Sometime this summer, I will be preforming final tweaking prior to sheetrock.  The 2x6 outside walls are insulated (open cell R24.5); subfloor in vented crawlspace is same open cell R30.  Post sheetrock, I will spray an elastomeric roof coating on the ceiling deck to air seal and eventually blow in R38 cellulose into the vented attic.

So as usual, I am obsessing with final insulation tweaking prior to sheetrock and am asking anyone here willing to chime in to validate or shoot down my potential punch list.

1. Should I put a layer of caulk between any double studs on outside walls?  i.e. double top plates, double vertical studs,  etc. (most of these studs have virtually no gap between them, but any caulk or coating would airseal any potential air leaks, infiltration)

2. Should I put down a bead of caulk between subfloor and bottom plates on outside walls?

3. the gaps between doors/ windows and adjacent studs ranges between 1/2" and 3/16".  On the bigger gaps, caulk would be futile, but I'm a bit concerned that expanding foam from a can might put too much pressure on the window frame.  Is this a valid concern?  Frames are insulated fiberglass (Alpen 700 series).  Same issue/concern around doors.  On the smaller gaps (i.e. 3/16"), caulk will have to be good enough as it is not enough gap to shoot foam into.

4. There are numerous spots in the walls with holes and cracks that are missing the last 1-1.5" of foam. I'm guessing these were revealed when the shaved the walls flat and didn't feel compelled to go back around, refill these small holes and re shave.  Should I be concerned about the slightly diminished R value on these areas?  I can always spot fill them while I'm doing any other areas.  And them re shave them when they set up.

5. I feel the amount of tweaking would take numerous standard handheld cans of expanding foam.  Is there a larger size that I can buy (for a DIY) that would be more appropriate?

6. Any other final pre drywall insulation tweaking I should consider?

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One last issue. This house is a plain rectangle.  All 4 sides of the roof are hipped (12:6).  So the corners (and due to the not steep slope, even all around the edges) will be hard pressed to achieve R38.  I plan to stuff 6" batting into the 4 corners, as I'm sure they will not be blowing very diligently into those tight corners when they blow the ceiling.  I have actually contemplated blowing the ceiling myself (renting the equipment from Home Depot and buying the cellulose) to ensure the edges of the area near the soffit get as good as R value as possible. 

I know I should have foamed under the roof deck and nixed the vented soffitt, but they wanted $10k for that and it would have completely blown up my budget.

I'd review here about the pitfalls of caulk (and spray foam). Tape, gaskets or compressible foam are better. Small gaps and caulk (without bond breaker) are not compatible.

Taping the joints that I alluded to earlier might be difficult, given the fine layer of open cell dust residue from shaving the walls after filling the stud cavities. That stuff is everywhere and it would keep any tape from sticking.

I might be better off stuffing the larger cracks (around windows and doors) with a pliable foam (or product like Great Stuff) and then trying to seal with a silicone caulk after it dries.

And just using a silicone calk where the sub floor meets the bottom plate and caulking the seam between the 2 top plates and any vertical double studs staked together . I think tape would be a fools errand unless great pains were met to clean the studs of the fine dust reside left over from shaving the foam (in an attempt to get the tape to stick)

It's not clear to me that caulk will stick to anything that the better tapes won't. In any case, I suspect that a quick wipe with a wet rag would fix it. Do fill large gaps with backer foam before caulking.

Put Dymonic 100 between overlapping wood and they will be sealed and glued together (ie, low chance of the gap opening up).

If you can get it the Knauf Eco Seal system it's the way to go. Seal the king ,jack studs as well as the double top and bottom plates. If you removed the sheathing from your house you would see a lot of daylight coming in. I've seen it myself, it's eye opening. Silicone caulk is the worst product to use. Sorry I just reread your post. The caulking should have been done before the foam.. You can try a good quality latex caulk with silicone at every joint and stud cut.

