California's Green Building Standards Code: 4.503.1 Fireplaces
Clean, Safe, and Efficient Fireplaces & Woodstoves
Traditional fireplaces use an open burning area and a chimney to vent exhaust gases. Direct vent fireplaces do not require a chimney so they can vent horizontally through a sidewall or vertically up through the roof. Direct vent systems are also much more efficient than an open chamber since they draw air directly from the outside rather than from the room itself. This means that the conditioned air in the room stays in the room rather than being drawn up and out of the chimney. The direct vent units have enclosed chambers that keep exhaust gases from entering the room. This system eliminates the possibility of backdrafting where a fan in the house could pull exhaust gases back into the room. The front glass enclosure allows radiant heat to pass efficiently into the room.
Code Excerpt: Any installed gas fireplace shall be a direct-vent sealed-combustion type. Any installed woodstove or pellet stove shall comply with U.S. EPA Phase II emission limits where applicable. Woodstoves, pellet stoves and fireplaces shall also comply with applicable local ordinances.
The venting for a direct vent fireplace is usually accomplished with a double-walled pipe. The outer pipe brings in outside air for combustion and the inner pipe is for venting the exhaust stream. The outside air is preheated by the inner pipe which improves the efficiency of the unit.
Direct vent fireplaces offer a variety of configuration options since they can be freestanding or installed in a wall or retrofitted into an existing fireplace. They can save space since furniture can be positioned next to the sides of the unit because the sides are protected from radiant heat. Direct vent fireplaces come in a variety of styles and configurations. Some look like traditional fireplaces, some have modern styling.
Per the U.S. Environmental Protection Agency (EPA): “Indoor and outdoor wood-burning appliances and fireplaces may emit large quantities of air pollutants. Research shows that breathing wood smoke is not healthy. Wood smoke contains hundreds of chemical compounds, including nitrogen oxides, carbon monoxide, organic gases, and fine particles (also known as particulate matter or PM). Even limited exposure to smoke can be harmful to human health, particularly to the health of children, the elderly, and those with chronic conditions. Fine particles (i.e., particles smaller than 10 microns or about 30 times smaller than a human hair), can aggravate heart or respiratory problems, such as asthma, in people of all ages.”
This CALGreen section also applies to woodstoves and pellet stoves and requires that they meet EPA Phase II emissions requirements as applicable. In addition they must comply with any applicable local ordinances.
Compliance
For woodstoves and pellet stoves, EPA Phase II regulations have been in effect since 1992. All woodstoves manufactured after this date must comply with Phase II limits of 7.5 grams/hr (4.1 grams/hr if catalytic equipped).
An EPA certified wood stove or wood heating appliance has been independently tested by an accredited laboratory to meet a particulate emissions limit of 7.5 grams per hour for noncatalytic wood stoves and 4.1 grams per hour for catalytic wood stoves. All wood heating appliances subject to the New Source Performance Standard for New Residential Wood Heaters under the Clean Air Act offered for sale in the United States are required to meet these emission limits. An EPA certified wood stove can be identified by a temporary paper label attached to the front of the wood stove and a permanent metal label affixed to the back or side of the wood stove (See examples below).
The contractor must specify and install products meeting these criteria. The code official will verify that the installed product meet the regulations and that best practices are used in installation.
Best Practices
- Vent pipes on direct vent units get extremely hot. When running pipe in walls or ceilings, most building code regulations and manufacturer specifications require passing the pipe through a wall thimble or ceiling collar. These galvanized-steel devices ensure the proper clearance between pipes and combustible material, such as wall studs and ceiling joists.
- Ensure the pipes are properly sealed to prevent toxic gases and vapors from leaking into the building.