| Author |
Message |
Anonymous
| | Posted on Thursday, October 16, 2008 - 07:31 pm: |    |
Can anyone offer some insight on principle of using vapor barriers on interior walls of separately conditioned (in this case, large computer) room? It's only schematic, so specific design is not refined; are there specific concerns/issues that I'm not aware of? |
Lynn Javoroski CSI CCS LEEDŽ AP SCIP Affiliate
Senior Member
Username: lynn_javoroski
Post Number: 817
Registered: 07-2002
| | Posted on Friday, October 17, 2008 - 09:50 am: | |
Since the room is separately conditioned, if it also has a need to be humidity controlled (differently from the other adjacent areas), that could be a reason to separate it. |
Anonymous
| | Posted on Friday, October 17, 2008 - 11:21 am: | |
My (layperson) presumption is the need for lots of cooling capacity and very low humidity control...and thus, possibly creating conditions for condensation between/with surrounding, "normally" (office-type occupied) conditioned spaces. My initial inquiry was to solicit anyone previously encountering such on a project, what some considerations might be, and how, if at all, was resolved. If vapor barrier is determined (by mech engr calcs), then to what degree does one consider just foil-faced insulation batts, foil-back gyp bd, "continuously-sealed" polyethylene sheet, or something "more robust"? |
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre
Post Number: 839
Registered: 07-2002
| | Posted on Friday, October 17, 2008 - 12:26 pm: | |
if you need an interior vapor barrier, then make sure that you also have the mechanical system adjusted to handle the difference in moisture. You want most of the moisture/conditioning difference to be taken up mechanically with the vapor barrier mostly there to confine the mechanical system to one room. (you don't want the mechanical system sucking the moisture out of all the adjoining rooms either.
Think of it in reverse: in a very wet area such as a steam room, you want to confine the moisture only to the steam room and for it to be vented out of that room. so you put the vapor barrier in and increase the venting mechanically.
so, the long answer: you need to find out how the mechanical system will handle the issue and then provide the vapor barrier that corresponds to that. |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 124
Registered: 01-2008
| | Posted on Friday, October 17, 2008 - 12:56 pm: | |
Anonymous,
Foil-faced anything and "continuously-sealed" polyethylene sheet are about a robust as you can get, short of self-adhesive air/vapour barriers which are the "most rubust."
Less robust are paper faced batts or vapor retarder primers. Which in the PNW are just fine but maybe not for the conditions you vaguely describe.
Listen to Anne. |
Anonymous
| | Posted on Friday, October 17, 2008 - 12:38 pm: | |
It is HIGHLY unlikely that you need a vapor retarder for an interior partition. Unless there is a delta T and delta RH large enough to create condensation via vapor diffusion (and I highly doubt this), you do not need a vapor retarder. Vapor retarders do nothing to prevent by far the biggest problem with moisture transfer across wall assemblies - bulk air transport through holes in the assembly. Plug the holes and you've solved 90% of the problem. Vapor retarders are for diffusion, and only needed for extreme conditions (think N Alaska). Don't believe me? Read Lstiburek's body of knowlegde on the subject at his web site buildingscience.com. He's got lots of "science digests" posted for free download. |
Anonymous
| | Posted on Friday, October 17, 2008 - 02:36 pm: | |
anonymous: try explaining to the owner why they are getting mold on their wall partitions in the same corridor as the steam room. |
Curt Norton, CSI, CCS
Senior Member
Username: curtn
Post Number: 118
Registered: 06-2002
| | Posted on Friday, October 17, 2008 - 02:41 pm: | |
with a steam room you have a large delta for temperature and rh, that is not the condition Anon described. |
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