I'll try to be succinct and just provide needed info... Let me know if you need more! - Thanks in advance!!

- 2000 sq. ft. home in northern MN (built mid-50s) No AC - just heat.

- building an efficiency apartment in 1/2 of the basement

- It will be insulated 4 walls (and ceiling) (and floor) - (for both sound and because the other half of basement is not insulated).

- 2 stage Trane 77,600 btu (LP powered) furnace.

- upstairs there are 3 bedrooms, liv. rm., kitchen, and bath.

- downstairs a laundry room/bath and a furnace/workroom - and the "new" apartment.

- Everything has worked "fine" for many years - I'd guess that furnace and ductwork upgraded maybe 10-15 years ago.

- (We've owned it just a year)

- Furnace is on one end of house - Two main trunks (16 x 8 down center for bedroom side) (12 x 8 down one side for liv. rm/kitchen side) and a return trunk t(also down center of house) hat's half 20x8 and half 10x8

- essentially "all" branch runs are 5" round.

- "Originally," in this 1000 sq. ft. basement, the "apartment side" had two 6x10 supply registers directly out of trunk and no returns. The laundry area (260 sq. ft.) had one 6x8 register out of other trunk and no returns. The furnace has one 6x12 return directly on return plenum.

- The apartment is essentially 250 sq. ft. of liv. rm/kitchen -- 100 sq. ft. of bedroom -- and 60 sq. ft. of bathroom. My "plan" for the apartment is to close up the two registers that are there. Then run three registers to "outside" wall - two in liv. rm/ kitch area and one in bedroom. (the bedroom is furthest from the furnace).

- Then, I was going to add two returns, on the "inside" wall, at floor, one in bedroom and one in liv. rm./kitch. area.

- So essentially, I'm adding one supply and two returns to what was already there. (but moving them further from trunk and to floor.)

- From what I read, I'm relatively confident the furnace is large enough, my main questions are about duct and register size...

- *notes - This basement has been cool in the summer and "mildly uncomfortable" in the winter. There's been no water infiltrating but it has been prone to condensation on the floor. (hence the floor insulation - "dri-core" underlayment).

- Be kind, because I've already started and just got "smarter" as I went along and figured I'd better run some of this by some people who actually know something... ;-)

- I've got three 6" takeoffs installed in the top of the trunk and was planning two 6" returns...

- I'd REALLY rather not rip those off (it'd be ugly) but I could "reduce" them...?

- I have a bunch of 2 1/4 x 10 duct for the walls and was planning 6x10 registers. That could all be returned...

- So.... What "SHOULD" I be doing here?

- I'm curious if bedroom duct (furthest from furnace) needs to be downsized to keep velocity up?

- As the future renter will have minimal control over heat, I was considering three "Flair Smartvents" for registers....

- I'm also inclined to install one more small (3" or 4") round supplies directly out of trunk in bathroom.

- One of the main issues is that I really have no "feel" for what this will all be like after it's built and insulated. I don't know if it will be freezing or too hot. - I'm a little worried about too hot in winter (hence the smartvents) and too cool in the summer but I guess they can always open a window then...

and are smartvents enough? Do I need dampers too? It would be tough to make them "accessible..."

- Lastly - Should I damper the 2nd main trunk (12x8) to liv. rm side of house? - so as to "throttle" a little more air to the side with the apartment?

Okay.... Sorry - but that's me being "succinct." ;-)

I REALLY appreciate any thoughts you might have to share!

Chuck