What is a solar tube and how does a sun tunnel work?
Sun tube, Sun tunnel, Sky tube, Solar light tube, Light tunnel, and Solar tube, a lot of different names for same thing, made by different manufacturers, but they all achieve the same purpose. Capture sunlight or daylight, transmit it down either a solid reflective aluminium tube or a shiny flexible ribbed plastic tube in the least number of bounces possible. See the video at the bottom of the page for installing a flexible Velux sun tube.
The main choice with sun tunnels is flexible or rigid. Flexible tubes lend themselves to awkward spaces very easily, sometimes with bad or no internal roof access a flexible sun tube can be the only answer, this is because you don’t need to climb into the loft space to screw it together as is required with a solid tube. Rigid sun tubes will transmit more light however, especially in low light conditions or over longer distances, unfortunately a solid tube normally costs a little more to buy.
How a sun tube works - A solid or flexible reflective tube channels directs sunlight or ambient light in the least number of bounces possible to a diffuser ( opaque double glazed ceiling ring ) which you position on the ceiling.
Click pic to enlarge
Do sun tunnels work
Yes. I’ve been fitting them for many years now and the results can be very surprising even if you’re used to seeing the before and after results. If you install sun tubes for a living like I do it can often be a difficult balance to advise a customer on how good a sun tube will be without either overselling it and setting up for a disappointment, or under selling and putting a client off unnecessarily. No one wants to see an unhappy face after the completion of a job, and so far everyone has been pleased with the results.
Please read the article and view the video further down to learn more
Which sun tunnel or tube is the best
If you have been trying to find sun tunnel reviews or compare them it can be almost impossible to get like for like figures for light levels, brightness or light output in watts. So if you’re thinking of fitting a solar tube or sun tunnel, I bet you’d like to know two things in the most uncomplicated way possible…
- How much light will I get from a sun tube
- Which sun tube should I buy
Important questions, and I will try to answer in the simplest possible way. Over the years I fitted a few different brands of sun tube that employ slightly different strategies for capturing light, and they will all argue with percentage figures to back them up that their system is the best. This can make choosing a sun tube quite confusing. I can honestly say though they are all fairly comparable to the naked eye in my opinion, we’re probably talking a few percent difference like for like. Could you tell the difference between a 100 watt bulb and a 110 watt bulb if you couldn’t switch between the two? No neither can I, but keep reading and we’ll go through the important factors in getting the brightest sun tunnel possible.
How much light will I get from a sun tube
This really depends on a few factors but here are the main ones…
Position - Can you sit it on a south facing roof? This will obviously harvest the best quality of light and is desirable, but a sun tunnel doesn’t have to face south as ambient light will still make quite a difference.
Length of sun tube – What is the length of the tube required internally to transfer the light from the underneath of the roof, to the ceiling where you want the diffuser to be fitted?. The longer this tube is the more “bounces” the light has to make to reach its destination, and therefore the more light you will loose.
Rigid or flexible sun tube ?
Flexible tube - Most suited to shorter distances, normally 1.8 metres or less (6 feet). Although cheaper to purchase and install because of faster fitting and a cheaper purchase price, the slightly crinkly reflective material will lose more light in a long tunnel. This is because the minute creases in the flexible tube bounce the light around a lot more than it’s rigid counterpart. Having said that, if you’re south’ish facing and don’t require more than 1.8 metres in length, it can produce very good results.
Rigid tube - The best option if you are looking to capture the most light possible. If you have a long distance between the roof and the ceiling, or maybe if you cannot fit a sun tunnel on a south face and need to capture the most ambient light. Rigid sun tunnels are really essential for a sun tube length over 2 metres as you will lose a lot less of the captured light.
How bright is a sun tunnel and how much light will a sun tunnel give me
A lot of sun tube or sun tunnel companies give out figures based on Lux or Lumens, but to the average potential sun tube buyer this will mean very little as we are so conditioned to household light bulbs and wattage figures.
We can also not be clear on the manufacturers test conditions or setup, and their figures whilst I’m sure they are scientific and accurate, may bear little relation to what you will actually perceive when a sun tube is fitted. Those who do quote their light levels or light output in watts can sometimes seem slightly over optimistic at times, especially when compared to what I have seen with my own eyes in real life settings. For that reason, whilst I’m sure the manufacturer’s own solar tube reviews may be accurate any differences may not be visible installed in a house.
Sun tube light output in watts
Lets assume we’re fitting a 12″ to 14″ sun tunnel ( 30cm to 35cm )
In the average suburban house with an average ceiling height of 8 to 9 feet ( 2.4 to 2.8 metres ) you can expect the sun tubes lights to illuminate an 8 foot by 8 foot area quite well depending on the factors mentioned above.
