While not exactly a framing question, I am concerned about my next step...

I am enclosing an area to become a 3 season sun room. The ceiling (overhang roof) is insulated, and 2 of the walls are current exterior walls. The two existing walls are fully finished with siding, house wrap, insulation, vapour barrier,and interior finish.

The question - Should I be using house wrap on the new two exterior walls?

We're in a cold climate (Manitoba, Canada) where temperature extremes are -40 C in winter to + 30 C summer. Humidity also swings low to high. The new sunroom construction is standard 2 x 4 stick construction with an OSB skin and I plan not to insulate.

thanks,

bryon

If your constructing a three season sun room then there would be really no need to use a wrap on the wall.
However.
There are several factors to take into consideration here.
1. What does the local building code tell you? MY guess is to use the wrap.
2. Almost every three season room I have seen has been converted to use year round. Not having the wrap in this case would not be wise.
3. The cost of wrap is not so much that it would break the bank. You going to side this structure? Use the wrap then your covered regardless if you need it or not.
4. I strongy urge you to insulate the walls if your planning to finish the inside. Even as a three season room. having insulation on the walls will keep the room quite, and prevent the excessive cost of tearing down the finished walls once you decide to make this a year round room. Which like I said happens almost all the time.

But if your not finishing the inside at all, and your sure your not going to do so in the future. No need to wrap. Unless again the code says you need to.
Personally I would do this. OSB plywood although some is graded for exterior use it does not fair well if it gets wet to many times. Using the house wrap over it will help protect it if a leak does enter behind the siding, which it will.

Home Care is right on!

The difference between a 3 season and a 4 season usable room is minimal. In a cold climate, most 3 season rooms get converted (either by a mind/situation change or a planned, conversion for later).

Even if it is a tax dodge, it does wonders for resale since it can be converted easily later.

Go for the house wrap and the insulation and use something better than the fiberglss junk (cellulose).

My son did a 3 season add-on that is very usable when needed because it is so convenient. He added. He added a 20x304 on real structural permanent posts and insulated under the floor (area was a deck). Vaulted ceiling, ceiling fan and plenty of good operating windows and a direct vent gas fireplace, but no connection to the central heat/air. He left the double french doors and the window to the kitchen and added a door to a lower patio.

Despite that it can get cold during a winter day, he can open it up, turn on the fireplace and have a great space when needed even at -20 F thermometer and -50 F wind chills.

In his area, he was subject to close scrutiny by inspectors, but the 720 sf addition was not including the square footage for taxes, but it can be converted easily.

Do it right and plan ahead. That makes it a good use of time and money.

Thank you to both THCLLC and concretemasonry for you comments, opinions and suggestions.

I agree that to not wrap and complete the interior (insulate & vapour barrier) may prove to be a false economy.
The question arose when my boss (wife) questioned the use of the warp on what we essentially only plan to use for part of the year.

thanks again

Your boss can do whatever he/she apparently wants. Skimping on wrap on only two walls on a usable area is just a fooloish penny-pinching decision - forgine me, but that is the most polite way of putting it.

If you don't care about installing windows properly (1 or 4 season) for mositure and anything in the future, that is the way to go by saving a couple of dollars/loonies.

You should really protect the exterior, whether OBS or anything else, although I have many relatives with OBS outhouses that hold up quite well. Tar paper does hold up well and can be replaced.