Can a old HVAC system be zoned? (floor, how much, furnace)

[rubytue]

We need a new a/c. I don't know if it will happen this summer, but within the next year. I keep hearing about zoned systems, and it sound like what we really need. We have a 40-year-old split-foyer (bi-level) home. Needless to say, its 10-15 degrees warmer upstairs than downstairs. Since upstairs in our main living level, this is very frustrating.

My husband is convinced this can't be done with the ductwork we have. Our HVAC (oil furnace + a/c) is in the garage on the lower level. There is one main duct that runs down the middle of the house and everything branches off this. Upstairs the vents are in the floor, downstairs they are in the ceiling. Can this be zoned? I think it can be done with fans and dampers (husband disagrees). If I am right, the main duct run is in a finished ceiling (main trunk is in a bozed in chase below the joists but the branches run in the ceiling) - how much drywall work am I looking at?

Thanks!

[M3 Mitch]

Might be easier and more practical to get a largish window unit air conditioner or heat pump, put it in a North-facing window if possible. Depending on the age/condition of your central AC unit it may be cheaper to run, give better value in terms of BTU's removed from the house per dollar spent. Consumer Reports has a recent issue with some window unit A/C's rated.

One thing you didn't mention is the *intake* to the central A/C. Where is it? Probably it pre-dates the central A/C and is somewhere low on the floor of the lower level. If you can find a practical way to modify it so it takes a suction from the upstairs ceiling while using the A/C (probably you'll have to manually open the new, upstairs intake in spring, shutting the downstairs intake, and the reverse in the fall).

You can look in various catalogs and find in-duct fans, etc. that can help you boost the flow of cool air to the upstairs. What's not clear without looking at the system is if these sort of things will make a practical difference in your particular situation. Remember it's better to boost air flow than to shut dampers and reduce it, from the standpoint of efficiency. These in-duct fans can probably be installed without any drywall work. I personally like the stuff in the "Improvements" catalog, and/or Plow and Hearth.

But, definitely think about the window unit(s). This will for certain work.

[rubytue]

Intake? Like return vents? We have two, one upstairs and one downstairs. However, neither one is truly ducted. Both are just vents in the wall and rely on the studs and drywall to funnel the air. The basement wall is currently opened up, and I want to duct that return (I'm sure the fact the wall is open and that the basement return is pulling from the ceiling of the basement isn't helping our efficiency right now - LOL). However, it never occurred to me we should chance the intakes for the seasons.

I realize from an efficiency standpoint, window units have their advantage. But I hate them. Mostly b/c they are too noisy for me to sleep, but the ugliness factor does contribute to my hatred. I've lived with them before, but would prefer not to.

One more thing - you mentioned heat pumps. We are just a bit too far north for a heat pump. They can and are done in this general area - in fact, our last house had one. But the electric bill was out of the world in Jan and Feb. I guess I could go with a heat pump with an oil supplement (gas is not available here without a tank). FWIW, we only went through about 575 gallons of oil over the past year (oil hot water heater, too), but it was a mild winter and we keep it cool.

[Donn2390]

If you want a real zoned system, here is the answer...
Home Comfort Zones | MyTemp | Overview (http://www.homecomfortzones.com/mytemp.htm?gclid=CKiEyauQ3JMCFQwxiQodc04EZQ - broken link)
They can zone it from room to room, by installing valves in the duct work to each room, so the heat or A/C is only on in the room you are in at the time.... not the rest of the house.
We saw it in a new model home, so I called for a demonstration. It's a fantastic system, but they wanted more money than I was willing to spend. Better for new construction.
I know you weren't talking about anything this space age, but it's interesting to know about new, trick stuff now available

[sunsprit]

Why not get a BID for a "zoned system" from a local HVAC professional?

At least you'll have someone who knows the products and possible configurations that can be done to your options in your house instead of guessing at what might be possible.

Most contractors would be happy to provide such a BID without any obligation on your part.

[rubytue]

Because...
(a) I'm just doing research now
(b) I'm 6-12 months out
(c) I don't want to waste their time when I am 6-12 months out
(d) I like to have a clue what I am talking about when they do come give a BID
(e) When we have gotten BIDs for work before, its 50/50 if they show up, 50/50 if they are honest, 50/50 is they charge for the BID
(f) The wonderful users of city-data have always been good about helping out and providing information, even guesses, before.

FYI - My husband is in the trades. I know how bids and estimates work. Get at least 3 estimates, yada yada. But, I prefer to go into the bid/estimate process knowing what I am asking for. I prefer being an informed consumer.

[Mikieo415]

I am in the hvac trade. Scrap the zoning idea. It will cost too much money and is not practical for your application, if it can even be done. The wall cavity return is perfectly acceptable, but I would attach the return outlet directly to the furnace and make sure all rooms have a way to get the hot air to the return, whether through a grille in the door or leave doors open. Use cieling fans on the upper levels. Cold air sinks and will stay down if you don't move it around. You will not have a well balanced house because of the way it is designed, but you can make the best of what you have.

[crazyma]

Go ahead and get some bids from reputable companies even if you are several months out.
Someone good can explain various pros and cons to either type of system, what would work best for your situation and pocketbook. You will gain a better understanding by having it explained in person on the actual site. Consider it research.
IMO

[E.R.A.]

I would get someone to see if it's even possible for a zone system. Dampers, fans, etc. are just cheezy, and if you can do that, you can zone it. As for the system we always recamend a system with a variable speed blower in it. Split level with one system is not good, but you can make it good with a 2 stage system with zoning.

[cerequas]

I am also in a split level as follows:
2200 sq ft total
Gased forced air furnace and central a/c

1st level is halfway below grade on slab with family room, 1/2 bath; and laundry room where the HVAC equipment is also.

2nd level is main living area: kitchen, dining room, living room

3rd level: 3 bedrooms, 2 baths

4th level: large finished attic room.

Current system is only 1 zone with thermostat on level 2.

So level 1 is too hot in winter and too cold in summer.

Level 4 (attic room) needs a window air conditioner march - oct.

I also hate window air conditioners, way too noisy.

Just had 2 HVAC companies out to give me estimates. Both are about the same price
The first company says we do seem to have good ductwork, sized right, insulated right.
So that's one thing in our favor. He is also coming back tomorrow for a more thorough analysis.

Both are recommending a new 95% effciency furnace and new central a/c.
(Our current compressor sounds like a jet airplane when its running and I am sensitive to noise)

Here is where they differ. First guy wants to also add a zone system with 3 zones:
one each for levels 1,2,3 as I descibed above. And yes variable speed blower and 2 stage furnace and central a/c.

2nd guy is concerened that zoning wouldn't work as well. So he is suggestioning new 95% furnace, since he thinks our existing furnace is 80% efficient or less and that is why level 1 is too hot, since the furnace is radiating out the wasted heat instead of putting it in the ducts where it belongs.

And then he suggests 2 new central a/c systems. One replacing the existing central a/c for levels 1 and 2 with the existing themostat on level 2. The 2nd new central a/c system would go in the empty attic area over the 3 bedrooms with its own new ductwork and vents to the 3 bedrooms and level 4 (finished attic), and its own themostat on level 3. This should then also do a good job of cooling the funished attic which is important to me.

This way in the summer we could set the thermostat on level 2 to a higher temp (so level 1 would also not be too cold). And the thermostat on level 3 to a cooler temp to make the bedrooms and finsihed attic more comfortable (levels 3 and 4).

Any opionions on which general direction we shoud go in?


Thanks!
Jennifer C