Recently I asked about zoning our new home. It will be ~3200 s.f. and most of our living areas will face the south (we live in s.e. Michigan – winters aren’t “too” bad here). The only tricky thing is that we’ll have a bonus room over our garage, it will be about 25′ x 12′. A good friend of mine just finished a 2800 s.f. home w/same bonus room over garage set up and he installed TWO furances. A regular one in the basement to heat/cool the 1st floor and a second one (very small one apparently) tucked in the attic near the bonus room, that one heats/cools the 2nd floor. He said he chose this over zoning because a) the cost for the second unit was not that much more than zoning and b) he’s heard that when the “baffles” in a zoned unit go bad it’s a real headache – hence expense – to repair.
Thoughts?
– Rob
Replies
Down here in Texas we don't have heating issues (well, we do, but only for a week), however, multiple a/c units are very common. Usually found in two story houses, but sometimes in spread out ranches. Works well.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
The house we bought to renovate was previously converted to an up-down duplex. It is a 2-1/2 story, and there is one high efficiency gas furnace in the basement to heat the first floor, and another in the 3rd floor attic dormer to heat the second and third floors. We have a pocket door on the first-second stairwell to seal off the floors. I really like it. We basically only heat the floor we are using at the time, and we have a backup furnace in case one goes bad in the winter. Another advantage/disadvantage, is that you could get by with a smaller central AC unit if you chose to only cool one of the zones.
The only drawback in our arrangement is that they had to cut additional holes in the hardwood floors since the furnace was now supplying air to only one floor. But those old unused ducts from the basement sure made it easy to pull new wires. ;-)
I have a similar situation. I have a Hydro-Air system. One boiler in the house provides heat for two air handlers, one in the basement for the first floor and one in the attic for the second floor.
I also have 2 compressors for AC. One for each air handler.
When we built our house the first floor was finished years before the second. When the babies came along and we needed the 2nd floor we simply put the second (smaller) air handler in the attic.
" b) he's heard that when the "baffles" in a zoned unit go bad it's a real headache - hence expense - to repair."
It uses a motorized dampner and control logic. Need to make sure that it is accesible and also that the person working on it understands how it works.
But I see on basic problem with using a zoned system for the bonus room. As I read you message, which migh not truely indicate the overall conditions, you have one area of 3200 sq ft that has common climatic/thermo characteristics and 300 sq ft that has different ones.
That is a way too unbalacned difference for the system. Would probably require multi-stage equipment. That cost and the cost of the dampner/controller would likely approach that of a 2nd system.
However, I wonder if there aren't other "climates" in the main space that would be better controled with a zoned system; ie rooms with lots of activity and lots of windows vs rooms with low activity and few windows.
In that case you might end up with 3,4 or 5 zones including the bonus room.
Or you might end up with 2 systems just for the main space. And the bonus room might be zoned off of one of those or a 3rd systme.
One type of system to look at for the bonus room would be a Split-ductless heat pump. Now I don't know how much of the time that the resistive heat would be on or how much you would use that room. BUt it makes for a simple installation without any duct work and ideal for a small standalone area like this.
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BTW, what is a BONUS ROOM.
Is that where if you are good clients and the builder has a good year that he builds this extra room at no cost?
I have always tried to figure that out.
I know what an employee bonus. You agree to work for a salary and at the end if the year if the your and/or the company made their goals you would get a bonus over and above the orginal agreed on salary.
Does a bonus room in a new house work the same way?
Good info, thanks guys. I see I need to look into this more seriously. Right along with windows, flooring, cabinetry, etc. I'm starting to see why some people like buying cookie-cutter homes vs. custom. Thank God my wife stays home to tackle 80% of this stuff.
Do you happen to have a link to any info on this split-ductless heat pump?
Thanks, Rob
If you do a google on ductless split heat pumps you will get all kinds of hit.
Of course they are also available in AC only units and you might want to look at using a direct vent gas heater. You can get them in wall units or get then as fireplaces with remote controls and thermostat.
Our southern MN split entry (bottom floor half-buried) has two furnaces. They're side-by-side in the downstairs utility room -- one is an updraft unit feeding the top floor and the other a counterflow unit that feeds transite ducts in the bottom floor. (Yep, transite, so we get asbestos AND radon, but that's a separate issue.)
This has worked out fairly well. In this part of the country it's nice to have a "backup" when one furnace goes down (which has happened from time to time over the past 28 years), and as it works out in this case we only need AC on the upper floor's furnace. (Also have the humidifier only on the top-floor furnace.) The biggest negative is simply the additional space that all this takes up in a relatively small utility room. From a control standpoint it's much simpler than a single furnace with dampers.
Dan
That is so weird.
My house is also 2 stories, with the bottom walkout (I am on a hillside) ans have 2 drsastically different "climates" so I have 2 furnaces in a utility closet, one down draft and and one up.
And only AC on the upstairs.
The main differences is that I have metal ducts in the floor and my is not split level, the main entrance is 1/2 flight above the 2nd story.
BTW, I have your email and there are a number of other things like this that are somewhat parallel in our lives.
Lots of old Victorian houses I've worked on had more than one furnace. One had 4 furnaces, all originally coal fired, later converted to gas. I imagine they had a full time fireman to run things in the winter :)
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