Dual Zone HVAC benefits?

[Quattro Pete]

As I understand it, main benefit of dual zone HVAC is that I could have a separate thermostat in say my basement vs. main and 2nd floor. But couldn't I somewhat achieve similar results just by manually adjusting vent flaps around the house to direct more or less air to certain parts of the house? Of course, that would be more hassle.

Are there other major benefits of dual zone HVAC that I should consider? The builder I'm working with wants an extra $3,600 to upgrade from single zone to dual zone, so I'm just trying to weigh in pros and cons.

 

[benjamming]

I'm not aware of anything close to being able to justify a fraction of that cost with dual zone.

 

[tbm5690]

I'm not aware of anything close to being able to justify a fraction of that cost with dual zone.

I disagree.

OP - if in your particular home you have considerable variation in temperature between your proposed "zones" then that sounds like a deal to me for comfort and, over time, efficiency gains. Motorized valves located closer to the air handler output mean that you aren't sending air individually to each register still like you would by just closing vents. Inevitably, if you closed all vents in one zone there is still leakage and the efficiency of the system to heat/cool the desired zone is reduced as opposed to a proper damper that directs all air flow only to where you want it.

 

[Quattro Pete]

OP - if in your particular home you have considerable variation in temperature between your proposed "zones"

Hard to tell since the home hasn't been built yet. Granted, the basement will be 3/4 below ground, so I would expect it to stay much cooler during summers compared to the "zones" that are above ground. Also, during winter, the basement will not need to be heated much, except maybe when we have guests/family visiting and actually spending considerable amount of time in it.

 

[thastinger]

we are doing dual zone in the house presently under construction because the upstairs bedrooms will be occupied only part time.

 

[UncleDave]

As I understand it, main benefit of dual zone HVAC is that I could have a separate thermostat in say my basement vs. main and 2nd floor. But couldn't I somewhat achieve similar results just by manually adjusting vent flaps around the house to direct more or less air to certain parts of the house? Of course, that would be more hassle.

Are there other major benefits of dual zone HVAC that I should consider? The builder I'm working with wants an extra $3,600 to upgrade from single zone to dual zone, so I'm just trying to weigh in pros and cons.

The real benefit is hands off accurate temp control of a given area without affecting the others.

IS this worth 3600 - only you can say.

It is for me as I have frequent international guests that reside on a second floor that has a completely different thermal profile than the ground floor on a 100+ degree day.

My parents are also sensitive to temp - preferring it basically freezing to the point of walking around in the summer with coat and long pants on. (?!??!? I know)

If it were just the wife and I - I probably wouldn't do it.

 

[BMWTurboDzl]

As I understand it, main benefit of dual zone HVAC is that I could have a separate thermostat in say my basement vs. main and 2nd floor. But couldn't I somewhat achieve similar results just by manually adjusting vent flaps around the house to direct more or less air to certain parts of the house? Of course, that would be more hassle.

Are there other major benefits of dual zone HVAC that I should consider? The builder I'm working with wants an extra $3,600 to upgrade from single zone to dual zone, so I'm just trying to weigh in pros and cons.

Yes you could but you'd be running from floor to floor to adjust the dampers. We have a 3-zoned system and it was not commissioned correctly.

The zones must be balanced which means each damper must remain partially open to bleed off excess air from the zone which is "calling" for heating/cooling. This has to be done because your system is going to be sized for the entire house.

Our system was not set up this way. The dampers are fully closed and they instead installed a by-pass duct which routes excessive air back into the air handler. The duct was entirely too short and it helped kill off our AC compressor (our evap coil didn't have a TXV but that's another story). These systems should never have a by-pass duct. Our system has a single stage blower and AC compressor so it's very crude. Newer systems with multi-stage blowers/compressor would do a better job.

I don't know how the systems are designed today but our dampers are inside flex duct just on the exterior of the plenum. Any work on the dampers requires cutting into the flex duct.

Now our equipment (Honeywell) has never had to be replaced. It's original (24 yrs old).

Here's a link of a guy in GA who does HVAC design nationwide. I would have someone design the system rather than rely on a HVAC company who has been eyeballing these systems for decades.

https://www.energyvanguard.com/blog/to-zone-or-not-to-zone-and-how/

 

[edyvw]

Hard to tell since the home hasn't been built yet. Granted, the basement will be 3/4 below ground, so I would expect it to stay much cooler during summers compared to the "zones" that are above ground. Also, during winter, the basement will not need to be heated much, except maybe when we have guests/family visiting and actually spending considerable amount of time in it.

