Two Story Home Return Vent Magnetic Covers Questions

Here questioned last week on methodologies by a neighbor as I used to do this a few years back.
 
1 - Winter - cover all return vents on second floor or cover all return vents on the first floor
2 - Summer - cover all return vents on first floor or cover all return vents on the second floor.
 
I read that this was a bad thing to do and quit doing it.  Neighbor did it and stated that the heat is getting to the right places now in his two story home.
 
I do leave my single unit HVAC multispeed fan running 24/7.  I also use two sets of filters in the integrated electronic air cleaner which by default I change once a month (one is a charcoal filter).
 
Some stuff I have read:
 

In the case of the ECM (electronically commutated motor), a high pressure will cause the motor will ramp up in an attempt to maintain proper air flow. An ECM is much more efficient than a PSC motor under ideal conditions, but as it ramps up to work against higher pressure, you lose that efficiency. You still get the air flow (maybe), but it costs you more.
 
The majority of blowers, however, are of the permanent split capacitor (PSC) type, which is not a variable speed motor.
 
The PSC motor, on the other hand, will keep spinning but at lower speeds as the pressure goes up. Thus, higher pressure means less air flow, and, as we’ll see below, low air flow can cause some serious problems.
 
The important thing to remember here is that no matter which type of blower motor your HVAC system has, it's not a good thing when it has to push against a higher pressure.
 
Closed vents increase pressure
In a well-designed system, the blower moves the air against a pressure that's no greater than the maximum specified by the manufacturer (typically 0.5 iwc). The ideal system also has low duct leakage.
The typical system, however, is far from ideal. Although most systems are rated for 0.5 iwc, the National Comfort Institute, which has measured static pressure and air flow in a lot of systems, finds the typical system to be pushing against a static pressure of about 0.8 iwc. Now we're ready to address the question of closing vents.
When you start closing vents in unused rooms, you make the duct system more restrictive. The pressure increases, and that means an ECM blower will ramp up to keep air flow up whereas a PSC blower will move less air. Most homes don't have sealed ducts either, so the higher pressure in the duct system will mean more duct leakage, as shown below.

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Here in the midwest temperatures outside have been around 0°F to 10°F (-18°C to -12°C) outdoors.
 
Curious if anyone is doing anything proactively to keep the heating temperatures even in their homes.

I'd imagine what he accomplished was to make his inefficient setup run even more inefficiently but perceived a comfort improvement.  So, ignoring the energy costs, it would seem like he'd accomplished his goal.  But cost him more in the process. 
 
Few people track their energy consumption data at all.  Or, if they did, have the skills necessary to correctly calculate it (factoring outdoor conditions, etc).  

Here I do but do not look rather enjoy watching my weather graphs more.  Neighbor did have his whole 10 year old HVAC system replaced (well two of them).  Not sure if the company put in more returns as its a bit difficult to do after the fact.
 
Here I just cranked down the whole house humidifier a touch as I started to see some effects of the humidity levels on the bottoms of the windows.  I also added the very old vaporizer to the master bedroom for nights as it goes some 3 nights on one fill and it does keep the master bedroom comfortable.
 
The old home had two zones with smaller HVAC units on the two floors.  The design was not efficient at all though on the second floor as the supplies came from the attic to the ceilings and there was only one large return in the hallway.  Keeping the bedroom doors shut didn't work too well.  Here there is just one larger HVAC unit in the basement which does a good job to the second floor.  I did have to redo the bathroom fan ducts as it wasn't insulated (some 8 feet ducts from the floor to the ceiling of the attic)...I was getting water dripping down from the condensation inside of the bathroom fan ducts.  The design here is way better as most of the rooms have multiple high and low returns plus multiple supplies covering much of the rooms. 

A properly designed system needs to have the right balance between the supply and return ducts.  Unless the system was installed with too many return ducts, closing all return ducts on the first or second floor is a bad idea.  Although if there are both high and low ducts in a room, then closing just one or the other is ok.
 
If you close too many return ducts, you can actually cause an over-temp condition in the furnace since there will not be enough air moving through to keep the temperature within normal operating range.  If the burner overheats, the limit switches should shut it down.  But then you are depending on those safety devices working properly for everyday operation, rather than just for an exceptional condition.

Closing off the returns would start to starve the furnace for air.

DELInstallations said:

Closing off the returns would start to starve the furnace for air.

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It's six of one, half-dozen of another.
 
It's not so much that you're 'starving it for air' but that you're making the fan push harder to get enough air to circulate.  That, in turn, creates higher air pressure which results in more wasted energy and wear on the fan.  That and since most duct systems aren't very well sealed it results in a lot of that higher pressure air being moved through places that won't help condition the living space.  Pulling in air from unconditioned areas the ducts go through, like a musty crawl space or an overly hot/cold attic.
 
