Posted By Matt G on 03 Jan 2011 06:52 AM
Check out this BuildingScience.com article.  And this one.

Thanks Matt
Great info

Posted By chadman51 on 03 Jan 2011 06:44 PM
thanks Dana. I do have ice and water shelid on the entire roof. Is that a problem?

Possibly, since it forces you to set it up to dry toward the interior-only.  Wince the Ice & Water Shield is vapor-impermeable it won't let water vapor out of the sheathing to  the exterior, and winter moisture can build up in the sheathing.  If going with closed-cell foam it means you're limited to ~2" max (any climate) unless you give it a vent channel below the roof deck.

If going with open cell foam or cellulose or a combination of closed-cell foam + fiber it depends on local climate. 

What's your zip code?

19720
Was looking at open cell. I was reading the stuff on the links that Matt posted and now I'm really confused.

I was looking at this detail.

http://www.buildingscience.com/docu...oof-design

page 6

Dana
On a side note. What way do you think is best for the walls?
I have 2x4 walls. Should I put a 1x on them to stop thermal bridging?
I was thinking of foaming these walls also.

Thanks

Take a peek at this one: http://www.buildingscience.com/documents/reports/rr-1001-moisture-safe-unvented-wood-roof-systems

Particularly look at Table 3 p.11 (p12 in .pdf pagination.) With zero capacity to dry toward the exterior, in DE to go un-vented you'll be better off going with a 1-2" shot of closed cell on the roof deck to provide a tolerant condensing surface, with the remainder of the total fill as wet-sprayed cellulose (which wicks and redistributes any condensation that forms during cold weather.) An all open-cell setup would work only if you provided venting under the sheathing. With the metal roof inherently vented (with 20/20 hindsight), you would have been better off using semi-permeable roofing felt rather than vapor IMpermeable Ice & Water Shield.

With to use open cell you'll have to provide a vented cavity to keep the sheathing dry. It needn't be much- 3/8" or so would be ideal. But since you only have a 5.5" deep rafter bay perhaps the best option at this point is to is go unvented, but with 5" of the medium-density Icynene product, which is lower R/higher perm than generic closed cell foam. It's only down to 1.3perms @ 3", (as opposed to under 1 perm @ 2" for ccSPF), so at 5" you'd be at about 1 perm and R25, which is more than the R20-ish you'd get with half-pound foam. see: http://www.icynene.com/assets/documents/pdfs/Products/ICYNENE-MD-R-200-Specification-Sheets-US.pdf It's significantly cheaper than most ccSPF, but more expensive than open cell. The cheaper unvented alternative would be 1" of closed cell polyurethane + 4.5" of wet-sprayed cellulose, which would run R22-ish. Figure on at least a buck a square foot for the ccSPF, but the sprayed cellulose would be pretty cheap relative to most open cell, and would perform comparably (or better.)

As for the walls, if you're stripping the siding, add at least an inch of exterior XPS as a thermal break, and leave a 3/8" vent gap (aka "rainscreen"), between the XPS & siding, and dense-pack cellulose in the wall cavities. If you're gutting the interior you can wet-spray cellulose in there after air-sealing with caulk & spot foaming to get better price/performance than open cell foam. The steady-state R of open cell and cellulose are similar, but the thermal mass of the cellulose is an order of magnitude higher, which gives it a somewhat better dynamic performance.

Alternatively, for more money you can get a higher R going with 3" of ccSPF (~ R18) at ~$3.25-3.75/square foot or 3" of the MD-R-200 Icynene (~ R15) for ~$2-2.50/foot (get real quotes- prices vary by region & installer), or going with full-depth dense-packed JM Spider, or Certainteed Optima (specify 1.8lbs+ density for either) noo-skool ultra-fine fiberglass, which will also run ~ R15. Similarly, a "flash and fill", with 1" of closed cell polyurethane on the exterior, with wet-sprayed cellulose for the remaining depth yields an honest R15 cavity fill in 2x4 construction.

With a rainscreen gap under the siding, or with closed cell foam cavity fill you can basically not worry about vapor permeance of the interior layers. Without a rainscreen you'd want to use a vapor-retardent latex primer on the interior walls with open cell or fiber cavity fill.

