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#928135 - 12/05/17 03:10 PM Insulation and condensation.
Anonymous
Unregistered


I have a basement foundation that is floored with 3/4 plywood. I have a 6/12 pitched roof with a metal roof that has a vapor barrier under the steel. My question is about insulating the joists below the floored uncondtioned attic space above. The basement will have heat and air and is in Missouri. I want to finish the bottom of the joists/ceiling with corrugated steel. The joists are 2x10 rough sawn pine. How do I insulate this closed space and do I need a vapor barrier? Can the corrugated steel go directly to the joists? Thanks for the help.

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#928154 - 12/05/17 06:51 PM Re: Insulation and condensation. [Re: Anonymous]
Just_Bill Offline
Carpal Tunnel

Registered: 01/27/02
Posts: 23238
Loc: Wilmington, Delaware
Most of what you suggest makes no sense to me. Where is the plywood, where will the steel be??? Steel in an unconditioned space is inviting moisture problems. A few pics might help.

And please register. I hate talking to a nony mouse.

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#928209 - 12/06/17 04:33 PM Re: Insulation and condensation. [Re: Anonymous]
Able_Dog Offline
Carpal Tunnel

Registered: 12/07/03
Posts: 52531
Loc: So. Florida
There should be adequate ventilation of the attic space which you make no mention of. Corrugated steel on the ceilings is a first for me, but I always have maintained "different strokes for different folks". The corrugated can be attached to the joist if it runs perpendicular to the joists. May want to check with a string and shim where necessary.

You have to insulate the ceiling before you put the corrugated steel ceiling up since the attic is floored. I would think you don't need a vapor barrier on the underside of the insulation, but see what others have to say.

I have stopped asking "why are you doing it this way", so I won't.

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#928230 - 12/07/17 01:36 AM Re: Insulation and condensation. [Re: Anonymous]
JimTheTinkerer Offline
" Humming Bulb "
Carpal Tunnel

Registered: 03/25/03
Posts: 22521
Loc: US
Read carefully:

https://insulationinstitute.org/im-a-homeowner/about-insulation/preventing-moisture-issues/

Similar to the ground space, the attice is
either sealed off from below and well-vented,
or closely sealed in the conditioned space with
extensive ventilation running up the roof.
Things like maintaining a seal when there's expansion
and contraction have to be covered.
(Like, nails with wider drilled holes and seal washers, etc.)


There are currugated steel roofing materials, but they are
specially made for that, so they don't rot away.

_________________________
"Pay no attention to the man behind the curtain!"
--The Wizard of Oz

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#928248 - 12/07/17 11:40 AM Re: Insulation and condensation. [Re: Anonymous]
Outdoors Offline
first timer

Registered: 12/05/17
Posts: 1
Thanks for the so far. I hope I can better explain my question. Here it goes.
I have a floored uncondtioned attic space.
Below is a conditioned, heat/cool, living area.
The ceiling right now is 2x10 joists with 3/4 plywood on top. No air gaps.
I want to install a used corrugated steel to the bottom of the rafters. Cabin look.

Should I install a vapor barrier on the under side of the joists after I insulate between the joists with fiberglass face barting?
Does anyone see a monster problem with doing it this way.

Thanks for the help

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#928332 - 12/08/17 01:49 PM Re: Insulation and condensation. [Re: Outdoors]
JimTheTinkerer Offline
" Humming Bulb "
Carpal Tunnel

Registered: 03/25/03
Posts: 22521
Loc: US
Maybe if it was described from the putside (top) in...

Are you thinking:

---------------------
(roofing shingles, tarpaper??)
--------------------
(3/4" plywood)
--------------------
(2x10 spars)
--------------------
(corrugated steeel)
-----------------------
(Living space...conditioned, not?)
----------------------

Is tht it?

That makes for a big airflow space....which can be good.
But...stuffing the 2x10 space w/insulation and no
airflow can be trouble.
They do sell thin foam baffles you can put against the roof.
You need bottom and ridge venting.

It's worth a bit of browsing at the contruction sites.

_________________________
"Pay no attention to the man behind the curtain!"
--The Wizard of Oz

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#928454 - Yesterday at 02:02 AM Re: Insulation and condensation. [Re: JimTheTinkerer]
Lawrence Gonzale Offline
newbie

Registered: 10/16/17
Posts: 2
Originally Posted By JimTheTinkerer

They do sell thin foam baffles you can put against the roof.



Do they come in different types and qualities? What should I look for In them?

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#928457 - Yesterday at 07:39 AM Re: Insulation and condensation. [Re: Lawrence Gonzale]
CabinConnection Offline
Bigfoot
Carpal Tunnel

Registered: 01/20/04
Posts: 50487
Loc: The Indianhead's Left Nostril....
Outdoors and Lawrence Gonzale -

Welcome to HW. smile

Are you the same person, and also the "Anonymous" that started this thread? Or are we trying to address three different questions/locations??? crazy

Please update your profile to show your location. It makes a difference when talking about insulation.

Thank you, Al

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