I have a house that was originally built in 1972. The original owner (we're the 3rd owner) added a 2 story addition in 1987 that included a 17x24 extension of the master bedroom. The addition has a vaulted ceiling with 2 ceiling air vents. The extension is at a right angle to the original part of the house. It seems we've never had proper air flow in the house, and the Master is always either the hottest (in summer) or the coldest(in winter) of all the rooms in the house. It is also the furtherest away from the furnace. On the other side, daughter's room is right over top of the furnace and is either the coldest (in summer) or hottest (in winter). Both rooms had/were additions to the original house. Is there anything you would suggest, short of putting in new duct work or adding a 2nd zone? Also, the original metal ductwork in the attic was/is wrapped in insulation that is old and fraying. Should we redo it?

First thought is the h/cooling were probably designed for the original house and isn`t big enough to handle the extra added on living space,, even a change in the duct system probably would not help,, you now need to think about upgrade to something that is big enough

Do the ducts have any dampers in them? Partly close the ones closest to the furnace and make sure any ones to the master bedroom are open. If you don't have dampers, add them to the closer ducts. Maybe then check the heat rise and increase the speed of the fan.

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Originally Posted by wmproop

first thought is the h/cooling were probably designed for the original house and isn`t big enough to handle the extra added on living space,,,,,even a change in the duct system probably would not help,,,,,,,you now need to think about upgrade to something that is big enough

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We upgraded the furnace from the original to a higher tonnage/seer when we bought the house. The home inspector said that with the additions that had been done, the original furnace/ac wasn't adequate to take care of the square footage. Since the problems are with the room over the furnace and the master bedroom at the end of the house, that's why I'm wondering if it's not something with the duct work.

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Originally Posted by labman

Do the ducts have any dampers in them? Partly close the ones closest to the furnace and make sure any ones to the master bedroom are open. If you don't have dampers, add them to the closer ducts. Maybe then check the heat rise and increase the speed of the fan.

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We've closed off 1 of the 2 vents in the over the furnace and partly closed the other. However, the 2 vents in the master in the newer part are wide open, as is the 1 in the older part.

You say to increas the speed of the fan. I'm not exactly sure what you're talking about.

If you dampen down the ducts allowing less air to flow to the closer rooms, you may not have the flow through the furnace to give the most efficient temperature rise. Many motors have several leads allowing you to select the best speed for your system. Changing the motor speed gets to be a little tricky and might be the time to bring in professional help.

You might look at switching to a bigger duct to the cold room.

Try this, take a coffee stir straw and suck on a McDonalds milkshake with it. You will get some but your cheeks will suffer! Your ductwork is like a straw. Hot air is like the milkshake. Do what you can to add both supply and return air to the troubled areas. Oversize the return air ductwork if you can, or add a second system to heat/cool the addition.