Central A/C into closed room & motorized ducts

I'm in Florida and have a 400 sq foot room that is nearly all windows. It is the kids play room, but is only used seldom in the evenings and is used on the weekends. Ideally, I'd like to only A/C that room when it is being used.
I have sealed French doors that can close the room off to the return duct. So I hoped that when the door was shut, there would be positive pressure in the room that would act to shut off the 2 A/C ducts. But it does not. Cold air still blows from them. I can only assume there is a lot of leakage in the room around windows, etc. So my plan is to spend a weekend sealing everything I can.
However, if the air still comes out a significant amount, I would like to install motorized ducts assuming it does not cost a small fortune (more than $200 per duct). I don't need variable control. Just on and off. Either controlled by timer or by simple switch. I thought about installing a linear actuator myself to control the flapper in the existing register, but it would have to be on the outside and would be visible in the room.
Any suggestions?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
http://www.smarthome.com/307107.html
Motorized dampers, available in various sizes, about $60 each.
One thing to watch out for: depending on a number of factors, you could reduce airflow in the A/C system enough that the evaporator could freeze - not something you want happening!

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Aug 16, 9:41 am, snipped-for-privacy@gate.net wrote:

Personally I'd just get some of those magnetic vent covers and slap those over the vents when I wasn't using the room.
Maybe get fancy and attach a string to them so I can pull them down without a ladder.
-Nathan
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
nhurst wrote:

Hmm what if he has aluminum vents?
--
Zyp



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Then get CU/AL rated magnets, silly!
--

Christopher A. Young
You can\'t shout down a troll.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
on 8/17/2007 1:19 AM Zyp said the following:

...or plastic, like mine? I tape clear saran wrap over them, and the returns, using blue painter's tape. That way, I don't have to mess with closing the louvers, which isn't really airtight anyway. Looks bad, but the tape doesn't leave a residue. I was thinking of trying some magnetic plastic tape (the soft kind used to make refrigerator magnet business cards, etc.), taped under the edges of the vent, and then use the same, but untaped, magnetic tape to hold the saran wrap on the outside. I don't have any magnetic tape to see if it would be strong enough to attract through the plastic vent cover.
--

Bill
In Hamptonburgh, NY
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.