[Dieselbear]

The previous owner built what they called a sun/3 season room, to me it's just a mud room. For whatever reason they didnt put any insulation in except for around the windows, which seems pointless being here in NY as it makes it useless from late nov through april...
So here's what I did...
It's a 2x4 wall. I cut enough plastic sheeting for each wall to allow it to form along each cavity and over top of the studs(so the studs are to the outside) Then stapled in rolled faced insulation( paper to the inside) and taped all edges.
Now im about 3/4 done with putting up new cedar board on the inside and while looking something else up, I stumbled across some topics where it looks like I may have done this all wrong...

I went this way because I wanted to keep the new cedar from getting any mositure on it and water marking like what happen to the original boards. So putting the plastic to the outside seemed like the best idea, keeping moisture as far away as possible...

Should I have put the insulation in the cavity first then the plastic sheeting to the inside wall or wont it make a difference?
The room isn't heated currently btw.

 

[jklingel]

IF you feel you have to use a vapor barrier (as opposed to a retarder) it always goes to the warm side. If on the outside, it will be cold, and when air gets through your fiberglass (I assume) insulation, and plenty will, the moisture in the air will condense on the poly and you will have water galore if you have any moisture in the air. Your best bet, IMO, is to NOT use the poly, to use Roxul batt insulation, and to air seal the room real well. Google airtight drywall approach. Now is the time to do this.... after you remove the cedar. Sorry about that.

 

[Dieselbear]

IF you feel you have to use a vapor barrier (as opposed to a retarder) it always goes to the warm side. If on the outside, it will be cold, and when air gets through your fiberglass (I assume) insulation, and plenty will, the moisture in the air will condense on the poly and you will have water galore if you have any moisture in the air. Your best bet, IMO, is to NOT use the poly, to use Roxul batt insulation, and to air seal the room real well. Google airtight drywall approach. Now is the time to do this.... after you remove the cedar. Sorry about that.

I see what your saying...I think. But if I didnt put something to the outside then the insulation it seemed like it would get wet from moisture due to weather. Which I know it shouldn't but when they had this built, there was no house wrap or anything put underneath the exterior siding to barrier the inside wall. It was just exterior siding-complete empty wall cavity- interior wall.
I had been contemplating replacing the exterior wood of this small room in the upcoming spring/summer, so would an acceptable solution be if/when its replaced, cut out the poly and wrap the outside with Tyvek or similar prior to installing new siding?
Tearing out all the insulation to replace with the mentioned Roxul is not an option. I can't afford to do that.

 

[jklingel]

if you are worried about exterior water getting into the wall, then that needs to be addressed first and foremost. p, eos. any way to cover the wall w/ tyvek, add firring strips, then new siding? you have a tough deal there.