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Manage heat on second floor of 2 story great room

Novice Builder's picture

I'm planning to build a home wiht a two story great room.  It will have a 2 cathedral ceiling and a loft.  Having never been in a loft that wasn't signifigantly warmer than the first floor, I am looking for advice on how to retulate the temperature  there and at the peak of the ceiling so as to save energy on heat on the first floor and cooling for the loft.  Will have a forced are system and an efficient fire place or stove.  Radiant heating will not be considered an option.  Thanks!

Zoned heating and fans. (post #207470, reply #1 of 5)

Zoned heating and fans.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Trying to acheive uniform (post #207470, reply #2 of 5)

Trying to acheive uniform comfort for both heating and cooling with a single system is very difficult, and you may have added complications that create more incompatibility between spaces with large areas of glass facing the sun.

Assuming that your climate is heating-dominant, I would design the system to have floor supply registers on the lower floor of the great room area, and  the return located up near the ceiling. During winter, the heated air will rise and be recirculated. You can also run the furnace blower on low speed continuously to keep the air from stratifying between run-times of the burner.

In the cooling season, this arrangement will not work well for cooling of the loft, so I suggest that you install a separate, large duct with its own in-line fan that takes cool air from the lower level and throws it out across the ceiling of the upper level. This fan would run only in the cooling season, and could be run indepentently of the main system at times, or be run along with the main system.

I believe this is preferable to a zoned system, and the installation cost should be comparable. With a zoned system, you still have to choose between floor supply registers or ceiling supplies. Either way, the air will stratify uncomfortably in either the heating or cooling season. Ceiling fans are not as effective to combat stratification as the fan-powered, separate duct  would be,

Exactly - you need to break (post #207470, reply #3 of 5)

Exactly - you need to break the stratification layers up and churn the air to get a balance of temp and humidity.  Colonial homes with big open staircases have exactly the same problem.

Since this is an open area, you can solve this in one of two ways:

  1. Big Ceiling fan - there is a company called big [JOBSITE WORD] ceiling fans IIRC that advertize in FHB.  Ceiling fans blow hot air straight down in summer to blend with the cool air and give you a gentle breeze, they are reversed and pull air up and wash down the walls in winter so you don't feel the air flow directly.
  2. Reversing ducted fan.  This is more of a conceled option that has a low power DC fan continously blowing or sucking air up or down from the top to the bottom of the space.  A simple double throw switch tells it what to do, Summer being up, winter being down, and off in the middle.

EDIT:  Here is the website

YAY!  I love WYSISYG editing!  And Spellcheck!


Air is not good at transferring heat, water is 4000 times better (post #207470, reply #4 of 5)

You will always be uncomfortable and irritate with warm air moving to keep a high ceiling room warm at floor level.

While you write that you do not want underfloor hot water radient heating, it is never the less the best form of heating for a high ceiling room, as it provides low level heating exactly where you are and the cost of running the set up will be low.

The joy of under floor heating, is that the floor can be split into sections, with the area in front of windows delivering more heat where its cold and other areas set lower or off.

As writen elsewhere, with warm air heating, the temperature at ceiling level will be very high,, while you are trying to keep the near floor level area warm. This means that your heat loss will also be high. You will need at least 8 inches of closed cell insulation between the rafters and another 3 inches below the rafters to make this economic.

I agree, water is better at (post #207470, reply #5 of 5)

I agree, water is better at transferring heat