I watched a few of the Knauf Eco Seal videos. That product looks very similar to the Latex Elastomeric Roof Coating product I plan to use to seal my Sheetrock ceiling prior to blowing cellulose. If I cleaned the studs a little (maybe brush and wipe) I could use this roof coating to seal prior to drywall? Of course I will need to stuff some sort of gasket material in the larger cracks prior to using the latex elastomeric sealant? I will have an airless paint machine on site. I'll just need to find one of those close application nozzles. Thanks for this.

I suppose I should have sealed as much as possible before the open cell application, but everything I read (much of it on here) suggested open cell was reasonably effective of air sealing the walls. Particularly the seam between the wall sheathing and vertical studs.

If the cracks are that big use the straw foam you can buy at the home a rama store. $3 something a can. The reason for the Eco Seal is to seal the cracks with a bead. Not sure how to install with a brush or airless sprayer. Try a shop vac and a wire brush to clean the joints.

Posted By smartwall on 09 May 2016 02:34 PM
  Not sure how to install with a brush or airless sprayer.

If you watch one of the Eco Seal you tube videos, they show it being applied with an Airless paint sprayer (and a close distance tip) and indicate the preferred psi setting on the airless

My local lumber yard has the equipment it's just an open tip

John-

You mentioned putting foam around the windows. The general recommendation is to use foam that has limited expansion characteristics to limit any distortion of the frames. It should indicate that it is for windows on the can.

Yes, I saw that. I was at a hardware store yesterday and see that Great Stuff, makes a product specifically for windows and doors (right on the front of the can) and a little reading indicates that is the purpose, as to not expand so much it puts the door or window in a bind. I will use this stuff around the doors and windows, a more aggressive expanding in king stud gaps (where necessary) and then seal all areas with a latex elastomeric sealer using my airless paint sprayer. I just need to try to find the proper tip for this application. Home Depot and Menards didn't have these types of tips and I have not had a chance to look on line.

I have about 60 days before I drive to the job site to do all final pre drywall work.

I've looked extensively at the Eco Seal product. Very cool stuff, but pricey (5 gal buckets cost appx $300 and good for about 1200 lineal feet of bead). While I won't balk at that high price, my research has revealed that the painter equipment needed to apply it is pushing this solution out of budget for me. It would require a Graco painter costing around $2k, possibly more (along with extension wand and tips). While I am planning to buy a Graco to paint the interior (down the road), I could get away with one that cost around $500-700 instead of $2k. So I am trying to pursue/consider other options.

A friend of mine turned me on to a caulk called Big Stretch. The main selling point of this caulk is that it does not shrink and has much better stretching capabilities over standard caulk one would find at home improvement stores. This is a "contractors caulk", according to many. Reviews are excellent. https://www.amazon.com/gp/product/B000H5OOPU/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Again, just sealing bottom plates to subfloor, king studs, double top plates and areas around doors and windows (after filling gaps with low expanding "Great Stuff" foam).

Or...I could clean and tape the joints. Can anyone recommend the type and brand of tape that is used in this application? Maybe I use a combination of several products, tape in some areas, Big Stretch caulk in others, etc...????

Looks like "Big Stretch" is actually an ASTM C 719 25% movement caulk. Ie, poor even for a caulk. I'd use tape (like 3M 8067 or Siga) as much as possible. Where you can't, consider Dymonic 100 sealant - because besides being overall better, it is strong enough to hold two plates together (ie, prevent movement in some cases).

Remember, gaps change in size. To larger than the day you installed some hardening foam or smaller - which squeezes out some caulks and then leaves you with an air gap when it opens up again.

John - all double plates and studs and the floor joint get a bead of acoustic caulk. Ugly stuff to work with but will remain flexible for ever. We have done a number of renos were acoustic chalk was used in the initial construction and thirty years later it is still just as flexible and messy as the day it was install. There may be some tapes around that do the same but I doubt any have stood the thirty year test.
If you are concerned about caned foam shrinking, leave it back about 3/8 inch and top with acoustic caulk. Just pick up a small tube at the local store and play with it.

