[Notmyfirstrodeo]

There is a Nudura dealer in Greenland, NH not too far from you (no sales tax!). The owner is a fantastic guy and very knowledgeable.

Nudura has a product called Homemega. Homemega is EPS with embedded 1x3 strapping. The sheets are 4x8 with lap joints and come in varying thicknesses. Cost will be similar to ISO and install FAR easier, just run tapcons through the strapping into concrete. Further, it's screw base for drywall- insulation and and framing in one step. R-values aren't as high as ISO, but this won't be too far off. I'd strongly encourage you to consider.

You'll have to work around obstacles as you wondered, keep the insulation as continuous as possible. Caulk the sill to the foundation (critical), and airseal any potential leaks. If you carry the Nudrua to the underside of your joists, you can pack the rims and box ends with mineral wool and wouldn't need any other drywall nailers. The cut-and-cobbled insulation that you intend to use is very labor intensive.

This is the Nudura distributor:

Welcome to Atlantic Builders Supply - Atlantic Builders Supply

Atlantic Builders Supply meets your construction needs with more than 50 years of construction industry and concrete expertise, combined with industry-leading Nudura® ICF systems.

atlanticbuilderssupply.com

 

[Notmyfirstrodeo]

If you were to use ISO, strapping will still be easier. Don't bother gluing to the walls, tape all seams with aluminum tape.

 

[Notmyfirstrodeo]

Surprising sometimes how many fasteners you use. Possible that either system is splitting hairs. Homemega is exceptionally easy, haven't really looked back since Joe recommended. I use foam as sparingly as possible, but basements are difficult. Have you crunched the numbers against studding up walls and using mineral wool batts? Hold the framing off the wall a smidge and fill the cavities with R23 leaving no air gaps. It'd be higher performing. Of course, different considerations for moisture/ vapor management.

If you're unfamiliar with Johnson's Fastener Warehouse- they're in Portsmouth and are nothing less than tremendous- what an exceptional resource! They sell online, I usually pick stuff up in person.

Do you have a rotary hammer? Drilling concrete without one is arduous.

Johnson's:

Fastener Warehouse

 

[Notmyfirstrodeo]

Also, I only use foam on basement walls if I don't have room to stud up walls. Biggest bang for your buck will be thorough air sealing around the rim, sill, and box ends. Tescon Vana is a favorite air sealing tape, but caulk is pretty easy too, just use something elastomeric.

 

[Notmyfirstrodeo]

Skip the foam at the box ends and the rims, use packed mineral wool. Likely, your walls are 8" concrete with a 2x6 PT sill, and the rim sits to the backside of that. There are a lot of difficult transitions here if you're using foam. You'd end up with foam against the rim only, and still have exposed pesky areas.

Run foam sheets sheets full height, floor to floor. This will leave cavities above the walls that you can pack (prior to installation of the sheets). Leave no air gaps, important that all cavities are full. This will give you a lot more insulation in an area where it's very critical.

Caulk the sill to the top of the foundation and caulk the rim to the sill. Press the caulking into place. Caulk any other gaps, penetrations, windows and doors. Or, use Tescon Vana around the windows and doors- ahead of myself- you may have to pack insulation into the window and door jambs, then caulk or tape. Window and door framing may require air sealing too- any place framing components come together or meet concrete. Caulk or tape the foam to the slab and whatever it meets on top, presumably the first floor deck.

Air sealing is a line item on building projects for me now- I treat it like any other major construction component. It's that critical. The first house I contracted, the insulators used cans of spray foam to seal the electrician's holes in the exterior stud walls to help prevent drafts at the receps and switches. I thought that was great! Of course, if the insulation had been installed properly, that would be unnecessary. This is all pretty simple stuff that is often neglected.

3M has an air sealing tape too- available at Middleton Building Supply locally. Performance Building Supply in Portland is another good resource.

 

[Notmyfirstrodeo]

Thanks again. This is all very helpful. For the box ends your saying don't put rigid foam board in those cavities and and spray foam them into place and instead use caulk to seal up all those seams between the rim joist and sill plate, sill plate and foundation wall etc... then stuff with mineral wool batts and then finally put a full sheet of board up and seal that to the floor joists aboe and slab below??

