# Which is better? (Non-vented roof construction with indoor pool)



## acorn construction (Feb 19, 2008)

*roof decking.*

There are several companies that make a self venting roof panel. usually a 2"insulation board with 3/4" air passages that are secured to wood decking. We used it on a Church 10yr ago that had major Ice Dam problems. Stopped the killer Ice. So we had intake and exaust venting buildt in. Be careful to not have to many Vapor barriers. And I hope you havc people have the room completely separate.


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## Ed the Roofer (Jan 27, 2007)

Atlas Insulation makes vented polyisocyanurate insulation with an attached osb board decking adhered to the top.

Real quick edit: I found a JM spec for a similar product.

http://www.jm.com/roofing_systems/builtup/products/Vented_Nailboard_RS-5164.pdf

2nd Edit: Here is a link to the Atlas version of Cross Vent Insulation.

http://atlasroofing.methodfactory.c...s/commercial/atlas_nailable_guide_details.pdf

The rest of your question has too many unknown intangibles to properly answer at this time and will require more research by me.

Ed


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## rayt (Feb 19, 2008)

Thanks, Acorn.
The only redundant vapor barrier will be in the pool room to trap all the water in the pool room where it will be remediated with an air handling system as specified by a pro.

The radiant barrier, I guess would be another vapor barrier and it would be applied under roof decking so perhaps I need to rethink that part.

HVAC will be in a basement-level mechanical room separated from living space by the garage. 

Interesting idea about the self-venting roof panel, I'll have to check into that.


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## Ed the Roofer (Jan 27, 2007)

It is a little on the expensive side, but if moisture permeated the exterior of the decking, at least it has the opportunity to flow with a properly designed continuous intake ventilation and exhaust ridge ventilation system.

Ed


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## PKHI (Oct 23, 2007)

Ed would this be in your opinion a good place to use sleepers and have a second roof deck to achieve ventilation?


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## rayt (Feb 19, 2008)

Thanks, Ed. I wish I would've known of this forum back when I first began researching SIPs. 
To prevent moisture issues associated with the indoor pool I understand a hot roof (not vented) is best.

If you have a minute, will you list the intangibles so I might clarify for all. Tried to be comprehensive in my question without writing a novel, and it sounds like there's some detail I should add. Thanks again!


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## Ed the Roofer (Jan 27, 2007)

Nothing in particular, as the Hot Roof scenario is relatively new and not long term field tested yet.

By the way, check out the shingle manufacturers warranty limitations again. The last I checked, the unvented, or hot roof had a reduced down to a 10 year limit on materials from Certainteed.

Ed


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## rayt (Feb 19, 2008)

PKHI,
That's what we're thinking now for preventing ice dams.
The last replies on this thread about venting got us to thinking about venting and the concern of ice dams.
Since the indoor pool requires the roof to be sealed (not vented) we're looking at applying roofing over the top as you describe.

At the same time there's the concern of water vapor from the interior migrating into the roof and forming a sheet of ice in the underside of the roof deck.

A hot roof with sleepers, OSB, then finished roof might be just the solution.?.?.?


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## rayt (Feb 19, 2008)

Ed, thanks for the heads up on warranty. I saw you mention that on another thread--definitely will weigh in the decision. What do you think of this improvement suggested by PKHI?
With that added, the roof would look like this from the outside in:
shingle
ice shield
osb
sleepers
vapor barrier
osb
radiant barrier
14" BCIs filled in with damp spray paper insulation
TnG pine


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## PKHI (Oct 23, 2007)

The only reason I mentioned it is we sided a pool addition that was done with scissor trusses and the engineer spec'd filling the truss space with spray foam, and adding sleepers to get vent space.

FWIW I too have seen what happens to shingles that are on non vented roofs, they tend to get yucky pretty fast.


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## Ed the Roofer (Jan 27, 2007)

I am either having a brain cramp, or am not familiar with the acronym BCI, which obviously means insulation for the last "I".

From what I read, but without practical hands on experience to fall back on, the spray on closed cell insulation eliminates the necessity for ventilation.

If you need me to, I can post this question on another forum where several members are much more experienced with that technology, but it may take a few days for the responses.

Ed


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## rayt (Feb 19, 2008)

Thanks, Ed. A BCI is a wood I-joist. That's what we'd use for rafters, filling in with damp spray recycled paper insulation (from my research, its also called cellulose fiber insulation, the same as what you're referring to).

The BCI's are really what opened the issue for us as I'm not sure of the durability of the wood I-Joists (BCIs). And the BCIs will be replacing Glulams on our plan. 

So 2-fold:
1. Seems like we're getting to the bottom of the venting issue: build hot roof with a cold roof over it, basically.
2. Will my roof be strong and solid for many many years to come, constructed this way on top of BCIs rather than Glulams? Its a log house and the builder tells me the roof basically ties the structure together.

