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Frequently Asked Questions
About Masonry Heaters

Q. What is a Masonry Heater?
A.  A Masonry Heater allows you to heat your home with wood in a unique way.
The main thing that distinguishes a masonry heater is the ability to store a large amount of heat. This means that you can rapidly burn a large charge of wood without overheating your house. The heat is stored in the masonry thermal mass, and then slowly radiates into your house for the next 18 to 24 hours.

If you burn wood fairly rapidly, it is a clean fuel. If you try to burn it too slowly, the fire will change from flaming to smoldering combustion. The burning process is incomplete and produces tars. Atmospheric pollution increases dramatically. This is important if you are planning an energy-efficient house. The average energy demand of your house will be quite low. For most of the time, it may require only 1 to 2 kW of heat. For most conventional woodstoves, this is below their “critical burn rate”, or the point where they start to smolder.

Masonry heaters fill the bill perfectly. If you need even a very small amount of heat, such as between seasons when you simply want to take off the chill, you simply burn a smaller fuel charge–yet you still burn it quickly. The large surface is never too hot to touch. You have a premium radiant heating system with a comfort level that simply cannot be equaled by convection or forced air systems.

Q. Do Masonry Heaters have fans to circulate the heat?
A. No - Masonry Heaters are radiant heaters. As in floor radiant heat or as in an older building that had hot water radiant heaters spaced around the home or office - no fans needed.  Actually, a fan would cool the area as a fan would cool you on a hot sunny day.
Q. What makes a Masonry Heater work?
A.  The Masonry Heater consists of a firebox and a lambrith of flue(heat exchange) channels.  The flue gasses serpentine through these channels giving off heat to the masonry before reaching the exit flue.  After the fire is out and the damper is closed, the masonry mass gives off this captured and stored heat to the living space needing heat.

Q.  What if it gets too hot? 
       Example:  You had a fire in the evening and wake up to a nice warm
        sunny day.
A.  No problem.  A heater cools slower in a warm environment and faster when it is cool. So if the heated space reaches 75 degrees or more, the heater does not cool as fast as if the space was 65 degrees.  If that happens, you would skip the next one or two scheduled firings.  Also, you could open windows for some nice fresh air or turn a fan on to chill the air.  This is not a problem.

Q.  Do Masonry Heaters have a catalytic converter?
A.  No - catalytic converters work on wood stoves where there is no mass.  The catalytic converter is actually a miniature masonry mass that increases the flue temperatures for more complete combustion.  In Masonry Heaters the entire structure is a heat storing masonry mass, so the temperature is high enough for a complete burn.  Tested Masonry Heaters on an average burn cleaner than all wood stoves - even those equipped with catalytic converters and second only to pellet stoves.

Q.  What kind of wood do you burn in Masonry Heaters ?
A. You can burn any wood properly dried to less than 20 percent moisture and split to proper size in your Masonry Heater.  Size depends upon the heater design - ask your heater designer.  Usually two to three inches in diameter minimum to five to six inches maximum.


Q.  How much wood does a Masonry Heater burn?

A.  That depends on the model.  Smaller heaters can heat 1000 sq. ft. with 15 pounds of wood two times daily for a total of one cord per season in Western WA.  A medium heater could heat 1500 to 1800 sq. ft. with a 30 pound load two times daily for a total of two cords per season.  A heavy duty heater could heat 2200 to 2800 sq. ft. using 45 pounds two times a day for a total of three cords per season.   The first year, most people use 30 to 50 percent more wood than is needed and with time learn how much fuel to use for their needs.  New heaters for the first season use more fuel because moisture in the heater uses some of the heat energy.  Also, new homes have a higher moisture content and need more heat to feel comfortable.


Q.  What can I use for facing and what is best?
A.  Any hard dense natural stone or clay brick works best.  I do not recommend pumice block or manufactured stone.  They will radiate heat but at a lower rate than dense brick or natural stone such as granite, basalt, or soapstone.   Some units imported from Europe are clad with Kachel tiles made especially to store and radiate heat.


