I had the option to add some heating/copoling zones during my new construction, but decided that the cost would never be recouped, and I would just go with a single zone for my 1900 SF 2 floor house. While this seems to be working out for the heating season, I have been thinking more carefully about my cooling needs, and think I may have made a mistake here. For purposes of sleeping, I need a fairly cool bedroom (at most 62 degrees). THis means that for the summer months, I either need to cool down the whole house to this level, or run a window unit, neither of which appeals to me. So I would like to add a second zone for just my bedroom.



It is a ClimateMaster open loop system and forced air heating and cooling. Any advice on where I might start looking into this?



Can anyone give me some idea of what it entails to have an additional zone retro-fitted?



Does anyone have a better suggestion for my needs than adding this extra zone? (Like will running the window unit be actually more cost effective?)



Cost effectiveness of the sopplution is important, but not the only guiding factor.



thanks for any help.

I prefer arzel zoning for your purpose. Check it out at www.arzelzoning.com
They have a great product.

That is exactly the kind of system I was hoping might exist. In fact, it looks completely awesome at first glance. I may be able to add more than just one zone to my home with this and really have customized comfort in every room.

Amy I losing much efficiency of the heatpump having multiple small zones (I am thinking individual bedroom controls for all 3 bedrooms, and possible controls for each bathroom). I now know that I will get nothing done this evening as I read their web site. THanks for the pointer.

How many tons is your system?

Beware too small zones - they need to be sized so any one can take minimum airflow of the unit or a bypass or a barometric dump needs to be installed.

62 is a very very low cooling setpoint - even with zoning it will be tough to achieve - was the house manual J load calculation run with that in mind? That is 10-15 degrees below normal summer indoor design temperature.

Depending on summer dewpoint in you area, a 62 degree interior temperature could result in a temperature gradient across wall cavities promoting mold formation in stud bays, particularly on the back paper of drywall. You really want to avoid that situation.

If you are serious about maintaining a 62 degree bedroom, consider closed cell sprayfoam insulation for that rooms walls (possibly even interior walls) and densarmor or similar non-cellulosic drywall. Then install a mini-split ductless airconditioner in the bedroom sized for 62 degree setpoint. It will almost certainly be more efficient than trying to do this with a small zone off a central heat pump, and it stands a greater chance of actually working. Minisplits work like window airconditioners but so much better - no window needed, much more efficient, much quieter.

Trying to get your bedroom down to 62 degrees in cooling with a zoning system will probably lead to a freeze up.

 

Id look into a ductless ac unit by Fujitsu or Mitsubishi (fujitsugeneral.com or mrslim.com)

OK, great suggestions. I guess that the small zone is a bad idea, and I will stick with the single zone for the house (maybe add a second when I finish the basement), and go with a room conditioner for my sleep temp needs.

ALso, I don't want to maintain this temperature all the time, only at night while sleeping, so for about 9 hours per day.

thanks to all.

A couple more things regarding Engineer's comments.
I have successfully kept my bedroom at 60-62 most of my life using a window unit A/C. As I am now a homeowner for the first time, I would prefer a better solution, but I know that I can get the cooling I want from a window unit alone. The split ductless plus the central A/C should be able to do the job (I would hope).

The house is already tight and well insulated. I have 1" spray foam on all exterior walls plus r-19 fiber. If your concerns are moisture coming in from the outside, I would hope the house wrap plus the spray foam is going to do a pretty good job there, and the high degree of insulation should hopefully manage the temperature gradient within the wall. Or am being I too hopeful here.

As for within the house, the central AC will be keeping the whole house at 70ish anyway, as well as fairly dehumidified. I would hope this would keep the water incursions from being too big a problem with the interior walls.

I was looking briefly online at mini-split systems, and they look very promising from many standpoints.

The Amcor inverter heat pumps look very interesting to me. I like the lower temp deltas and the faster cooling, allowing a higher set point and shorter run time, all while using less power over time. Are these claims founded, and is this a reasonable way to go with the split system?

And to answer tuffluckdriller, my system is 5 tons. The house was rated for 4 tons for just about 2000 SF, and they upped it to 5 so I could finish and condition the basement (another ~1000sf). I certainly have the excess tonnage for the bedroom currently, but it is starting to sound like a bad idea.

I would second or is it fourth now?   Anyway I had always thought of split units as effecient window AC units.  I was really surprised to actually see one in action, much more quiet, better looking and obviously more effecient.

I missed the Fujitsu reccomendation the first read through. I think I should be able to get away with 9000BTUs since it is a 14x16 room that will also be conditioned by the central cooling. THere don't seem to be any smaller than that. This leaves me looking at:

Heat Pump 9,000 BTU Halcyon 9RLQ - 21 SEER by Fujitsu

very price competitive, and 21 SEER. Looks good on paper to a lay person.

Robkindovernh,

You may like this. It is a cooling and heating mattress pad, called Chilipad. Manufacturer claims it controls the bed temp from 46 to 118 degrees F. There are water loops in the pad for temp control. The motor is claimed to be quiet and fits under the bed. The picture looks very neat. Cozywinters.com has all sizes for $400 to $700. Target.com Offers queen and king sizes for $510 to $552. They come with a 3 year warranty.

Regards, Masoud

My concern is less with having enough insulation for thermal reasons - cooling at night is fairly easy.

I'm more concerned with the possibility of humid air from outside entering the wall cavity via the usual infiltration and then being cooled to below its dew point by parts of the wall system (principally the back of the drywall) that are 62 on the inside). Damp + paper = mold.

Yes, house wrap will help but it is hardly ever perfectly applied and gets perforated by nails, etc. Fiberglass insulation is a poor / nonexistent barrier to air movement.

engineer, htought the fiberglass is a non-barier to moisture, there is a 1" layer of spray foam insulation between the fiber and the outside wall. My understanding was that this did a pretty good job sealing the house from unwanted air coming through. I was hoping that that would keep the water vapor and moisture out.

Masoud, I Have dreamed of a chilled mattress pad for decades. I even considered making a chilled comforter at one point in my life, but was unable to find reliable information about accidentally inducing hypothermia. that is a more attractive option to me than chilling the whole room. Not only is it likely greener (and isn't that why we're all here), but the room itself will be more comfortable once I get out of bed. I am a little concerned as I use a tempurpedic mattress, but if I can find a place that has a decent return policy, I will try one out without any hesitation. That looks amazing, and just what I always wanted. EDIT-- I did find a vendor with a 30 day return policy on this item. THis will be much cheaper to buy than a split system, presumably much cheaper to run, and hopefully, more comfortable to sleep on. If they only made a pillow with the same technology...

Sprayfoam, if closed cell (feels rigid) is an excellent vapor barrier.

I hope the bedding option works out.