My concern for using tape was that there was too much residual spray foam dust left over from the insulation of the outside walls. So we performed an experiment using a sanding block and a damp rag. Hit a double stud lightly with the sanding block and wiped it down with the damp towel. Then tried to tape the cleaned area (3M8067). The tape stuck very well, so currently that is my plan for all double joints (top plates and double vertical studs). I plan to use low expanding Great Stuff around all windows and doors and then seal those areas with 3M8067 tape or Dymonic 100 White High Performance High Movement Polyurethane Sealant. I will look into the acoustic caulk, but I will still need to use the Dymonic where the subfloor meets the bottom plate as I am putting temporary 1.25" tall shims in that area as a guide for the sheetrocker to elevate the rock off the subfloor and I would be concerned the acoustic caulk would make that a gooey mess. Since the sheeoorck will be off the subfloor, I could always go back and put a bead of acoustic caulk later before I install my underlayment and tile. But I have to think the Dymonic will suffice.

Update: Thanks to all on this thread for your recommendations.

Just finished all pre drywall tasks and drywall will start next week.

1. I filled all cracks around doors, windows and sliders with low expanding foam. I used the "Great Stuff" semi professional gun (gravity feed, metal gun that can be cleaned) and multiple cans of the blue cans (low expanding). I also used the normal expanding foamon any larger cracks (especially corners of the house that the original insulation crew missed). For any that might think of using this Great Stuff gun, I will say it works very well! I was pleasantly surprised!

2. I used the Dymonic caulk along the area where the sub floor meets the bottom plates. A few other areas around windows also were caulked. Primarily areas where the gap was appx 1/8" and too slim to apply foam.

3. I bought about $500 of 3M 8067 tape (2", 3", 4", 6") tape and applied this to all double (or more) studs...top plates, king and jack studs, etc. I also taped around doors, sliders and even some windows. This stuff is amazing. Incredibly sticky. I had no idea a tape could be this sticky. We simply scraped all the studs with a putty knife (actually a 9 in1 tool), wiped it down with a damp towel and applied the tape. Sticks like crazy

The better approach would have been to air seal before the spray foam application filled the walls and sub floor. This was my oversight. But I am confident that this house is pretty tight now. I will get up in attic and tape/caulk certain areas on top of the ceiling drywall once it is installed (prior to blown cellulose). All my attic can lights and electrical outlets are vapor sealed style with foam gaskets, but I will apply additional tape and caulk to ensure those are sealed...and any drywall seams

My biggest air breach in the house is surely the fireplace. Closing the flu still leaves a sizable gap around that damper. Bathroom fans, even with back draft damper are probably the next largest air leaks. Third largest breach is the range hood, but it is double back draft damped (at the fan assembly and the roof jack)

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On another note, I also installed my American Standard air handler and HRV - LifeBreath (by Airia) on this trip. Heat pump will be installed on my next trip next year. But at least I will have air circulation and fresh air in, stale air out at this point. Emergency heat also (if needed) in the air handlers heat strips, but I doubt I will need them before the outside heat pump is installed. The American Standard air handler (same as Trane) is their TAM8, highest efficiency unit. Complete variable speed fan and the ability to control the companion heat pump's variable speed fan and compressor.

I also installed an attic cat walk that is 24" above the ceiling drywall (and lights and AC receps). I will always be able to get up and walk along the entire length of the attic without disturbing the blown cellulose!

I hope to be moving to the house next summer. Then begins the arduous task of all the interior work, most of which I am doing myself over the next few years.

Google "Chimney Top Dampers" - they work. We've achieved well below 1ACH50 on two houses with fireplaces by using these.
Sounds like good work on your house!

But I am confident that this house is pretty tight now.

I'd depressurize the house and go around looking for leaks. Ie test and diagnose vs assume.

Posted By jonr on 01 Oct 2016 01:25 PM

But I am confident that this house is pretty tight now.

I'd depressurize the house and go around looking for leaks. Ie test and diagnose vs assume.

I think I know how to depressurize the house: remove a door, seal it off with plastic and tape a box fan to a carefully cut hole in the plastic, blowing outside.

But what it is the preferred method to check for leaks at that point?

And depending on where the leaks are, in many cases not much you can do about it after drywall

Smoke or a wet hand. Even after drywall should be well worth doing.