The home will have one air handler and it can either go in the 1st floor mechanical room or the 2nd floor attic (conditioned space - below a steel SIP roof). The one problem with putting it in the attic is the ceiling height would have to drop form 8 feet to 7 feet in a closet, hallway and hobby room. If we put it in mechanical room, the duct work will run from that room to the 2nd floor attic and distribute to the 2nd floor rooms (of which there are 5 total, including bathrooms).

I am leaning towards keeping it in the mechanical room but I don't want to get the room all cluttered. I still need to install an HRV in the room, water heater, washer & dryer and finally a well water storage tank. The mechanical room is about 140 sqft.

Any input?

If you need the room, the HRV, water heater and pressure tank might be better choices to put in the attic.

Posted By jonr on 19 Apr 2013 11:04 AM
If you need the room, the HRV, water heater and pressure tank might be better choices to put in the attic.

I can see the HRV going into the attic but the water heater and pressure tank? The pressure tank is insanely heavy (40 gal), as is the water heater, and the risk of water leakage and the complexity of running water lines into the attic would not make sense.

I would have a tendency to put the lightest items in the conditioned attic if the attic height was tall enough. 

Do you already have the well and the water has been tested?  Will you need space in the mechanical room for water treatment units?

Posted By Alton on 19 Apr 2013 11:17 AM
I would have a tendency to put the lightest items in the conditioned attic if the attic height was tall enough. 

Do you already have the well and the water has been tested?  Will you need space in the mechanical room for water treatment units?

That makes sense. Either the air handler or the HRV would go into the attic. Attic height will vary from 3 - 6 feet.

No well as of yet but hydrology reports show that adjacent wells are 30-50 gpm at around 250-300 feet deep. The water is from an aquifer and arsenic levels are below government standards and the water is very soft, no water treatments will be needed except for a sediment filter. No hard water softeners needed.

Is 140sqft adequate size for a mechanical room? No furnace, it's all electric. The 1st floor will be cooled/heated with mini-splits. It's only the 2nd floor that will have a 2-stage/2 ton heat pump with air handler.

How long will the refrigerant lines be at either location? How many feet of rise between the compressor and air handler?

The 1st floor will be cooled/heated with mini-splits. It's only the 2nd floor that will have a 2-stage/2 ton heat pump with air handler.

You don't say if the latter is geo, but if so, I'd look at the efficiencies and capacities and see if there are conditions where a few ducts into the first floor would beat the mini-splits efficiency.

Posted By arkie6 on 19 Apr 2013 12:35 PM
How long will the refrigerant lines be at either location? How many feet of rise between the compressor and air handler?

The shortest run would be the mechanical room, as the air handler and outdoor compressor unit would only be 10-15 feet from each other. With the air handler in the attic, the outdoor compressor and the 2nd floor attic run would be 40+ feet from each other.

My main thing is it worth losing a foot of interior ceiling height in the closet, hallway and a hobby room (all would be 7 feet) in order to gain a foot of attic space?

Posted By jonr on 19 Apr 2013 02:52 PM


You don't say if the latter is geo, but if so, I'd look at the efficiencies and capacities and see if there are conditions where a few ducts into the first floor would beat the mini-splits efficiency.

NO geo for me. Two Mitsubishi ductless mini splits will cover the entire 1st floor area (except guest room). The 2stage heat pump and air handler will cover the guest room and the entire 2nd floor. It's a very open design.

the risk of water leakage

If for some crazy reason you put them up there, you would want to install them over something like a big shower pan that was connected to house drains.

Why are we talking air handler when we have ductless minis?

Is this the HRV and main trunks or is there another system?

You didn't mention the details on the water heater, except to say the house is all electric. A tankless water heater would save space, as they mount on the wall and are very compact. On the other hand, you are in a good local for solar thermal, but that would require a storage tank that takes some space. Another option would be a heat pump water heater to reduce electrical usage. The "waste cooling" would be an asset during the cooling season and a debit during the heating season. So many choices.

Posted By ICFHybrid on 21 Apr 2013 10:47 AM
Why are we talking air handler when we have ductless minis?

Is this the HRV and main trunks or is there another system?

It's a 2-story home, the 1st floor will be heated/cooled with 2 ductless mini-splits. The 2nd floor will be cooled/heated with a 2-stage (2 or 3 ton) heat pump setup with an air handler and duct work.

The HRV will have its own duct work. All 3 bathrooms will be vented, along with the kitchen and laundry room. The HRV can go in the mechanical room or 2nd floor attic, whichever works out better.

As mentioned, all electric, no gas. I've decided on putting the air handler in the mechanical room.

Curious why you aren't using minisplits on the 2nd floor?

Posted By Bob I on 21 Apr 2013 04:42 PM
Curious why you aren't using minisplits on the 2nd floor?

Couple of reasons:

1 - Design of home would require numerous mini-splits on 2nd floor, which is not economical.
2 - I want the ability to run an electric heater grid element if temps get below -15F (which is rare but can happen). The air handler will allow this.
3 - Don't want to clutter the 2nd floor rooms with the mini-splits hanging on the walls.
4 - The 1st floor design is open and more suitable for mini-splits.
5 - The house will technically have "central air" with the air handler.
6 - Don't want to run refrigerant lines on the outside from the 2nd story all the way down to the ground level. More work for the stucco crew and I don't want to gouge the ICF foam all the way down.

Air handlers are notorious for eventually leaking and damaging ceilings. I would put it in a mechanical room for that reason and easy access for maintenance.

Hey LBear, Being you have not started construction you could add a foot to the wall height to keep the hall way and other affected spaces at 8 ft. The rest of the first floor would be 9 ft, but that is a very nice ambience height. WB is available for 9 ft walls. Richm

Posted By richm on 22 Apr 2013 02:06 PM
Hey LBear, Being you have not started construction you could add a foot to the wall height to keep the hall way and other affected spaces at 8 ft. The rest of the first floor would be 9 ft, but that is a very nice ambience height. WB is available for 9 ft walls. Richm

The ceiling wall heights depend on the room, some ceilings are at 8', some at 9' to 14' (master bedroom), some are as high as 20'+ (living area), while a room with a window seat is down to 7'. It's a very open and modern design with vaulted ceilings in some areas.

if temps get below -15F

I thought you were in Reasonable Town, Arizona. Does it get THAT cold there?

Posted By ICFHybrid on 22 Apr 2013 07:14 PM

if temps get below -15F

I thought you were in Reasonable Town, Arizona. Does it get THAT cold there?

Currently I am in Phoenix but the future home location is in Chino Valley, Arizona just north of Prescott, AZ. Elevation is 4,800

It's a pretty moderate climate up there but vast diurnal swings of 30-40 degrees between sunset and sunrise are the norm. Occasional winter storms can drop the temps to single digits at night. The record low was -15F back in 1949.

Tomorrow's high is 77F and the low will be around 43F for Chino Valley.

With the crazy temperature swings the USA is experiencing I want to have backup heat source in case it gets too cold for the heat pumps.