Do i need to put something down on the slab for the polyiso to come in contact with? That edge is not foil faced. I could put foil tape on that edge, put the foam on a piece of PT lumber or leave it a 1/2" off the slab and spray foam that seam.

Yes, correct. Skip the cobbling. Go heavy on the air sealing, pack the rims with batts, and run full height foam sheets.

No PT at the slab. That'll be another weak point and more work. If you are concerned about moisture intrusion into the foam at all (don't think I would be), then tape the contact edge as you suggested. Leaving an air gap and spray foaming will require a smidge more work as you wrestle with the tapcons.

Have a spray nozzle and a compressor running when you drill the concrete. Drill the pilot holes deeper than needed, and blast them with compressed air. Same deal when you fasten plates for your walls to the slab- over drill and clean the holes thoroughly. Be careful though, not to drill through the slab. I'd use 1/2" wedge bolts here instead of the tapcons. Far less frustrating and much stronger. I quit using concrete nails 15 years ago.

 

[Notmyfirstrodeo]

The long walls of the foundation will meet the floor joist. So most of those pieces will hit the bottom of the floor joist first. Will I need to notch every floor joist to fit around the foam board and run it all the way up to the 1f plywood decking? If so, any recommendations on how to make those notches easily?

Notch the foam, not the joists! Cut with a hand saw, cuts only need to be as good as you'd like them to be. Spray foam larger gaps, caulk smaller ones.

 

[Notmyfirstrodeo]

Sorry. Typing too fast. Yea notch the foam not the joist. Got a recommendation on caulk to use to seal seams etc? Any reason not to use spray foam to seal the seams between rim joist and sill and sill to foundation?

Spray foam is a terrible air sealer and it is even less effective in thin seams. Use caulking along the rim and sill. Viscon Fiber is water based and great, but that can't be acquired locally- you'd have to go to Portland or order from 475. Otherwise, use a solvent based caulk like dynaflex, lexel, sidewinder, or similar. Really, whatever you get the best price on. Avoid Alex/ latex based stuff. It isn't stretchy. There are other widely available water based caulks, like Big Stretch, but the aforementioned solvent based varieties will perform better.

 

[Notmyfirstrodeo]

$10 Amazon guns work as well as $55 hardware store guns. They all become paper weights at some point as neglected foam curers inside the gun. Stick with the Great Stuff brand foam and be sure to use the gun cleaner. Store the gun with a charged can on it. "Gaps and craps" foam will expand a lot! "Window and door" much less.

Use the spray foam to seal the any large gaps after you cut around the joists. Use mineral wool, as discussed above, packed into the box ends and rim. Also, mineral wool cuts well with a hand saw.

 

[Notmyfirstrodeo]

Got any links on that? How much R value does it lose and over what periods of time?

There are 3 types of rigid foam: EPS, XPS, and ISO. Of the three, EPS does not experience thermal drift. ISO and XPS do. EPS has inert blowing agents and is preferred among green builders, ISO is a second choice, XPS is avoided becuase its an environmental train wreck. The Nudura product we discussed upthread is a high density EPS.

Reclaimed anything is great (XPS too)- Green Insulation Group out of Worcester is an option that'd save you a chunk of cash if you can pick the foam up, there is another foam reclaimer in Bennington, VT. While reclaimed foam is older and may have experienced drift (except EPS, that's consistent), the reduced price point vs. energy savings of new more than offsets the r-value loss. That is, you'd never recoup the cost difference through energy savings.

I have a small foam distributor, will to share his contact info but not publicly. It's ISO, send me a PM if interested.

Regarding your question, the walls should be reasonably smooth. Get rid of the large defects, hitting them with a hammer might be enough. I'd fill any holes with hydraulic cement before covering- like the ones from form ties. The foam should absorb smaller defects.

 

[Notmyfirstrodeo]

High global warming blowing agents have been outlawed for a couple years now.
LINK

Well, tickle me pink! Is this fully in effect? I will feel a little less guilty each time I throw a sheet of XPS in the back of my truck. I still make every effort to avoid foam, it's quite difficult. Kind of like a tub of lettuce at the grocery store. The more of an effort I make to eliminate plastic, the more overwhelming it becomes.