I like the crooked neck on this device, with a very clever low-cost adjustment to make it that the rotating part is level (cute use of geometry – simply rotate the two obliquely cut cylinders against each other and the tilt angle changes). I finished installing it today. I’ve been walking and crawling around on the roof a lot recently, since the last huge rainstorm we had. I’ve been diagnosing a number of issues with it, confirming a theory about some leaks, and moving around and fixing things. Added urgency piled on today since rumour has it that there will be a new rainstorm on Monday. Happily, I’ve now finished the roof, and you can see the (almost completed at the time) object I installed and sealed in place today. It’s about a foot across, and spins rather prettily in the breeze. It is an elaborate cover for a hole in the roof that vents the attic, basically, maintaining a good flow of air through it. I’m not convinced that having a spinning fluted vent such as this really improves the venting as much as it claims on the box*, but it looked very pretty and I had a moment of weakness in the hardware store because of that. Truth be told, it was about the same price as the fixed vent cover I was looking at, and so Professor Cheapskate went for the extra value of the wider mouth which allowed me to more easily vermin-proof the hole you can’t see with wire mesh.
-cvj
*Seems to me that if it is spinning, it is due to there being a light wind/breeze, in which case the wind would also pass in through the attic vents and out of this vent, by the intended design of the house. If there is no wind to do this, there’ll be nothing to make it spin. The only way it could somehow “suck” air through by spinning without wind would be if there was a motor attached. Just seems to me that they’re claiming a free lunch. It can’t force extra air through any better than a simple hole (the one it sits on top of). I could be wrong…
As to the question of whether there is an advantage if there is no breeze, I agree with you, it’s just another exit vent, allowing the ‘chimney effect’ to direct air outward.
Clifford, I saw one of these at a flea market, and had exactly the same question you did – if it was a vent, why spin? My internet research didn’t turn up anything except the guesses others have made here. However, I thought about this for a while and I have decided it’s not designed to vent air out, it’s designed to catch a breeze and bring it IN. The common home roof has its input vents in the attic walls (usually on the gable ends) and/or under the eaves. I think this is for a roof that needs more input air than that. It sits up higher on the roof and more easily catches any breeze coming from any direction (thus the round shape) and directs it down into the space below. This might be useful on larger buildings like a barn, or buildings with flat roofs like a warehouse, where input from wall and eave vents wouldn’t be sufficient. And since it doesn’t have a motor, it doesn’t require any electrical wiring, as an input fan would, so installation is easier and cheaper. Note that none of this actually requires it to spin, so I’ll guess that the spinning captures more air than a fixed scoop would, possibly by creating a downward vortex that actually pulls more air in. What do you think of this explanation? If you want to respond, pls use my email, I doubt that I”ll check in here very frequently.
my guess would be that the spinner allows the vent to catch any breeze, whereas, a static vent would only catch a breeze that crosses it directly. beyond that, just hype I would say…
“Work creates Work.”
No it doesn’t. (He says, looking up from the lecture about work and energy he just happens to be writing to give later today…)
-cvj
Turbine vents are dynamic in nature and work much better than static vents. Movement creates movement. Work creates Work. Similar to a pump.
As far as the squeaks go. They make them now with sealed bearings.
Check out the SupaVent. It is the best made. And I’m not just saying so because I sell them.
[advertising snipped out by cvj]
Guys I have exactly the same thing on my roof, on top of the chimney.
It squeals like helll!
I have used WD-40 on it in the past and it worked for a few months but now here we go again.
I’m gonna look for that graphite lubricate thingy…
I’m wondering if w15 car oil will work as I have some to spare.
Carl, just saw your remark… No no, no. You missed my point. I’m not asking for the basic principles of how an external breeze can turn a differentially oriented mechanism and make it spin. That’s more than a bit trivial. I’m talking about the belief that in still air having this is any better than not having it, for venting. I think it is not true. If you have an external driver, such as a breeze, then it can act through this device to help venting, yes. With no breeze, it’s just an elaborate hunk of metal. The roof cannot vent itself faster through a clever twisty bit of metal. There is no free lunch.
Best,
-cvj
Clifford, it doesn’t have anything directly to do with how a wind turbine sucks air out of your house, but you might find this article on the physics of the Magnus effect and wind mills of interest.
