Greenwood Furnace Series

The Greenwood Hydronic Wood Furnace represents the latest innovation in wood burning boilers.  Based on a tested design developed more than 20 years ago,  the Greenwood wood boiler is the most efficient, wood burning boiler you can buy for your home.  It is safe to operate, burns smoke- and creosote-free, and saves you up to 70% on your home heating bills.  Our wood boiler is also easy on the environment -- the fuel you burn is a renewable resource and does not contribute to global warming. Finally, the Greenwood hydronic wood furnace is easy to install and works with a variety of heating systems and applications.

Clean Burning -- produces no smoke or dangerous creosote

Why a Greenwood Works

To understand why the Greenwood wood boiler "burns clean," it is helpful to understand how wood burns.  Here's the scientific explanation...  when you kindle a fire, the temperature accelerates to around 500º F at which point the wood begins to breakdown chemically and throw off volatile gases.  These gases catch fire and accelerate the temperature to about 1100º F, at which point the wood solids begin to burn.  If the temperature remains at or above 1100º F, the fire consumes all of the wood gases and solid materials, and you have a "clean burning" fire.  If not,  you have incomplete combustion, which means unburned gases and particulates are vented by the furnace.  Some of it escapes out the chimney as smoke; the rest cools down and remains in the chimney in the form of creosote.

How the Greenwood is Different

Most wood burning furnaces and wood boilers on the market today are unable to sustain a temperature of 1100º F or higher.  They are built with a firebox made of steel which is surrounded by a jacket of water.  This water jacket serves two purposes:  it transfers heat from the firebox to the home heating system, and it cools the steel firebox and keeps it from melting.  The problem is, by keeping the firebox cool, the water jacket also cools the fire and prevents it from burning at temperatures needed for complete combustion.  That's why these units produce irritating smoke and potentially dangerous creosote.  

Greenwood's hydronic wood furnace is built in an entirely different way.  Our firebox is made of super-duty ceramic refractory, cast four to six inches thick, and surrounded by outer layers of insulation designed to keep the heat in.  The natural draft system pulls air into the furnace which fans the flames and creates a roaring fire with sustained temperatures of 1800º to 2000º F.  Heat from the fire is captured by a water tube heat exchanger located above the firebox in the path of the escaping superheated gases.  The furnace extracts heat from these escaping gases, not the fire below. 

This innovative design enables the Greenwood wood boiler to burn cleanly and operate at a very high level of efficiency.  By the time the escaping gases leave the furnace, they have cooled to around 300º F.  The 1700º F difference in temperature between firebox and the vent represents the amount of energy captured to heat your home.  The Greenwood hydronic furnace burns clean and delivers up to 85% of the wood's thermal energy to your home heating system.