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A · B · C · D · E · F · G · H · I · J · K · L · M · N · O · P · Q · R · S · T · U · V · W · X · Y · Z   entire Web this site direct-vent fireplace A gas-fired fireplace that vents combustion gases directly to the outside through a hole in the wall. Direct-vent fireplaces have enabled far greater flexibility in the placement of home heating units because they don't need access to a masonry chimney or a freestanding flue above the roofline. Prefabricated from metal, they use zero-clearance technology and have a glass door that securely seals the combustion from interior rooms. Air for combustion is drawn outside. Air for convection is drawn from inside the room, circulated through passageways around the firebox and heat exchanger, and then returned it to the living space without ever coming into contact with the fire itself. Direct-vent fireplaces burn very efficiently, extracting most of the heat from the combustion gases. Unlike wood-burning stoves, they produce virtually no particulates, require no user maintenance or clean-up, and are simple to operate, using a switch, or even a remote control, and a thermostat. On the other hand, although they burn cleanly and efficiently, they do use a non-renewable, fossil-fuel resource and, like all combustion devices, produce carbon dioxide, which contributes to global warming. Styling and options Direct-vent gas fireplaces come in a multitude of styles, both modern and traditional. One-sided models are the norm, but two-sided, three-sided (peninsula), and four-sided (island), bay-window shaped, and corner units, are also available. Sizes vary from about 30 to 48 inches (76 to 122 cm) wide, about 24 to 30 inches (51 to 76 cm) high, and about 13 to 18 inches (33 to 46 cm) deep. Nearly all manufacturers make both top- and rear-venting models. Top-venting types work well where if there isn't straightforward access out of wall. Depending upon the model, vents may run vertically or horizontally for quite a distance – up to 25 feet (7.6 meters) or more. Fans to boost the circulation of heated air may come as standard or as an option. Some models have a standing safety pilot light that burns continuously to light the main burner whenever the gas is turned on. Others have electric spark ignition, to save energy, or a piezoelectric ignition which doesn't require an electrical hookup. Some units use a millivolt generator so the fireplace can operate even if the power goes out. Related category    • FIRES AND FIREPLACES    • HEATING Also on this site: Encyclopedia of Science Transport Concepts & Designs (partner site) BACK TO TOP