There's a trade-off being made, perceived comfort vs making the HVAC setup operate even less efficiently.  The better solution is to correct the HVAC system, but that's often more involved than just shutting off a register.
 
In our new house there are three different air handlers; one for each floor. There's a wide open staircase between all three levels.  I was anticipating a lot of trouble with convection issues due to the stairway.  To my surprise that's not the case.  Each level manages to duct the air effectively enough to avoid problems with the stairs.  That and the walls being foam insulated helps.  The basement level is mostly underground and barely needs to run it's system at all, as the insulation keeps it very stable.  
 
In a conversation I've been having over on a mailing list we've been discussing programmable thermostats.  The latest results from Energy department studies is most efficiency improvements come not from programmable thermostats but from all the other insulation efforts or the outright replacement of an ancient system with a modern high-efficiency one.  Using setbacks (overnight/away daytime) are sometimes actually worse than leaving it stable.  This being for water or steam setups, mainly.  

wkearney99 said:

In a conversation I've been having over on a mailing list we've been discussing programmable thermostats.  The latest results from Energy department studies is most efficiency improvements come not from programmable thermostats but from all the other insulation efforts or the outright replacement of an ancient system with a modern high-efficiency one.  Using setbacks (overnight/away daytime) are sometimes actually worse than leaving it stable.  This being for water or steam setups, mainly.  

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I'd only be in partial agreement with that statement. I can't see where running a T-stat in an environment while not occupied is less energy efficient than keeping the temperature at a constant. A boiler is going to consume more energy if it is running than if it's not and the amount of time a building is in recovery and calling for heat is really not that long compared to a normal cycle with reasonable system hysteresis. I could understand if unreasonable setback values are used or even in a location where boilers aren't used, such as below the mid-atlantic in heatpump country or emergency electrical heat strip situations. Otherwise, I agree with it's easier to keep the heat in and create it more economically, however I can't see once a certain tipping point between insulation and sealing, where it's cost effective to keep the house, say at 68 degrees, 24 hours a day.

Yup; here do not do set back the thermostat and do leave it at 68 F 24/7 right now. 
 
The temperatures run pretty even on the three floors.
 
2nd floor to first floor is an open staircase with basement staircase behind a door. 
 
@Bill - by "air handlers" do you mean separate HVAC units or just terminal handlers pushing air?
 
A friend built a home recently and there are thermostats on each floor which are connected to the main furnace ductwork from what I could tell.

With our geo-thermal setup there's only one ground loop (three, 350' deep wells), but there are three different circulators that feed three different air handlers.  It's the air handlers that have an exchanger to condition the air being forced out to the zones.  
 

All of the geo compressor/exchanger coils are located in a basement utility room directly adjacent to where the ground loop enters from underground.  From these there's a high/low pressure line pair that goes to each air handler.  One is integrated and is right there.  It's got two zones (basement & theater) controlled by dampers on the air ducts.  The 1st floor air handler is across the basement (the high/low copper lines extend to it).  It's also the only one that has a natural gas burner for backup heat; the other two have electric.  The 2nd floor air handler is in the attic and is also fed by a high/low pressure line pair.  
 
Since the theater is only one room it wouldn't made economic sense for it to have it's own setup.  Thus it shares conditioning with the basement.  This way I can keep the theater cooler in the summer & winter (due to body & equipment heat) while the rest of the basement stays comfortable too.   When the theater has a lot of people in it during the summer months the system can push more cold air into it without the basement getting turned into an icebox.  Likewise, when it's warmer in the theater in the winter the system can still warm up the basement without theater getting too hot.  
 
The one thing a combined system can't do, though, would be to provide both heating/cooling at the same time to different zones.  But it's unlikely we'd ever need to do that given our climate and use patterns.  This is also a potential issue for how the ground loop operates.  Mainly because the geo loop depends on being able to exchange against ground temperature.  Not exactly sure how well the system would work, having two different exchangers on the same loop operating in opposite modes.  I know the air-zoned basement/theater can't, as it's just one geo zone.  But in theory I could have the 1st and 2nd floors in opposite modes.  I'm sure efficiency would go all to Hell.  But, again, there's really no likely situations where we'd ever need that.
 
The upside to the geo front-end expense is even with more than doubling the square footage our total gas & electric expenses are still about the same as the old house.  Before we spent a lot more on gas in the winter, for heat.  The geo system hasn't had to kick into emergency backup heat at all (neither gas nor electric).  It's managed to run off the ground loop entirely.  
 
