Home Repair forum - Plastic wrapped insulation sweating

Author

Plastic wrapped insulation sweating

nospamgoingjag

2006-05-28, 7:21 pm

I installed John Mansville fiberglass insulation in the cieling in a
new 12 x 24 addition that connects between house and garage. It is
the kind that has plastic all the way around it except for the ends.
It makes it much nicer to handle when installing.

As I went out this afternoon - probably the hottest day in we've had
in Connecticut since I installed the stuff - I noticed a drip coming
from the wood on the cieling. I have 3/8" plywood on the cieling
because I will be nailing up a tin cieling.

There are no pipes up there so I was baffled. I unscrewed a section
of the plywood and the water was coming from the inside of the plastic
in the instullation. I looked at the batt in the next area and it
wasn't dripping but it was clearly full onf condensation. It looks
like maybe each later of plastic is maybe a double and that the
condensation is between the two layers of plastic. The drip appears
to be coming froma batt where the two pieces of plastic have
separated.

Has anyone every heard of this before? I don't remember reading
anything about not using it in a cieling. It is a very shallow (2-3)
pitch roof. So there is very little space between plywood cieling,
plywood sheething and black rolled roofing.

Any thoughts? Looks like I'm going ot have to rip down all the
plywood and insualltion, even though the moisture does not seem to be
in the fiberglass itself?

Thanks for any help.

Joseph Meehan

2006-05-28, 10:21 pm

nospamgoingjag wrote:
> I installed John Mansville fiberglass insulation in the cieling in a
> new 12 x 24 addition that connects between house and garage. It is
> the kind that has plastic all the way around it except for the ends.
> It makes it much nicer to handle when installing.
>
> As I went out this afternoon - probably the hottest day in we've had
> in Connecticut since I installed the stuff - I noticed a drip coming
> from the wood on the cieling. I have 3/8" plywood on the cieling
> because I will be nailing up a tin cieling.
>
> There are no pipes up there so I was baffled. I unscrewed a section
> of the plywood and the water was coming from the inside of the plastic
> in the instullation. I looked at the batt in the next area and it
> wasn't dripping but it was clearly full onf condensation. It looks
> like maybe each later of plastic is maybe a double and that the
> condensation is between the two layers of plastic. The drip appears
> to be coming froma batt where the two pieces of plastic have
> separated.
>
> Has anyone every heard of this before? I don't remember reading
> anything about not using it in a cieling. It is a very shallow (2-3)
> pitch roof. So there is very little space between plywood cieling,
> plywood sheething and black rolled roofing.
>
> Any thoughts? Looks like I'm going ot have to rip down all the
> plywood and insualltion, even though the moisture does not seem to be
> in the fiberglass itself?
>
> Thanks for any help.

Well it looks like you need to lower the amount of moisture in your home
and more important you need a vapor barrier on the warm side of that
insulation. That plastic wrap is NOT a vapor barrier. It is intentionally
not vapor proof.

--
Joseph Meehan

Dia duit

Tony Hwang

2006-05-28, 11:21 pm

nospamgoingjag wrote:
> I installed John Mansville fiberglass insulation in the cieling in a
> new 12 x 24 addition that connects between house and garage. It is
> the kind that has plastic all the way around it except for the ends.
> It makes it much nicer to handle when installing.
>
> As I went out this afternoon - probably the hottest day in we've had
> in Connecticut since I installed the stuff - I noticed a drip coming
> from the wood on the cieling. I have 3/8" plywood on the cieling
> because I will be nailing up a tin cieling.
>
> There are no pipes up there so I was baffled. I unscrewed a section
> of the plywood and the water was coming from the inside of the plastic
> in the instullation. I looked at the batt in the next area and it
> wasn't dripping but it was clearly full onf condensation. It looks
> like maybe each later of plastic is maybe a double and that the
> condensation is between the two layers of plastic. The drip appears
> to be coming froma batt where the two pieces of plastic have
> separated.
>
> Has anyone every heard of this before? I don't remember reading
> anything about not using it in a cieling. It is a very shallow (2-3)
> pitch roof. So there is very little space between plywood cieling,
> plywood sheething and black rolled roofing.
>
> Any thoughts? Looks like I'm going ot have to rip down all the
> plywood and insualltion, even though the moisture does not seem to be
> in the fiberglass itself?
>
> Thanks for any help.
>
>
Hi,
Think, Breathing, vapour barrier, ventillation.
How do you vent the ceiling?

nospamgoingjag

2006-05-29, 1:21 am

Well duh on me, I did think that plastic was a vapor barrior...

I did put up those waffle things, and they go right to the ridge and
if I recall correctly, the builder did put ridge vents in, and in fact
the inspector made him drill large holes between the center beam so
air could pass back and forth.

