JUCA Fireplace Inserts - L

photo of an L-8 JUCA's Model L-8 Fireplace Insert (shown here) is designed to vastly improve the performance of an existing fireplace. JUCA CUSTOM-BUILDS each and every L-8 specifically for that unique fireplace. This approach provides the largest possible glass door, the largest firebox size, and the greatest heat-exchange area for highest performance. All this at a VERY REASONABLE price, (usually about $2,000).

The customer makes six measurements of the fireplace. JUCA's Computer-Assisted-Design (CAD) System then uses these dimensions to design a unique heat exchanger assembly as the firebox section of the JUCA L-8. This ensures the most efficient possible Fireplace Insert, because the heat-exchange area is maximized. A JUCA L-8 Fireplace Insert built for an average-sized fireplace usually has a Heat-Output Rating of about 80,000 Btu/hr! You can confirm the EXACT rating for a JUCA L-8 Fireplace Insert built for YOUR fireplace. This program duplicates (a simplified version of) much of the actual computerized design work for YOUR CUSTOM FIREPLACE INSERT to calculate the exact Heat-Output Rating FOR YOUR INSTALLATION! After placing an order, the finished, custom-built fireplace insert is completed and shipped.

A note can be added here regarding the airtight inserts that have an (optional at extra cost) 60 cfm blower available. Sales literature for such products often brags about 40,000 Btu/hr heat output. Well, in their laboratory, yes, they probably got that output. However, that tiny blower moves so little air that the air coming out of their insert has to be at around 400°F, dangerously hot, to carry 40,000 Btu/hr of heat. It is fortunate that their products rarely have to provide more than 10,000 to 12,000 Btu/hr which is commonly needed to heat the one room the fireplace is in! JUCA Fireplace Inserts have far stronger blowers, 465 cfm, so they move around 8 times the amount of air. In order to carry 40,000 Btus out to the room, the air only needs to be at around 140°F temperature, wonderfully warm but SAFE, too!

Other choices are also available. The door can open right or left; the electric power cord (for the included automatic blower) can come out the left or right side; the warm air supply can come out primarily to the left or right. The attractive mesh areas (the room air intake and warm air outlet) can be Black, Polished Brass, or Aluminum. (The main body is usually matte black). As a result of a remarkably visionary (female) customer, who special ordered a unique combination of colors for body and screens, JUCA has started allowing customers to choose any of the 35 standard JUCA colors. for the screens and body. To see all of the choices available on a JUCA L-8 Fireplace Insert, and prices, Click Here.

There are some "details" that fireplace shops never bother to tell customers as they are considering buying a $3,500 airtight fireplace insert! Such as the fact that they REQUIRE that the entire chimney be greatly reduced in size! A conventional fireplace that might have a 16" square chimney (256 square inches of open area for smokepath) is therefore filled in with concrete (PERMANENT) down to usually a 6" round (28 square inches of remaining open smoke path), which is compatible with their airtight insert. This extra requirement costs you up to $2,000 additional in parts and labor, but more importantly, THAT FIREPLACE COULD NEVER BE USED AGAIN WITHOUT AN AIRTIGHT INSERT IN IT! The chimney is now far too small! And it is a PERMANENT change that could never be undone if you should ever want the fireplace to "look normal" again! There actually is a valid reason that AIRTIGHT fireplace inserts require this reduction of chimney size, which has to do with the terrible tendency of airtight (suffocation) woodburners to create a lot of creosote. In the 1980s, there were many airtight inserts installed which created so much creosote in the chimney, and the large chimney size caused the smoke to move very slowly and therefore condense creosote on the chimney walls, that many houses burned down as the result of chimney fires. So they discovered that if they greatly reduce the size of the chimney, the smoke leaves faster and that problem of theirs is reduced! But at the cost of forever changing the chimney so it can never be used again as it was built. Often, $15,000 is spent in building beautiful fireplaces, but then the installation of an airtight insert forever eliminates ever enjoying it as it was originally intended. Amazing! (JUCAs are NOT airtight, entirely different, such that there is NO change needed in the chimney or fireplace! If someone wants to enjoy the fireplace as it was originally built, in just five minutes, the JUCA can be slid out and stored in the garage!)

Airtight fireplace inserts also require another "added expense", that of a "Direct Connect Kit" which is a flexible hose resembling a dryer vent hose, which connects the top of their airtight insert to the start of that 6" remaining hole. It is required for essentially the same reason as above, because some airtight inserts in the 1980s would fill the (hidden) volume of the fireplace firebox with creosote, often hundreds of pounds of extremely ferocious burning material, and houses would burn down.

