Monessen Exacta BUF 36" Vent Free Gas Firebox — Panels Optional, Pick Your Own Log Set
A 36" vent-free firebox with a 36" x 27" clean-face opening — no chimney, no vent run. The Monessen Exacta 36 is the enclosure half of a vent-free fireplace: listed to CSA/ANSI Z21.91, it hosts any listed vent-free gas log heater up to 40,000 BTU/hr input, sold separately. The circulating box and angled air channels push heat forward; the mesh screens, hood, junction box and two-piece hearth ship in the carton; and you buy it as an open firebox or factory-built with Stacked Traditional or Herringbone concrete panels — Reflective Black Glass is the modern option. from $629, with a 20-year firebox warranty.
Choose the Exacta 36 if you want a built-in fireplace opening where a chimney or vent run is impossible or too costly, at the lowest step into Monessen's 36" fireboxes — it frames into a 42-1/2" x 34-1/4" x 19-3/4" rough opening, straight or in a corner, sits directly on an ordinary combustible floor, and takes the 24" and 30" Monessen log set you pick separately. Its adjustable floor supports are made for heavy concrete log sets.
It is not right for a bathroom, or for a bedroom unless the heater you put in it is rated 10,000 BTU/hr or less — those limits come with any unvented gas heater, and it is supplemental heat, never a primary heat source. It burns room air and adds moisture to the room, so a very tightly sealed house that cannot spare combustion air or add mechanical ventilation is the wrong home for it. It never takes a wood fire, a vented log set or glass doors: if you want to burn wood or vent the flame outside, look at a direct-vent or wood fireplace instead.
Specifications
Frame a rough opening 42-1/2" wide by 34-1/4" high by 19-3/4" deep — add 1/2" to the width and 1/4" to the height if the trim kit will finish a cabinet or built-in; corner layouts are dimensioned on Figure 3.3, page 8 of the installation manual. The firebox itself is 42" wide across the face, 31-1/8" at the back, 34" high and 20" deep, and weighs 60 lb bare or 140 lb with concrete panels. Inside, the floor is 32-7/8" wide at the front, 24-3/8" at the back and 15" deep, with 25-1/2" of height at the front and 22-5/8" at the rear — the numbers to check against a log set's minimum firebox size. Clearance to combustibles is 0" at the back, sides, top and bottom; keep a perpendicular side wall 9" from the opening, the ceiling 42" above it, and anything flammable 36" from the front. Combustible mantel and mantel-leg clearances depend on how far the mantel projects — see Figure 7.1 on page 18 and Figures 7.2 through 7.4 on page 19 of the installation manual. Non-combustible facing up to 4 inches thick may cover the metal front faces. The gas line enters through side or bottom knockouts; the junction box takes unswitched 110-120 VAC when the log set or an accessory needs it.
How the Exacta 36 compares to the other Exacta sizes and the Attribute ACUF36
The three Exacta sizes share the same 27"-tall opening, 34" x 20" firebox height and depth, 34-1/4" x 19-3/4" framing height and depth, hood, screens, junction box and interior choices; they differ in width and in the log set they take. This 36" opens 36" wide in a 42"-wide box and frames 42-1/2" wide at from $629; the 32" frames 38-1/2" wide at from $609 and the 42" frames 48-1/2" wide at from $729. The 32 takes 18" log sets and the 36 and 42 take 24" and 30" sets. Within the 36" size, the Attribute ACUF36 at from $949 shares the opening, framing and hearth exactly but ships with reversible multitonal fiber panels standard, where the Exacta is sold bare or with concrete panels.
Features
- 36" x 27" clean-face opening on a circulating firebox — the angled box and air channels push heat into the room
- Vent-free enclosure listed to CSA/ANSI Z21.91 — no chimney, no vent run; hosts any listed vent-free gas log heater up to 40,000 BTU/hr, sold separately
- Buy it as an open firebox, or factory-built with Stacked Traditional or Herringbone concrete panels — Reflective Black Glass is the modern option
- Mesh screens that tuck into hide-away pockets, the required firebox hood, a junction box and a lift-out two-piece hearth all ship in the carton
- Zero clearance at back, sides, top and bottom — frames into a 42-1/2" x 34-1/4" x 19-3/4" rough opening on an ordinary combustible floor
- Blower-ready and light-ready — the optional GFK-160VF fan kit and MONAL-VF accent light wire through the included junction box
Answers to common questions
What’s included, what’s required, and what’s optional?