Seriously, if you're re-siding and re-windowing, think about going with 2-3" of iso (not XPS) on the exterior and using spray cellulose in the wall cavities, which would put you at ~ R25-30 center-cavity. That would have been a cheaper-easier upgrade to the roof R too, had the metal roofing not already been installed. 3.5" thick nailbase iso panels from Atlas or Hunter runs ~R19-ish, at which point a fill of open-cell Icynene or wet-spray cellulose in the rafter bays would have rounded it up nicely to code R-levels, but with R19 of thermal break over the rafters for even better performance. See: http://www.hpanels.com/2009/pages/pdfs/Lit_Prod_Color/H-Shield-NB.pdf (more 20/20/ hindsight, I s'pose.)

Confused even more now? ;-)

holy moley
I have the siding already done.
I used Mastic Structure EPS. Which has 1" of foam behind it.

So let me see if I got this correct.
Roof
So I have these options.
1 - add continuous vent and go with open cell that was quoted
2 - have Icynene reprice it at 5" of medium density
3 - put the xps board between the rafters and have cellulose sprayed to that

Wall
1 - spray 1" of open cell and fill the rest with sprayed cellulose
2 - fill cavity with medium density foam
(not sure which is better)

I think im pretty confused. Should I have a headache after ready this????


thanks I really appreciate it.

Also my quotes are
Icynene light density non CFC/HCFC
Demilec Agribalance

Are these comparable products?

Posted By chadman51 on 04 Jan 2011 04:19 PM
holy moley
I have the siding already done.
I used Mastic Structure EPS. Which has 1" of foam behind it.

So let me see if I got this correct.
Roof
So I have these options.
1 - add continuous vent and go with open cell that was quoted
2 - have Icynene reprice it at 5" of medium density
3 - put the xps board between the rafters and have cellulose sprayed to that

Wall
1 - spray 1" of open cell and fill the rest with sprayed cellulose
2 - fill cavity with medium density foam
(not sure which is better)

I think im pretty confused. Should I have a headache after ready this????


thanks I really appreciate it.

Also my quotes are
Icynene light density non CFC/HCFC
Demilec Agribalance

Are these comparable products?

On the roof options, forget about option #3- cut'n'cobble fit + seal on XPS is more trouble/expensive than it's worth.  1" of closed cell polyurethane will form a more reliable air seal than you can get with a cut'n'cobble on XPS, with a comparable (in the end, if you did the XPS right), installed price.  Your best option is #2 IMHO.

On the wall option, #1 should be CLOSED CELL POLYURETHANE + spray cellulose.  The open cell is too vapor permeable to protect the sheathing at only 1" thickness.

If the min-thickness of the insulated siding is 1" of EPS on the exterior you've added another ~R4 to the stackup, but that increases to ~R4.5 when it's below freezing.  In your climate this then gives you another option: Seal + spray cellulose only as the wall cavity fill.  With more than ~25% of the total R on the exterior of the sheathing, and cellulose up against the sheathing A: The number of hours in a season that the sheathing is below the dew point of the interior conditioned-space air (between 35-40F, assuming it's 69-70F, 30-35% RH indoors) has been much reduced, and B. The wicking action & buffering capacity of the cellulose minimizes moisture absorption by the sheathing & studs.  If you go this route it's worth air-sealing each stud bay at the sheathing with caulking before insulating. (With foam that step might be overkill, but not with fiber.)  If the sheathing is plank sheathing and you didn't detail the exterior foam to make it a near perfect air-barrier, or the thin-part of the insulated siding is LESS than 1" thick, it's probably worth going with the 1" of closed cell + cellulose, or a full cavity fill of low-density/mid-density foam.  Vinyl-clad EPS like Mastic Structure is semi-permeable at ~5perms, but not an inherent air-barrier, and doesn't provide a drain-plane, and not NEARLY as out-ward drying as a rainscreened siding would be.  (Hopefully there's some housewrap or #15 felt between it and the sheathing as a drain-plane & air-barrier.)


