Fact or Myth? #HVAC #Zonecontrol can save energy

First of all, if you are not familiar with HVAC Zoning (Zone control) for your home you can click here and learn more about how it works.

Sometimes, zoning is pitched as a device that can be added to your current HVAC system that will "save you energy" because you are able to turn "off" heating and cooling to areas that are not being used.  Sounds good, right?  Well...there a "but."  This as actually a highly debated or more aptly put... highly contested claim among HVAC professionals.

The simple fact is that it isn't a simple answer but the simplest version is:  HVAC Zoning CAN save energy in some applications.

Not all applications of zoning are intended to save energy, some are set up to optimize comfort.  In these situations, energy savings may not the top priority but it can still be set up to help save energy when the comfort is not in demand.

Zoning puts the control in the hands of the user (homeowner) via the thermostats.  These thermostats can be set to optimize energy savings or comfort... or, most likely, somewhere in between.

Some believe the primary purpose of zoning is comfort & I would agree, but, SmartZone can be used in some applications to save energy by reducing necessary run-time.

As far as I have found there have been very few and NO independent studies on the energy savings capabilities of hvac zone control but I have personally been in the industry for 14 years and I believe I know why.  Every test I have seen is try to prove some % of energy savings and yet there is a flaw with even the question that is being asked.  The problem with this question is that it is looking for an automatic percentage saving when zoning is installed.  I think this gets to the heart of why the professionals that dispute zone control's ability to "save energy" do so. 

This is an IMPORTANT NOTE:  HVAC Zone Control by itself will NOT save energy.  However, it CAN be used to save energy.

A proper study to prove that zone control CAN save energy would be straight-forward.   Two identical houses with identical hvac systems, one with a 2 zone system & the other with a single thermostat.  On the house with zoning, set one thermostat to OFF 12 hours per day and the other thermostat to run a normal 24hr / 7 day schedule.  The thermostat schedule should be the same as the 24hr / 7 day schedule in the house with only one thermostat.  This study would show that zoning can save energy if used in certain ways.

SmartZone has been around since 2004 and we have over 200,000 installed in the field.  We have seen direct feedback that empirically shows energy savings, not just in isolated cases but in extremely high volume.  First hand, real-world experience shows that it can be done, but it also shows that in cases where comfort is the priority... energy savings isn't a guarantee with zone control.

Check out SmartZone at ZoningSupply.com

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Honest discussion on homeenergypros about zoning advantages.

Are Zoned Heating/Cooling Systems a Good or Bad Idea?

Excerpt from homeenergypros discussion about HVAC Zone controls.

QUESTION by Jon LaMonte

For starters, I live in Atlanta, Ga and I am not an HVAC pro so this is a serious question that I would like answered for one of my clients.  I understand the premise of a zoned system and on the surface, it sounds like a good idea. Then I considered the fact that I have always told my customers that it is a bad idea to close off vents in rooms they are not in because of duct leakage.  Also, the second law of thermodynamics simply states the hot goes to cold, so now the unheated areas are doing their best to rob warm air from the heated areas.  Finally, if your zoning a single system, aren't you creating on oversizing issue because the unit (that was probably oversized in the first place) is now servicing a smaller area than what it was designed for?

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Reply1 by Chris Heenan

Zoning has benefits beyond temp control. Most often the home does not require the full 2 stage heat or cooling as the system only needs to satisfy a portion of the home. So, then if 1/2 the heated air goes through a properly sized and balance bypass, the return air (from home) will mix with warm supply (from bypass) before going thru the system again. You may not need to go beyond 1stage heat (or cool) except in extremes. This is most beneficial in raising supply temps from heat pumps when in winter mode. Most supply vents feel 'cool' to homeowner. Not so when zoned and not call on all zones.

Flip it to cool, and the bypass send dehumidified cooler air across the coil. Decreasing high side pressures and amp draw of compressor. Then the air gets more heat extracted and further dehumidified. Pulling out additional condensate and running less. Remember systems have to be careful not to oversize as dehumidification is crucial to comfort. Dry and cool temps out supply vent. Not too shabby.

Reply2 by dale conner

Zone sytems are rarely installed properly but can be efficient if properly designed. The goal is to be able to set back the temperature a few degrees in a zone that isnt being utilized while keeping another zone comfortable that is being utilized.  A single unit with a zone system will have a by-pass duct sytem to dump the air thats been cut off from one zone back into the duct system to be used in the zone that is being used.

*Reply3 by James Jackson on

Have you ever been driving down the interstate hwy and come up on an exit ramp that has traffic backed up? As the traffic backs up and eventually fills the exit with cars you end up with a slight back up on the entire highway. this is the closest scenario i have been able to come up to help people understand why closing doors and vents is a bad idea. if you have a run off of a main trunk and you close the outlet or register you will cause the air to back up into the trunk causing turbulence in the trunk line resulting in a decrease in air flow in other areas on the system. this can also cause multiple other problems like pulsing and excessive noise from the increase in pressure.

another thing to remember when you shut doors in a home with no return air you cause a difference in pressure in the home. The room you have closed is now significantly positively pressurized and the house is now under a negative pressure. This why some homes have the doors undercut by 3-4 inches trying to allow the air to get back to the return.

Ok as far as the zone system goes... There is so much more thought involved in properly setting up a quality zone system that i see very few done correctly. If you want to do one correctly you first need to make sure you are using a multi-stage HVAC unit so the unit can run on low speed if it is only conditioning one zone. A bypass or crossover duct with a barometric damper is needed if you are conditioning a small zone and the air handler is still supplying too much air, but if you are going the zone route don’t use contractor grade units and piece it together with a simple zone controller. Get a high efficiency v speed unit that is designed for this application.

But what happens when you change the temps in a zone in the house 4-5 degrees?? Energy moves from hot to cold so you end up indirectly heating or cooling the entire space regardless. This brings us to another scenario. The return air in the zone that is off. My experience with working on correcting issues with homes using zone systems has been the returns are never dampered so if the zone is completely shut off you have just installed a permanent blower door. if the zone is off one you are returning hotter or colder air to the system and two you are causing that zone to have a negative pressure.

Just some things to think about !!

Learn more at www.zoningsupply.com

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BETTER with Zoning done right!

Single thermostat can have issues

My editorial conclusion:
Zoning CAN be effective if and ONLY if it's designed and installed properly.  This means ducts, dampers, equipment size (tons).  It also means the right zone panel setup with energy saving features like SmartZone.  Finally, to make zoning work best and comfort control and energy savings, the home owner must properly control the thermostats.  Zoning isn't a "set-it-and-forget-it" system, it must be managed to be effective.  More articles about zoning

See full discussion: http://homeenergypros.lbl.gov/group/hvac/forum/topic/show?id=6069565%3ATopic%3A7207