Area

Indication

Possible Causes

Suggest Solutions

Windows

Condensation on most inside surfaces of inner pane

·      Abnormally high humidity

·      Lower thermostat setting at night

·      Sudden change to colder weather

·      Poor air circulation

·      Control humidity sources

·      Add layer of glass or plastic on inside to increase interior surface temperature

·      Condensation should disappear as house warms up (adjust thermostat setback slightly higher if condensation is severe')

·      Ventilate home to lower humidity level; control sources of moisture (humidifier, showers, etc.)

·      Improve circulation by opening drapes; moving furniture or objects blocking registers; running furnace fan continuously  

Condensation on upper storey windows only

·      Cool air leaking into lower level, warm air leaking out upper level

·      Improve caulking, weatherstripping to reduce cold air infiltration; ensure there are adequate fresh air and combustion air supplies

Condensation on windows on one side of house only

·      Cold air in on windward side, warm air out on downwind side

·      Improve caulking and weatherstripping to reduce cold air infiltration

Condensation on north windows only

·      Inner surfaces cooler than south windows in daylight

·      Open drapes and improve circulation; add layer of glazing on inside

Condensation on windows, 1-2 rooms

·      Room(s) cooler than rest of house

·      High humidity rooms: laundry,

·      room w/humidifier

·      Improve circulation by opening drapes; leaving room door(s) open;

·      run furnace fan continuously

·      Exhaust dryer to outside; shut off humidifier

·       

Condensation between layers of glazing

·      Air leakage from inside into space

·      between glazing

·      Outer storm window sealed

·      Broken seal

·      Seal inner pane between glass layers with caulking or replace weatherstripping between sliding units

·      Seal inner unit; allow outer unit to breathe to exterior

·      Replace window with good new sealed unit capable of withstanding relative humidity levels

Condensation on window frame

·      Air leakage: rough opening space, poor weatherstripping

·       Air leakage: frame, sash, meeting rails

·      Poor quality metal or plastic frames

·      Seal between frame and rough opening space; improve caulking and weatherstripping

·      Install sealed interior plastic or Plexiglas storm or shutter

·      Replace with good quality wood or units with a thermal break

Condensation on doors

·      Uninsulated door

·      Replace with insulated door; add storm door

Doors

Condensation on door

·      Air leakage around door

·      Replace, adjust weatherstripping, threshold; add storm door frame/threshold

Condensation on lock, knob, hinges

·      Air infiltration due to negative pressure inside

·      Replace weatherstripping; add fresh air duct to heating system; add storm door

Walls

Condensation on closet walls

·      Poor air circulation around clothes

·       Improve air circulation; open doors; add louvres, grilles; undercut doors; leave space by outside wall

Condensation and

staining below window

·      Melted window condensation Window in humid area

·      Insulation missing

·      Improve window as above.  

·      Eliminate window unit, insulate opening

·      Add insulation to wall cavity

Condensation on many walls

·      Abnormally high humidity

·      Poor air circulation

·      Missing insulation

·      Control humidity sources

·      Run furnace fan continuously

·      Add insulation to wall cavities

Condensation in corners

·      Incoming air

·      Thermal bridging, missing insulation

·      Poor air circulation

·      Caulk siding corners, window brick moulds, siding – parging joints, etc. to exterior

·      Add insulation in wall or on outside

·      Aid circulation: move furniture/objects blocking registers; run furnace fan continuously

Mould on wall

·      Abnormally high humidity

·      Poor ventilation

·      Poor air circulation

·      Control humidity sources

·      Use fans; add mechanical ventilation

·      Aid circulation; move furniture/objects blocking registers; run furnace fan continuously

Frost on basement walls

·      Abnormally high humidity levels

·      Air leakage at sill plate, uninsulated walls

·      Control humidity sources

·      Seal and insulate basement walls

Condensation in corners

·      Incoming air

·      Thermal bridging, missing insulation

·      Poor air cirdculation

·      Caulk siding corners, window brick moulds, siding-parging joint, etc. to exterior

·      Add insulation in wall or on outside

·      Aid circulation: move furniture/objects blocking registers; run furnace fan continuously

Mould on wall

·      Abnormally high humidity

·      Poor ventilation

·      Poor air circulation

·      Control humidity sources

·      Use fans; add mechanical ventilation

·      Aid circulation: move furniture/objects blocking registers; run furnace fan continuously

Frost on basement walls

·      Abnormally high humidity levels

·      Air leakage at sill plate, uninsulated walls

·      Control humidity sources

·      Seal and insulate basement walls

Condensation around electrical outlets

·      Incoming cold air

·      Seal under plates

Water on basement floor or walls

·      External sources like runoff, rain or ground water

·      Abnormally high moisture level

·      Seal wall; install weeping tile; direct gutter drains away from wall; maintain ground slope away from wall: check that existing weeping tiles are open

·      Control sources of moisture

Stains on ceiling

·      Frost buildup melting in attic when weather warms

·      Leaking roof

·      Add vents to overcome inadequate attic ventilation; seal air leaks into attic space from below

·      Repair roof leak

Frost on exposed nails in attic

·      Small amount of warm air leaking into attic space

·      Occurs normally during cold weather in most homes (check for adequate ventilation)

Ceiling/Attic

Large isolated frost  deposit in attic

·      Indicates large volume of warm and moist air leaking into attic space

·      Inadequate attic space ventilation 

·      Identify source; caulk or seal leak at ceiling level (large amounts usually occur around stacks or from poorly sealed exhaust ducts - make sure all exhausts vent to exterior, not into attic space)

·      Add attic vents

Other

Condensation on cold surfaces such as pipes, toilet tank, etc.

·      Abnormally high humidity level

·      Cold water supply

·      Control humidity sources

·      insulate pipes or toilet tank

Exterior paint peeling

·      Lack of air/vapour barrier

·      Rain penetration behind siding 

·      Add air/vapour barrier to interior or paint with vapour barrier paint on interior surfaces; seal around electrical outlets

·      Identify and caulk any leaks or gaps on exterior; repair flashings

Structural damage to studs, joists or rafters

·      Bacterial action due to warm, moist and dark environment

·      identify cause of leakage (external or concealed condensation); replace

·      damaged members' seal wall, floor or ceiling assembly to prevent recurrence