The attic audit is the highest-value twenty minutes in home energy work, and its tools are a ruler, a flashlight, and a place to kneel: attic insulation depth converts to R-value by simple arithmetic, coverage sins announce themselves visually, and the dirty-streak map hands over the air-sealing to-do list for free. This guide covers the measurement, the conversion, the coverage reading, and the top-up done in the right order.
The measurement and the conversion
From the hatch, with footing only on joists or boards (the drywall between holds nothing): push a ruler or tape to the drywall at several representative spots, center, mid-field, and toward the eaves, because depth varies and the low readings govern. Convert by material: blown fiberglass (white or pink fluff) about R-2.5 per inch; blown cellulose (gray, newsprint-like) about R-3.5; fiberglass batts by their labels or thickness at R-3.2 per inch; and mixed layers add up. Against the regional targets, R-49 needs roughly 13 to 14 inches of blown material, R-60 about 16 to 18, and the glance-level rule works from the hatch: joists visible above the insulation means under-insulated, since ceiling framing runs 6 to 10 inches and every target exceeds it. Old houses add the identification duty: vermiculite, a pebbly, gray-gold mineral fill, is the stop-and-test asbestos suspect, undisturbed until a lab says otherwise, the one finding that pauses everything else on this page.
Reading coverage: the sins list
Depth is half the audit; the flashlight tour finds the rest. Dirty streaks and gray-matted patches are the air-leak map, insulation filtering escaping house air at every top plate and penetration, each streak a to-do item below it. Wind-washed and bare eaves report missing baffles, either insulation blown thin at the edges or soffit air scouring through the fiber, the ventilation-and-baffle detail that preserves both intake and eave R. Gaps and canyons, bare drywall visible at chases, around the hatch, and where trades dug and never refilled, cost per the gap math in the installation sermon. Buried heat sources: older recessed can lights not rated for insulation contact must stay cleared or be replaced or covered airtight, the fire-and-leak double item. Compressed storage zones, plywood and boxes flattening a foot of fluff to inches, spend R for shelf space, with raised platforms as the compromise. And moisture evidence outranks everything: matted, water-stained, or moldy insulation, rusty nail tips, and darkened sheathing route the project through the attic-moisture and leak references first, wet insulation being dead insulation and a symptom besides, with the bath-fan-into-attic finding as the usual arrest.
Topping up, in the right order
The sequence is the whole craft: one, fix the moisture sources and reroute any fans; two, air seal the ceiling plane, plates, penetrations, chases, cans, hatch, while the framing is still reachable, since sealing under two feet of new fluff never happens; three, install eave baffles in every bay to hold the soffit channel open; four, add the fill, blown cellulose or fiberglass over the existing layer to the target depth (rental blowers make it a long DIY day; crews make it two hours), or unfaced batts crossways over old, never a vapor facing trapped between layers per the vapor rules; five, finish the details, depth markers stapled to rafters so future audits read at a glance, the hatch weatherstripped and topped with its own insulation, dams around the hatch and any cleared cans, and walkway boards where service access matters. The energy-audit route wraps the same scope in incentives and blower-door numbers where rebates run.
The bottom line
Ruler to the drywall, times the material’s R, against the zone’s target: joists showing means the answer is already no. Read the streaks as the sealing list, the bare eaves as the baffle list, and any wet fluff as a moisture case first. Then seal, baffle, and blow to depth in that order, and staple a ruler to a rafter so the next audit takes one flashlight beam.