Factory-Made Attic Hatches
I hoped a home builder would stop by, and would order a few insulated attic access hatches. This is much less expensive than framing in and drywalling the surround of the usual leaky drywall plunker with a useless R38 batt tied on. Know that a batt often pulls away from drywall in closure, and has no insulating effect, just one more bad joke on a new-home owner. This is tolerated by jurisdictional authorities, some smart enough to know better. Exit too from harm to those struggling upon a stepladder, worried about defacing or breaking the fragile drywall, about to fall. I imagine a finger-grip in the drywall face; push up twist and tug down, and stow clean against your hallway wall. There is some weight, from 5/8" drywall for a ceiling with 1/2" drywall, compensating for gasket thickness.
A worker in the attic may close the hole behind himself while working, for many good reasons including his safety. This is allowed by the topside handle.
Here are drawings of the show access hatch.
Let's do Portland, Oregon gas-heated home Insulation Math on this hatch:
Here is math for the stated U = 0.11:
Insulation is. Dow Styrofoam Blue Board (extruded polystyrene, XPS), is R5 to R5.4 per inch, R7.8. The R-value of wood is about 0.94 per inch, 1.41.
1/(Reff + 3) = .14/(1.41 + 3) + .86/(7.8 + 3) ; Reff = 6.0
Add three and invert, for U-value: 0.11.
The plug assembly is 18.25" x 20", 2.53 sf
R7.8 foam is 16.75" x 18.5", 2.15 sf
Wood frame at R1.4 is 2.53 - 2.15 = 0.38 sf
2.53/(Reff +3) = 2.15/(7.8+3) + 0.38/(1.4 +3). Note ratio 2.15/2.53 = 0.85. This hatch has 15% of area as strength structure.
Annual heat cost = 2.4*2.53/(6 + 3) = $0.67
vs. R38 floor: 2.4*2.53/(38 + 3) = $0.15
Vs. no access, this plug adds 52 cents per year to home annual heat cost. No cobbled-up drywall plug with a stapled-on batt will have lower operating cost. With usual difficult drywall edging, a cobbled-up plug will have higher installed cost.
Here are plans for a hatch installed in an Oregon City garage.
Note "step-upon" framing at short ends. The petite hatch frame can't carry weight, and its' length of gasket is vulnerable to damage.
Here is the finished appearance of the open garage hatch. This garage attic will not be accessed for storage; else 2x4 bottom elements of trusses would be strengthened in a deeper floor.