Hello, Newb here. I have done weeks of searching online, not finding any answers and this forum looked to be the most helpful. I have to install 4 egress wells on a new NUDURA ICF basement for my house. Nudura suggests marking the lines for the well, cutting away the waterproofing membrane and foam, then drilling and screwing the wells directly to the concrete. After, fill it back in with expanding foam. The windows are being attached to bucks that sit flush with the styrofoam. My question is, won't I lose 2'' in depth of the well to the window? Wouldn't this make it less than the required 36'' depth and no longer egress compliant? Would there be any harm in installing these to the plastic webs or using longer tapcon screws to mount them flush to the foam and screw into the concrete? If they are back-filled anyways, won't they have more than enough support?

If you are lined up with the ties I would just screw them in place. If not, tapcon through foam to concrete. You are correct that the window well may not provide egress if the 2.5" +/- is lost from EPS thickness (can check local code to confirm).

Once the backfill is in place the well can't really move too far...

How wide is the flange on your window well where it attaches to the basement?

One option would be to remove 1-1/2" of foam next to your window bucks, then rip down some treated 2x4's to the same thickness as the foam, i.e. 2-1/2" or whatever thickness your foam is, then attach the ripped 2x4's to the concrete with construction adhesive and screwed into the side of the window bucks. This would bring the face of the ripped 2x4s flush with the face of the window bucks. Fill in any gaps where you cut the foam and the new ripped 2x4 with spray foam. This would provide solid backing for the window well which may have considerable force applied to the basement wall due to backfill pressure when wet/saturated.

You definitely need to provide a solid backing for the well and just placing it against the EPS will not accomplish this in my opinion. I suspect that the EPS would deform over time given the loading. I would also be hesitant about placing any wood below ground level. Perhaps you could grout in some brick in lieu of the wood. Brick would have plenty of compression strength and will not rot. However, I think I would just do what Nudura recommended. If you have basement windows that already meet code (opening size and height from floor/ground), I think the well requirement is to only provide a 5.7 sf of crawl space that a fire fighter can pass through. Most wells are significantly over-sized in this regard, so I would be surprised if losing 2.5” of depth would cause that to be violated, but you should definitely confirm this. How are you planning to waterproof the below ground level ICF and well/ICF interface?

Thanks guys, lots to think about. I will likely follow NUDURA's suggestion, honestly I was looking for a faster, easier solution as the weather is getting cold quickly here in MN and we need to get the basement backfilled.
The basement contractor covered all the exterior walls in MEL_ROL waterproofing membrane. I won't be able to finish off the exposed area around the windows inside the wells until the spring.

Another idea I had is to cut back and remove the foam to the concrete, the width to match the flange on your window well. Now cut a 6" wide or so strip of 1/2" plywood and screw it to the face of your window buck with the plywood covering the area where the foam was removed and overlapping onto your waterproofing a couple of inches at least. Now take some good quality duct tape such as Gorilla Tape and tape the outside and bottom edge of this plywood to your waterproofing. But before you install the plywood, mark and drill a 1-1/2" or so hole at the very top of the opening in the foam. After the plywood is attached to the window bucks, attach flexible vinyl tubing and a large funnel to this hole using the duct tape. Now get some high strength non-shrink precision grout and mix it to pourable consistency. Now slowly fill the void behind the plywood with this grout using the funnel while tapping the plywood with a hammer to insure it flows down and air pockets are removed. You might also want to cut a 1/4" or so notch in your plywood at the very top of your 1-1/2" fill hole to allow air to escape as the cavity is filled (do this before attaching the plywood). Follow the instructions on the grout bag regarding cure time and when the plywood form can be removed. You can attach your window well by drilling through the grout into the concrete and installed tap cons or anchor bolts. Another option that could be done before attaching your plywood forms to the window bucks would be to lay your plywood on your window well flanges, mark, and drill holes for anchor bolts in the plywood to match the window well mounting holes. Now set anchoring bolts in the plywood with nuts and washers on both sides of the plywood to hold the bolts in place at the proper head depth. This would need to be carefully planned and measured if using separate strips of plywood as the likelihood of getting them mis-aligned would be high.

If using the pre-set anchor bolt option, you might want to use a full sheet of plywood cut down as necessary to be slightly wider than the outside of your window wells. Now when you lay these on your window well to make a template for the mounting bolts you can screw the entire piece of plywood over the window opening insuring level placement and correct alignment of the mounting bolts to the window well.

Advantages are that no wood is used below grade, non-shrink grout in pourable consistency is stronger than your concrete, and a better seal is formed between the grout and existing waterproofing.

Once the form is removed, if any voids exist in the grout, some more grout can be mixed to a thicker consistency and placed in larger voids or RTV silicone or construction adhesive can be injected into smaller voids.

Called the window well company, they recommend "You can mount the areawall directly to the foam, being cautious not to draw the flange into the foam.
An alternative method is to place 1"x4-6" treated lumber between the areawall flange and the foam to act as "washer", preventing indentation against the softer foam surface.
Blue masonry screws, 1/4" diameter are recommended, mounted 12" on center from top to bottom."

This is what I did today. Ties didn’t line up but used a couple 1/2” wedge anchors easy peasy.