In any case, it is amazing but virtually ALL installers today seem to assume that the chimney relining and the direct connect kit are mandatory parts of installation. They are actually right, IF the insert is an airtight fireplace insert, BECAUSE it totally alters how the fireplace works. A JUCA fireplace insert is entirely different, in that it allows the existing fireplace to operate nearly exactly as it always had! That means that it does NOT cause massive creosote (JUCAs do not suffocate the fire but allow it to burn as fireplace fires always had, with plenty of oxygen available).

This can actually represent a problem, IF there is an EXISTING airtight fireplace insert that is old and needs to be replaced. IF it was installed with the filling of the chimney with concrete, then a JUCA CANNOT be used! We need the fireplace to actually be able to work as it was originally designed, like a fireplace, in order for the JUCA to improve it! So, in the event that there is an old fireplace insert that now needs to be replaced, you NEED to find out of the chimney has been modified like that or not. If not, a JUCA can be used. But if the chimney has been reduced in functional size to 6" or 8" round, that means that an installer altered it (permanently) and that the ONLY choice (forever) is to buy another airtight insert for it! Quite an arrangement for the fireplace shops!

Normal (Rectangular) Fireplaces

Drawing of the front view of an L-8 Drawing of the side view of an L-8
Normally, JUCA builds an L-8 to overlap the fireplace's brickwork by about 3 inches. Such a unit usually resembles the drawings here. Sometimes, however, customers have very rough surfaced fireplaces or otherwise prefer to have the L-8 be an "exact fit." This does not overlap the facing at all and requires high temperature caulking to seal the edges to the fireplaces. The precision of the measured fireplace dimensions must be very accurate for this option, and JUCA requires an accurate paper template of the fireplace opening to make sure of an exact fit. This is only possible for larger-sized fireplaces.

By the way, did you notice the sloping back wall of the heat exchanger portion? That's done to better match the sloping back wall of the individual fireplace! (Whatever the angle or size of that sloping fireplace wall, the L-8 is built to match it.) Also, note the heavy legs that support the heat exchanger structure. This keeps the heat exchanger up above the ash accumulations in the fireplace, to make sure that our FOREVER WARRANTEE will never need to be activated. It also allows a small amount of air and smoke flow up outside the heat exchanger area to gain even more heat from its outside walls!

Arch-Top Fireplaces

Drawing of front view of an Arch-Top L-8 Drawing of side view of an Arch-top L-8
When customers have an arch-top fireplace, usually installing a competing brand's Fireplace Insert covers over everything and hides the arch. Since JUCA's Fireplace Inserts are individually Custom-Built, the JUCA L-8 can usually be made in several different ways. Of course, a normal (rectangular) L-8 can be made where the heat exchanger portion still is as large as possible in the firebox. But (as an extra expense option), the top portion of the front section of an L-8 can usually be made to follow the arch motif of a Flat-Arch fireplace, either with an overlap fit or as an exact (inside) fit! (This is probably not available for Full-Arch fireplace, since there would be nowhere to put the blower and grilles!)


See-Thru Fireplaces - L-8X

(Front room view . . . . . . . . . . . . . and . . . . . . . . . . . . rear room view)

Drawing of an L-8X front room view Drawing of an L-8X rear room view

L-8X Photo - Front Room

photo of front of an L-8X

L-8X Photo - Rear Room

photo of rear side of an L-8X

For applications where a fireplace connects two rooms as a see-thru, JUCA can make an L-8X See-thru Fireplace Insert. From one side the unit looks just like the normal L-8 (Left drawing and upper photo). When the unit is slid into place (from that side), the back(??) side of the L-8X slides through the fireplace right up to be almost flush with the fireplace facing in the other room. This allows the glass area in that room to look like it really belongs there! (Right drawing and lower photo above). There are warm air outlet grilles along side both the glass areas to feed warm air to both rooms. More advantages of each JUCA unit being custom-built!

The dimensions we need to build an L-8X are a little different from those for a normal L-8. We want to have the width and height of each opening, and we like to have the diagonals of those openings, too, to make sure the openings are actually square. (Usually, sketches of each side opening with the dimensions is a good idea.) We also need to have the distance through the fireplace at each corner of the fireplace. In principle, these four are all the same, but again we're just making sure! Finally, we want you to measure the floor diagonals through the fireplace. These again should be the same. If they're not, one opening is down the wall from the other, and we would have to make a distorted unit to fit in a distorted fireplace!

