What Is the Size for a Natural Gas Fireplace?

Fireplace Opening

• Selecting an appropriately-sized firebox depends on the size of your fireplace’s opening. A natural gas fireplace with a correctly-sized firebox will also produce a fire that fills the combustion chamber once lighted. On the other hand, a fireplace opening that is too small or firebox that is too large will reduce energy efficiency. Natural gas fireplaces with undersized openings result in poorer performance, since the fireplace will not produce enough heat for the room. Likewise, fireplace openings that are too large will overheat the room. The shape of the opening also affects performance in fireplaces. For instance, higher fireplace openings require taller chimneys. The fireplace opening’s height increases radiant heating in the room and the need for additional room air.

Room Dimensions

• Your room’s dimensions will impact how and where you install your natural gas fireplace. It will also impact whether a large fireplace is more important for your den area versus a kitchen or dining room. Although design and location are important for interior design, room size also influences fireplace operation. The Brick Industry Association publication “Technical Notes on Brick Construction” provides a table with suggested sizes for single-faced fireplace openings. For example, the association recommends fireplaces with openings ranging from 30 inches to 36 inches wide for rooms that are approximately 300 square feet.

Home Insulation

• Check your home’s insulation capabilities when deciding the size of your fireplace. Determine whether your rooms have a low or high R-value, which will influence the size and model appropriate for your heating needs. R-value is the measurement of the room’s resistance to heat flow. If your windows and walls have poor insulation, then smaller models will be less efficient and increase your heating needs. Other home components, including ceilings, hallways located between rooms and outdoor temperatures, will help determine which size fireplace is capable of heating your room.

Expert Insight

• In addition to firebox design, nationally syndicated newspaper columnist Tim Carter, Ask the Builder, recommends using smaller flues to match chimney heights. He states, “When using the smaller flue size, you will be required to raise the height of the chimney. Taller chimneys draw better than short chimneys of the same flue size.” The height of the smoke chamber and fireplace damper are also important for optimal performance. Fireplace dampers should be installed no less than 8 inches above the top edge of your fireplace’s opening.