Yes, the screws are going all the way through the OSB. No, we are NOT screwing into the floor joists because we're preparing for tile, and the tile experts at johnbridge.com say not to. We did buy some Hardibacker screws, and they seem to be working when everything else didn't. I know they're for Hardibacker boards, but they are able to grip and countersink. For now, I think we're okay, but in case anybody else has this problem, maybe this will help.

Every time I run into PB it comes out and is replaced with 5/8 BC grade plywood underlayment. The 1/2" plywood underneath is a CDX grade with no T&G so that is no good for anything without an underlayment over it. Particle board underlayment is fine underneath carpet because it can breath. It has no holding power for staples or cleats, neither does the CDX sheathing grade plywood subfloor. I've seen many floors installed over PB that are very loose and gapped. That said, I have seen a couple that looked fine. Also once PB gets covered over with felt and a wood floor it can't breathe anymore and it can start to do funny things.... well, not funny :), but nothing it may want to do is good. You would have no mfg. warranties either.

putting foam sheathing doesn't do anything but insulate the storage area flooring. it is a waste of time money and effort. in adding foam sheathing you are adding a vapor on top of the batts/blown insulation. batts actually work better on slopes because it is the uniformity of the insulation. as you will see, the blown will vary in depth in this area. it would behove you to get up into the attic before they finish and take a look. ask the R-value per inch of whatever blown insulation they are installing. figure out how many inches need to be in place to achieve this quoted R-value. take a yardstick or some form of measurement and measure the depth of the install in several areas. or ask them to do it while you shine a light to see if the depth is reached. any low spots should be filled. blown settles so depth should be a few inches over quoted inches. types of insulation have different qualities so some compacts (settles) more than others. if they are using cellulose..the air sealing is more important than ever.cellulose has a fine dust that will enter thru the smallest of areas. the bath fan for instance has openings in the housing. the cut where it fits thru ceiling is oversized. this cut should be sealed with mastic tape. back draft damper should be properly installed and vented out of insulation..perferably out of attic. the sloped ceiling is another place that will de-rate the overall R-value of the install. as are each recessed light (1 unsealed IC light = 1 sq ft of uninsulated attic space) you can see by the dirt on the batts how leaky the can lights are. if they don't address them from in the attic you may be able to install an ICAT insert and trim from inside the house. expect to pay $15 for insert, plus trim. you will need to brand name and model number of the recessed light. once you retrofit them use cfl's for more savings. if the attic is 1200 sq ft, and bid is for 944 sq ft, then 256 sq ft is the storage... I guess. I don't know what your starting out R-value is or what they plan to install. but as an energy rater (note rater not auditor) we have to deduct for areas like sloped ceilings, recessed cans, storage areas and all areas that have less insulation than overall. the attic staircase when not properly sealed and insulated derates the insulation install, and air leakage from this and recessed cans further are also penalties. I'm learning that these are some of the many differences between raters and auditors..and when utilities are involved in providing work for auditors and incentives the quality of the audit/rating is in question. if some company is paying a portion of your fee, you are not unbiased and working 100% for the homeowner. I've found hvac companies to be bad at sealing their own work.. best of luck.

The problem with interior bracing is that it usually does not connect with the floor structure as well as exterior sheathing which can overlap and be nailed to the perimeter band joist of the floor framing. Remember, lateral bracing depends more on fasteners than on the strength of the panels and if the forces are not transmitted to the foundation you have achieved nothing. To get effective results from interior panels (5/8" drywall is pretty effective) you need to add tie down brackets at the base of the wall studs (see Simpson catalog). Adding bracing is most effective at the corners where the greatest lateral forces occur. Tie down brackets at the studs near the corners and 5/8" drywall or diagonal steel braces will probably be enough unless you are in earthquake or hurricane territory and, if so, you need to hire an engineer.