But it looks like my main problem was thinking that was a vapor
barrier, and that the waffles would also provide enough air transfer,
but they must not on such a shallow pitch that sees nearly full time
sun.

Now so I get this right, could I just put up a vapor barrier over the
plywood before I put up my tin cieling? If that would work do I have
to worry about the fact that I'll be putting a small nail hole about
ever 6 square inches to hold the "tin" up?

By the way someone mentioned the moisture level in my house. Although
that may be an issue with my old stone foundation, it technically
doesn't apply here as this is a new on slab addition which can't pick
up much moilsture from the main house or garage as there are entrance
doors. I haven't measured the moisture in the addition, but it
doesn't seem any higher than elsewhere. It is currently unheated, and
I used a kerosene heater in it during the winter to do the
insallation, sheetrock and playwood work. I didn't really notice a
moisture issue one way or the other then.

There are 5 large windows in the room so I can circulate air if need
be, but I'm not sure what a reasonable moisture level should be. If I
ever get the thing done, I will be moving the washer and dryer to a
room that is built within that addition, but right now it's just a
passthrough from garage to house.

Thanks to the two posters who responded already.

On Mon, 29 May 2006 01:27:16 GMT, Tony Hwang <dragon40@shaw.ca> wrote:

>Hi,
>Think, Breathing, vapour barrier, ventillation.
>How do you vent the ceiling?

Jay Stootzmann

2006-05-29, 12:21 pm

Check out the information at
http://www.buildingscience.com/resources/homeowner.htm

on the proper design of a vapor barrier system.

I would suggest bringing in a local professional to assess your situation
and help you redo it right.

Just my opinion. Good luck.

"nospamgoingjag" <nospamgoingag@yahoo.com> wrote in message
news:5erk72d33mfmlld26g3r78pt5r0oldeunn@4ax.com...
> Well duh on me, I did think that plastic was a vapor barrior...
>
> I did put up those waffle things, and they go right to the ridge and
> if I recall correctly, the builder did put ridge vents in, and in fact
> the inspector made him drill large holes between the center beam so
> air could pass back and forth.
>
> But it looks like my main problem was thinking that was a vapor
> barrier, and that the waffles would also provide enough air transfer,
> but they must not on such a shallow pitch that sees nearly full time
> sun.
>
> Now so I get this right, could I just put up a vapor barrier over the
> plywood before I put up my tin cieling? If that would work do I have
> to worry about the fact that I'll be putting a small nail hole about
> ever 6 square inches to hold the "tin" up?
>
> By the way someone mentioned the moisture level in my house. Although
> that may be an issue with my old stone foundation, it technically
> doesn't apply here as this is a new on slab addition which can't pick
> up much moilsture from the main house or garage as there are entrance
> doors. I haven't measured the moisture in the addition, but it
> doesn't seem any higher than elsewhere. It is currently unheated, and
> I used a kerosene heater in it during the winter to do the
> insallation, sheetrock and playwood work. I didn't really notice a
> moisture issue one way or the other then.
>
> There are 5 large windows in the room so I can circulate air if need
> be, but I'm not sure what a reasonable moisture level should be. If I
> ever get the thing done, I will be moving the washer and dryer to a
> room that is built within that addition, but right now it's just a
> passthrough from garage to house.
>
> Thanks to the two posters who responded already.
>
> On Mon, 29 May 2006 01:27:16 GMT, Tony Hwang <dragon40@shaw.ca> wrote:
>
>

nospamgoingjag

2006-05-29, 11:21 pm

Thanks for the pointer to that web-stie Jay, useful info on many
things. especially moisture related stuff.

I
On Mon, 29 May 2006 10:03:26 -0600, "Jay Stootzmann"
<Jay.Stootzmann@NOSPAM.ZIP> wrote:

>Check out the information at
>http://www.buildingscience.com/resources/homeowner.htm
>
>on the proper design of a vapor barrier system.
>
>I would suggest bringing in a local professional to assess your situation
>and help you redo it right.
>
>Just my opinion. Good luck.
>
>
>"nospamgoingjag" <nospamgoingag@yahoo.com> wrote in message
>news:5erk72d33mfmlld26g3r78pt5r0oldeunn@4ax.com...
>

nospamgoingjag

2006-06-02, 8:21 am

In checking to get the exact name of what I installed, it clearly
states effective vapor barrier on the front of the plastic.

I have a couple of calls into Johns Manville to see what they have to
say.

On Mon, 29 May 2006 00:28:03 GMT, "Joseph Meehan"
<sligojoe_Spamno@hotmail.com> wrote:

>nospamgoingjag wrote:
>
> Well it looks like you need to lower the amount of moisture in your home
>and more important you need a vapor barrier on the warm side of that
>insulation. That plastic wrap is NOT a vapor barrier. It is intentionally
>not vapor proof.

LinkBot