What Materials Are Best for Underfloor Heating Reflective Films in Construction? Heat Resistance And Ease of Installation of Aluminum-plastic Composite Films

A Contractor Couldn't Answer His Client's Question

A few months back, a friend who runs a floor heating installation business told me about a situation. He was working on a villa project and the homeowner asked him something he couldn't answer: "That reflective film you're laying under the heating pipes — what's it actually made of? How long will it last?" He's been in floor heating for over a decade, always using aluminum film rolls, but honestly — the market has so many different types of reflective film. Kraft paper with aluminum coating, non-woven fabric, pure aluminum foil laminate — he'd never really compared them carefully. The homeowner's question made him realize he couldn't explain the difference.

This is more common than you'd think. Floor heating reflective film looks like just a thin layer, but it has a massive impact on heating performance and system longevity. Pick the wrong one, and the first couple of years feel fine. Three to five years in, problems show up — reflectivity drops, the base material cracks, layers delaminate. Heat escapes downward, energy bills climb, and the homeowner starts complaining that the heating doesn't work like it should.

What Does a Floor Heating Reflective Film Actually Do?

Let me explain how it works. When the heating pipes warm up, heat travels upward through conduction, but a significant portion also radiates outward in every direction as infrared waves. Without reflective film, that downward radiation passes straight through the insulation board and dissipates into the slab or foundation below. Aluminum's natural infrared reflectivity sits between 85% and 99%. Lay a reflective film and most of that downward radiation bounces right back up.

The film also handles two side jobs. First, it blocks moisture from reaching the insulation layer — XPS boards that absorb water see their thermal conductivity jump from 0.028 to 0.05 or higher, which wrecks their insulating ability. Second, most films come printed with 5 cm or 10 cm grid lines, so installers can space pipes accurately without guessing.

Material Choices and Where They Differ

Reflective films on the market fall into roughly four tiers. The bottom tier is kraft paper with a thin aluminum coating — reflectivity around 60-75%, oxidizes and fails within three to five years, basically obsolete. Second tier: non-woven fabric with aluminum film, reflectivity 70-85%, lasts five to eight years, cheapest option, still used in budget projects. Third tier: metallized PET film, the so-called "metallized reflective film," reflectivity 92-96%, lifespan eight to fifteen years, currently the market mainstream. Fourth tier: pure aluminum foil composite reflective film — PET base with 20-30 micron aluminum foil, reflectivity 97-99%, lifespan twenty to thirty years, used in high-end engineering.

Where does the gap actually show? Two things matter most: heat resistance and durability.

Floor heating environments run at 35-50°C continuously, and temperatures right above the pipes can briefly hit 60°C or more. Kraft paper and non-woven bases can't handle that kind of sustained heat — they become brittle and deform. PET handles it much better. Its glass transition temperature sits around 70-80°C, so floor heating temperatures are well within its comfort zone. Pure aluminum foil composite film? Aluminum melts at 660°C. Floor heating temperatures are completely irrelevant to it.

On durability, the metallized layer is vacuum-deposited, only 0.03-0.05 microns thick. It's cheap, but it doesn't tolerate bending or scratching. One wrong step during installation and the coating develops micro-cracks — reflectivity drops locally. Pure aluminum foil at 20-30 microns is a solid metal layer. It handles bending far better, and rough installation won't easily breach it.

Installation Ease: A Factor Too Often Underestimated

Anyone who does construction work knows the drill. Whether a material is good on paper is one thing. Whether installers can use it properly is another entirely. Reflective film comes in rolls. You unroll it across the floor, cut it to size, join the seams, and fix it in place. Too thin and it tears. Too stiff and it won't lie flat. Too slippery and you're skating on it. All of these are real problems that affect both installation speed and quality.

A good aluminum-plastic composite reflective film gets several things right. Width comes in at 1 meter or 1.2 meters, so fewer seams. The PET base gives enough rigidity that the film stays flat without curling or wrinkling. The aluminum face points up, grid lines are crisp, and pipe installation aligns at a glance. The bottom side has a fiberglass reinforcement layer, tensile strength hitting 80N/5cm lengthwise and 60N/5cm crosswise — stapling or clipping it down won't tear it apart.

Then there's seam treatment. A quality film bonds to aluminum foil tape cleanly and stays bonded, forming a continuous vapor barrier. A poor film? Tape won't stick properly, or the film itself delaminates at the surface. Moisture sneaks through the seams into the insulation. A few years later, the insulation board is compromised.

VWIN's Aluminum-Plastic Composite Reflective Film

We supply aluminum-plastic composite reflective film for multiple floor heating projects. The structure is a multi-layer composite of PET, aluminum foil, and reinforcement base material, with reflectivity above 97% and a working temperature range of -40°C to 120°C — well beyond any floor heating scenario. Width, grid spacing, and bottom reinforcement can all be customized to match specific project requirements. Every shipment includes measured reflectivity and tensile strength data.

If you're working on a floor heating project and want to evaluate reflective film options, or if you're a distributor looking to offer better solutions to your clients, get in touch. We can provide samples and help with material selection.