Demilec is normally installed and specified at 0.7.lbs density, while open cell Icynene is a half-pound density foam. The Demilec will add another ~R1.5 or so to a 2x4 stud bay compared to Icynene, but they are otherwise fairly similar.   (They're claiming R15.6 on for 2x4 construction on their spec sheet, compared to low density Icynene at R13, but I expect real-world variances in density would make that slightly optimistic.)  Wet spray cellulose would be ~ R13 in a steady-state ASTM C 518 type test, but would slightly outperform Icynene in a dynamic test due to both thermal mass and changes in R with temperature on the foam that are more dramatic with the foam. The R value of cellulose is nearly flat across a fairly broad temperature range- not so with foams.

I live just south of Charlotte, NC and am considering either a radiant barrier or spray foam to the underside of my roof. My builder put the AC units in the attic (house on a slab), that area is only 6 feet high, and very hot in the summer despite the roof vents and soffits.
My questions are:
1. in my region is foaming the roof deck recommended? (I'm thinking closed cell)
2. will either the radiant barrier or the foam significantly shorten shingle life?

Thank you very much for any help you can provide.

(Hopefully there's some housewrap or #15 felt between it and the sheathing as a drain-plane & air-barrier.)

Dana
 I have The mastic siding LINK with Tvyek than 1/2" plywood sheathing on the sencond floor.
The first floor has 4" block with a black type of drywall behind it.

If this was your house. Which way would you go for the wall?

Thanks a bunch

Posted By chadman51 on 05 Jan 2011 01:28 PM

(Hopefully there's some housewrap or #15 felt between it and the sheathing as a drain-plane & air-barrier.)

Dana
 I have The mastic siding LINK with Tvyek than 1/2" plywood sheathing on the sencond floor.
The first floor has 4" block with a black type of drywall behind it.

If this was your house. Which way would you go for the wall?

Thanks a bunch

The don't really specify an R value for the siding, only "...up to 1-1/4" of insulation..." which isn't much of a spec, since the profiles of the different styles are all different. Figure on R3, not more from a thermal point of view, and don't count on it to keep the sheathing warm enough to be condensation-limited.

So the first-floor is masonry, with an asphalt-loaded sheathing on a studwall, and hopefully a gap between the sheathing & brick(?).  Check to see that there are both weep-hole vents on the bottom course of masonry, and vent slots in the top course of the brick so that the gap is actually vented to the outdoors (sometimes they get filled in by home-owner re-pointing, which increases the moisture loading of the studwall behind the masonry.)

Were it my house I'd weigh the costs between a flash'n'fill with 1" closed cell polyurethane + wet-sprayed cellulose vs. 3" of the MD-R-200 Icynene.  Either would be fairly air-tight and ~R15 and 1-2 perms, and neither would require an interior-side vapor retarder.  In most cases the flash'n'fill will come in cheaper- probably cheaper than a full cavity fill of Demilec, which WOULD need attention to interior side vapor retardency to protect the sheathing from moisture.

Before insulating pressurize the house with a window fan and find/fix any air leakage witharound window/door framing, in each stud bay etc.  It's amazing just how leaky the house can be even with 4x8 sheathing and a housewrap. If you fix the first 90% of the problem BEFORE the insulation goes in, it'll make a difference in the quality of the air-seal provided by the spray foam. Pay special attention to band joists and stud plates, plumbing & electrical penetrations, etc.

Also, if this place has a basement or crawl, seal & insulate the band joist and foundation sill with 1-2" of closed cell foam (any manufacturer, just not open-cell) when you have them out there to do the walls/roof. It's the most-often overlooked major air leak.  If you want more R to make it similar to the above-grade wall you can add to it later, or better yet, insulate the entire basement/crawlspace wall with 2-4" of unfaced rigid EPS beadboard (either now, or as a later project.)  Rigid EPS is cheaper per unit/R than any spray product, and does well in below grade applications.  Keep the perm rating above 1 for anything you put on the foundation- it needs to dry toward the interior to keep from driving moisture up into the foundation sill and above grade portion of the foundation, increasing rot-risk on the sill and efflorescence/spalling on the foundation.  (BSC has handy short-sheets on their website about how to go about that too.)

