I recently bought a new home and am looking for easy, yet effective, ways to reduce my heating/cooling bills. I did find one product, called the Activent, that is a vent that automatically closes or opens when the desired temperature of that particular room is reached which allows your heater/AC to not run as long and thus reduces electricity use. The website is www.theactivent.com. has anyone heard of this product or know of other products that could be useful? Thanks!

The #1 most cost effective measures that can be taken on most homes is air-sealing, verified with blower-door testing.

Closing off ducts affects the overall balance of the duct system, and will drive air infiltration by inducing even higher pressure differences between rooms than would occur in Manual-D duct design, all vents open. In a super-tight house this isn't a problem, but in typical new construction the losses from the increased infiltration is usually higher than the savings from the reduced heating/cooling load due to the more moderate temperature of the rooms with the throttled-back vents.

Like many energy saving innovations, they make great promises based on a simplified model, but take those savings estimates with a pound of salt, eh? The real savings are elsewhere. (The caulking gun is mightier than the sword, and insulation is it's trusty shield.)

I would get an energy audit. Basically you are paying an expert to give you advice for your exact situation.

I have done some more intensive research and I managed to track down a couple people that have installed these vents and they report close to the $ savings that were advertised by the company....

You can also get customer testimonials that mouse-milk in the exterior paint reduced their cooling bills by 40%, but unless the data factors in more variables (actual indoor/outdoor temps and solar gains, measured duct tightness & whole house tightness, occupancy, equipment oversizing factors, etc.) the it's nearly meaningless. At the very least they should be tracking HVAC energy use against cooling or heating degree-days rather than arm-waving seasonal savings testimonials or 1-off test house examples.

The fact that they close vents completely means that they can increase whole house air infiltration, but the amount of that increased infiltration will vary with the whole-house air leakage, the duct design, and the air-handler. They recommend using them on at most 1/3 of the registers in a heating zone, which limits the amount of infiltration-drive they might induce, and limits the increase in air-handler power for the new higher pressure load it's seeing. I'd have greater confidence in real-world performance if the product clearly was modulating the air flow rather than stopping it. (It's not clear in any of their website info whether it's a bang-bang or a modulator, but the li'l vidi only shows it closing.) If "closed" was actually just 50%-75% reduction in cross sectional area it might be better in the leaky-house situation.

I wasn't impressed that they didn't bother air-sealing the gap between the duct and the finish-ceiling as part of their video either. By not sealing that interface "closed" means "redirected part of the air flow into the joist bay".

The thing might work well enough to be cost-effective in some situations, and I'm sure it increases comfort levels in homes where the room-to-room balance is way off, but in strictly energy savings terms applying that money toward duct-sealing &/or whole house air-sealing efforts would probably a better investment in most homes. (You can buy a LOT of caulk, duct-mastic & 1-part foam for the cost of 2-3 Activent registers.)

The Lawrence Berkeley National Labs and PG& E have done extensive studies of the energy use related to ducts and closing off of registers. (Lots of nerd-world data is available online, if you're so inclined.) At typical (or even fairly tight) duct-leakage factors and typical whole-house leakage factors, simply closing a duct is not usually going to be an energy saver. Unless your house is already under 3 ACH/50, air sealing the house & ducts should take priority, if it's energy savings you're after.

Some of the ways are:

- Turning down the thermostat
- Use fans wisely
- Turning down the water heater
- Keep heating vents clear

It is widely known that clogged or too restrictive of air filters will cut the efficiency of a furnace or ac by a 1/3 or more. In simple terms lower air flow carries less of the heat/cold into the house. What heat/cold that is not distributed is lost ie lower efficiency. So unless you have a multi-stage furnace AND ac you are introducing a restriction In to the system in the same way that a dirty filter would.

As another reader pointed out pressure imbalances increases air leakage to the outside and if you have ducts outside of the thermal/air boundary its an even bigger penalty. A Florida Solar Institute stduy shows that setting the fan to run continously increases the mositure or latent heat load by 200%. With the duct work outside the envelope duct leakage to the outside was now occuring all the time versus intermitently. You could be having a similar effect on your house.

To the OP, the starting point is to have an energy audit. This will identify the weakness in YOUR HOUSE and give you a game plan to improve efficiency. You can do it in stages but it should be done in a particular order.

Roberth: I've never heard of the Florida Solar Institute- did you mean the Florida Solar Energy Center? ( http://www.fsec.ucf.edu/en/ )

I'd be curious to see the study, if it's available online.

Ducts in unconditioned attics or crawlspaces (even tight ones) are something of an energy disaster. In a FL or TX attic it can easily double the peak cooling load numbers. Sealing and insulating such ducts is a band-aid, but is very cost effective, even if it never quite brings the load & losses down to what they might have been were the ducts entirely within conditioned space.

I'm wondering if GreenOholic is just a paid astroturfer for the product rather than a poster with a real question. (Wouldn't be the first or last here, but hopefully I'm mis-perceiving the intentions..._)

It's not hard to measure room pressures and adjust inlet and outlet registers to keep room pressures neutral. Or leave doors open.