Thanks you all for your advise on this. Its been really helpful this far!!


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## Ed the Roofer (Jan 27, 2007)

I have posted a link to this topic thread in a forum hoping to get noticed by an expert in this field, whos knowledge about this is much more extensive than mine, and whos years in the field and expertice is highly revered by myself and many other fellow posting members on an inspection site.

Ed


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## ncgrogan (Dec 3, 2006)

Where are you located at? Location makes a big difference as to which direction your moisture drive comes from most of the year. It changes from winter to summer. with winter usually having the biggest temp. differential. I would do a hygrothemal analysis on your system using WUFI or a similar program. Convential wisdom I don't think will take you very far in this situation.


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## rayt (Feb 19, 2008)

Thank you, Ed.

NC,
I'm in the foothills of the Bighorn Mountains, north--central WY, 4400', high desert (only 9" of rain last year), into 100s in summer and this winter was unordinarily harsh reaching -50.
I read the info on buildingsciences.com that explains much lower indoor relative humidity is needed in the winter. We *are* working with a specialist to design a humidity control system for the pool room, but want to make sure we take every precaution with the building (roof), as well.
Not sure what you mean by "hygrothemal analysis on your system using WUFI"--that's greek to me so I'll web search it and follow up.
Thank you.


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## ncgrogan (Dec 3, 2006)

good lord :laughing: that is one heck of a temperature swing. WUFI is a software developed in germany and is sponsered in the states by oak ridge. Its a great tool but can take quite a bit of time to make use of. Its simple to use and complex to understand if that makes any sense. There is a free version available but it doesn't have some of the bells and whistles the full version we have here at work does. 

http://web.ornl.gov/sci/btc/apps/moisture/

Would be interesting to see what you decide. We have a project right now which is going to have an indoor pool on the 17th floor. Somehow I'm sure it will be a problem later down the road.


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## rayt (Feb 19, 2008)

17th floor, Wow! 
Thanks for the link. Found some stuff here http://www.ibpsa.org/ too. Doesn't quite look like DYI, but far more helpful than what I've dug up so far.

The funny thing is people keep telling me I don't need to worry about humidity because its so dry here. When in reality, humidity from the pool room will naturally want to go into the dry living spaces. And I'll actually have *more* evaporation from the pool surface with such dry air.


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## ncgrogan (Dec 3, 2006)

Thats correct...not to try and scare you but I've seen a case study where an indoor pool was causing moisture problems (efflorescence, cryptoflorescence, mold, etc. ) from as far away as 150' from the pool. Good luck with your project, best advice I can give you is to COMPLETELY seperate the area with the pool from your house. In otherwords I would have an expansion joint from roof to foundation between the pool room and your house. That way if you have issues down the road at least its in a confined area. Sorry I can't help more but I'm not touching that with a 10 foot pole especially with your climate.


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## Ed the Roofer (Jan 27, 2007)

elbartree,

I did not forget about you. The gentleman I contacted was unable to register on this forum for some reason, but just from the preliminary information I had given to him last week, he responded with the following message. 

P.S. I also e-mailed him the original post for him to view the attachment.

Ed


This is the message:

_"Ed: still haven't been able to get on the DIY site._

_If I were to build a pool (extremely high air rh's), I would probably_
_use a spray on, high density, closed cell polyurethane. It produces an_
_airtight surface, has high R value and is a high quality vapour barrier-_
_really needed in this pool environment. Have to make sure that there_
_are no thermal bridges through the foam layer as these will lead to_
_condensation/dripping._

_It would be good to see the roof design and structure though; it may_
_change my recomendation or I may need to make a few suggestions/recommend_
_changes._

_Brian"_


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## rayt (Feb 19, 2008)

Thank you, Ed!

My appologies for only just now following up on this. 

I'm not sure if the BCI (wood I-joist) will create a thermal bridge, but our current plan *is* to use closed-cell spray foam insulation (as opposed to our plan a month ago to use damp-spray cellulose), for the waterproofing qualities Brian points out. Updated description of roof construction accordingly:

shingle
ice shield
osb
sleepers
vapor barrier
osb
radiant barrier
14" BCIs filled in with closed-cell spray foam insulation
TnG pine

I have the framing plan, but its just a bunch of I-joists. The structure is 2 volumes:
1 volume is the pool room, pool systems room, and airlock entry
2nd volume is typical living spaces 
They are separated by a 2x6 framed wall topped by a clerestory.
This creates 2 opposing shed roofs with the high point of the small volume 4' lower than that of the large volume (with a short window wall filling in the gap).

Maybe this cross-section helps. The small (left) side is the pool room.


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## Ed the Roofer (Jan 27, 2007)

I once again relayed your recent post and concers or questions along to Brian at that other forum.

I will let you know what his comments are.

Ed


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