Don't even think! GO WITH IT!
I have a dual HVAC, one for the basement, and another one (this one includes AC) for the first and second floors.
Temperature variations are serious issues, and if you have a single zone, you will have to either overheat or overcool some zones. And IT WILL have an impact on your wallet. $3,600 is wise investment in this case!
If zoning can address this, good. If not, I would go two separate HVAC unites, one in basement without AC.

 

[MyWifesBoyfriend]

Worth it from the comfort perspective alone, but it really has to be properly designed. We don't have dual zone and our ground floor is significantly colder than our second floor during cooling season, even with all of the vents shut. But this is a 1980's house built with no cooling in mind, so there are lots of variables involved.

 

[wwillson]

Are there other major benefits of dual zone HVAC that I should consider?

We just put our 2nd floor in its own zone with a new mini-split. The 2nd floor was hot in the summer, so hot that it was hard to sleep. The first floor was just right and the basement was frigid. The A/C ran pretty much all the time during hot summer days.

Now the second floor is always just right. The new mini-split is uses about 1/2 of the power that the old whole house A/C uses, so we leave the doors open on the second floor so the cool air can flow down to the first floor. Both the second floor and the first floor stay at about the perfect temperature. There are 100F days that the first floor A/C will run some, but rarely. The basement doesn't get cold.

Our electricity cost easily went down by $75/mo and each level of the house is the correct temperature. Dual zoning for us was a total win.

 

[PWMDMD]

I have a two floor + partially finished basement 3600 sqft house in central MA with central AC on the first and second floors and oil baseboards in the basement, first, and second floors. In 10 years I have never turned the heat on in the basement (boiler is down there so that does produce some heat) and it's never been less than 67F (even when it was -5F) and there is no AC down there and it has never been more than 72-73F down there during the summer even when it's 95F outside. Basement is fully buried so there is that but I'd really stop and think about how fancy you need to get with heating and cooling the basement.

 

[RhondaHonda]

That seems cheap. Is this electronic damper controlled or a second system? Either way, do it.

I have 4 separate systems for different areas and wouldn’t have it any other way. We cool the master bedroom down a lot on the main floor at night which I’m not even sure would be possible with one system. Basement is not zoned separately but stays very comfortable (within a degree or three of the main floor zones above it).

 

[benjamming]

I disagree.

OP - if in your particular home you have considerable variation in temperature between your proposed "zones" then that sounds like a deal to me for comfort and, over time, efficiency gains. Motorized valves located closer to the air handler output mean that you aren't sending air individually to each register still like you would by just closing vents. Inevitably, if you closed all vents in one zone there is still leakage and the efficiency of the system to heat/cool the desired zone is reduced as opposed to a proper damper that directs all air flow only to where you want it.

My comment was in view of the thousands of dollars & wasted time & frustration from the system being unreliable & not working correctly due to HVAC companies rarely getting this right, at least in this neck of the woods.

 

[Leo99]

I have dual zone for the main floor and second floor. The basement is unregulated and stays pretty cool in summer and not too cold in winter.

 

[Leo99]

My comment was in view of the thousands of dollars & wasted time & frustration from the system being unreliable & not working correctly due to HVAC companies rarely getting this right, at least in this neck of the woods.

I have two totally separate units. A larger one for downstairs and a smaller one for upstairs. Or is it vice versa. I forget. I haven't decided if it's best to close all the doors upstairs to isolate the systems or open the bedroom doors and let the two systems blend together.

 

[fsdork]

If done with separate units, redundancy would justify a few grand to me. This assumes there isn't already a supplemental heat source like a wood stove.

 

[Rand]

I would only do it if the dual zone is separate hvac and for upper floor.
that way your AC isnt always running in summer just to cool upper floor.

But I'm not a pro.

 

[RhondaHonda]

The redundancy of a second system is great. If one system dies you aren’t at the mercy of a high-pressure HVAC salesman when you are sweating or freezing in your house. The second system can keep the house livable and let you get more quotes and explore your options.

 

[MyWifesBoyfriend]

While you're at it, get return vents in each bedroom

 

[skyactiv]

Get a variable speed air conditioner if you can afford it, or at least a 2 stage. Carrier has one that varies from 25-100% and can pull much more humidity out of the home than a single stage unit.