Sun tube lighting – An 8′ x 8′ x 8′ cube, lets call this the sun tubes ‘Footprint’. I will now do my best to describe how many watts of light you will get if you were to stand not underneath the sun tunnel but just outside its footprint in comparison to a light bulb doing the same job. I have chosen 8 x 8 because this will give you a practical indication of light and area.
Let me explain further, if you put a 100w bulb in a small box room it would be bright because the light reflects off all surfaces and illuminates an area. Now imagine the same 100w bulb inside a pitch black aircraft hanger, now the bulbs illumination would look very bad. Even though it’s the same bulb and wattage.
Now rather than complicate matters about how many degrees to the south or not your house faces, whether its spring or summer or which country you live in, lets just split it up into two camps, ambient light and sun light in spring or summer. I realise this is less technical, but it will probably provide you with more realistic light levels unless you are familiar with the complications of Lux and Lumen.
Ambient light – Lets call this an average non sunny day or a house where the suntube is not positioned facing south, here are the light levels you can reasonably expect.
- Flexible tube - 2m = 40 – 60 watts
- Flexible tube – 1m = 60 – 80w
- Solid tube - 2m = 80 - 100w
- Solid tube - 1m= 90 - 110w
South facing sunlight - The ideal sun tunnel install that will supply the perfect light for a sun pipe to fulfil its potential.
- Flexible tube - 2m = 80 - 100 watt
- Flexible tube - 1m = 100 - 110w
- Solid tube - 2m = 150 - 200w
- Solid tube - 1m = 150 – 250w
Solar tube review of light output
Rather than lots of pictures to click into and back out of, here I have compiled a video of sun tube installations. They show Velux sun tunnels and Solatube sun tunnels installed in the home in various locations, both Flexible and Rigid.
See my video of Velux sun tunnels and Solartube solar tubes, with before and after photos reviewed after installation in the home here… Sun tunnel before and after
The Sun tunnel installation video is further down the article…
Sun tube Chart for light levels and light output
Light output chart – Here I have collated some technical data rather than my guesstimating and made it into an easy reference chart. The data is fairly accurate according to 2 sun tunnel companies.
Click pic to enlarge
It is difficult to know how to explain how much actual light you can expect from a sun tunnel, and can be hard to articulate unless you have fitted quite a few in different situations and seen the effect first hand. This is quite a good daylight calculator from Velux – Velux sun tunnel calculator and provides light levels in Lux.
Sun tunnels Compared
If you have been reading sun tunnel reviews or trying to compare solar tubes, it can be quite difficult. I have fitted two or three different brands for customers who have specified a specific make or model and apart from size, and tube type i.e. flex or rigid, it’s almost impossible for me to tell them apart. I would say however go for a well known manufacturer as this will ensure quality and spare parts should something get damaged.
Velux sun tunnel – Probably the best known maker of sun tubes, a very good constantly updated and improved product, and simple to install in most circumstances. Velux flexible tube or rigid options available in 10″ and 14″ ( 25cm or 35cm ) and the Flat roof sun tube.
See the product on their page Velux sun tunnels
Solatube – Another quality sun tunnel company with some innovative features such as the ‘ Raybender ‘ and ‘ LightTracker ‘ technologies, designed to capture more light than other sun tubes. Available in 250mm and 350mm diameter tubes.
See their product pages Solatube sun tunnels
See their product pages Fakro sun tubes
Solarspot – A brand I haven’t come across until now if I’m to be honest, but one again promising to be brighter than the competition. I’m sure its a very good tube, feel free to research it and look for reviews.
See their product pages here Solarspot tubular daylighting systems
See their webpage here Monodraught sunpipes
How to install a sunpipe
This video shows how to a install a suntube in a residential property. The one in this example is a Velux flexible model and is being installed into a low height roof space with no internal access. If you think you could fit a suntube like this where there is virtually no room to work in, you certainly won’t struggle under normal circumstances.
In this video we show you how to install a Velux sun tunnel in a roof space, as well as the end result in terms of light increase.
What is the quality of light from a sun tube
Now I know I’ve just compared sun tubes to the brightness of a bulb, and this is a little unfair because the quality of light from a sun tunnel is far better than a normal household bulb and much better than an energy saving bulb. The light quality of a sun tunnel is much higher than a comparable bulb in just simple wattage terms because the warmth or quality of the light is real daylight, therefore just like a window the light is brighter, has a fuller colour spectrum and is therefore more illuminating than a bulb in most situations.
Colour temperature in lighting is measured in degrees Kelvin and this is a measure of the part of the colour spectrum that is found in light.
1900K - Candle light, sunlight at sunrise or sunset
2000K – 2700K Incandescent - light gives a warm and cosy feel
3000K – 3200K Energy saving bulb and Led lights
3500K - Fluorescent strip lighting
4000K - Used in general lighting, factories, parking lots and warehouses
5000K – 5500K Daylight lamps, horticulture, aquariums
5600K – Nominal sunlight, midday summer sun
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