If you have started shopping for a gas fireplace, you have run into two terms that sound interchangeable but are not: insert and zero-clearance. Choosing the wrong one means a unit that physically cannot be installed in your home. The distinction takes about a minute to understand.
The short version
An insert slides into a fireplace you already have. A zero-clearance unit frames into a wall you are building. If you have an existing masonry firebox, you are shopping for an insert. If you are not, you are shopping for zero-clearance. Everything else follows from that.
What is a gas fireplace insert?
An insert is designed to slide into an existing masonry fireplace — the kind built from brick with a chimney. If you have a wood-burning fireplace you no longer use, an insert converts it to clean, efficient gas heat while reusing the existing opening and chimney chase.
The defining requirement is that you must already have a masonry firebox, and it must be big enough. Kingsman's smallest, the IDV24, needs a minimum opening of 24 1/4" W x 18 1/2" H x 14" D. The largest, the IDV44, needs 32 7/8" x 25 3/4" x 18". Measure before you shop — full dimensions for every model are in our wood-to-gas conversion guide.
What is a zero-clearance gas fireplace?
A zero-clearance fireplace is a self-contained firebox engineered to be framed directly against combustible materials — wood studs, drywall — with no existing masonry required. "Zero clearance" refers to how little gap the unit needs between its body and the surrounding framing.
What you need instead is a correctly sized rough opening. A few from the Kingsman range, per current published framing dimensions:
| Model | Framing (W x H x D) | Input max (NG) |
|---|---|---|
| ZCV36 Clean View | 36 3/8" x 37 1/4" x 17 1/2" | 18,000 BTU |
| ZCVRB36 Linear | 36 3/8" x 37 1/4" x 17 1/2" | 17,500 BTU |
| ZCV39 Clean View | 39 1/2" x 37 7/8" x 18 1/2" | 25,000 (28,000 ceramic) |
| HB4224 traditional | 42 3/8" x 37 1/4" x 17" | 24,000 BTU |
| ZCVRB47 Linear | 47" x 38 3/4" x 18 1/4" | 24,500 BTU |
| ZCVRB60 Linear | 66 9/16" x 43" x 19 1/4" | 35,000 BTU |
| MCVST42 See-Through | 43 1/8" x 51 3/8" x 23 1/16" | 30,500 BTU |
Per the Kingsman Fireplaces United States Price List, effective March 1, 2026. Note that framing width is always larger than the model name — the ZCVRB60 needs 66 9/16", not 60".
That last point catches people out. Model names refer to viewing width or model designation, never to the rough opening. Always frame to the published framing dimension.
Which one does your home need?
| Your situation | Best fit |
|---|---|
| You have an existing brick or masonry wood fireplace to convert | Insert |
| You are building a new home or finishing a new wall | Zero-clearance |
| You are remodeling and adding a fireplace where none exists | Zero-clearance |
| You want a modern linear or see-through look | Zero-clearance |
| You want the most heat for the money and have the opening | Insert |
That last row surprises people. The IDV44 insert produces 34,250 BTU — within 750 BTU of the 60-inch ZCVRB60 linear — at roughly half the price and with no framing work. If you have a masonry opening, an insert is usually the better value.
A note on venting and enclosures
Most modern zero-clearance gas fireplaces, including the Kingsman models Lumiflares carries, use direct venting: a co-axial pipe that draws combustion air from outside and exhausts outside, sealed from your room air. Efficient, safe, and no chimney required — but it does need a vent run terminating through an exterior wall or roof, worth planning early.
Zero-clearance units can also carry enclosure requirements that inserts do not. The ZCVRB60, for example, needs up to 200 square inches of ventilation and a minimum enclosure height of 76 inches if you want cool-touch walls and reduced mantel clearances. That shapes the whole feature wall, so resolve it with your builder before framing.
Why most new fireplaces today are zero-clearance
Because they do not depend on existing masonry, zero-clearance units give designers far more freedom — including the clean-face, frameless, and linear looks that define modern interiors. The Lumiflares lineup reflects this: from the compact ZCVRB36 Linear and ZCV36 Clean View, to the ZCVRB47, the great-room ZCVRB60, and the double-sided Clean View 43 See-Through.
Whichever path you are on, installation should be performed by a licensed gas installer to meet local code and protect your warranty. Requirements vary by model, configuration, and jurisdiction.
Not sure which category you are in?
Send a photo of your fireplace and its opening measurements, or your rough opening if you are building. We will tell you which path fits and which models work.
Call +1 (877) 879-9191 (Mon–Fri, 8:00 AM–5:00 PM ET) or email support@lumiflares.com.
Frequently asked questions
What does zero-clearance actually mean?
It means the firebox is engineered to sit directly against combustible framing with minimal gap, so you can build a wall around it rather than needing masonry. It does not mean zero clearance to mantels or finishes — those requirements still apply and vary by model.
Can I put a zero-clearance fireplace inside my existing masonry fireplace?
Generally no. That is what an insert is for. Ask us before assuming either way.
Is the framing dimension the same as the model width?
No, and this is the most common costly mistake. The ZCVRB60 is a 60-inch fireplace that needs a 66 9/16-inch rough opening. Always frame to the published framing dimension.
Sources
Specifications drawn from the Kingsman Fireplaces United States Price List effective March 1, 2026, and model installation manuals.