L-8X Photo - Front Room

photo of front of an L-8X

L-8X Photo - Rear Room

photo of rear side of an L-8X

Many Other Subjects
Solar Heating??
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And the L-8 Price???

Usually $1,999 (plus shipping) Details, Options

Measuring Your Fireplace

Front View

drawing of an L-8 showing front features
A drawing of a front view of a JUCA L-8 Fireplace Insert. Shown are the large glass area in a narrow frame; the grilles on either side for drawing in room air and sending it back out into the room after being heated; the slide draft control beneath the door. Dimensions and proportions are for illustration only; the actual dimensions and proportions are specified by the dimensions of the specific fireplace which it is custom-built to go into.

Rear View

drawing of an L-8 showing rear features
A drawing of a rear view of a JUCA L-8 Fireplace Insert. Shown are the generally tapering width; the rear wall which is vertical at the bottom and which then slopes forward; the hollow heat exchanger chambers which surround the firebox (the inner walls of which are super-heavy 1/4" plate steel); the heat exchanger tubes above the fire, which span the firebox, but which still allows a relatively open top, so that the fireplace can operate "normally" as it always had before; the rear legs, which keep the heat exchange structure up out of the ashes, which can be corrosive under certain conditions.

The relatively open top is an important characteristic of the JUCA L-8 Fireplace Insert, and it's unique to JUCA's products. ALL other efficient fireplace inserts operate on an air-suffocation (or air-tight) principle of operation. That approach NECESSARILY requires major changes in how the fireplace operates, from how it worked before the insert was installed. These effects require designs which have small fireboxes, limited heat exchange areas, and a closed fire chamber (with a closed top), and a direct-connect flexible hose kit to make sure that the creosote it produces is not deposited in the hollow space behind the body of the insert.

JUCA uses a totally different approach. Our NON-air-tight design allows the fireplace to operate very similarly to how it operated before the installation of the insert. (You could still roast marshmallows or make popcorn in it. Competing products cannot be operated with the door open because the design theory doesn't allow it.) Our custom designed heat exchange structure incorporates the largest possible firebox size, the largest heat exchange surface areas, the largest glass viewing area and the largest door for feeding wood, and a blower that is MUCH stronger than any competitor.

All these characteristics combine to capture the most heat possible from the fire's output, while not messing up the fireplace's original operation. That original operation always included very clean burning, which the JUCA L-8's design maintains. JUCA L-8s do NOT share the air-tight inserts' problems of huge creosote and pollution creation. JUCA's non-air-tight design allows capturing all that heat while burning so cleanly that a "catalytic combustor" or "secondary burn" are not even necessary or desirable!

This difference between the JUCA's non-airtight design and ALL competing fireplace inserts (which are ALL airtight) has some other implications. Because those airtight products developed a bad reputation in the 1980s for creating a lot of pollution and creosote (because of the suffocation of the airtight operation), the EPA and other government agencies passed stringent laws applying to them. Commonly, the chimney must be re-lined ($$$) and a special assembly called a Direct-Connect Kit ($$$) must be installed ($$$) (which is often pretty involved). The Direct-Connect Kit includes a large flexible stainless steel hose that connects the airtight insert up into the inside of the chimney.

As long as the present fireplace is safe to use to start with, a JUCA L-8 Fireplace Insert does not require all that, and the EPA and other agencies agree. The fireplace actually still operates as it originally did with the only difference being that the JUCA L-8 has captured much of the heat that would have gone up the chimney. Building fires is the same as before, and it behaves as you have come to expect it to behave. That is definitely NOT true of airtight fireplace inserts, which operate VERY differently!

Why are JUCAs different from all competing Inserts?

The answer to that is pretty complex, and it's why we have hundreds of informational pages in our web-site. A capsule version:
Back in the 1970s, only Potbelly stoves, Franklin stoves and barrel stoves existed. They all produced huge amounts of heat, but TOO MUCH, and for only an hour or two. Great temperature variations in the room were common. So the problems were: too much heat and too short a burning period.

Two solutions arose. The Airtight design and the JUCA design.

Another unique characteristic of a JUCA Fireplace Insert, which is only possible because of the non-airtight design, is that it has an open bottom! When you look inside, you see the original fireplace floor! Why is this good? If you already have an ash dump, or a gas line for a log lighter or gas logs, or an outside combustion air inlet, those features still work like they always did! What a deal!

