plastic sheet as "vapor" barrier in attic??
john shoosmith
Our attic ( in Arizona) has blown fiberglass all over the floor. The
above part is bare - which is kind of weird compared to an east coast
home, but everyone here says that this is normal.
This is our first home here. A neighbor states that the summer temp
in his attic was about 140 degrees on a summer day before he made
modifications.
Anyway, to the point...
I have heard or seen that plastic sheeting secured over the fiberglass
insulation will improve the insulative quality of this hot attic.
I've also heard such things as "the wood needs to breath"..etc. Is
there any drawback at all to staple-gunning plastic sheet over the
insulated part of the attic? And what would happen if I did that to
the bare part up above too?
Thanks a bunch!
John Shoosmith
Tempe Az
Richard
John, Sounds interesting, have you gotten any responses? What was it
that your
neighbor did, its not quite clear.
Thanks Richard
foxeye
foxeye wrote:
I would not see what the plastic will accomplish. Yes, wood needs to
breate and so does your house. I would think IMHO that plastic would
entrap any moisture etc. I know arizona is dry, but your house still
gets some moisstute from cooling, cooking and water usage. I may be
wrong, but I am interested in this topic from a curiosity standpoint.
It counters everything I have ever read or heard about using plastic
to seal up a residence. Drafts are one thing, breathing is another,
and a house needs to breate.
curious foxeye
On 7 Apr 1998 01:17:05 -0700, jps...@primenet.com (john shoosmith)
wrote:
>
>Our attic ( in Arizona) has blown fiberglass all over the floor. The
>above part is bare - which is kind of weird compared to an east coast
>home, but everyone here says that this is normal.
>
>This is our first home here. A neighbor states that the summer temp
>in his attic was about 140 degrees on a summer day before he made
>modifications.
>
>Anyway, to the point...
>
>I have heard or seen that plastic sheeting secured over the fiberglass
>insulation will improve the insulative quality of this hot attic.
>I've also heard such things as "the wood needs to breath"..etc. Is
>there any drawback at all to staple-gunning plastic sheet over the
>insulated part of the attic? And what would happen if I did that to
>the bare part up above too?
>
>Thanks a bunch!
>
>John Shoosmith
>Tempe Az
>
The opinions expressed are mine, and mine alone.
My wife had no input whatsoever.Remove www from
email for correct address.
NAR #70031
bvi...@weir.net
Your biggest problem you will probably have is with condensation. An attic is
should breath.
1) A vapor barrier should be between the insulation and the room that is
being insulated. You should not place a vapor barrier between the insulation
and the attic space.
2) You shouldnt insulate the rafters in an attic. If you have a finished
attic (ie. drywall, paneling, or such) You can insulate the ceiling of that,
but you must leave the rafters open (yes to breathe). Condensation can occur
or you might cause the life of your shingles to shorten because of the
trapped heat. I live on the east coast, and I have never seen a house here
with insulation in the attic floor and rafters.
3) If you have a heat problem in your attic, I suggest you install more
vents. That is how an attic is designed to work. By creating an intake and
release of air, it cools and carries off the humidity.
In article <3529e062...@news.primenet.com>,
jps...@primenet.com (john shoosmith) wrote:
>
>
> Our attic ( in Arizona) has blown fiberglass all over the floor. The
> above part is bare - which is kind of weird compared to an east coast
> home, but everyone here says that this is normal.
>
> This is our first home here. A neighbor states that the summer temp
> in his attic was about 140 degrees on a summer day before he made
> modifications.
>
> Anyway, to the point...
>
> I have heard or seen that plastic sheeting secured over the fiberglass
> insulation will improve the insulative quality of this hot attic.
> I've also heard such things as "the wood needs to breath"..etc. Is
> there any drawback at all to staple-gunning plastic sheet over the
> insulated part of the attic? And what would happen if I did that to
> the bare part up above too?
>
> Thanks a bunch!
>
> John Shoosmith
> Tempe Az
>
>
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/ Now offering spam-free web-based newsreading
bvi...@weir.net
A note concerning my last post. I understand that you live in AZ and the
humidity is quite low. I still recommend the additional vents because of the
reasons I stated.
danh...@millcomm.com
This shouldn't be done in the frost belt (since the plastic will trap
moisture), but it's probably OK in your area. You should also check out
the ventillation in the attic.
In <3529e062...@news.primenet.com>, jps...@primenet.com (john shoosmith) writes:
>
>Our attic ( in Arizona) has blown fiberglass all over the floor. The
>above part is bare - which is kind of weird compared to an east coast
>home, but everyone here says that this is normal.
>
>This is our first home here. A neighbor states that the summer temp
>in his attic was about 140 degrees on a summer day before he made
>modifications.
>
>Anyway, to the point...
>
>I have heard or seen that plastic sheeting secured over the fiberglass
>insulation will improve the insulative quality of this hot attic.
>I've also heard such things as "the wood needs to breath"..etc. Is
>there any drawback at all to staple-gunning plastic sheet over the
>insulated part of the attic? And what would happen if I did that to
>the bare part up above too?
>
>Thanks a bunch!
>
>John Shoosmith
>Tempe Az
>
>
Dan Hicks
Hey!! My advice is free -- take it for what it's worth!
http://www.millcomm.com/~danhicks
Wendy Jones
Covering everything can be done but as I have read here in this group many
times, one of the drawbacks is that the attic can become "to sealed". In
this case because of all the plastic stapled, condensation can accummulate
and cause problems with the roof and shingles. Again, this is just what I
have read here over the past few months. Hope it helps.
Richard <castl...@rocketmail.com> wrote in article
<352A922E...@rocketmail.com>...
> John, Sounds interesting, have you gotten any responses? What was
it
> that your
> neighbor did, its not quite clear.
> Thanks Richard
>
> john shoosmith wrote:
>
Green Home Inspections Ltd.
> Hi,
I'm not really sure who to address this answer too as I did not get the
original message. Stapling plastic on the top or cold side of the insulation
is NOT a good idea. If you want to improve the effectiveness of the
insulation you can put a semi-permeable membrane down on the top, but it MUST
allow moisture to leave the house. Putting plastic sheeting on top of the
insulation traps moisture trying to leave the house within the insulation. On
colder days this water will condense and you will see beading of water on the
underside of the plastic. In addition fibreglass when wet does not insulate
anymore AND even if it dries out it will not insulate anymore. You may put
plastic on the insulation if you plan to add more insulation, but only if the
ratio is two thirds of insulation on the cold side of the plastic.The plastic
sheeting on the roof itself will do no benefit. The attic itself should be
the same temperature as outside, if you have heat build up you should consider
adding roof vents.
Good Luck,
Jonathan Ham
President, Green Home Inspections Ltd.
Ottawa, Canada
> >
danh...@millcomm.com
You're posting from Canada, but the original post, as I recall, was from
the US southwest. It's arguable that the humidity will be higher outside
than in there, and, in any event, it won't get cold enough to cause
condensation under the plastic. Having said that, though, I too would be
more comfortable with a permeable layer such as housewrap.