Reflective Tubes: Look Beyond the Headline Reflectance Figure
The reflective tube is at the heart of every tubular daylight system. It carries the natural daylight captured at roof level into the room below. However, when choosing a daylight system, buyers often focus solely on the highest reflectance figure.
Although this may seem logical, a single percentage does not tell the whole story.
Laminated or Coated Reflective Tubes?
Over the years, several technologies have been developed to create highly reflective internal surfaces. The most common solutions are laminated reflective tubes and aluminium tubes featuring a specialist coating applied using Physical Vapour Deposition (PVD).
At Techcomlight, we have many years of experience with both technologies. In the past, we supplied and installed both types of reflective tube across a variety of daylight systems.
This has allowed us to compare not only laboratory data, but also long-term performance under real-world conditions.
The Highest Initial Reflectance Is Not Always the Best Choice
A laminated reflective tube can offer an exceptionally high initial reflectance. This is an important advantage, but it should not be the only consideration.
Our practical experience has shown that laminated constructions can be more sensitive to long-term exposure to temperature fluctuations, physical stress and damage. If the laminated layer begins to separate from the tube, its reflective performance can be affected immediately.
Based on this experience, Techcomlight ultimately chose coated aluminium reflective tubes. Their reflective layer is applied through a Physical Vapour Deposition process.
Although their initial reflectance may be slightly lower than that of some laminated systems, we expect this technology to deliver more consistent performance over a longer service life.
Not All Coated Tubes Are the Same
There can also be significant differences in quality between coated reflective tubes.
The coating material, manufacturing process and level of reflectance can vary considerably between manufacturers. It is therefore important to ask which technology is being used and whether the stated performance has been independently tested.
Consider the Daylight Output of the Complete System
The overall performance of a tubular daylight system is arguably more important than the reflectance of the tube alone.
A daylight system consists of several components, all of which influence how much natural light ultimately enters the space:
- The roof dome
- Any reflector fitted inside the dome
- The reflective tube
- Bends and extension sections
- The ceiling diffuser
Even a system with a high-quality reflective tube may deliver less daylight if its other components restrict or absorb too much light.
For this reason, we recommend looking beyond the tube’s reflectance percentage and comparing the performance of the complete daylight system.
Ask for Independent Test Results
When comparing tubular daylight systems, always ask for objective performance data.
Useful measurements include:
- Light transmittance values
- Total lumen output
- Independent light measurements
- The testing method used
- The conditions under which the measurements were taken
These figures provide a far more accurate indication of real-world performance than a single reflectance percentage.
A high-performing daylight system is not defined by one impressive figure in a brochure. Its true quality depends on how effectively all components work together and how consistently the system performs throughout its service life.
