Vent Miser: Pass or Fail?

Convenient, yes. The best item for the job, in my opinion, no. Cheaper and easier to just keep the vent closed when you aren't using that room and open it when you are. I'd rather not buy another basically unnecessary gadget.

Yea, unfortunately these vent gizmos (there are others) are really not useful for actual energy savings. More for personal comfort of the people in the room. Even then, only if the room does not have its own heating zone to begin with. If it does, no need to muck with the vent.

But as mentioned, the only thing that turns your furnace or boiler on/off is the thermostat. Blocking a vent does not. It would also be wise to consult a real HVAC expert as messing with the airflow (and hence, the return air as well) can wreak some havoc with the heating system itself.

So in summation, these things fall into the same category as those water misters for central air conditioning units. They might work under very specific circumstances and with very careful application, but in general they cause more harm than good.

Wouldn't that be "miser"?

I think something like this could work.

Yes, your heater, controlled by your thermostat, will be pumping out the same amount of heat, but by closing vents it will make the rooms more evenly heated, meaning less energy is spent heating up rooms that are comfortable to warm up cold rooms.

Living in an old house, I know how hard it is to make sure the rooms are evenly heated and cooled. Our second-floor rooms, for example, are almost always colder than our first-floor rooms. But closing the vents in the first floor rooms makes them colder during the times we need them to be warm.

And while, yes, some heat would leak through, closing vents has long been considered a way to manage airflow. I fail to see how automating this process doesn't make sense. And I fail to see how automating the process is a bad thing. Hasn't Treehugger always encouraged the use of programmable thermostats? This is just a further extension of the idea.

Look at it this way: Would it be better for someone to buy an automatic vent, or should they buy a space heater and continue to run their furnace full blast?

Hmmm, I think it is interesting. Since the furnace is running and pumping air as controlled by the thermostat, as Bio Willie says, then if the vent meiser closes down one or two rooms, more air is going to come out elsewhere, changing the temperature faster and affecting the thermostat sooner. The furnace is working a smaller volume of space and is going to respond accordingly.

Lots of high-tech commercial systems have variable volume dampers, which is kind of what this is. The next step is to have an X-10 type remote control system and hook it all up to your computer or to occupancy detectors and build a smart heating or cooling system.

The batteries are an issue; I think conditional pass.

I vote "other." If you're living in a 2-bedroom apartment like I am, it seems pretty silly. If you're wealthy and living in a gigantic house with wings that might not be used for weeks at a time, it makes a lot of sense.

As a (green) remodeler, I am excited to finally see a product like this. I know it is not for everyone, but I have come across numerous examples of where a few of these could help. I have been talking w/ a local HVAC sub of mine for almost a year about trying to find/make something like this, because most people's existing systems are not uniform, and for homes where sleeping and living areas are not stacked, a "smart" vent like this makes a lot of practical sense.
In a nutshell, there are certain vents in a person's home which get much more air at better temperature control than others (especially the ones closest to the air handler.) If you can reduce the flow to these vents, it will push more air to the one's which need it the most - (like the one's furthest away.) And really: why heat living areas in a split story home at night where the ambient temperature in those rooms WILL NOT affect the 2nd floor thermostat? It's a total waste of energy.
Granted it's true that it's cheaper to go around and close vents in areas not occupied, but how many families out there are actually going to remember to do that twice a day even if they know they could save energy? Some would much rather have me install a bunch of these just like the 50 dollar programmable thermostat. Who's in this day & age is going to adjust their thermostat 7 times a day?
But I must say that before all this, please spend the money first on your weatherstripping, air sealing, and insulation around your house, and perhaps get an energy audit to validate your efforts. That's still the best money you can spend on your home.

For a guest bedroom? No, you don't need something programmable--just close the vent manually.

But to direct heat to different parts of the house at different times of day, it could be just the ticket. For example, program them so that at night, the bedroom vents are open and most of the others are closed. It's true that the heater will keep going fully throttle until the main thermostat setting is satisfied, and if the thermostat is a long way from the bedroom, that won't happen very easily, and the heater might have to run _more_ time, thus using more energy. But if the main thermostat is turned _way_ down, like to 50 F, then it will be easily satisfied, and the heater will run just a little, keeping the bedroom warm enough, and letting the rest of the house get cold.

