Room design

[Sibling Zono (anon1mat0)]

Living in the very hot place I live in I was wondering if there is a way to have the benefits of the sun (ie: light) without the drawbacks (heat!) while designing a room.

One of the ideas I had goes for a house I have in mind with huge windows on the opposite side of the sun to light the full house, but the house design is quite different from the average and the glass would have to be security glass (hurricanes...) making it expensive.

I had a different idea today:

The idea is to have the sun landing on an aluminium plate on an angle which would depend on how low the sun goes and how perpendicular it can be depending on the time of the year. The glass would isolate both the room and the plate which then could be used to heat water (pipes not drawn).

Is it a fair assumption that most heat would be trapped in the compartment? is there a better way to accomplish good lighting without the heat?

[Aggie]

Sun pipes.

http://www.sunpipe.com/24.htm

I'm not sure to what degree the compartment would isolate heat from the rest of the house; it would certainly trap some, but the glass is also a fairly good conductor of heat (unless you go with triple glazing or the like).  That is, even if the compartment traps most of the heat, it'll leak some into the room through the second pane of glass.

If you are going for indirect lighting, the sun pipes (or similar product) might be a better and more hurricane-proof way to go.   Your design is accomplishing something similar, but with more surface area (and therefore more light).  As designed, there will be a trade-off between how much water heating/heat removal you want to do and how much light you want to reflect to the room.

I'd think that any time you are admitting direct sunlight, even if it's reflected, you are likely to have some heat transmission.  OTOH, south-facing windows with a large over above can be dialed in to disallow sunlight during the hottest parts of the year/day, but still let in plenty of diffuse light. I'm not sure whether there is a 'cool' part of the year during which you'd want to have full sun coming in, but the angles can be tuned to allow this in northern climates.

[Griffin NoName]

The Sun Pipes look interesting. Shame they don't give the prices online. They saythey will pay back in terms of your lighting costs, but I would think they are pretty expensive to install (3 hours) and lighting costs are not a massive outlay normally. At least, mine aren't. I only have two lights on at a time.

[Sibling Zono (anon1mat0)]

I suspect it will take a substantial amount of time to pay for light pipes if you use efficient light bulbs as a comparison: a ~U$15 LED 7W bulb is fairly brilliant and will last for ~10+ years (perhaps much more), I pay a bit more than U$1 for 10 KWH so:

Say a usage of 16 hours a day (over use)

Say 3 bulbs ~ 20 W * 500 hours = 10 KWH = $1*

500/16 = 31.25 ~ a month

That means that the expenditure in lighting in a month is a bit more than a dollar.

The installation of one fixture is not likely to cost less than U$1000 so it would take 1000 months/83 years to pay for itself assuming a very low cost of installation.

Their best case scenario would be double energy prices and double the wattage of the bulbs in which case it would take 20+ years to pay for itself.
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But it would be natural light...



*it's a bit more but not too much, perhaps 10% more

[Aggie]

If you consider HVAC costs for letting in a similar amount of light via skylights or especially windows (the sunpipes should let out less heat, although I would note that they will still allow substantial convection within the unit), then I could see a quicker return on investment.  For just light? No.

[Sibling Zono (anon1mat0)]

The assumption being that you would be boarding your (existing) windows and instead using the light tubes? And even then some heat would come in (as opposed to none if you use only efficient lights).

Perhaps cost effective as SAD therapy?

[Griffin NoName]

Both the lights I have on are economy bulbs

[Aggie]

I think the comparison is to skylights.  Compared to what you intend (designing from scratch) I would think that the sunpipes might be more economical than the setup depicted above, once design and material costs were in.  I think your design would be far superior in terms of how much light was transmitted, although I'm not sure whether it would solve the heat issue or not.

I like how you are using reflected sunlight to give illumination.  I wonder if the same effect could be had with a covered porch along the south side of the house, with the floor of the porch painted white? It should stay relatively cool, and also reflect diffuse light back up through the south-facing windows, although the windows themselves would stay shaded.

I'm not up on the latest coatings and glass treatments available, but I seem to think that there are some out there that specifically block infrared.  For your idea of heating water while keeping the house lit but cool, it would be ideal to have the reflector surface able to reflect as much visible light as possible while adsorbing nearly all the infrared.

[Sibling Zono (anon1mat0)]

I guess the point is that a setup like mine makes sense if you are building from scratch rather than modifying a house (because it would be even more expensive than the light tubes and only justified on the water heating setup if at all). The other is that the materials while some costly (like the top glass which would have to be safety glass) are relatively easy to find and the setup shouldn't be that hard to make. In that same context, light tubes may be even cheaper if you make them your self (although the roof installation may be tricky) but bought and installed quite likely not.

As for the coatings you are absolutely right, that would require some research but it's likely that the internal glass would use a coating. Also, when I was thinking on the internal space, I considered that it may have some air circulation or not, depending on how efficient is the plate (too much and it radiates energy, too little and it will not heat water) or perhaps to be open or closed depending on the time of the year.
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On a completely unrelated note, I was looking and it seems that you can get 280W PV panels for ~U$380 making them closer to affordability. After some numbers I would need about 20 panels to cover my electricity budget which installed I would think cost ~U$10K and be paid in about 10 years of electricity bills.

[Griffin NoName]

but loosley connected

It will take 1 year and 1 month with paying my kindle subscription to the Guardian to save the amount I paid for the Kindle and accessories from not spending the extra money it was costing to have the paper edition (plus delivery). ie. if my kindle lasts > 1year then financially I made a good decision

[Roland Deschain]

Infrared reflecting glass has been a reality for over 10-15 years now, as I remember reading about it in New Scientist that long ago (I thought of it straight away, but was beaten to the punch with its mention ). A search on your favourite search engine for "Infrared reflecting glass" will bring up thousands of results. Volkswagen use it in their cars for the windscreen, etc, and I imagine other manufacturers use it too. I'll hazard a guess at it being expensive, especially if you want it to be hurricane-proof as well, but i'm not sure how cost-effective it will be to use. Highly-polished aluminium (or mirror-polished stainless steel if the weight is ok) being used to reflect light and absorb heat is a great idea, and it seems that in principle it should work. A combination of the two would be perfect.

Those light tunnel thingies also look really cool. Natural light is so much better than artificial.

[Lindorm]

A somewhat late addition to the thread: Over here in Sweden, triple-glazed windows with an insulating gas layer between at least two of the sheets of glass is quite common, and almost all new houses are built with such glass. The glass insulates both from heat and cold, and can achieve insulations values better than old-ish house walls in quite a few instances. Is there perhaps something similar available where you live?