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  1. #1
    Join Date
    Oct 2001
    Posts
    63
    My son bought a rowhouse in Baltimore that has been completely gutted. His plan is to have a finished basement and add a third floor master suite and roof deck above the current 2nd floor. When discussing HVAC, he would like a duct system so that AC registers would be near the ceiling and heat registers would be near the floor. Is this worth pursuing in terms of efficiency and comfort? How is this type of system set up? Would it be more efficient to put the AC on the roof and use a high velocity air handler in a closet in the new roof addition? This would seem to take advantage of gravity to distibute cool air down through the building. Would a single 90% furnace in the basement with traditional ductwork handle all 4 levels? In a high velocity system, how are the cold air returns tied in? Any recommendations or guidance would be greatly appreciated. Also are any of the professionals on this site that are versed in these types of systems located in the Baltimore area?

  2. #2
    Join Date
    Oct 2001
    Posts
    63
    To simplify the questions...
    What is the best placement for feed and returns to provide both efficient cooling and heating?
    What determines when a system should be split into two seperate units?
    Does it make sense to split heating and cooling?
    When do you consider HV AC?

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,448
    Doing that will cost a bundle. A/C is best coming from above. He can put an air handler in the attic with supplies in the ceiling and then have his furnace in the basement with floor supplies. He won't like the amount of his bid but the ultimate comfort is doing it this way.

    If he really wants comfort, put in a boiler and either infloor radiation or baseboard for heat and cooling from above. THAT'S COMFORT.

    High velocity is best when you can't do regular ducts. But with it gutted, I'd go conventional with a variable speed air handler. Higher efficiency.

  4. #4
    Join Date
    Feb 2003
    Posts
    1,996
    Listen to the Bald Master, he's always right! I would also vote for the boiler in the basement with zoned radiant flooring for each floor. You could even put a hydro coil in the air handler to supliment the radiant with a humidified warm air. The ultimate system.

  5. #5
    Join Date
    Apr 2003
    Location
    the Great Pacific Northwest
    Posts
    607
    Originally posted by holabr
    To simplify the questions...
    1 What is the best placement for feed and returns to provide both efficient cooling and heating?
    2 What determines when a system should be split into two separate units?
    3 Does it make sense to split heating and cooling?
    4 When do you consider HV AC?
    1 High velocity,Placement doesn't matter as long as you follow installation instructions, I prefer high sidewall and ceiling. conventional systems, heat - floor supply with floor return. Cool high supply with high return. for conventional ceiling supplys use "b" boxes with adjustable curved blade diffusers.
    2 Diversity of loads, say one area need more cooling as a percentage of system capacity than it does heating. almost all structures have diverse loads and would benefit from zone control. you must have your installing contractor do a room by room load calculation to determine the system requirements. Multi story structures need zone control for good comfort.
    3 Yes for comfort, but cost vs. benefit makes it prohibitive for most folks. In floor radiant with boiler in a high heat demand area makes a lot of sense as it gives the best comfort and saves energy.
    4 Consider HV for the ease of running supply ducts without having to consume a lot of space with soffits. Also a HV system delivers superior comfort over a conventional systems. These systems must be installed properly to work right, so select a installer who is versed in them.

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