Gas comes with a minimum usage charge so we went with a gas water heater, dryer and range.  We also have a natural gas backup generator also, thus I couldn't go without gas.  Anyway, while we spend more on electric than before, but a lot less on gas, so it essentially evens out.  I'm sure with all the fuel price fluctuations there's nits that could be picked, but I don't care THAT much.
 
The point is modern systems can be remarkably more effective than systems even as recent as a decade ago.  You're still at the mercy of proper design and installation methods, but the underlying gear is really THAT much better than before.

DELInstallations said:

I'd only be in partial agreement with that statement. I can't see where running a T-stat in an environment while not occupied is less energy efficient than keeping the temperature at a constant. A boiler is going to consume more energy if it is running than if it's not and the amount of time a building is in recovery and calling for heat is really not that long compared to a normal cycle with reasonable system hysteresis. I could understand if unreasonable setback values are used or even in a location where boilers aren't used, such as below the mid-atlantic in heatpump country or emergency electrical heat strip situations. Otherwise, I agree with it's easier to keep the heat in and create it more economically, however I can't see once a certain tipping point between insulation and sealing, where it's cost effective to keep the house, say at 68 degrees, 24 hours a day.

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The sheer number of variables doesn't make it easy to apply any 'absolute' statements.  Especially when radically different heating systems are involved.  What works for one doesn't necessarily work for others.  
 
I think the point being made is that, in order to see greater savings, folks are likely better served putting efforts into sealing & insulating.  As opposed to making things worse with excessive setbacks via programmable thermostats.  The average consumer barely understands most of this and ends up with some rather wrong-headed thinking regarding their use.  The perceived 'cheapness' of energy has allowed for that.  The costs & the stakes are getting higher as a result, unfortunately.  So getting folks back in tune with insulating and upgrading to considerably more efficient systems seems to be getting more push lately. 

Thank you Bill.  Very nice.

wkearney99 said:

The sheer number of variables doesn't make it easy to apply any 'absolute' statements.  Especially when radically different heating systems are involved.  What works for one doesn't necessarily work for others.  
 
I think the point being made is that, in order to see greater savings, folks are likely better served putting efforts into sealing & insulating.  As opposed to making things worse with excessive setbacks via programmable thermostats.  The average consumer barely understands most of this and ends up with some rather wrong-headed thinking regarding their use.  The perceived 'cheapness' of energy has allowed for that.  The costs & the stakes are getting higher as a result, unfortunately.  So getting folks back in tune with insulating and upgrading to considerably more efficient systems seems to be getting more push lately. 

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Agreed,

The missing point is the delta-T variable in relation to the inside and outside. A house will lose heat faster if the temperature difference between the inside and outside temperature is greater in comparison to a more comparable inside/outside range. A 20 degree outdoor temperature and a 68-70 degree house will lose that heat faster than a 60 degree space. Usually swinging a programmable stat 10 degrees will result in considerable savings however there is a diminishing return when dropping more than that.
 
That said, the same holds true when it comes to efficiencies of the equipment when it comes to investment and payback over time....some times it just doesn't make sense to spend a multiple of $X to obtain a 3% increase of efficiency when it will never pay for itself in say, 30 years worth of operation unless the form of energy increases substantially. This is what holds true with items like oil sands, until a bbl of oil drops below X, it is still economically viable to extract the petroleum from the oil sands. The same parallel could be said about a heat pump that is a 13 SEER vs. one that has a 25 SEER. If the equipment costs 10X for the higher SEER and the electrical rate isn't exorbitant,  the end user will never see the return on the investment.
 
Insulation and sealing a home, barring some items (replacing windows, etc.) is generally the cheapest way to keep a home warm or cool instead of purchasing X, Y or Z and controlling the same to attempt to realize some savings on it.

Hmm, when things like ROI get bandied about, I worry that folks have lost sight of the fact that it's not SOLELY about individual energy costs at the PRESENT time.  We've lived off excessively cheap materials for far too long.  Which have wreaked a ridiculous amount of havoc over a VERY short period of time.  It's time to make investments in using as little energy as necessary, not just playing games without how much of the environment we can rape further because it's cheap.
 
The ROI here is avoiding adding to the mounting disaster, NOT just saving a buck while Rome burns.

Most folks are not like you Bill.   I do envy you for stating your piece of mind while Rome is burning.
 
Typically folks if they custom build from scratch or subcontract to do a tear down they will leave it in the hands of the contractor relating to their heating and cooling and insulation stuff.
 
In order to meet the near future demands of using more energy in an alloted time frame we will probably have to go with nuclear energy as advances in alternative energy mechanisms are not even close to being efficient or ready to utilize.