Zoning v. mini-split

[dal2dal]

I recently added a 400 sq ft room addition (basically a really big sunroom with windows on 3 sides and a cathedral type ceiling -- 4th wall is against my garage.) I've been told that my AC / Furnace can handle the extra space, but the duct work can't and therefore the room is typically 5-10 degrees off the rest of the house (too hot in summer and too cold in winter.) As a point of refernece, it's a 2,600 sq ft ranch house on a slab. The thermostat is on the opposite end of the house from the room addition as is the furnace which is up in the attic.

My current furnace / AC have another 10-15 years on them and I've been told the solution to making the room addition more comfortable is to either zone the house (3 zones) or add a mini-split ductless system.

I've gotten 4 estimates, and 2 of them are really pushing the mini-split. One of the other two told me that the mini-splits weren't really up to code anymore nor do they meet government standards and that they are probably being pushed in order to get rid of existing inventory.

Not sure who to believe as all four estimates / recommendations have come from reliable (no BBB complaints and recommended by friends) companies.

Any advice would be appreciated in regards to the code/standard issue on the ductless system, and which option would be better from an energy efficiency / best investment / keeping the room comfortable perspective?

Many thanks for your help,

Bob

[johnsp]

If your current HVAC system is working well for the rest of the house, why mess with it. I don't think all the mini-split makers are gonna drop out of the market. I also don't think the new SEER requirements apply to them. Anyway they have 13+ SEER units available, they just cost more.

The sunroom has different heating /cooling requirements then house. A mini-split is a great solution for a single room add-on.

[xandair]

is you current furnace/ac going to be able to handle ALL the load?? Did any of your contracters load out house w/ new addition??. Can you get duckwork to new addition?? Mini-splits are just ok, i have had decent luck with some, not so good with others.

[dal2dal]

There's duct work already running to the sunroom, but all the contractor did was cut into the main ductwork for the central part of the house and run it to the sunroom. I've been told the furnace (5 ton Trane) and AC (3.5 ton Trane) can handle the load, it's just that the ductwork for the central part of the house is too small to handle the addition as well.

I have no idea what the original contractor did as I finally had to hire a lawyer to fire them 8 months into the project (long story, bad ending.)

I work from home and spend 80% of the day / evening in the room addition as it's my office and family room.

The quotes I've received are only about $800 difference between 2 ton mini-split and 3 zone damper system.

Xandair -- What kind of problems have you had with the mini-splits and did the units provide both heating and cooling?

[johnsp]

if the ductwork can't deliver the air, what's a damper system going to do for you? Try to make another part of the house suffer to force more air to the sun room? Spending for a solution that might not work doesn't sound like a solution to me.

[dal2dal]

With the 3 zone system, they would redo the ductwork, running new ductwork to the room addition as well as fixing any problems with the old duct work, i.e. missing insulation, gaps, etc. The would also upgrade the filter to a media filter.

[xandair]

without doing an actuall load on the room and the house its hard to say what you really need. in a room like that you will need some pretty serious cfm to keep room comforatble. I think in your situation a mini-split will be the way to go. I will not bash any companies splits, but do with reputable manufacture ie. Samsung, Mits, and take a look at Union Air also. If you will be heating and cooling, conside the heating element built in, as the heating capeablities will be good down to about 15 deg. f ( with low amb. ). I think most come with a remote but to me that would be handy as well ( some mount near ceiling ). If you go the zone route make sure the contractor does a load, and why can your existing furnace handle this addition??? is this something you planned for, or was it just that much oversized??????

[airworx]

9 out of 10 contractors will say not to zone.
9 out of 10 dont understand the basics of zoning they undestand the basics of keep it simple never learn and never get the facts kinda like pour bleach down the drain. heat pumps are made for the dessert, there no hell. get it.
zoning works, it will keep your you utilities lower, service and repair bills lower. we install them all the time and get nothing but thanks and more thanks.
now if this was industrial heavy commercial the system would already be zoned, they been doing it for years and its still done but residential contractors are leary because they dont have the knowledge of this technlogy

[xandair]

if done right no doubt zoning will be better, but at what cost?? i am in mn, so the furmace/ac in the attic is not really my thing. if it is only $800 more i say zone all the way. But to take down existing, add 3 zones worth duct, dampers, stats,and im sure you must wrap all duct, wire it all, control board, fix sheet rock from existing, i would double check my bid to see if all these issues are addresed. Both will work fine if sized, and installed correctely.

[BobbyBJr]

Xandair is right, either way properly sized and installed will work fine. When I built a 600 sq ft addition to the back of my house, my load calc told me that my present downstairs unit would heat and cool it fine, so I installed a Carrier 2 zone controller with dampers and such. Basically, my unit switches from one zone to the other and does a good job. I did look at installing a mini split, but was worried about getting the throw of the air all the way across the room without using two air handlers. That idea ran the price up, so I zoned it and it has worked fine.

Bobby

[odcman]

I'd put in a good quality duct fan with a thermostat to that room. That will allow you to get the temp you want, when you want and keep just minimal flow when its unoccupied. Fantech makes duct facns for rectangular and circular ducts that fit the bill. I used one to boost the flow to our upstairs in our old house and it worked like a charm on it's own setback thermostat.

[airworx]

thats funny.

[firecontrol]

My vote goes with the zoning. I would go with the contractor that supplies you with references of other zoning jobs he's done where the people you call say "Job well done, totally satisfied". Get a contract that spells out specifically what you expect for comfort throughout the house when all is done.

One quick (less than scientific) way to find out if your system has got a chance of handling everything is to turn the main blower of the furnace to constant on for a day or so and see if the sunroom temps even out with the rest of the house.

[xandair]

DUCT FAN ?????, that is funny

[ttstrutt]

Duct fans are for dumbies who cannot size a duct system properly.

It sounds like someone just connected a duct in the closest and easiest spot in the existing duct system, instead of actually checking the duct system to possibly find an area in the ducts that could provide enough air without robbing to much air from one or two rooms.

If the system can handle the additional load, but the ducts cannot then there should have been problems with insufficient air previously.

[totalcomfortservices]

I'd go with the mini split if I had the $$$$. Though zoning is a great choice when installed correctly, you can't beat the quietness of a mini split. Keep in mind that with zoning, when the addition is the ONLY zone calling, you will be trying to force ALL of the air into that zone therefore increasing the air VELOCITY which is NOISE. The you will have to set up a bypass damper to alleviate that...Then setup...discharge air sensor....blah blah blah... Mini splits are remote controlled too. I think their pretty cool....Check out http://www.mrslim.com

As for a duct booster fan.... who came up with the genius thought that if the system is already moving all of the air that it could through a duct, that it could be further increased by a low torque, 1/25 motor??? haha the duct fan is more of an impedance to air flow than anything... And why take away air from the rest of the house??? Do you turn off a light in the house before you turn another one on?

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[Edited by Jultzya on 02-27-2006 at 09:25 AM]

[referguy64]

3.5 tons of air sounds a little light for 2600 sq ft living space in which 400 of that could double as a solar gain experiment. mini split is for you.

[wyounger]

I'm usually a fan of zoning, but this isn't the greatest application for it, especially as a retrofit on an existing system. Sun rooms are tough because they are so different from the rest of the house in terms of solar load and insulation (the insulation value of a cutting edge high-tech window still can't touch that of a basic insulated 2x4 stud wall).

There's nothing wrong with mini-splits. They're quiet and efficient. In this type of application I generally recommend either a mini-split or a PTAC/PTHP (the through-the-wall units you see in most every American motel room). The latter isn't as quiet, efficient, or elegant as a minisplit, but they are cheap in comparison.