I suspect that Activent doesn't adjust both registers - so bad idea.

Dana

You are right. I new is was Flordia Solar, just didnt have the whole name

Greetings,

You should have aluminum ducts in the attic.  They help reflect heat energy.

Also check "koolcoat.com".  This is a company that supplies the micro ceramic beads, like NASA uses, and they can be mixed with a clear acrylic paint and spayed on the underside of the roof sheathing.  I've used this product and it is very effective. 
You can also mix it with a light colored paint and paint the exterior of a house, including brick.

Dana1, Would mouse-milk in paint cost less and work as well as micro ceramic beads? In other words, are there any published data to support claims of R-20 for micro ceramic beads added to elastomeric paints? If so, can you list independent research and lab results confirming high R-values for micro ceramic beads added to paint?

Greetings,

There is an ongoing debate as to whether ceramic beads "reflect" radiant energy (RE) or uses another method of rejecting RE.
If reflection, or low absorption/ emissivity is the process then "R" values do not apply.  You need to know the reflection efficiency.
We know that it is above 90% and probably approaching foil efficiency, 97%.

You cannot extrapolate The "k" reflective s into "R" values values which are based on a "u" factor.
There is a debate going on as to whether "R" values for so called conductive resistant insulations are legitimate when you consider the emisivity of the base materials and the extremely high ratio of mass to air volume.


You cannot use the beads in a paint that contains a carbon content. The carbon absorbs and re-radiates the RE thereby greatly reducing the effectiveness of the beads, other wise, as far as I know, you can use it with any type of paint.

For more info on this subject I would recommend that you contact Chuck at "koolcoat.com"

like Roberth, I can see scenarios of increased fuel consumption, lowered comfort or possibly even equipment damage with a duct damper system if not properly designed or installed.
instead of spending the money on after market products, bump your thermostat 1-2*.
j

Dana1,

I have a could contentions with your original post. First, the fact that the Activent creates more pressure in the system and that that pressure wants to push out somewhere else is what makes the Activent work as it forces more heating and/or cooling into the other areas of the house/office. Second, you say that this added pressure will push out through leaky ducts and around the vent boot and out into space (attic/basement area) wasting the air. Well wouldn't sealing these leaks be something you would want to do ANYWAYS? It is not as if regular vents don't waste air due to leaks, correct?

To the post about ceramic microbeads, there is a (funny) story about an insulating paint salesman here: http://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-paint-salesman-tripped-his-own-product

UltimateAir is right about the trade off between solid insulation and quality air flow. It's an aspect of green building that people often ignore

Fixing leaky ducts is a better investment than active register louvers. If you haven't had the ducts pressure tested & remediated to a fairly tight level, the duct losses will likely exceed any potential gains by smart registers. The fact that the gap between the duct and finish ceiling wasn't sealed as part of the installation procedure tells me they're not really paying attention.

There's no credible 3rd party evidence that ceramic bead additives dramatically improve the thermal performance of paints.

Reflective coatings work best on the exterior where the radiated heat transfer is highest (the delta-Ts on conditioned space interiors are too low to matter), but it has to be sufficiently emissive in the infra-red spectrum to re-radiate the heat that is not initially reflected- it's a balancing act. (This is why bare aluminum or chromium laid flat on the groung gets hot in the sun despite being extremely reflective- it's not emissive enough to shed the heat that isn't reflective, and convective cooling isn't enough.) The Cool Roof Rating Council used 3rd party data to confirm both the solar reflectivity and IR emissivity of the products listed. While ceramic additives can alter the reflective & emissive properties of a paint, it isn't usually by very much. To be effective at lowering the interior side radiation temp the paint needs to be low-E, but to be effective at shedding heat to keep the exterior side from heating up and conducting heat to the interior the paint needs to be high-E. One additive can't do both.

Foil radiant barriers on rafters work on the interior of attics despite rising to a fairly high temp due to the low emissivity of the interior side limiting the heat transfer across the large air gap between the rafters and attic floor, and the high reflectivity of the exterior side reflecting most of the heat radiating off the hot roof deck back to the roof deck. But it's only useful at high temperature differences with air gaps, where the radiated heat transfer dominates.

If we lived in a vacuum with no convective heat transfer and a high radiation temp on one side (the sun) and very low radiation temp on the other (outer space) we could control our environments completely with reflective insulation (ergo the stressing of NASA data by reflective insulation folks.) But here on earth convective cooling of exteriors is a large mitigating factor on both wall and high-pitch roof heat gains. Yes, reflective materials can be useful there, but mostly at the temperature extremes.

Stuart there is advertising available to purchase here.

Another thing that has not been brought up yet, is that if your AC is cycling(turning on and off) a lot it will reduce the lifespan and efficiency of your AC, and these dampers have the potential for your AC to cycle to often. An Air Conditioner does not reach rated efficiency until 10-20 minutes of runtime. If your house runs your AC for 2-5 minutes each time it comes on you are actually ADDING to your utility costs and later down the road, your repair costs.