Re “Where’s the flaw in my reasoning?”. The wind makes the turbine turn because the turbine is not balanced. That is, one side catches the air, the other does not. So it is caused to rotate. To see this, consider what happens if you don’t let the unit rotate. Looking at it, you can see that the wind will catch it on the left more than on the right (small rotations cause a larger change in volume contained on the right than on the left), and so it will spin with the left side going away from you. (I.e. clockwise as seen from above.)
Upon rotation, the turbine effect causes air to be sucked out of your attic. This effect shouldn’t need explaining in that it is clear that if, in the absence of wind, you spun the turbine it would act as a centrifugal turbine and would expel air.
I think the turbine is just there for added efficiency in the presence of an external breeze; in still air any spinning it does because of a chimney effect will not make it vent more effectively, but it might help to keep out rain.
If there’s wind blowing, then of course the situation is different. Then there is an external energy source. But if still, then I suggest that it can’t make a difference.
Then the problem with it only working in this enhanced mode when there’s a wind is that it is precisely when there is little or no wind that you need the greatest effect. But perhaps a little goes a long way, which would be nice. Less energy use on cooling the house in the Summer.
Cheers,
-cvj
It may well be true, but I’d very much like to hear how the spinning will help, all other things being equal. The “chimney effect” is fine, and I’m happy with that on any chimney-like arrangement… What I am stuck on is that I just don’t get how I’m to get more throughput by using the very air I’m trying to move to turn a turbine. The energy it could have used to get away is now being used to move a turbine. Seems to me that I’ll just break even. Where’s the flaw in my reasoning?
Cheers,
-cvj
These things pull air from your attic using a turbine effect. If there’s no wind, they will allow ventilation to occur due to air temperature differences and the chimney effect (which will be improved if you paint them flat black so that they get hot faster), but with a little wind, they can move the air much quicker than it would otherwise move out of your attic.
Here’s a test. Wait until it’s a 5 to 10mph day. Crawl into your attic. Measure the air speed up the vent by using a piece of tissue paper to see how fast the air moves. Now jam a stick in your air turbine and repeat.
I bet that you will find that the thing does assist in ventilation.
As far as stopping one from squeaking, clearly if it stops squeaking when you oil it you have found the problem, the issue is that the oil doesn’t last. To make the oil last longer, either use a thicker oil (like one that’s designed for this use), or better, go with a non oily graphite lubrication that won’t attract dust or dry out.
The neck on the vent reminded me of the arm and leg joints of the Atmospheric Diving Suit.
My mother has some of these vents on the roof of her home and they can really squeal on a windy day. We’ve tried lubricating them, but it doesn’t seem to last. I should mention that they are at least fifteen years old.
No no no… you’re missing the point, I think. No matter what processes give rise to air flow that makes is spin, the spinning has nothing to do with improving that airflow, or making it more likely, I think.
Let me put it another way. It would be like claiming that if I start with two light aircraft sitting on the runway, one with propellers and one without (but otherwise identical), the one with propellers is better able to spontaneously start barreling down the runway and take off. I find that hard to believe. It takes work to turn the blades.
Cheers,
-cvj
Damn physics gets in the way of advertising, who woulda thunk it? However, one could also surmise that the there are any number of micro weather systems that can develop around this. The outside surface of the roof would heat up creating some air currents, particularly along the contour lines of your shaped roof. Likewise temperature differences around your property, your neighbors, and so forth, may stimulate air movement that could induce spin in the vent. The only restricting factor that you haven’t mentioned is the sophistication (or particularly the lack thereof) of the ball-bearings in the vent housing. Less friction would encourage spin with less air flow across the blades, i would think???
Yes, that’s my point, Jonathan. The publicity for the thing on the box and so forth makes a big deal of the spinning as being the important feature, and I’m simply not convinced.
-cvj
Shouldn’t it work by chimney effect? The warm air in the attic should want to rise out of the hole, and the draw of the chimney, it seems to me, should be proportional to its height (and to the temperature difference between inside and outside). The cap’s rate of spinning could be augmented by whatever upflow there is. Without knowing the internal design of the cap, though, I can’t guess why the spinning would help. I think it’s for cosmetic purposes.
I have two of these vents. It seems that there is nearly always a breeze in my town in Coloado. They make a huge difference in my attic, but then again, since I live in a hodgepodge of a house designed and built by my ancestors, not always to code, they’re the only venting I have. When you said “crook on a roof” for some reason, I thought of me, since I’m a Crook.
Guess: if it spins, it’s hard for animals to get in or for it to get clogged.