air conditioning options for an old house

I live in a 90 yr old city townhouse with radiators and no central air conditioning or air ducts.
I happily had several window units cooling my bedrooms and living room in my house- kept the livable areas very nice even in 100 degree weather.
But since my son started walking I see the reasoning behind whole house A/C- it's just problematic going from room to room closing doors. I also have a problem that my townhouse has no overhang on the back roof and we had troubling water issues that mean I close those windows tight in the summer. I don't want to install air ducts throughout the house. I have a flat roof that would support an AC unit. I have a small crawlspace between ceiling and roof.
Is it feasible and cost efficient to look into some kind of roof-mounted AC unit with ducts leading from roof to the 2nd floor ceilings? I have a 25k btu window unit on my first floor which behaves flawlessly as far as I'm concerned and cools the whole downstairs, but a similar unit would not work so well upstairs with individual rooms.
Has anyone seen an installation like this? Is it worth pursuing?
Neighbors installed air ducts and they just cut into the living space too much.
thanks,
Don
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I offer this as a alternative http://www.warmair.com/html/ductless_split.htm
Getting rid of the condensate may be an issue for ya as well from the above idea.
A ducted system may be a better approach, returns will need to be considered. In my experience just one return up stairs will not be satisfactory.
Best plan is to start talking to pros in your area and get an idea of what they recommend. The best equipment in the world can perform like crap if not installed correctly.
Call a couple of realtors and see what the a/c increases your property value.
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here you go:
http://unicosystem.com /
they are not cheap, but they work very well. These systems are made specifically for retrofit of older homes.
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wrote:

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There is also www.spacepak.com The quote I got was about 30% over that of a conventional system. But they supposedly work better than a conventional system. Something about stirring the air better.
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In alt.home.repair on 28 Jul 2005 08:37:19 -0700 snipped-for-privacy@gmail.com posted:

I am not a big fan of room air, because of the noise and the windows that don't open (if they are installed in windows.) but a few comments.

Put springs on the doors so they shut themselves. Your son will quickly get the hang of them.
Even if you get AC, you shouldn't be cooling rooms where no one is, if the room has a door. Alternatively, you should be cooling the rooms that you use, and not the whole house, if the rooms have doors.

Buy/Build a little awning over the window, or an overhang.

I generally close all my ac vents except for those on the seccond floor. I figure the cold air will get down there soon enough, and it does.
Maybe my first floor vent louvers leak some, but I think 90% of the first floor cooling comes from the second floor.

Meirman -- If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary.
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meirman wrote: .....

That can cause problem of freezing over the evaporator unit due to insufficient air flow. The likelihood of it happening depends on the installation.
--
Joseph Meehan

Dia duit
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In alt.home.repair on Thu, 28 Jul 2005 16:31:15 GMT "Joseph Meehan"

Thanks a lot. I sort of wondered if there could be a problem. In fact I was going to ask, and then my little mind concluded that if it was bad to close the vents, they wouldn't have doors on them.
I'll keep my eyes open. Definitely hasn't happened yet (3 years, including 40 days of AC)
Meirman -- If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary.
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Yes, there are systems specifically designed for your situation referred to as mini-duct or high-velocity air conditioning systems. You can google those terms for more info. Basically they are a central air unit and the cooled air is piped through mini-ducts (I presume they just snake these through interior walls) that end in little round ports in the rooms. Sounds kind of like those whole-house vacuum systems in reverse. I don't know anyone who has installed one so can't comment on effectiveness, reliability, noise etc. -- H
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I had a 200+ yr old cape on south shore of Boston. Put in cast iron baseboards first floor and fin tube on the second. Depending on your layout, consider zoning the second floor. Possibly the first floor too. The original heating system was forced air on the first floor only. The new system was steam throughout. When it came to A/C, I went for a horizontal whole house unit in the attic. You having a flat roof, be sure to have the structurals of the house checked by a professional before doing anything. If cleared, go for the rooftop unit. Also try the trick I did. Install floor grates on the second level with small ducting to the ceilings below. They will still be in keeping with the age of the house. I know you have building wrecking yards in your area. That's where to find them. If you have raport with an HVAC man, he can tell you what sizes to look for. And get one size larger in each room situation. Also follow another's reply about getting awnings. If the span between windows on the back of the house is minimal, make it one long awning almost the width of the house on both levels. You'll be amazed at the difference it will make. A one piece of material with 2 "flagpole" struts about 6"-8" wider than each window would look good.
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Thanks for all the great ideas. When I worked with my contractor to rebuild the back of my house (it's a converted porch) he told me there was nothing he could do with about 8 inches of space between roof and windows. The idea about the whole house awnings makes a lot of sense. I am planning to have my roof redone this fall and will get the structurals set for possible AC and ask about the awning idea. I have been hesitant to use the upper floor in the back for anything permanent due to water leakage in 2003- I'm definitely concerned about potential issues.
the awning on the first floor wouldn't work because we installed a (historically correct) bay window.
We have a store that sells construction antiques that is booming during the home renovation bubble here. I can get all manner of authentic grates, ceramic doornobs, brass fixtures, in matching sets without scouring the junkyards. but in DC, like Boston, we pay for that privilege.
thanks to everyone for excellent, excellent ideas!
Don
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