The insulation guys are at work. First they sealed the 2 x 6 stud bays with a minimally invasive foam, then they started installing the mineral wool insulation. As I mentioned in my insulation choices I talked about the difficulties of installing batts well. Insulation is graded I, II, or III based on how well it covers the stud bays. Grade I is the best.
A class I installation - see the picture below from Alison Bailes Energy Vanguard blog
He says that it is one of only TWO class I fiberglass installations he has ever seen as a home energy rater.
The criteria for a class I installation include:
- Minimal gaps in insulation coverage
- Compression or incomplete fill (up to 30% of intended thickness missing)- up to 2% of total area
- Walls, rim or band joist between floors - enclosed on all 6 sides, in contact with interior or exterior sheathing
- Ceilings - in contact with interior sheathing
- Floors - in contact with interior sheathing (subfloor)
- Floors over outdoor air or vented - enclosed on all 6 sides
This is from "Insulation Inspections for Home Energy Ratings - Assessing insulation gaps, compression, and incomplete fill provides a way to measure installation effectiveness" by Bruce Harley in Home Energy Jan/Feb 2005 pp 20-23.
So here is an example in the shop. This photo shows the minimally expanding foam with some pretty well installed mineral wool around the top but not the bottom.
The next photos show the installation of the batts.
Neither of these installations is a class I installation for 2 reasons - too much compression and it does not completely fill the stud bay. You will not get the stated R-value because compressed insulation does not trap air as it should. It functions as a solid material that conducts heat.
What to do about it? Now that's another question. If I was off tomorrow I would get a ladder, put on protective clothing and I'd fluff the stuff up. I'll talk to my contractor and we'll figure it out.