So the first-floor is masonry, with an asphalt-loaded sheathing on a studwall, and hopefully a gap between the sheathing & brick(?).  Check to see that there are both weep-hole vents on the bottom course of masonry, and vent slots in the top course of the brick so that the gap is actually vented to the outdoors (sometimes they get filled in by home-owner re-pointing, which increases the moisture loading of the studwall behind the masonry.)

Were it my house I'd weigh the costs between a flash'n'fill with 1" closed cell polyurethane + wet-sprayed cellulose vs. 3" of the MD-R-200 Icynene.  Either would be fairly air-tight and ~R15 and 1-2 perms, and neither would require an interior-side vapor retarder.  In most cases the flash'n'fill will come in cheaper- probably cheaper than a full cavity fill of Demilec, which WOULD need attention to interior side vapor retardency to protect the sheathing from moisture.

Before insulating pressurize the house with a window fan and find/fix any air leakage witharound window/door framing, in each stud bay etc.  It's amazing just how leaky the house can be even with 4x8 sheathing and a housewrap. If you fix the first 90% of the problem BEFORE the insulation goes in, it'll make a difference in the quality of the air-seal provided by the spray foam. Pay special attention to band joists and stud plates, plumbing & electrical penetrations, etc.

Also, if this place has a basement or crawl, seal & insulate the band joist and foundation sill with 1-2" of closed cell foam (any manufacturer, just not open-cell) when you have them out there to do the walls/roof. It's the most-often overlooked major air leak.  If you want more R to make it similar to the above-grade wall you can add to it later, or better yet, insulate the entire basement/crawlspace wall with 2-4" of unfaced rigid EPS beadboard (either now, or as a later project.)  Rigid EPS is cheaper per unit/R than any spray product, and does well in below grade applications.  Keep the perm rating above 1 for anything you put on the foundation- it needs to dry toward the interior to keep from driving moisture up into the foundation sill and above grade portion of the foundation, increasing rot-risk on the sill and efflorescence/spalling on the foundation.  (BSC has handy short-sheets on their website about how to go about that too.)

There is a gap. Not sure about the weep holes.
The Demilec will need a vapor barrier? Demilec should be cheap? I can send you the 2 quotes if your interested.

How do you pressurize a house with all the gaps from construction?

Bot sure what BSC is.

Thanks again I really appreciate it.

 

BSC = Building Science Corp.

Demilec wouldn't need a vapor BARRIER, but do seek out and use vapor-retardent latex primer under the finish paint.

BSC: http://www.buildingscience.com/documents/guides-and-manuals

on basements & crawls:

http://www.buildingscience.com/documents/information-sheets/5-thermal-control/basement-insulation/files/bscinfo_511_basement_insulation.pdf

http://www.buildingscience.com/documents/information-sheets/5-thermal-control/crawlspace-insulation/files/bscinfo_512_crawlspace_edit.pdf

With the windows & doors installed you should be able to block any temporary large hole, and use blower doors or window fans to get the air flowing. Closing the door to a room and testing for air-flow at the bottom of the door tells you whether you have air leaks in that room (and approximately how much.) Air sealing is far more important for moisture control than vapor-retardency- a square inch of air-leak is worth a whole house's worth of vapor permeance though unpainted wallboard in terms of the amount of moisture condensing in a wall structure. (It's also has the best bang/buck for energy efficiency too.) Glue the gypsum board to the studs, don't just screw them, and foam/caulk every electrical & plumbing penetration- it makes a difference.

Thanks Dana
What do most of you guys do for sound between floors?

Is it to use a sound insulation like rock wool between the studs for sound transmissions?

