Venting from stove to addition in home

Hi folks!

What I'm trying to figure out is what many of you have likely before, how to distribute the heat of my stove from one side of my house to another using duct through the attic.

Going to try to keep it simple:

What I have is a 1-story original cabin home with a 2-story addition built on(3b/2ba/1600sf). The addition steps down about 20" from the original cabin (so getting heat to travel down to it can be a challenge as one single 34"x78" door way connects them) The original cabin houses the stove and we keep it around 76 in that area. The bedrooms in the addition side are coldest about 12F lower than the original side.

What I was thinking about doing was adding a duct with a blower to blow from my stove area to the stairway in the 2-story addition to help distribute to bedrooms.

I am masonry contractor and can do about anything I just don't have the know how for this project so here is a few easy questions bear with me:

1) What size ducting should be used, the vertical run is 3' and about 30' horizontal run. It is a straight shot. I would assume I should avoid flexible ducting?

2) What size blower fan? Should these be wired on their own circuit or could I add it to another with little on it?

3) The room has a flat ceiling (attic above) but does have one cave style skylight very close to the stove would it be better to draw air from the skylight inner wall vs. flat ceiling plane?

Thank you for your help in advance. I am sure I may have a few more questions but I'm really excited to get some input and get started on my project !

Are you placing this duct in the attic above the stove? Then running the duct into the other part of the house thru an attic?

Whats the layout of the addition?

Thanks for your response.

Yes the duct is in the attic above the stove, not looking to tie into pipe or anything was just thinking of moving hot air from warmer room to colder area either through a vent in the ceiling near the stove or in skylight tunnel (if that's better)

I will try a simple ASCII diagram here.

+------------------------------+
| [[[stairs]]-> |
+----------------------------------------+ |
| *stove* xxxx | |
| xxxxxxxxxxxxx | |
| original 1 story cabin 2story add. |
| +------------------------------+
| |
+----------------------------------------+

All bed room are in 2 story addition two on bottom floor and master upstairs.

X shows where I am thinking of running duct. I don't have tons of clearance for a huge duct maybe 12"?

Edit: ASCII drawing did not work with forum code I'll figure out how to upload a drawing this evening. Thanks

You need the most volume of air , more the better so the biggest duct size you think is reasonable. Insulate the duct work so it doesn't loose heat.
If code is ok put the duct opening above the stove as the heat is rising naturally straight up above the stove. The sky light may be a cold area that will cool some of the heat rising. On the other hand the skylight recessed area may capture some of the heat. By having a large volume of air with a slow moving fan you will not create drafts. On the other hand if you try and use a smaller duct size and have to speed your fan up the extra air flow creates draftiness and has a cooling effect. I learned that from when I used to burn a wood furnace with a duct system.

If the door way you speak about leads to a hall way that runs the entire length of the addition place a fan on the floor down at the end of the hall way and blow the floor level cool air towards the warm room, you will find the warm air will migrate towards the addition thru the top of the hall ways as the cool air along the floor moves towards the heated room.

Before trying the vent and moving the warm air, why not first try something really simple that works really well and that is using a small desktop fan. Set it on the floor in the doorway and on the lowest setting. Blow the cooler air towards the stove room. You will find that moving cool air is easier than trying to blow warm air towards the cooler air. That is because cooler air a more dense. So if you blow cool air into the warmer room, some of that warm air will blow back into the cooler part.

For example, we have a long hallway. If it gets too cool in the back, we have a really small vornado fan and set that in the hallway, low speed, aimed toward the stove room. In 10-15 minutes it is amazing how warm it gets in back. However, if we try to blow the warm air toward the back, there is very little if any temperature change in the far rooms.

If this works, which I suspect it will, you will save yourself a lot of time and some dollars too.