Buildings have used reflective insulation since the eighties. Back then, the product was a foil-layer laminated to a bubble-layer similar to the familiar packaging material. Around 2006 a new ASTM burn test was developed to simulate a full room burn. The reflective insulation manufacturers, comprising about 10% of the insulation industry, realized that the foil / bubble product would not pass this new burn test and their market share would disappear altogether if they could not pass this critical test.
Foil based reflective insulation wouldn’t pass a full room burn test (or an improved tunnel burn test) because it would not quickly burn away from the flame. The material would remain in direct contact with the flame to the point of ignition.
The industry looked toward the past to engineer a solution for the future.
Going back to the late seventies, spacecraft used reflective insulation has for thermal protection. These constructions are slightly more complex, as you might imagine being for other-worldly applications, but are fundamentally the same. The spacecraft insulation consists of multiple reflective layers separated by non-conductive spacer material and assembled up to forty layers depending on the spacecraft operational environment.
Low-emittance (high reflectance) is the foundation of spacecraft insulation. Materials with low emittance reflect energy, heat, away from the structure. Or, they can also reflect heat back toward the structure to protect from the cold. The space industry has been using films for thermal protection for nearly three decades. Could space-age film materials be the solution here?
Yes! A brilliant company with spacecraft heritage engineered such a product. Film has been used as the reflective layer ever since and is used in all forms of reflective insulation from bubble to board and bulk.
Where should reflective insulation be used?
Reflective insulation can be used independently or in conjunction with mass insulation, like fiberglass. This increases the r-value of the bulk insulation by making it low-e (emittance). Thus, any structure using mass insulation can benefit from reflective technology. The benefit increases substantially the closer you get to the equator where radiant energy is more intense.
Furthermore, reflective insulation is ideal when there isn’t much space. Both bubble and board insulation are a fraction of the width of a bulk insulation system. In walls and other areas where space is limited, reflective insulation is often the best choice. The only thing reflective insulation needs to function is an adjacent air gap. The air absorbs the heat and acts as an insulator.
Why isn’t reflective insulation used more frequently?
The largest barrier for reflective insulation is the performance predictability. When an architect is designing a building there needs to be cost justifications, a calculated ROI. The number of variables and calculations for energy savings are complex, so architects rely on simulation models to calculate. Most of these programs do not take into account the value of the reflective insulation.
An example is the Energy Star Program. Their position is that the reflective surface has no value. Their quandary is not based on the product effectiveness, but rather the uncertainty on how to measure and predict savings. As a result, no reflective insulation product carries the Energy Star label.
Building shape, materials, air space and other variables play a part in calculating the r-value that can be achieved with a reflective product. Until the benefits of reflective technologies are incorporated into programs to calculate energy savings, the technology will never attain widespread adoption no matter the impact of the actual savings.