When it comes to building foundations, insulation is a regulatory requirement and it’s a critical element that can make or break your build’s energy efficiency, durability, and overall performance.

Traditionally, polystyrene insulation has been the go-to choice for insulating foundations. In this article, we take a closer look at polystyrene’s R-value and what it really means for your building project.


The Basics

R-value is a crucial metric in understanding thermal resistance—a key factor influencing the efficiency of insulation materials. Simply put, the higher the R-value, the better the material can resist the flow of heat. This principle underscores the importance of selecting insulation with optimal R-values, translating to reduced energy consumption and enhanced comfort levels within your home or building.

Whilst polystyrene has been the go-to foundation solution for year, let’s consider its environmental footprint and real-world performance. Derived from fossil fuels and notorious for its non-biodegradable nature, polystyrene poses significant environmental concerns throughout its lifecycle—from production to disposal.

Moreover, while polystyrene boasts respectable R-values on paper, factors like moisture absorption and thermal bridging can significantly impact its effectiveness as insulation. Moisture infiltration, in particular, can lead to mold growth, structural decay, and compromised indoor air quality, posing potential health hazards.

Acknowledging the foundational significance of R-value in the realm of building materials,we next take a look at thermal performance, specifically through the lens of fRSI— the “Factor of Resistance to Surface Inside.”

While R-value remains a cornerstone metric in assessing thermal resistance and insulation efficiency, fRSI offers a nuanced perspective, particularly concerning internal surface temperatures and comfort levels within buildings. fRSI evaluates the thermal “strength” of nodes or junctions in a building’s thermal envelope concerning internal surface temperatures. This evaluation is crucial for ensuring consistent internal temperatures, which directly impact occupants’ comfort and well-being.

In essence, a high fRSI value signifies effective management of thermal bridges or junctions, resulting in even distribution of temperatures across internal surfaces. This achievement holds paramount importance for both new constructions, which we deal with here at QPOD and energy retrofit projects, emphasising the need for comfort-centric design considerations alongside energy efficiency.

QPOD has a higher fRSI value than polystyene, which ultimately leads to a drier home. Couple this with the fact that while polystyrene insulation, with its initial promise of decent R-values, may seem appealing, its long-term thermal performance can be compromised by factors like compression, settling, and exposure to UV radiationm which aren’t factors to consider when considering QPOD.

Despite its initial insulating properties, polystyrene’s susceptibility to degradation over time underscores the need for a more comprehensive approach to insulation selection and application. In conclusion, while R-value remains a critical metric in evaluating insulation materials, the integration of fRSI considerations offers a holistic understanding of thermal dynamics within building structures. By prioritising both R-value and fRSI, we can ensure not only energy efficiency but also sustained comfort and well-being for occupants—a cornerstone of responsible and forward-thinking building practices

The R-Value Comparison

With an enhanced fRSI value in mind, let’s circle back to the discussion of R-Value. Polystyrene often emerges as the go-to choice over QPOD, purportedly due to its perceived superior R-Value. However, let’s delve into a direct comparison:

To ensure a fair comparison, we’ve pitted polystyrene against QPOD, analysing data with no edge insulation. We’ve examined both 100mm and 150mm wall thickness layouts. Surprisingly, the maximum R-Value difference between polystyrene and QPOD was a mere 3.45%. On average, the difference between the two 100mm wall options was just 2.48%, with the 150mm wall option exhibiting an even lower average of 1.83%.

In essence, while polystyrene may appear to have the edge in terms of R-Value, the actual difference when compared directly with QPOD is minimal.

Summary and More Resources

In conclusion, while R-value remains critical, integrating fRSI considerations offers a holistic understanding of thermal dynamics within building structures. Prioritising both R-value and fRSI ensures not only energy efficiency but also sustained comfort and well-being for occupants—a cornerstone of responsible building practices.

As stewards of the built environment, it’s essential to weigh insulation options carefully, considering environmental impact, long-term performance, and occupant comfort. Let’s choose insulation solutions that leave a positive legacy for generations to come.

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