Of course you do, why else are you fitting it? A solar tube is probably unique as a consumer product as it only has one function – to bring in daylight into your home, office, school or factory. Therefore you want to make sure that the product you are fitting is the one that will give you the most light, and that is the one with the highest efficiency is the size category you are considering.
Independent, comparative testing using internationally recognised methodology – it’s as simple as that. And the thing to look out for is an efficiency figure. If a manufacturer is confident about the performance of their system they will quote an efficiency figure and then show how this compares to competitor products. Solarspot are the only manufacture of solar tube type systems to publicly publish these figures and that is because we know that, size-for-size, no one else will give you more daylight through a tube.
Efficiency is a measure of the ability of the solar tube to deliver light from the top (dome) to the bottom (diffuser), regardless of the time of day or time or year. To suggest otherwise is like saying your car is faster on a Thursday or gives better MPG when there’s a ‘Y’ in the month. This is just a pile of bunkum put out by manufactures like Solatube trying to muddy the water. Read the independent BRE test summary of Solarspot D-38 and Solatube 290DS
Size is important, as the saying goes, but it’s not the end of the story. A wider tube will deliver more daylight than a narrower tube of the same length and with the same reflectivity. So it’s no surprise than that a Solarspot D-38 (380mm diameter) will deliver more daylight than a Solatube 290DS (350mm diameter) as the D-38 is roughly 10% wider. But the Solarspot D-38 will actually give you around 70% more daylight so how does that work? Well that brings us back to efficiency. The Solarspot D-38 44% more efficient than a Solatube 290DS, and when you then allow for the extra volume of the tube, the difference in the daylight delivered is massive. So-much-so that the smaller 250mm diameter D-25 will give you as much light as the larger, less efficient Solatube.
All Solarspot systems are double-glazed just below the dome, and for good reason. Firstly, this acts to trap air in the tube to limit and heat gain or loss from the room below. Secondly is prevents any condensation, a natural situation that occurs in all solar tube systems, from getting into the tube itself. The Convas™ lens in the Solarspot contains any condensation, that may occur in cold weather, inside the dome and allows it to escape harmlessly onto the roof, unlike systems that are ‘double-glazed’ at the ceiling where condensation can actually get in the tube and onto the reflective surface.
Whilst it may seem desirable to limit the impact of the number of domes on a roof by spurring off a number of tubes from one source it simply isn’t practical or effective. It would result in complicated configurations of longer tubes that result in a very inefficient system. As with many things in life, keeping it simple will give significantly better results.
Actually there are no specific specifications written for tubular day light systems or ‘solar tubes’ as they are generically known. Ask yourself this question, ‘if they needed building regulations then how can they be sold without a certificate of any kind?’ The largest supplier of these systems worldwide is Velux and they don’t have one, and that’s because 99% of solar tube system customers don’t actually need one.
Unless you are a developer that wants to include the solar tube in the 10-year NHBC cover then the answer is no. For the vast majority of customers retro fitting into their homes, fitting in their own self-build project, retro fitting into an office as part of a refurb or a new commercial development, you don’t need a BBA certificate. The BBA certificate is no guarantee of performance. In fact the only other sun pipe to hold a BBA certificate was the Sola Skylights Skytunnel, the worst performing solar tube ever tested by the BRE. Read the BRE test summary of flexible sun pipes.
Basically because it’s the only thing that have that no other sun pipe supplier offers (or who has bothered to get). They use it to make people believe that they may be doing something wrong, taking a risk… ‘after all, it is your home and your safety that is at stake’* when the systems that they supply for residential use are not actually covered by the BBA certificate as they are now supplied with acrylic domes. *taken from Solatubes website.
You will see both materials being offered by solar tube manufactures. Polycarbonate is very strong and offers some advantages when particular specialist fire standards need to be met – specific commercial situations only (contact us for details). But polycarbonate has two disadvantages when compared to other materials; it has a relatively poor transparency rating and, rather alarming for a product designed for outdoor use, it goes cloudy and yellow when exposed to UV in as little as 12 months. Acrylic, also known as Plexi-glass and PMMA, on the other hand has most efficient light transmittance factor being even better than glass. It’s also strong enough to withstand the rigours of whatever the weather, or a clumsy builder, can throw at it. Read the acrylic vs polycarbonate summary of the BRE test.
For around 95% of customers the question is irrelevant. As such, there are no regulations that determine that you need to have one or other material so the choice is yours. The exception to this is when the roof of a building is determined to be a fire-break between two buildings. To explain this fully would require an entire website (or all 260 pages of BSi Fire regulations covering all aspects of building design*). *There are various, and relevant, regulations that concern fire spread within a building but as is not an issue affects the choice of dome material we won’t cover that here. For specific information on fire regulations please contact us directly. In general terms, if the construction of your roof in flammable, in other words made of wood, then it is irrelevant what the dome is made of. If you have a roof that requires polycarbonate domes for proximity protection then these can be supplied on request but it must be noted that light levels will be reduced and the domes life-span will be reduced due to polycarbonate-yellowing.
