[jerzey79]

I want to add central AC to my row house, which is over 100 years old. It has no ductwork. The house is 2 stories with a basement. There is little yard space. So I'm considering a rooftop/attic system.

The problem is the attic space. The roof is flat. The attic is 3 ft high at its highest point. It is also divided into two parts because there was an addition to the house at some point in its history. The old attic and the addition attic are not connected. Do I need to make modifications to the roof/attic if I want central air?

 

[JJboy]

Post some pictures.:thumbsup:

 

[jerzey79]

I couldn't do photos quickly, so I made up the attached section view diagram.

 

[vsheetz]

Mini-splits - multi-room mini-splits - may be an option to consider.

 

[JJboy]

3 tf is your problem.

 

[yuri]

What do the other neighbors have? Sounds like mini splits may be the only answer. Google: ductless mini split for more info.

 

[jerzey79]

I had to look this up on This Old House. So let me know if I got this wrong.
There are ductless mini split systems: http://www.thisoldhouse.com/toh/video/0,,1630888,00.html
And there are high velocity mini-duct split systems: http://www.thisoldhouse.com/toh/video/0,,20047036,00.html

A ductless system saves you from running the ducts in the walls and ceilings, but it requires some amount of wall interior wall space to mount the fan unit. With the mini-duct system, the air handler is usually located in the attic, but it can also be located in the basement.

With the mini-duct system, the air handler is in the attic, with a trunk line running along the perimeter of the attic. The trunk line at the attic perimeter is a problem. If I could give up some ceiling height on the first floor, would it be possible to keep the air handler in the attic but run the trunk line above the first floor ceiling?

 

[yuri]

ACs in attics are downright HORRIBLE. Techs hate going in there so it is hard to get them serviced properly. If they leak water you get ceiling damage. If buying a minisplit buy a GOOD large name brand like Fujitsu or Mitsubishi or Sanyo. There are all kinds of clones and el cheapos out there now and you get what you pay for, Very difficult to get parts for them later or service info etc.

 

[jerzey79]

Ok, so if I put the air handler in the basement instead of the attic, is is feasible to run the trunk lines between the first and second stories? (essentially 1 floor away from the air handler in either case).

 

[yuri]

I have never seen a high velocity system other than on dis ole house hour. Hang in here for a day or two some of the other techs here may have.

 

[jerzey79]

Here is a drawing to illustrate. And another question comes to mind. If the air handler is in the basement, do I have to run a return air duct from the top floor down to the basement unit?