And, up above, since the space between our heat exchanger tubes is also open, an extension could be added to the existing fireplace throat damper, so it hangs down between the JUCA's tubes. This would allow normal adjustment of that damper, just like before!


drawing of an L-8 showing inner air-flows
This (transparent) view of a JUCA L-8 Fireplace Insert shows the side-to-side airflow, coming from the front-mounted, automatically activated blower; through the tubular heat exchangers and all the way around the firebox (generally split about equally between these paths); and then back through the main wall passageway for the warmed air to leave the heat exchange chambers and get out into the room.

This configuration allows a JUCA L-8 heat exchanger to capture the radiation from the fire in all directions, because our heat exchange chambers totally surround the fire. It also captures much of the heat being carried away in the hot smoke, primarily by the presence of the tubular heat exchangers above the fire.

There are also a variety of more subtle design features incorporated in a JUCA L-8 to enhance performance. JUCA designers (and JUCA computers!) have gone to a lot of effort to maximize the performance of each and every Custom JUCA L-8 Fireplace Insert made.

We have even arranged for a way for you to know a little about such a Custom-Built JUCA Fireplace Insert specially made for your fireplace! (At least for single-sided fireplaces!) This program uses the six dimensions of your fireplace and duplicates some of the design work our people would do during construction of it. The program then estimates several useful bits of info about the unit.

The actual unit might have slightly different dimensions or ratings. These are just preliminary estimates that are usually quite close to the final figures.

Before you get too excited about wanting to get one of these, please read the Production Schedule info. Then, you may want to look at Plan B below.


Plan B

OK! So we know that we cannot please ALL the people ALL the time! There are several situations where a customer might actually dare consider NOT getting our L-8 unit!
For these people, we have an alternate suggestion. It does not actually involve anything we manufacture, and the heat collection is much less, but there is great flexibility of appearance, where the fireplace could look very "standard". In many cases, since we can supply these set-ups at our normal discounts, the final cost is actually even less than that of our L-8 (in some cases, as low as about $900)! (Pretty effective job of salesmanship, huh?)

If this interests you, please An Alternative to a Fireplace Insert.

JUCA Super-Fireplace Info Sheet Index for an Index of Many More Subjects.

JUCA Varieties.

E-mail: JUCA at JUCA e-mail


Totally Heating a Home with Solar Heat??

We have a sister company in Solar Heating that has just as much technology and expertise as we do! If you have interest in really high performance in a Solar Heating system, you might want to visit the Solar Heated House web site. Most of the Solar systems are based on a patented system.

Even better, the Version 1 System includes a sub-system that is also a way of entirely Air Conditioning virtually any existing house in the United States nearly for FREE! In a spirit of hoping to assist California homeowners from enormous summer electric bills (and power outages), this sub-system is being made available, for FREE, at Air Conditioning We hope that, if enough California homeowners would install the simple system, maybe the power companies and the energy grid could keep up with the Summer high demand for electricity. Since we're giving this information away, you could probably help some of those California homeowners to tremendously reduce their summer electric bills and maybe help avert blackouts out there, so let any of your California friends know about that possibility available to them!

We are also involved with a variety of other projects that are meant to give benefit to society in one way or another. Some are social or intellectual presentations, meant to help find solutions to things in our lives. Others are products or services that also are meant to somehow improve our lives. If you have curiosity about this, you might want to visit a directory page we set up for these Public Services Home Page. If you are civic-minded or otherwise motivated, a number of those projects could benefit from the participation of additional people.

Energy-Related presentations in this Domain:

