Surprising reach of Solatube light

While there’s not nearly as much light shining on my indoor veggies from my Solatube, above them, as I wanted, or had hoped, there is a surprising amount of light shining into my previously very dark, still narrow, hallway.

On the top shelf of this candle heating cart are plants. This is directly below the Solatube. But there's no shadow cast.
On the top shelf of this candle heating cart are plants. This is directly below the Solatube. But there’s no shadow cast.

1/7/2014 ~ When deciding where I wanted my Solatube installed, I assumed that light from it would be brightest directly beneath it. When I asked about the intensity of the light, I was told that Solatube illuminates a ten foot area. No one said where, in that ten foot area, the light would be brightest. So, I continued imagining that plants situated closest to the ceiling opening to the Solatube would get the most light.

Now, it doesn’t look as it that’s true. If it were true, then the pots of plants on the cart, and the large pots of water would intercept the Solatube light and cast shadows. You can see from the picture that shadows like that are not present.

On the other hand, you can see a thin line of faint shadow running diagonally across the central tile under the cart. That shadow results from the GE Plant Light I have over my squash seedlings that are on the hearth, to the right of the green pot in the upper right corner of the picture.

Floor tiles in front of the green pot are illuminated by the GE Plant Light, enough, in fact, so that I’ve moved my carrots into that position.

There is a faint shadow cast by the green tubtrug that catches water from the leak, though the leak may be mended at this point. I’m hoping so.



The shadow on the wall, against the Solatube light, is from me and my Rollator
The shadow on the wall, against the Solatube light, is from me and my Rollator

What surprises me, and the reason for this page, is that twenty feet away from the Solatube, and beyond, it’s doing quite a good job of reaching into a previously dark hallway and making it quite a lot more lovely than ever before in the hallway’s life.

On the Saltillo tiles in the picture you can see a long, thin shadow. That’s from the upright of my Rollator (walker with wheels and a seat).

I opted to have shadows in the picture so that you could get a clearer idea of the light intensity ~ with a shadow present you have something to which you can compare the light.

Similar shadows in the kitchen, on the other side of the hallway wall
Similar shadows in the kitchen, on the other side of the hallway wall

On the other side of the wall, from that in the picture above, is my kitchen. From the picture of my feet, standing in the kitchen, you can see that there are shadows in my kitchen with the same angularity as those in the hall, both of which match up to the orientation of the Solatube light source.

What’s surprising about the shadows in the kitchen, is that there’s a skylight overhead. I would have thought that the skylight would provide so much light that any other source of light would be unable to cast a shadow.

I was wrong.

Clearly the Solatube, more than twenty feet from the skylight in the kitchen, is giving more light than the skylight. I must say, with emphasis, I’m surprised!

Curved nature of Solatube light
Curved nature of Solatube light

I probably shouldn’t be surprised, given that I took a picture of Solatube light the very next day after the Solatube was installed. You can see at left that the light clearly curves. The curve is not as visible, or not visible at all, if the diffusers are in place. I opted not to have the diffusers attached, so that the light would have its natural intensity.

Thus, I’m able to see that the round Solatube produces what appears to be an arc of light.

Having been looking at this arc for nearly two months now, I’ve begun to realize that what I see is the arc as it appears about three feet behind the Solatube. To the left and right of the Solatube you can see that the light is increasingly lower as it is more distant from the Solatube.

The eventual result is that my hallway,  twenty feet away, is getting a nice bit of light from the Solatube, while my plants directly beneath the Solatube are not getting more light as a result of being so much closer.

This raises a question: Were I to have another Solatube installed, say fifteen feet from the first, would that Solatube direct more light onto my plants? And, would the additional light justify the cost? And, equally important, would the second Solatube be in a location on my roof that is unshaded by parapet shadows?

Today my friend is coming to help me with some tasks. One of them will be to move my old, laser printer to a rolling cart so that it can be stored in a closet. (My newer Canon printer uses something like 12 watts, whereas the laser printer used 750). When the printer is removed from my desk there will be room to put a plant in its place, and possibly some insulation behind it, with the reflective tinfoil side facing the interior of my living room… and hopefully increasing light to the plant.

I’m really curious to see how this works.

1/8/2014 ~ Laser printer moved, yesterday. Now, it’s just a matter of deciding on what vegetable to put in its place, to see if there’s more light (of the kind vegetable plants need to grow) on the side of the room opposite the Solatube.

What I really need is two identical pots with the same soil mix and same vegetables planted in it, so that I can place one on either side of the room. Sigh, but that requires buying pots. And, well… But, maybe I could try seedlings in little pots left over from buying plants last year.

It looks as if my Ancho peppers are coming up in the BioDome, so maybe I could try those in two small pots, one on either side of the room. Sounds like a plan.

1:22 p.m. ~ I just realized that I can’t compare light from my Solatube on one side of the room, to that as it reaches the other side of the room because I’ve had the French-door look frame taken off the doors to my deck, which added at least a quarter of a Lux in light to the area of the room where the Solatube is installed.

I suppose, however, that while I can’t compare the growing results provided by Solatube, one side of the room vs the other, I can still see if vegetable plants will grow in the light on the side of the room opposite the Solatube.

I’m moving a small pot of celery over right now.

Celery across the room from the Solatube
Celery across the room from the Solatube

1/23/2014 ~ The picture at left of my celery, both Safir (the darker leaves) and at the back, was taken a week ago when I could see that they were clearly growing well on the opposite side of the room from the Solatube.

Today the stalks are even taller. So, it seems as if the light on the other side of the room from the Solatube itself, is find for growing vegetables.

The arugula I transplanted into a pot next to the celery is also growing.

The down side is that I don’t have as much heating for the plants on my desk.


2 Replies to “Surprising reach of Solatube light

  1. Why did you take the diffuser off? Wouldn’t the light have spread evenly over the 10 ft area in the middle where the plants were, if the diffuser was on? What are the Lux/nanometer readings with the diffuser on?

    1. Hi Joyce, Yes, I sure wish I’d had a light meter in the beginning, not just “had it” but used it.

      The “problem” was that I expected the light to look like light coming in a window, that kind of bright intensity. Solatube light isn’t like that at all with the diffuser on, so when I had the diffuser taken off and some of the light was like that, I was pleased.

      At present plants on the opposite side of the room, celery in particular, are doing very well. I want to try a tomato there, but I have armadillo bugs in the pot I want to use, which I found when they ate my first tomato…

      My plan, at present, is to get another one, installed so that the distance from the plants places the arcing bright light on the plants under the first Solatube.

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