September 06, 2018

How Fire Brick Insullates the Stove, Reducing Harmful Emissions & Producing Optimum Heat

The fire brick found in the back of the firebox of most wood and pellet stoves serves an important purpose. Fire brick helps optimize the stove's heat output and produces a cleaner burn, benefiting the environment. In many stoves fire brick also ensures proper heat flow. The fire brick insulates the heat inside the stove, reflecting the heat off the boards instead of letting it get absorbed by the stove walls. This increases the temperature inside the stove which transfers more heat through the heat exchanger so more heat comes out the front. This helps keep your room toasty.

For some pellet stoves, it is an intricate part of the design. Whitfield stoves for example, have an exhaust chamber behind the firewall where hot exhaust smoke travels. The fire brick encloses this chamber. Because the fire chamber doesn't have a wall of its own, the fire brick is an absolute must for the exhaust air to flow properly behind it. Without the fire brick, hot exhaust smoke would come back inside the firebox and not be channeled properly to the exhaust blower and venting.

The way fire brick insulates heat also reduces harmful emissions, benefiting the environment. It is actually one of the key reasons fire brick was developed. Back in the early 1970's there weren't any restrictions on emissions from wood or pellet stoves. That changed in 1988 when the EPA established
emissions standards. Engineers discovered that in order to achieve a cleaner burn, it was necessary to put firebrick in the combustion chamber to make it hotter. This insulates the heat inside the firebox, making it hot. Ideally, it creates a temperature of over 1000F. This burns more harmful particles in the smoke such as hydrocarbons so they are not released into the air.

Designing an area inside wood or pellet stoves that maintains sufficient heat for complete combustion required engineers to improve how stoves are insulated. Baffle boards and blanket insulation were invented for this purpose. Baffle boards are a type of rigid insulation such as fire brick, whereas Blanket Insulation is soft insulation behind the firewall in the back of the stove or behind a metal plate in the back of the firebox. Fire brick baffle boards have the benefit of not having to be installed behind something. They stand on their own, better deflecting heat off the stove walls. They can be made to look like real brick, which creates, a warm homey look.

Secondary combustion is when more warm air is introduced into an already high temperature zone or secondary chamber of the stove. Usually, the hot air comes through a combustor into the secondary chamber. Many modern wood stove manufacturers use catalytic combustors because they burn smoke at low temperatures, releasing chemicals to burn the smoke better, but most pellet stove manufacturers achieve a cleaner burn through higher combustion temperatures.  For pellet stoves it is not necessary to use a catalytic combustor because pellets do not include tree bark, so those impurities don't have to be removed.

Baffle boards or Firebrick were originally constructed of cast iron or actual brick, but these materials did not provide sufficient insulation to reach the high temperature required to achieve a
clean burn. Vermiculite based fiber insulating boards were then designed into many stoves. Now many stoves use ceramic boards.
Ceramic fiber boards can be used with stoves with fire temperatures as high as 2200F.

We sell the OEM as well as durable after market Fire-Tek fire brick

Superwool fiber for baffle boards is a customizable fire brick alternative if you have an older stove with discontinued parts or your stove didn't come with fire brick and you'd like to maximize combustion. It is available in different thicknesses, and can be custom cut. It has low bio-persistence and can with stand high heat like ceramic boards. There are examples of proper use in the link blow in the product pictures.

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