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Kathleen Alberding
Senior Member
Username: kalberding

Post Number: 7
Registered: 06-2004
Posted on Friday, July 07, 2006 - 03:59 pm:   Edit PostDelete PostPrint Post

I am working on specifing a paint system for an unfinished CMU wall in a natatorium. The wall has a vapor impermeable air barrier system on it's exterior face with insulation outboard of the barrier in the air cavity. Epoxy paint has been recommended for the interior face but I am concerned about trapping moisture in the block. Does anyone have experience with this type of wall assembly?
Ron Beard CCS
Senior Member
Username: rm_beard_ccs

Post Number: 139
Registered: 10-2002
Posted on Friday, July 07, 2006 - 04:33 pm:   Edit PostDelete PostPrint Post

What “vapor impermeable air barrier” are you specifying??? ......air barriers are intended to be permeable; vapor retarders should be impermeable.

Is the project located in the deep south? How much insulation [R-value] and what type of insulation? Has the location of the dew point been determined?

Vapor drive is very high in natatorium type applications. You are justified in being concerned about the proper design of this type of wall. But there are a whole host of questions that need to be determined before a “correct” answer is selected to include the design of the HVAC system, what type of siding/veneer is to be used on the outside of your CMU wall, ventibility [sp?] of the cavity, etc.

Wherever coating you use on the inside face of the CMU wall should, as a minimum, be cleanable, imperious to moisture and have high elasticity to bridge current and future hairline cracks in the CMU.

Ron
Russ Hinkle, AIA, CCS
Senior Member
Username: rhinkle

Post Number: 8
Registered: 02-2006
Posted on Friday, July 07, 2006 - 04:38 pm:   Edit PostDelete PostPrint Post

Don't forget to address the ceiling/roof as well. It can be as big and issue as the wall design.

Last pool I did, I worked with my paint rep. to specify High performance coatings; primer, 1st coat and 2nd coat were all high performance the was applied to the walls and ceiling. The coatings on the inside of the wall were our vapor barrier (located in Michigan).
Ron Beard CCS
Senior Member
Username: rm_beard_ccs

Post Number: 140
Registered: 10-2002
Posted on Friday, July 07, 2006 - 05:11 pm:   Edit PostDelete PostPrint Post

Russ is correct. In my haste, I did not mention the roof. On one project a while back we had a research facility with large vats of frogs, fish, and seaweed with a roof system consisting of pre-engineered wood trusses, plywood roof sheathing, vented insulating panels [with an internal 1" air space], and a standing seam roof. We used a high-end air barrier [Blue Skin] and we also coated the exposed galvanized gussets plates with an asphaltic based coating before painting the wood trusses and underside of the plywood roof sheathing.

On another project we used HP coatings for both the exposed steel joists and metal deck.

The last few projects had lots of glass walls which makes calculations as lot easier. <g>

Ron
Ken Moore, FCSI, CCS, SCIP
Intermediate Member
Username: kjmoore

Post Number: 4
Registered: 06-2006
Posted on Saturday, July 08, 2006 - 05:23 pm:   Edit PostDelete PostPrint Post

If roof construction is metal deck and trusses, suggest metal deck be galvanized; trusses be primed with a zinc rich organic primerer.

Spec deck be mechanically fastened to steel framing, not welded. Welding will burn off galvanized coating and acellerate rusting.

Spec a spray applied epoxy coating that will go over galvanized deck, zinc rich organic primer, galvanized duct work, conduit and roof drainage system. Be selective, not all epoxies can be applied directly to galvanize.
Ron Beard CCS
Senior Member
Username: rm_beard_ccs

Post Number: 141
Registered: 10-2002
Posted on Sunday, July 09, 2006 - 01:44 pm:   Edit PostDelete PostPrint Post

Ken:
In applications such as this, I use a urethane zinc-rich and epoxy primers, polyurethane intermediate coats, and a fluoropolymer polyurethane finish coatings.

Translation: “Series 90-97 Zinc Primer,” “Series 161 Fascure Primer Coat,” “Series 1075 Endura- Shield,” and “Series 1070 Fluoronar Finish Coat” all by Tnemec.

Ron
John Bunzick, CCS, CCCA
Senior Member
Username: bunzick

Post Number: 550
Registered: 03-2002
Posted on Monday, July 10, 2006 - 08:44 am:   Edit PostDelete PostPrint Post

Ron, Just a note that it is not necessarily true that air barriers should be permeable. Here in Massachusetts, it is very common to use a vapor impermeable air barrier with outboard insulation. (I don't know where Kathleen's project is.) Thus, the air barrier is also the vapor retarder. By putting the insulation outside of the air barrier, you have a much simpler condition regarding vapor drive and dew point such that the one product can perform both functions.

However, Kathleen is right to have some concern due to a natatorium's high RH, and perhaps that's the reason for your comment. Acrylic paints tend to be quite permeable, so if the determination is that the wall needs to dry towards the interior, though with high humidity I'm not sure how it would, I'd look at this type of paint.
Kathleen Alberding
Senior Member
Username: kalberding

Post Number: 8
Registered: 06-2004
Posted on Monday, July 10, 2006 - 09:15 am:   Edit PostDelete PostPrint Post

The project is in Texas, but the architect has detailed the wall similar to how we would here in the Northeast. The air/vapor barrier is "Blueskin". There is a 2 inch airspace and then a Stucco skin.

My thinking is that epoxy would trap moisture but with acrylic paint the wall humidity has a chance of breathing or "equalizing" with the space. In either case, I am worried about leaching, paint peeling, mold, etc...
Kenneth C. Crocco
Senior Member
Username: kcrocco

Post Number: 57
Registered: 04-2003
Posted on Monday, July 10, 2006 - 11:48 am:   Edit PostDelete PostPrint Post

There are manufacturers promoting the use of exterior vapor permeable air barriers only. (Recommending against the use of vapor impermeable air barriers.) Contact Prosoco to hear what they have to say about this application.

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