>> What do most of you guys do for sound between floors? <<

On single family homes soundproofing between floors is usually not done.  OK - maybe on $1mil+ homes it is more common....  Anyway, on the apartments we build where sound isolation is a little more important we use resilient channel for isolation to fir ceilings and then screw the 5/8ths drywall to that.  Also, we use gypcrete on floors and it works well as a sound deadener.  You can also double rock the ceilings.  I built some town homes that had 3 1/4" of gypsum board between units including the 2" thick shaftwalls and the sound isolation was great.  You see, mass and isolation are the best things to block sound, as apposed to porous material like insulation - although insulation does help.  The use of insulation for sound control is more of just a market that the insulation manufacturers like Owens Corning created.  With regard to insulation the denser the insulation the better it works for sound control.  Fiberglass is the least effective, cellulose is much better, and then would be foam although spray foam would be cost prohibitive.  I think they sell rockwoll batts specifically for sound reduction in some parts of the country, but they don't sell that here so I have no idea of how effective it is.   They also have acoustic caulk (sealant) and acoustic glue for installing sheetrock or other wall/ceiling coverings. 

Also, hardwood floors on 2nd (etc) floors can are often problematic with respect to sound transmission between floors.

Blown rock wool and celluose both work pretty well, as does mid-density fiberglass. Dense-packing blowns goods isn't as effective at sound abatement as low-density blown goods despite the higher density, due to increased mechanical coupling of fiber under tension.

Be cognizant of the fact that insulation used for sound abatement also puts thermal barriers between rooms/floors, which can add to any heating-system imbalance issues with non-micro-zoned systems. Double-layering the gypsum with Green Glue for sound dampening is a lower-risk approach.

How far you take it depends on what your real needs are. To be sure, using cellulose in the exterior wall cavities is NOTICEABLY quieter than open cell foam or low-density batts.

Posted By Dana1 on 06 Jan 2011 01:18 PM
Demilec wouldn't need a vapor BARRIER, but do seek out and use vapor-retardent latex primer under the finish paint.

Demilec would need this but Icynene would not?

On my quotes Demilec is quoting 8.6" on the roof Icynene is quoting 5-6".

Icynene is saying they meet the code with the performance.

The prices are pretty close.
What would you guys do?

Posted By chadman51 on 07 Jan 2011 10:29 PM

Posted By Dana1 on 06 Jan 2011 01:18 PM
Demilec wouldn't need a vapor BARRIER, but do seek out and use vapor-retardent latex primer under the finish paint.

Demilec would need this but Icynene would not?

On my quotes Demilec is quoting 8.6" on the roof Icynene is quoting 5-6".

Icynene is saying they meet the code with the performance.

The prices are pretty close.
What would you guys do?

The LOW density Icycene would also need vapor retardent paint, MID-density Icynene would not.

Icynene company hype has been to under-spec the R on some theoretical performance comparison to a fictional fiberglass insulation infiltration rate. It's for the most part BS, blowing smoke in the local inspector's eyes. They pass FTC scrutiny since they're not over-stating the ASTM C 518 measured R value, but they're flying in the face of real-world  best-practices performance, scrimping on R relative to what codes actually REQUIRE.  For the deceptive marketing reason alone I'd be more inclined to go with Demilec,  all else being equal (which is isn't. )

For the same money, I'd go with whichever yields the higher R, which in easy this case:  8.6" of Demilec is ~R38, which actually meets code, and is substantially more R than either density Icynene at only 5-6".

Dana
Would you add to the 2x4 walls?
I was thinking of adding 1 1/2" metal studs to the exterior walls.
If I do that could I add Cellulose to fill the rest? If I flash it with closed cell?
Would you recommend that?

I'm not sure adding studs to the exterior make sense at only 1.5"- particularly with metal studs, which have far more thermal bridging than wood. Adding that amount of thickness as EPS without the thermal bridging would deliver a higher clear-wall R than 1.5" of even closed cell foam WITH the metal studs as a thermal short. Filled with cellulose you'd be looking at ~ R3, filled with closed cell foam maybe R5.

Alternatively, you needed more mechanical rigidity for hanging heavier siding, a layer of 3/4" XPS held in place with 3/4" furring at each stud and cut'n'cobbled 3/4" XPS (or closed cell SPF) between the furring strips would add ~ R7+ to the clear-wall R.

If you're talking about taking up interior space with those metal studs, instead use wooden 2x2 or 2x3s run laterally (instead of full length onto the stud edge), and fill it with cellulose for a cheap additional ~ R5. See: http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm