let's dig into the design...
What Matters in Slab Design
A successful slab moisture control system depends on many interrelated factors, including:
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Soil type
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Subbase material and depth
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Insulation used or not
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Vapor retarder properties, including permeance, toughness, and installation quality
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Concrete mix design
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Drying of the concrete slab prior to flooring placement
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Flooring adhesive sensitivity
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Floor covering permeance
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Indoor operating conditions
We consider all of these factors alongside the complex, coupled heat and moisture transport mechanisms that govern slab performance. Through thousands of hygrothermal WUFI simulations, we’ve identified the variables that truly impact long-term results — and we provide this insight through our design assistance, products, installation support, and verification services.
Our Support Includes:
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Design support
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Pre-slab planning meetings
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Real-time project guidance
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CAD drawings, instructional videos, and step-by-step instructions
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In-person or virtual installation reviews
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As-built models of your slab’s performance, projecting heat and moisture profiles for decades of operation
Whether you want detailed modeling from the start or basic guidance based on our modeling R&D and literature findings, we can provide:
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Comparisons of the moisture condititions resulting from your specified options versus SlabTECK solutions
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Value-based insights based on predicted slab performance, not guesswork
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Custom-designed moisture control systems for your specific building assembly
See our full hygrothermal consulting design and support options HERE
Proper Science:
The physics behind heat and moisture transport are complex and coupled. That is, the heat transport
depends on the moisture condition and the moisture transport depends on the heat condition. (See
the WUFI description of the calculations in the figure below.) To solve the equations requires
hundreds of iterative calculations per timestep at each finite layer of the construction. This results
in hundreds of millions of calculations over a decade-long simulation.
Why temperature matters:
There are several reasons...
When convective flow (vapor movement with bulk airflow is shut off), vapor's only means of travel is diffusive
flux. Diffusion is driven by the H20 partial pressure difference between adjacent locations. Relative Humidty, RH, is a measure of the amount of moisture in the air divided by the maximum amount of moisture in the air (also known as saturation). RH also equals the actual pressure divided by the saturation vapor pressure. Relative Humidity = Actual Pressure / Saturation Pressure - (1)
The saturation vapor pressure, in the clausian clayperon zone, has an exponential relationship with temperature. Explicitly, as the temperature increases, the saturation vapor pressure increases exponentially while the actual pressure only increases linearly based on the ideal gas law. Since the saturation vapor pressure is in the denominator of the RH equation (1), as temperature goes up, and all else is equal, RH goes down. now, couple that concept with the standard slab construction situation where we have 70 (or so) degrees farenheit indoors and 55 (or so) degrees below the slab. This creates a natural decrease in humidity between the top and bottom of the slab for any given moisture content which then greatly lessens the diffusive drive. Depending on the level of allowed drying of the slab, we'll end up with some starting RH above the vapor retarder between 90 and 80%.
Consider a simillar situation below the vapor retarder. If there is a stone capillary break, that allows vapor to freely move, and depending on the depth of the capillary break, we end up with a humidity level some where between 95 and 85%. Couple that with the starting RH value within your slab, you may end up with very little vapor drive at all- and depending on a few other factors (like the use of insulation), you may up with with a downward drive of moisture! Either which way, when we do the math and physics analyses may result in a minute difference between the results from using a vapor retarder and using what other manufacturers coin as "barriers". In most scenarios the difference ends up being a percent or two difference over a 100 year building life!
This is why we advise you to consider engineering your solution instead of specifying the most expensive products and systems without any real related gain in performance. Contact us to learn more about our consulting services or to schedule a meeting.
Want to learn more?
Call or submit the form below to learn more. 303-305-3802