Then in the morning, before people wake up, the other vents open, the bedroom vent closes, and the thermostat setting goes up. The heater then warms up the rest of the house before people get up.

Why use this, batteries and all, instead of just doing it manually?

1) If there are a bunch of vents to close, it's a pain to walk around and close them all.

2) It can open them and start warming up the rest of the house before you wake up.

It would be even better if they were networked and there was a smart central control system. Then instead of setting the main thermostat to 50 to keep the bedroom at 60, you could just tell it to keep the bedroom at 60. I think there is a system like that available, though it's much more expensive. One danger with this is that you might goof and turn off all the vents at once, and then the heater works like crazy and can't warm up the house at all!

But as Matt Dirksen says, do the air sealing and insulation first!! (And if you can do that well, the temperature differences between different rooms will be reduced, making this less important.) And make sure that includes sealing the ducts--if you close off many ducts and there's a leak somewhere, you'll force lots of air out the leak!!

While closing vents to safe money seems logical enough, it is actually completely inaccurate. A Department of Energy study in 2003 at the Lawrence Berkeley National Laboratory showed that closing vents increases duct leakage and therefore energy use.

http://www.consumerenergycenter.org/myths/vents.html

It seems like this gadget would only decrease HVAC efficiency.

Reduction in CO2 emmissions is extremily important. In our company we reuse 550 million apparel hangers annually that are sold to apparel manufacturers. If we didn't reuse these hangers they would either go to a land fill, be recycled and made into another product but add more CO2 to the atmosphere recycling the plastic. Where can someone go and find out how much co2 a process such as reuse of plastic hangers reduces that would normally go into the atmosphere.

From the mouth, no, fingers of an energy consultant, this should work, but not make a huge difference. It's called a multizone variable air volume system (VAV) and almost all commercial buildings with modern air systems use this method. There are boxes up in the ceiling that control how much air enters each smaller room (zone). The drawback is that you home fan will not scale back, its constant. You will get heating/cooling savings though since the area with the main thermostat will be conditioned faster than the area you're closing off.
I wouldn't suggest this if you have a small home (hopefully you do) and I would suggest a programmable T-stat way before these things. Oh and DONT EVER close the vent that is closest to your T-stat!

Not a great idea, the vents in HVAC equipment are not really mean to be closed, doing so increases the pressure within the duct system (furnaces push the same amount of air irrespective of how many vents are open).
With more presure in the ducts you'll get more leakage from holes and joints between duct boots and floors or ceilings.
If your ducts run through the attic or in a crawl space you'll just force more air into areas you don't want it to go.
Imagine taping off half your sprinkler heads, you'd get pipe blowouts all over the place.
Better off making sure all your ducts are well sealed (mastic not tape) and buying a can of foam to seal up all the holes in your ceiling to attic barrier (round light fixtures, electrical holes etc) then getting some more insulation blown in.

Why are you even talking about forced air systems for heating on a "Green" site? You loose so much heat with forced air systems. It shoots the heat across the roof or up the walls, instead of across your floor to radiate up...

Radiant is the way to go.

Energy-Efficiency

Many manufacturers claim that radiant floor heating is more economical to operate because the temperature setting may be set to 20ºC (68ºF) rather than the usual 21-22ºC (70-72ºF) as required by other types of systems. A study by CMHC (Thermostat Settings in Houses with In-Floor Heating, #01-106) has shown that people tend to keep their thermostats set the same as if they had a forced air system. Even so, the warmest air is at the floor where it is desired (and not at the ceiling) and there is reduced heat loss through the ceiling and walls.

Zoning a variety of rooms with the options for different temperatures has the potential to reduce energy consumption.
Energy Source Compatibility

Since radiant floor heating has a low operating temperature, a wide range of sources can be used to heat the water–a ground-source heat pump, a condensing or non-condensing boiler, solar or even district heating.

Vent systems are not as carefully tuned as auto exhaust systems, but still shutting a vent off, especially in carefully designed larger systems, could lead to excess air friction elsewhere in the system as the hot air backs up or just sits stagnant. In extreme situations, you could even get a vapor-lock kind of stalling which would inhibit the efficiency of the rest of the system. Only if the duct was shut at the branch from the larger duct could that be prevented.