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Included in the box: 36" x 27" clean-face firebox opening; Painted open firebox interior — no interior panel on the base model; the concrete or glass interior panels are optional upgrades; Two mesh firescreen panels on screen rods, with hide-away screen pockets; Firebox hood (must be installed); Junction box for the electrical hookup; Two-piece hearth with lift-out lower access panel and adjustable firebox supports; UL listing to CSA/ANSI Z21.91:20 (ventless firebox enclosure); 20-year firebox warranty (3 years labor).
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Required to complete the installation, purchased separately: Vent Free Log Set (burner + logs/media) - make sure the Exacta BUF 36" Firebox meets the minimum firebox dimensions. For a 36" box, The Torch Guys recommend 18" - 24" log sets; Gas Line - run by a qualified installer or licensed plumber to the side or bottom knockouts before the wall is closed, with a regulator upstream if line pressure exceeds 1/2 PSIG.
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Optional: The IA36BCF contemporary front or ASD-36 operable cabinet doors, the GFK-160VF blower, MONAL-VF accent light, IAL36TK trim kit, and the AKD outside air kit with ID4 or UD4 duct — the firebox operates fully without any of them; electrical power is only needed when the log set or an accessory calls for it.
What do I get if I choose No Thanks on the interior panel?
The base BUF36A — the same firebox with a painted, open interior and nothing fitted over it, which the price book sells with no additional item required to complete. Stacked Traditional Concrete and Herringbone Concrete are three-piece concrete panel sets factory-fitted on the BUF36-T and BUF36-H, and Reflective Black Glass adds the A36BGL glass interior to the base firebox. The opening, hood, screens, clearances and framing are the same whichever you pick; the concrete-panel versions weigh 140 lb against 60 lb bare.
Does it need a chimney or a vent?
No — nothing about this firebox vents outside. The heater it hosts uses air from the room, so the installation must provide adequate combustion and ventilation air and stay out of drafts from exhaust fans, ceiling fans, return-air registers, windows and doors; an extremely tight home needs additional mechanical ventilation, and the optional AKD outside air kit ducts combustion air in through the side of the firebox.
Which log sets fit?
The firebox floor measures 32-7/8" across the front, 24-3/8" across the back and 15" deep, with 25-1/2" of height at the front and 22-5/8" at the back — those are Monessen's minimum-hearth figures for sizing a set. The 36" takes Monessen's 24" and 30" log sets, and any listed vent-free heater up to 40,000 BTU/hr may be used as long as the firebox meets that heater's own minimum size. Above 2,000 ft the heater's input is reduced 4% per 1,000 ft.
Where can it go — and where can't it?
Any ordinary living space that can spare combustion air — framed into a flat wall or a corner, directly on a combustible floor, with a perpendicular wall at least 9" from the opening and the ceiling at least 42" above it. Keep flammable objects 36" from the front, keep carpet and vinyl 14" back from the opening, and over carpet, tile or vinyl set it on a metal or wood panel covering its full footprint; vinyl that runs to the wall calls for 14" of floor protection in front or a 12" raised opening. The heater cannot go in a bathroom and goes in a bedroom only at 10,000 BTU/hr or less.
How high must a mantel or shelf be, and what about a TV above it?
The mantel answer depends on how far the mantel projects: combustible and non-combustible mantel and mantel-leg clearances are charted in Figure 7.1 on page 18 and Figures 7.2 through 7.4 on page 19 of the installation manual, and reducing them means building the surround in non-combustible material to 12 inches above the framing height. Send us your mantel depth and we will read the chart with you. For a television, Monessen prints good-faith guidelines only — 17" from the top of the opening to a combustible mantel, 12" to a non-combustible one — with the TV maker's own maximum operating temperature the deciding limit, so verify the actual TV temperature at installation.
Does it use electricity?
Only if something in it needs power. A junction box is built into the firebox and is wired to unswitched 110-120 VAC (the rating label reads less than 3 A at 115 V); not every log set needs 110 VAC, so a millivolt set can run with no power at all. Rough the circuit in before the wall is closed if you might add the GFK-160VF blower or the MONAL-VF accent light — their controls mount in the firebox or in a remote wall box — and a circuit near a sink or in a bathroom must be GFCI-protected.
How does the warranty work if something goes wrong?
Hearth & Home Technologies warrants the firebox for 20 years on parts and 3 years on labor, the concrete panels and any glass liner panels for 2 years, and the junction box and electrical parts for 2 years — valid only on a purchase from an authorized dealer, and transferable to a later owner of the home. The Torch Guys is an authorized Monessen dealer and handles the claim for you: keep your invoice and the model and serial numbers, and we deal with the manufacturer on your behalf rather than handing you a phone number.
