Daylight systems on test at the BRE

Solarspot® – More efficient than the Solatube® or Sunpipe®

When considering a daylight system for your business or next project, how you evaluate which of the plethora of offerings available will deliver the levels of light that you are looking for.

Look at any sun tunnel suppliers’ website and they will probably tell you that their system is the best, the brightest, the most efficient etc. in order to persuade you to buy from them. So how do you know who’s telling you the truth and who’s leaving you in the dark when it comes to the facts?

To say that some manufacturers make claims that are open to interpretation is giving them the benefit of the doubt. A less charitable person might reach the conclusion that they are giving out false and misleading information. A couple of manufactures, who will remain nameless, are claiming to be ‘95% efficient’, when what they actually are is 95% reflective – not the same thing and the net result in terms of light delivery is massive. In fact, no system in the world is 95% efficient and systems with reflective values of only 95% are actually so poor that we discounted them in these tests.

Solarspot D-38, 34% more efficient than the sunpipe and 44% better than the SolatubeBuilding Research Establishment

BRE (Building Research Establishment) is an independent and impartial, research-based consultancy, testing and training organisation, offering expertise in every aspect of the built environment and associated industries – that’s what it says on their website so who are we to argue.

We asked them to take our Solarspot® D-38 system and compare it to a Solatube® 290DS and Sunpipe® 450 and test them to see which was the most efficient at delivering daylight – when you think about, what other reason is there for including light tunnel into you specification? We’ve also referenced a couple of the very popular flexible duct systems to see how they perform.

So why test these systems and sizes?

There are many systems and sizes available and it would be impractical, and expensive, to test every single system and size on the market, so we picked the countries best-selling rigid system; the Sunpipe from Monodraught and the Solatube, apparently the world’s leading daylight system. The Sunpipe system has a diameter of 450mm and has a claimed reflective value of 98% whilst the Solatube has a diameter of 350mm and reflective value of 99.7%, so the Solarspot sits in between, size wise.

All three systems were just over 2m long and the tests were carried out under a natural overcast sky – this is Britain after all. The tests were performed at the BRE’s headquarters in Garston, Hertfordshire.

The test results and what it means in terms of light delivery

Each system was tested three times to ensure that there were no spikes in light or freak results and the average of the efficiency of the three readings is given as the result.

“Taking the three double/single glazed tubes, the Solarspot with Convas lens product had the highest transmittance, 0.57, compared to 0.43 for the Monodraught and 0.40 for the Solatube. In relative terms, it was 33% more effective than the Monodraught at transmitting light, and 44% more effective than the Solatube.”

BRE Test report number 280962

As the table shows very clearly, the clear winner in efficiency terms is the Solarspot D-38 with results that are roughly half as good again as the other two. So what does that mean in terms of light delivery.

Simply put, if you had two systems, side-by-side, in the same roof, facing in the same direction, and both tubes are the same length, then if one was half as efficient again as the other, then you would expect half as much light again as the other. But you also need to take into account the width of the tube.

For example; if you put a Solarspot D-38 and Solatube 290DS together – as suggested above – because the Solatube is 25mm narrower, it has less volume. In turn, the Solarspot would be delivering around 69% more light in the same conditions.

Flexible-duct systems

Easily the best selling systems in the UK, flexible duct systems can be a very tempting option for designers and contractors, but how much light do they actually deliver? In tests previously carried out by the BRE for Solalighting Limited, (BRE test number 248038a) measuring the efficiency of two 350mm diameter flexible-duct systems. The best figures that the flexible unit were able to return were only around 6%. This was with the ducting being pulled tight and with the tube completely straight. In reality the tube will not be totally straight and with some slack in the system; given this more realistic scenario the figures are likely to be nearer 1.5-3%.

In conclusion

It’s clear to see that there is a resounding winner, and we hope that the winner is our customers. If you would like to read the full report from the BRE you can download it using the link at the top of this page.

If you would like more information about how Solarspot can transform your next project with natural daylight, please call us today on 01908 299117 or use our contact form.

System specifications as tested
Solarspot® D-38* 375mm diameter, clear dome with RIR Light Funnel, single-glazed diffuser, Vegalux tubing; 99.7% reflectivity, 2280mm in length
Solarspot® D-38** 375mm diameter, clear double-glazed dome with RIR Light Funnel and additional Convas lens, single-glazed diffuser, Vegalux tubing; 99.7% reflectivity, 2280mm in length
Solatube® 290DS 350mm diameter, Raybender dome with Light Tracker reflector, double-glazed diffuser, Spectralight tubing; 99.7% reflectivity, 2280mm in length
SunPipe® 450 450mm diameter, diamond dome, double-glazed diffuser, Supersilver tubing; 98% reflectivity, 2280mm in length

* This system is available on special order only and is subject to 28 days delivery.

** Convas lens is supplied as standard to provide maximum protection against condensation and improved thermal performance.