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Insulation Moisture Infiltration → Thermal Performance Halved (U-Value Doubles)

Likely causes

Vapor barrier damage — pinholes/cracks in polyethylene film form moisture migration paths

Check: Scan exterior walls with thermal camera — cold bridges and moisture zones appear 2–5°C cooler than surroundings. Without thermal camera: use surface thermometer to map interior wall — zone 3°C+ warmer than surroundings indicates insulation damage

What to do: Double layer PE moisture-barrier tape or butyl rubber patch over pinhole areas. If moisture content >5%: consider panel replacement. Moisture >10% or U-value more than 100% above design: replacement required

Panel joint sealant deterioration — PU panel sealant shrinks and separates after 5–10 years

Check: Visually inspect panel joints — check for sealant shrinkage, separation, and cracking. Spray water on joint from outside, check for condensation inside

What to do: Remove old sealant, refill with cold-resistant polyurethane sealant rated to −40°C. If roof-wall junction waterproofing is aged, redo waterproofing

Field tip

On-site moisture content measurement: extract insulation core sample → gravimetric method (dry at 105°C, compare weights). If >5%, measure U-value on-site (design: 0.20–0.25 W/m²·K for freezer). If U-value is >50% worse than design, repair immediately.

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