Self-Sufficiency - Many Suggestions A thorough presentation
Global Warming - The Physics of the Process. (June 2004, June 2008)
Global Warming and Climate Change - The Physics (June 2004, Feb. 2007)
Alternative GREEN Water Heater - Non-Fossil-Fueled HeatGreen - A Simple Water Heater, HG3a (biodecomposition) (March 2007)
Alternative GREEN Furnace with no Fire - Non-Fossil-Fueled HeatGreen - A Simple, Home Heating Furnace, HG3a (biodecomposition) (March 2007)
Solar Heating - Low-Tech Active System Low-tech, low cost approach (April 2007)
Heat and Cool a House Naturally, without a Furnace or Air Conditioner (1977, Nov. 2000)
Energy Supplies of the World - Petroleum, Coal, Gas, Uranium. Oil, Natural Gas, Uranium supplies and consumption (May 2010 Report)
Asphalt Pavement - Black Surfaces and Sunlight Environmental Effects of Asphalt Pavements, Roofs, and Parking Lots (August 2007)
Earth Spinning Energy - Perfect Energy Source From the Earth's Spinning (1990, Nov. 2002)
Earth's Spinning - Perfect Energy Source (1990, Dec. 2009)
Tornadoes - The Physics of How They Operate. Tornadoes, including How they Form. A potential energy source (Feb. 2000, May 2009)
Electricity - Unlimited Source of Solar by an Artificial Tornado. Tornadoes, including How they Form. A potential energy source (Feb. 2000, May 2009)
Survival Ark - 60-Acre Hexagonal Artificial Island, Floating Communities for Survival For Sealevel Rising (July 2008)
Electric Power Plants - Climate Effects
Global Warming Effects of Carbon Dioxide
Hydrogen as a Fuel for Vehicles. (August 2003)
Solar Heated House NorthWarm Totally 100% Solar Heated House - Version 1 (1979)
Solar Cells Photovoltaic Cells, PV, Electricity from Sunlight (Jan 2002)
Driverless Vehicles - High-Speed Transportation 200 mile per hour TRANS Super-Efficient Transportation System (invented in 1989)
Electric Cars, Hybrid Cars, the Physics Battery-Powered, Hybrid Cars and Hydrogen-Powered Vehicles (April 2006)
Wind Power, Wind Energy, Practical Windmills Practical Wind-Generated Electricity (Residential, some Watts) (1975 and April 1998)
Tower Windmills and Electricity, Modest Efficiency Practical Large-Scale Wind-Generated Electricity, 1200 KiloWatts (Community, a thousand homes) (a million construction jobs and 12,000 MegaWatts of electricity Nationally) (June 2007)
Earth Energy Flow Rates due to Precessional Effects (63,000 MegaWatts of Energy) (Sept 2006)
Power Plant Wastes - Productive Usage of Nuclear Waste. Productive Disposal of Nuclear Power Plant Wastes (1980s, Sept 2005)
Conserving Energy - Methods and Processes
Energy Storage - Methods - Efficiencies Various Methods
Solar Energy - How Much Energy Comes From the Sun
Sun and Stars - How the Sun Works - Nuclear Fusion. Creating Light and Heat
Energy Inventions - Many Forms of Energy Supplies. Related to Energy Crises
Solar Energy - Generating Electricity From solar, wind or other sources nearly 24 Hours a Day (2001, tested 2003)
Solar Energy - Generating Electricity, Improved A Unique Method of Using Solar Energy to Generate Electricity (late 2010)
Alaska Pipeline - Alyeska - Physics. Pipeline Local Climate Effects (August 2005)
Home Air Conditioning Natural, GREEN and FREE! (1978, December 2000)
Hybrid Vehicle - An Improvement. An Entirely Different Approach to a Hybrid Vehicle (1992, May 2008)
Woodburning Furnace - JUCA Fireplace, Woodstove - JUCA Super-Fireplaces (designed 1972, manufactured 1973 on, still not matched)
Burning Wood for Heating - The Physics. Wood as a Heating Fuel (published 1978)
North Pole is Heating Very Fast. Faster than anywhere else on Earth.
Global Warming and Climate - Possible Solutions
Aerodynamic Lift - How Airplanes Fly. Bernoulli Effect, Reaction Lift (April 2003)
Efficient Airfoil Flight - Active Surface - TURCAN. Greatly Reducing Turbulence and Drag for Aircraft and Airfoils, TURCAN (summer 1998)
Construction School for GREEN Technologies. My Concept of a GREEN Campus (1990, Dec 2008)
Conservation of Angular Momentum - An Exception or Violation. A Violation of the Conservation of Angular Momentum (Sept 2006)
Hurricanes, the Physics and Analysis A Credible Approach to Hurricane Reduction (Feb 2001)
Automotive Engine - A More Efficient Approach. Significant Improvement (2001)
Global Warming - The Politics and Business Why No Leaders Seem to See Urgency in Global Warming
Energy from the Moon - A Version of Tidal Energy Collection. (Artificial Tides) (1998, 2010)
Energy from the Moon - Version of Tidal Energy Collection 2. (Energy Harvesting) (1975, 2010)
Electricity from Solar, Wind, Water, More. Make All Your Own GREEN Electricity (2001, 2003, 2010)
Woodstove Energy Production and Efficiency, from a Radiant Woodstove (published 1979)
Firewood Ratings. Firewood Info Chart.