Newer energy-efficient homes are well-sealed to prevent heat loss and infiltration of cold air. Furnaces are adapted to new building codes and housing requirements. Some homes require multiple fresh air intakes to keep indoor air quality at safe and comfortable levels.
Every fuel-burning furnace needs a source of oxygen to operate efficiently. Air is drawn into the combustion chamber from inside the house. (Gas-fired hot water tanks and ranges also draw air from the house.) Fresh air intakes replace air that is used and expelled out of the exhaust vent.
Why a Fresh Air Intake Is Important
It requires 10 cubic feet of air to completely burn one cubic foot of natural gas. Furnaces draw surrounding air when burning. A fresh air intake into the house or directly into the furnace room replaces the air used during combustion and/or provides a constant supply of oxygen.
Air used during furnace combustion is replaced by air drawn through gaps and poor window and door seals in older homes. Newer homes are much more airtight and require one or more fresh air intakes to maintain a healthy indoor environment.
Fresh Air Intake For Furnace Operation
Furnace combustion uses air inside the house. Forced air furnaces also push air out of the house when operating. Fresh air intakes replace air used by burning and provide fresh air to replace any lost because of positive indoor air pressure. Intakes located near the furnace provide a steady supply of fresh air for combustion.
Lack of sufficient oxygen causes your furnace to burn inefficiently for longer cycles to provide the amount of heat needed to keep the house warm–increasing fuel costs and shortening furnace lifespan.
Fresh Air Intake For Safety
Incomplete combustion or poor ventilation can cause carbon monoxide (CO) build-up. Keeping carbon monoxide out of the basement is the most important safety function provided by a fresh air intake. CO is responsible for many health problems including headaches, nausea, dizziness, chest pain, and death.
Lack of fresh air inside a house can cause excess humidity. (Relative humidity should be 30% – 50%.) Too much humidity is responsible for:
- Mold growth and dust mites–not only in the basement but throughout the house.
- Bacteria and virus growth and circulation.
- Increased respiratory problems including asthma.
- Increased distribution of contaminants in the house–such as formaldehyde–because the furnace will draw air from crawl spaces, attics, and other unused spaces.
Adding Fresh Air Intakes
Fresh air intakes can be installed in older homes. Kits are available online or from home improvement outlets. Cutting a hole through the exterior building envelope and sealing it properly can make it a bit of a challenging DIY project.
Hiring a contractor for a simple fresh air intake installation costs about $500.00. Complicated projects could cost well over $1000.00.
If you are concerned about too much cold air entering the house, consider adding a damper to the intake installation to control airflow. Never completely block an intake with anything to stop the airflow. It defeats the purpose of the vent.