Q.  Why do Masonry Heater cost so much?
A.  Consider a Masonry Heater an investment compared to a masonry fireplace.  True, they cost $4,000 to $5,000 more than a fireplace.  However, a masonry fireplace is at best 10 percent efficient, where a Masonry Heater exceeds 60 percent efficiency and up to 80 percent.  Part of the cost assures performance.   Masonry Heaters are complex and we use more materials, higher quality materials and more than twice as much labor to construct as a comparable size fireplace.  The original cost is greater, but the added value and heating convenience and resale value is always greater than the original cost.


Q.  What are the drawbacks to a Masonry Heater?
A.  1. To some people it is the cost.

       2. To others, it is the delay in heat output versus fueling cycle.  Masonry
            Heaters unlike other heat sources need to be recharged (fired) on a  12 or
            24 hour cycle.   Today's fire is tomorrow's heat.  The fire lasts about 2
            hours every 12 hours.

        3.  To most, it is the short fires - not enough time to enjoy the aesthetics.


Q.  What are the benefits?
A.  1. Easy to use, convenient, low tech and it works.
      2.Clean heat for people with allergies or asthma etc. - no indoor pollution.
      3. Low cost quality heat and efficient.
      4. No power needed to maximize heat output.
      5. Safe, never too hot to touch, except the metal or glass doors when the fire is
      6. Can be custom designed to your needs.
      7. Can be custom designed to any decor.
      8. Value added for resale and aesthetics.
      9. No utility bill - uses renewable fuel.
    10. Good for the environment.  Does not add to the greenhouse effect.
    11. Exempt from EPA, Certified in WA, CO, MN and other controlled air
     12.  Reliable old technology proven in Europe over 300 years ago.  (Not an
           unproved theory.) 
     13. Standard model core kits can be installed by any quality mason.
     14.  Low maintenance. Yearly inspection minimum, but if properly used the
            cleaning cycle may be needed only every two or three years.
     15,  Unlike other heater sources, bakeovens and heated benches (hearth) are
             common in Masonry Heaters.
Q.  Which heater is best?
A.  Hard question - all heaters are good.  They all range within 10 percent of each other.  A greater difference from heater to heater is the operator and the fuel used.  But given what is currently on the market, the Biofire, Kachelofen is one notch ahead of the rest - i.e. there is no standard model.  All are custom designed to fit the space to be heated.

Q. What about ovens?
A.  Any of the heaters can have ovens except the Swedish Country Kakelugn, a small pre-designed core.  A traditional Swedish Icon.

Q.  How do the ovens work?
A.  There are two types of ovens:  a black oven and a white oven.
Black ovens:  As the name implies in a black oven you build the fire to heat the mass.  After the fire is out, you rake the ask to the side or take it out then cool or bake.  Most ovens you see in restaurants are black ovens.  In most black ovens you need to calculate the heat needed beforehand, and then let the fire go out.

White ovens: The white oven is like the gas fired oven in most fast food pizza restaurants.  The heat comes form outside the oven.  On masonry heaters the oven is above the firebox.

It is a matter of choice.  Some European purest will only consider the black oven citing flavor, ambience or tradition as the reason.   White ovens are perceived to be cleaner.


Q.  Can I have a coil to heat hot water to heat the floor?
A.  Yes and no.  In my opinion you would need a lot of coil to heat enough water to replace a gas or electric hydraulic system which are very efficient.  I have however put coils in a heater that supplied hot water to a small radiator in a bathroom etc.  If you were to try and heat a hydraulic storage supply the area would be heated from a heater and the hot water floor would not be needed.

However, I do recommend a coil to preheat your domestic water for showers and laundry etc.  I would recommend a preheat tank and a thermo siphon system as opposed to a pump system.   WARNING - use only stainless steel coils, never cooper in a masonry heater.  I have found the coil works best in the flame path (firebox).


I hope this answers all the questions you may have.  Hopefully this helps you decide if a masonry heater is for you and which system suites your lifestyle and decor.  If you have any questions not covered here, you can email: lopezquarries@frontier.com

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