Parabolic mirror for light redirecting?
June 26, 2018 2:04 PM   Subscribe

I manage a hotel in San Francisco, and some of our rooms are on the inside of the housing block, and thus get a bit dark from about mid-afternoon on. I was thinking of wall-mounting a convex mirror at the top of the inside lightwell/shaft, to bounce more sunlight down to the lower floors (3-floor building).

My google-fu is weak and I can't find anything other than 3 billion Pinterest images that are kinda what I want, and I'm guessing there might be a special jargon-y name for this thing?

NB: What I am NOT looking for is in-wall or wall-mounted tube skylights, which is what fills my search results.
posted by slater to Home & Garden (11 answers total) 2 users marked this as a favorite
posted by bgrebs at 2:11 PM on June 26, 2018 [2 favorites]

There are a bunch of high tech options if you google "sunlight pipe."
posted by rhizome at 3:53 PM on June 26, 2018

Response by poster: Heliostat
Hmm... I guess that's kiiiinda what I want? Though that seems to focus (heh) more on heating?

There are a bunch of high tech options if you google "sunlight pipe."
Which is exactly what I don't want :)
posted by slater at 4:43 PM on June 26, 2018

Not sure of the search terms exactly, but this commercial heliostat looks like it might suit your needs.
posted by cnc at 5:34 PM on June 26, 2018

I read years ago of a (possibly 3M) product that would diffract light into a room. Very hard to search on but 3M would know. Ahhh - I found it daylight-redirecting-film . The lighting in the brochure looks a little suspect but who knows.

The only light pipe solution I've found which seems viable and even remotely viable was a Finnish system, - I have a quote for it somewhere but it was through the roof.
posted by unearthed at 5:47 PM on June 26, 2018 [2 favorites]

Right, you don’t want a light pipe and I don’t think you want a heliostat either. You just want some large outdoor convex mirrors.

Uline has several sizes, I’d think 30” is a good starting point.

You don’t need fancy computer-controlled motors to move light around, because you know where the sun will be and where the windows are, and what time of day you want this to work for.

There will be some seasonal fluxuation depending on the slope and aspect of your hotel, and you may want to add more mirrors and rejigger them a few times to get the right effect, but this should get more light in the rooms and not cost all that much, assuming you have a staffer who you already pay who could manage the relatively simple mounting.

I think a handful of these mirrors would work well in combination with the 3m film linked above, but it shouldn’t be necessary.
posted by SaltySalticid at 6:58 PM on June 26, 2018

Wouldn't using a convex mirror diffuse the light too much to be useful? Not to mention that a huge part of that light would be pretty much going back up, towards its source. The problem is getting the light reflected where you want it. That's where heliostats come in handy. Now, finding the right one for the job is another problem.
posted by bluefrog at 7:03 PM on June 26, 2018

What about a fiber optic sunlight system? For example, Himawari?

Mirrors will be bright spots in the field of vision, and therefore irritating/blinding unless you're pretty careful where you put them (says the guy who tried to use mirrors to bounce light deeper into his condo a few years ago).

On the other hand, a traffic mirror (while crappy IME) is cheap so you can probably afford to just see how it works for you.
posted by aramaic at 7:18 PM on June 26, 2018

It might not be possible depending on the situation (or you've already done it) abut painting the lightwell white or another light colour could also substantially increase the brightness in the lower rooms, although there is higher maintenance for a whitewashed wall versus say a brick one. If you could get a mural done (still in light colours obviously) then a room with the inside view might be a little better received by guests.
posted by Homeboy Trouble at 7:24 PM on June 26, 2018

To clarify: The idea of the convex mirror is that it will bounce light down toward the lower windows from a much wider range of angles than a flat mirror would, and this helps obviate the need for heliotstatic mechanisms.

It is true that some light will also bounce back up, but that’s a feature, because you can place some low on the wall too, as in the pic linked by op. In principle you could slice each mirror in half and mount one low and one high (slicing off the top of the top mirrors and the bottom of the bottom mirrors in the example pic), but that introduces other problems and is probably not worth it.
posted by SaltySalticid at 7:52 PM on June 26, 2018

Half done acrylic mirror

Mylar mirror

Mirrored Mylar film

Mirror spray paint
posted by at at 5:18 AM on June 27, 2018

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