Question for Insulation Experts

[Pack Rat]

I framed in a back porch. It has been sheathed, house wrapped, and vinyl sided.
The walls are 2X4 studs and I'm going to insulate them using Roxul comfort batt
mineral wool insulation. The batts are unfaced, should I use a vapor barrier with this
type of insulation? I've heard that I should not.

 

[rburke65]

I would but im no expert.

 

[The Cobbler]

I would. who told you not to?

 

[850xpeps]

Of course you should.

 

[ForceFed70]

In your location yes - 6mil poly vapor barrier is highly recommended.

 

[kelpaso1]

It depends. Will you be heating this space? If not, then no vapor barrier.

 

[Pack Rat]

In your location yes - 6mil poly vapor barrier is highly recommended.

I decided to use CertainTeed Membrain instead of poly.

 

[Scott H in Wheaton]

It depends. Will you be heating this space? If not, then no vapor barrier.

x2

if not a heated area you don't need the vapor barrier

 

[Bluevista]

Yes. you use a vapor barrier. I've been doing residential remodeling for over 40 years and you always use a vapor barrier on unfaced insulation. I prefer faced because you can glue the drywall, no nail-screw pops/callbacks.

Plus the video on the Roxul website says to use plastic.

 

[Angelfire]

I decided to use CertainTeed Membrain instead of poly.

Well done! The variable vapor retarder is the way to go

Cheers

 

[jack stand]

I assuming that this "porch" floor is open to the outside, what are you doing for floor insulation?
The reason I ask is I just built an addition where 4' of the living space is open to the (bottom) outside. I filled the 10" cavity with rigid p-iso foam (about 6.5 'R' per inch) and at 0-10* I can still feel the cold floor, not unbearable but very noticeable.
If you will be insulating this floor, use foam, and at that point I would suggest just filling your walls with foam as well, sealing all edges with "can foam" esp. if this is going to be living space. (3'5" in the walls is not much insulation)

 

[Pack Rat]

There is not much I can do about the floor. It's a concrete slab with ceramic tile and it
is cold. I will have to use area rugs. When the house was built in the mid 50's it was a
screened in porch. At some point it was walled in and used for storage space.
I tore down the poorly done framing and re-framed, sheathed, and sided it so I have a
12 X 14 room where I'll set up some ham radios, my desk, a book case, my fly tying bench,
my wife's desk, her sewing machine, and craft table. What used to be a home office will
be turned back into a bedroom for the grandkids when they come to visit.

 

[ForceFed70]

It depends. Will you be heating this space? If not, then no vapor barrier.

Yes If it's unheated, it's not required - but it won't hurt anything and allows you the flexibility of heating later. it's cheap and easy, you'd be silly not to.

 

[NUTTSGT]

Unheated now, maybe but what about the future ? I'd put in a vapor barrier now when it's the easiest.

 

[Bigwheels]

30 years in construction definitely a vapor barrier.

 

[Pack Rat]

I have to rely on ambient heating and cooling from the rest of the house.
The only way I could heat the room is with electric baseboard, portable electric heater, or
a kerosene room heater. None are very good options. A mini-split is out of the question.
Would a vapor barrier be advised for the ceiling? I have Roxul between the joists and
10 inch fiberglass batts on top of that. The attic is well ventilated with soffit and ridge vents
along with a power vent.

 

[Jlbc212]

I have to rely on ambient heating and cooling from the rest of the house.
The only way I could heat the room is with electric baseboard, portable electric heater, or
a kerosene room heater. None are very good options. A mini-split is out of the question.
Would a vapor barrier be advised for the ceiling? I have Roxul between the joists and
10 inch fiberglass batts on top of that. The attic is well ventilated with soffit and ridge vents
along with a power vent.

Yes, you need a vapor barrier there too.

 

[NUTTSGT]

I have to rely on ambient heating and cooling from the rest of the house.

Keep in mind, that works both ways. The warmer that room is, the less the house is exposed to a colder temperature on that side....basically becomes an airlock to go outside or buffer against the cold/warmer weather.

 

[Pack Rat]

Keep in mind, that works both ways. The warmer that room is, the less the house is exposed to a colder temperature on that side....basically becomes an airlock to go outside or buffer against the cold/warmer weather.

I understand what you're saying but I can only do so much when I have to work with
what I've got. I can close the door or open windows if I need to.
Looking at it, it's hard to believe it was once a screened in back porch.
Maybe I'll post some pics when I'm done.

 

[dolfans]

It depends. Will you be heating this space? If not, then no vapor barrier.

What if you want to install some kind of heat later on