Typical Renovation Junctions: How to Avoid Thermal Bridges and Condensation

In renovation projects, most heat loss and moisture problems are not caused by “bad insulation” but by weak junctions (typical nodes): wall-to-slab connections, window reveals, roof edges, balcony penetrations, and utility openings. When insulation is interrupted, a thermal bridge appears—surfaces get colder, indoor humidity reaches the dew point, and condensation (and then mold) follows. In Los Angeles, where coastal humidity and large day–night temperature swings are common, these defects show up quickly around windows, corners, and ceilings. Start with continuity: the thermal layer must wrap the building envelope without gaps. At wall-to-floor and wall-to-roof joints, overlap insulation and avoid exposed concrete or steel. Use thermal breaks where possible (especially at balcony slabs and canopies). Around windows and doors, install the frame in the insulation plane, insulate the reveal, and seal in three layers: exterior weather-tight (but vapor-open), middle thermal/acoustic foam, and interior airtight/vapor-control tape. Control air leakage: warm indoor air forced through cracks carries moisture into cold cavities. Airtight membranes, sealed penetrations, and careful detailing at electrical boxes and plumbing sleeves reduce hidden condensation. Vapor control must match the assembly—don’t trap moisture between two impermeable layers. Finally, verify with infrared scanning or blower-door testing after key stages. Good junction detailing is the cheapest way to raise comfort, reduce HVAC loads, and keep renovated interiors dry for years.