Three approaches to ventilation

Insulation · Venting Living Spaces · printed page 242 (PDF page 243)

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Book index entries

House Ventilation – Three Approaches Three Approaches to House Ventilation Venting Homes Venting Living Spaces

Text in the illustration

1
exhaust only
example: clothes dryers, central vacuum, kitchen and bath exhaust fans
drafts
fan
PRO
cold, dry infiltrating air has drying effect on structure
CON
uncomfortable, drafty
can cause backdrafting of combustion appliances
no heat recovery
uses electricity
2
supply only
air leakage
example: central supply system
more fresh air is brought into the house
forces warm, humid house air into building structure
3
balanced
example: HRV
no pressurization or depressurization problems (better comfort)
may not have heat recovery

Generated explanation

Three schematic house sections compare exhaust-only, supply-only, and balanced ventilation, with airflow arrows and lists of advantages and disadvantages. Exhaust-only ventilation uses an outward-blowing fan and draws replacement air through envelope leakage paths; the annotations identify drafts and possible combustion-appliance backdrafting. Supply-only ventilation uses an inward-blowing fan and pushes indoor air outward through leakage paths, potentially forcing warm, humid air into the building structure. Balanced ventilation shows separate supply and exhaust fans, names an HRV as an example, and notes the absence of pressurization or depressurization problems. All three approaches are identified as using electricity, and the notes distinguish their heat-recovery limitations.

Components

exhaust fan supply fan building envelope exterior walls roof windows

Defects shown

drafts associated with exhaust-only and supply-only ventilation potential combustion-appliance backdrafting with exhaust-only ventilation warm, humid indoor air forced into the building structure by supply-only ventilation lack of heat recovery in exhaust-only and supply-only ventilation