In an effort to keep some money in the bank this winter instead of buying heating oil, I have purchased a wood-burning fireplace insert to help heat the house. Here's some background info and my questions.
The house is a 10 year old contemporary cape in Maine (think long winters). It is insulated well and has double-insulated windows. Overall, it is a pretty efficient home. The main heating system is an oil fired forced hot water system. The fireplace insert is modern, high efficiency and is located on he first floor (of an open floor plan) in a room with a 24 foot cathedral ceiling. It has a blower and is capable of heating 1800 sq feet of house (my house is approximately 1,850 sq ft). The bedrooms I want to get heated air to are on the second floor down a halway, with unheated attic space above.
My project: I would like to install an inline fan/venting system to draw the warm air from the upper reaches of the cathedral ceiling (off a wall where the bedroom hall goes back, not in the cathederal ceiling itself) back to the bedrooms. There are three bedrooms, with the run ranging from just a few feet to approximately 20 feet. I would terminate in the ceiling of each room with a typical forced hot air vent.
My plan: Cut up high into the existing wall and add a "return air" type vent opening to draw warm air from the upper cathedral ceiling area. Then I would run insulated ducting to an inline fan/motor in the attic, to which I have easy access. I would build some sort of insulated plenum(?) box and pull three runs of insulated ducting off of these to each of the three bedrooms. I'm guessing 6' duct or whatever the inline fan/blower required.
My question: Does this make sense to do? Currently I am simply placing a fan at the end of the hallway and blowing the warmer air down to the bedrooms. The current method seems less efficient than using the inline method described above. Would I lose the heat in the air over the runs described, or would the insulated duct presere it? Your thoughts?
Additional Concerns: (1) Would it be better to run individual returns/fans that are switched in each bedroom instead of one inline fan/blower for all three? Would this provide better balancing of heat distribution? (2) Are there any concerns about taking away combustion air from the insert, causing it to either not stay fired or possibly creating a hazardous situation?
Any advice or experience you could offer would be greatly appreciated! My main concern is that the heated air not be wasted by just sitting up in the cathedral ceiling area. I currently have two ceiling fans mounted there with them rotating to push the air down, but not down the hallway where it's needed in the bedrooms.
Hope I gave enough specific information to give you a mental picture of what I want to accomplish!?