Dual Zone HVAC benefits?

[Donald]

My home has a HVAC in attic for second floor and in crawl space for first floor. So along the lines of dual zone.

Some smart home systems have smart vent dampers that can control a vent damper to achieve a desired temp. No experience.

 

[Donald]

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.

The crawlspace dehumidifiers can be connected to the HVAC to remove humidity. Probably a lot cheaper in electricity if the goal is to remove humidity in the house.

 

[alarmguy]

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.

TO me dual zone is a must in a two story home and MUCH would prefer two units. Sounds like at that price it would be damper controlled two zone but better than nothing. What confuses me is why a concern with the basement?
I much prefer 1st and 2nd floor to have thermostats. Basement is the easiest to cool and can be regulated by adjusting the vents. Also have a stand alone dehumidifier would be a big plus and do a lot of the work.

Benefits are second floor AC would not be needed or can be set to a higher temperature than the first floor until night time. Having two separate units gives you a back up should one fail.

 

[alarmguy]

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

Yes, this is a big plus. Past house we recently sold was a 5 bedroom with master on the main.
Now that kids are gone, second floor just had our home office and my wife work office.
Second floor stat would be set to go up to 82 degrees at night and weekends when no one was up there.

IN winter first floor was gas heat and second floor heat pump. Since heat rises main floor stat did most heating during the winter using natural gas and second floor het pump would only kick on if needed. SO set back on the second floor when no one was up there would be 58 to 62 degrees. or so.

 

[Sequoiasoon]

What is the heating situation?

I have hot water baseboard and boiler. Basement is always warm and in summer hot even with doing an indirect water heater so it runs a lot less. I have a window unit that the kids run frequently down in basement.

I have a colonial with some poor insulation in different areas (kitchen mainly). House has t-stats on 1st and 2nd floor for heat for the baseboard. I have a 1 zone central air that does both floors which gets uneven. A couple years ago my old CAC died during covid, it was also very inefficient. When I finally got estimates to replace the CAC was more than a heat pump system due to incentives/rebates. I really wanted to replace with 2 systems due to old uneven cooling. That was too much money.

I ended up with a Bosch Heat pump setup, hooked up to old trunk/ducts. 2 speed air handler and 2 or multi-speed condenser. It is almost silent on low and still quiet on high. Heating is a bit noisier but still quiet, I hear the neighbors AC and not mine standing outside. The heat settings for HP is about 1-2 degrees higher than the t-stat for HWBB on 2nd floor. If really cold outside (below 20's) I set it about the same. When the HWBB turns on, the HP helps circulate the air, adds heat, warming things up quicker and a lot more evenly. The Bosch heat pump does heat down to I think 4F degrees. Other places now have arctic units.

For me when I got it the HP wasn't originally a thought. The cheaper cost and 0% finance made it a no brainer. When I looked I thought of the fact of having a backup heat source in case boiler went down. Having it now I'm very happy. Oil use is less, electric use is less, house is more comfortable summer and winter. The multi speed really helps eliminating humidity. PSEG also lowered my electric rate as now I am listed as having "electric heat". Wife's friend did the same system when her AC crapped out, first winter on multiple teen Fahrenheit days her boiler did fail and needed to be replaced. She was so happy she had the heat pump system and house stayed comfortable.

Wife is having hot flashes like crazy. The heat pump as AC is able to maintain 65F or colder on a 95F humid day.

2 systems would be best IMO, separate zones good, single works if that's what is there.

The potential savings of only cooling/heating what you need will pay back pretty quickly. I'll compare to old boiler in old house. It had a tankless coil and ran all the time so I had hot water. It died. We replaced with new Weil McLain boiler and indirect water heater. The fuel savings in gallons (and cost) paid for the new heating system in almost the first year when oil spiked up. Your saved energy costs from the multi- systems might take a couple years but after that all in your pocket savings.

 

[Quattro Pete]

What confuses me is why a concern with the basement?
I much prefer 1st and 2nd floor to have thermostats. Basement is the easiest to cool and can be regulated by adjusting the vents. Also have a stand alone dehumidifier would be a big plus and do a lot of the work.

Basement will be fully finished with 2 bedrooms, family rooms, and a bath, so it's really like another floor, but yes, I think I'd much rather prefer 1st and 2nd floors to have separate thermostats as well. The only thing I can think of why the builder is proposing basement to be on a separate thermostat is that it may be challenging to separate 1st and 2nd floors due to cathedral ceiling, but I'll ask him.

 

[alarmguy]

Basement will be fully finished with 2 bedrooms, family rooms, and a bath, so it's really like another floor, but yes, I think I'd much rather prefer 1st and 2nd floors to have separate thermostats as well. The only thing I can think of why the builder is proposing basement to be on a separate thermostat is that it may be challenging to separate 1st and 2nd floors due to cathedral ceiling, but I'll ask him.

Yeah, I figure there must be a reason.
Also your description changes the dynamics as to the use of the basement with those rooms. It might be preferable in this case to have a thermostat down in the basement. First and second floors to be regulated as you thought, adjusting the vents on each level. Cold air as you know sinks, hot air rises so dynamics will change by season.