If you are considering a Lightway sun pipe system you may be tempted by the claims made by their Bohemian glass dome. But dig a little deeper and the only thing Bohemian glass seems to have going for it is; it stays clean (well so does any dome shaped lens on your roof, regardless of what it’s made of) and it doesn’t go yellow (just like Acrylic). But glass, Bohemian or otherwise, has disadvantages. Firstly, despite what you might think, glass is not as transparent as some other material – acrylic in particular. The second, and probably more important, is that to withstand life on a roof it needs to be very thick when compared to plastic domes. In fact, the Lightway Crystal sun Tunnel dome is roughly 400% thicker than an equivalent sized plastic dome which consequently absorbs precious daylight that then doesn’t get through to the tube system.
According to the thermal engineers at the BBA, if a system is of similar size, with a similar construction and the same number of lenses then it will have much the same U-value as any other system of the same length and diameter. Not that you will read this if you look at a variety of our competitors websites. In truth, you can manufacture a U-value to virtually any level you like by insulating the tube to polar-like specifications and inserting numerous thermal lenses into the tube. One of our competitors quotes a U-value of 0.5 on one of their systems that the BBA tested and rated at 2.1. There’s no clear explanation of how this is done but what is not said is how much the light performance is diminished in the process. Clearly wrapping insulation will improve the thermal performance to a degree, and whilst this is not specifically required, it may be helpful in colder areas of the country. But this will only improve the U-value marginally – it’s like insulating around a window.
To significantly improve things you need to add additional thermal lenses into the tube system itself. Whilst this will help prevent heat escaping, it will also prevent a percentage of light entering the system. Roughly speaking, each thermal lens reduces the light level by around 10%. So whilst you could improve the thermal efficiency of a solar tube to around 25% of the standard model, you will probably require two or three more units to bring the light level back up.
In essence, all triple-lens units like ours, Solatube’s, SunPipe’s etc provide a thermally effective way of lighting an area via the roof. It all comes back to the most important function of any solar tube style system and that is ensuring that you are getting the maximum amount of daylight through the system size that you choose.
Solarspot systems are supplied and installed in standard form in countries from all over the world in every continent, in both northern and southern hemispheres. In really severe climates it may be advisable to add some installation to the tube but in UK conditions this should not be necessary. Whatever the weather, all Solarspot systems are covered by a 10-year guarantee
All solar tube type systems use ‘reflective’ tubing to transfer the light at the top to the room below. The reflectivity of the tube is one of the factors that will determine how much of that light is transferred, or lost through absorption. All Solarspot systems employ our Vegalux 99.7% reflective tubing – the most reflective material in the world. This compares with the majority of other sun pipe systems that employ either 98% or even 95% reflective tubing. Whilst this might not sound like it makes a great deal of difference there is another factor that has a big effect on the way light is bounced through the tube. With Vegalux 99.7% tubing all of the reflective value is what is known a specular. This means that as light bounces of its surface only 0.3% of the energy (light) is lost, leaving 99.7% to carry on to the next bounce. With a 98% (or less) reflective material around 5% of this reflectivity is diffuse which results in a light loss of nearer 6% per bounce. Over a relatively short distance this 6% loss per bounce quickly results in much of the light entering the top of the tube being absorbed before it can reach the room below. For more information see Vegalux tubing.
The simple answer is that they don’t. In independent tests done at the BRE, where they tested two flexible duct systems (Velux Sun Tunnel and SolaSkylights Sky tunnel) to performance was shown to be so poor that even a mediocre rigid solar tube system will give around 10 times the amount of daylight. Comparing the Solarspot D-38 with the best 350 – 400mm diameter flexible system available, the D-38 will give you around 17 times more daylight.
There is no minimum length for the tube so even on the shortest systems, flat roof and vaulted ceilings, the tube will work perfectly. In fact, the simple rule is; the shorter, the better as light loss only increases as the tube gets longer.
Due to the modular nature of the Solarspot system it is extremely unlikely that you would ever need to cut the tube. The design of the system allows the tube sections to ‘telescope’ into each other to adapt to the space available. In the unlikely event that you did need to cut a tube down it is relatively straightforward using a pair of aviation snips (tin snips).
All Solarspot systems are supplied a triple-lensed units so that any potential heat-loss or gain is reduced to a minimum. In the winter, air is trapped between the lenses so that cold air is prevented from entering or exiting the building and in the summer, the reflective surface of the tube screens out the light waves that cause solar-gain
In most situations you will want your solar tube system to deliver the maximum amount of daylight but there are certain situations where you might also control the amount of light. If you are fitting a sun pipe system in a bedroom or conference room you can vary the amount of daylight entering by fitting a Solarspot electric daylight damper. For details see our accessories page.