I LOVE this stuff my entire life but just as a homeowner and some knowledge of systems, no formal education in it at all, just self educated.
I carefully regulated my homes and upgraded/found weak spots in insulation. But as a layman I was fanatical (as I suspect maybe you too) about proper temperature control among rooms and also energy efficiency.

 

[JHZR2]

Maybe I missed it - dual zone as in two different units, or just some fancy air control?

Multi zone hydronic is great. Especially with a mod con boiler.

I love the concept of multi zone air conditioning since it allows you to only cool part of the house at night for comfort.

 

[Donald]

Maybe I missed it - dual zone as in two different units, or just some fancy air control?

Multi zone hydronic is great. Especially with a mod con boiler.

I love the concept of multi zone air conditioning since it allows you to only cool part of the house at night for comfort.

Also great for houses like mine with master on 1st floor and only guest bedrooms on second. We only heat/cool second floor when we have guests otherwise it's set to only provide minimum heating and cooling.

If 1st floor HVAC broke we could at least sleep in heated or cooled rooms on second floor.

 

[alarmguy]

Also great for houses like mine with master on 1st floor and only guest bedrooms on second. We only heat/cool second floor when we have guests otherwise it's set to only provide minimum heating and cooling.

If 1st floor HVAC broke we could at least sleep in heated or cooled rooms on second floor.

This was exactly our situation in our last house that we lived in for 16 and recently sold. Great set up

 

[Donald]

This was exactly our situation in our last house that we lived in for 16 and recently sold. Great set up

You can also "break" second floor HVAC if guests overstay their welcome!!

 

[Quattro Pete]

Maybe I missed it - dual zone as in two different units, or just some fancy air control?

Single unit, plus additional bulkheading to redistribute air differently.

 

[KrisZ]

Don’t think so would make the basement a separate zone. Zoning works best for the first and second floors. The basement can be on the first floors thermostat IMO.

I had two zone system in my house in California and now in Texas. It is just electric dampers and a separate zone control board, I have one air handler and one AC unit. It works very well in my case.

Edit:
As for the $3600 extra, I think that’s in the extra ductwork. The dampers and the control board aren’t expensive, around $100 each.

 

[zzyzzx]

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?

Yes. But that assumes that you have proper runs and vents to begin with. The whole "dual zone" is more of a marketing thing anyway. A window AC unit in an upstairs bedroom accomplishes the same thing for a fraction of the price.

 

[Donald]

I think most HVAC systems are far from installed perfectly. Even when done by a good HVAC company?

Flex duct pushed into non round with a dent by a gas pipe beneath

Flex duct support webbing bunched up so it acts more like piece of rope than a web. Same issue as gas pipe.

Sealing of the duct work.

Does any HVAC company put a thermometer in every room in the house with all interior doors open and try and get the temp in every room the same?

 

[BrendanC]

my house has a 3 and 3.5 ton ac. the 3.5 ton handles downstairs and the 3 ton handles upstairs. during the day the downstairs is set at 78 while upstairs is set at 80. at night this changes to 73 down and 78 upstairs.

2800sqf built in 1978 living in houston texas. needs blown in insulation but has radiant barrier.

we average 35KWH per day. i couldn’t imagine what it would be with a single 5 ton having to cool upstairs all day. i believe all two story homes should be atleast 2 seperate systems. i will be installing a mini split on the master bedroom and our office (we both work from home twice a week) to further save on energy usage down the road.

 

[Donald]

my house has a 3 and 3.5 ton ac. the 3.5 ton handles downstairs and the 3 ton handles upstairs. during the day the downstairs is set at 78 while upstairs is set at 80. at night this changes to 73 down and 78 upstairs.

2800sqf built in 1978 living in houston texas. needs blown in insulation but has radiant barrier.

we average 35KWH per day. i couldn’t imagine what it would be with a single 5 ton having to cool upstairs all day. i believe all two story homes should be atleast 2 seperate systems. i will be installing a mini split on the master bedroom and our office (we both work from home twice a week) to further save on energy usage down the road.

How many compressors do you want to have outside? For me two is enough.

 

[BrendanC]

How many compressors do you want to have outside? For me two is enough.

considering the upstairs unit in this house is over 20 years old, i have no qualms about placing 2 mini splits on the house.

 

[tbm5690]

Yes. But that assumes that you have proper runs and vents to begin with. The whole "dual zone" is more of a marketing thing anyway. A window AC unit in an upstairs bedroom accomplishes the same thing for a fraction of the price.

Most people don't want tacky A/C units hanging out of the window, and some windows don't accommodate them well either.

Dual zone is used primarily for heating here, and having the basement in larger homes with its own zone is useful to fight the naturally colder temps as opposed to the above grade floors.

 

[BMWTurboDzl]

Most people don't want tacky A/C units hanging out of the window, and some windows don't accommodate them well either.

Dual zone is used primarily for heating here, and having the basement in larger homes with its own zone is useful to fight the naturally colder temps as opposed to the above grade floors.

Not to mention that window units use a ton of power.