Foggy gas fireplace glass or white film

Fog that appears when you light a gas fireplace and clears as it warms up is normal condensation. Heat & Glo’s manual says it comes from gas combustion and temperature variations and disappears as the fireplace warms. A white film that stays is usually deposits on the inside of the glass: on a new unit, from the paint and logs curing; on an older one, often from combustion over time. Cleaning is typically part of an annual service at $175 to $350 per fireplace or a $150 to $300 service call. If the glass is etched or the gasket has failed, glass and gasket run $200 to $600. We give the firm number after we have seen the unit.

Fog that clears or film that stays

The new-fireplace film

Both manuals we work from treat the first burns as a curing period. Heat & Glo calls the film “a normal result of the curing process of the paint and logs” and says the glass should be cleaned within 3 to 4 hours of initial burning to remove deposits left by oils from manufacturing, adding that a non-abrasive gas fireplace glass cleaner may be needed. Napoleon’s B36 manual says to clean both sides of the glass after the first 10 hours of operation with an ammonia-free glass cleaner, and warns that glass not kept clean can end up permanently discoloured or blemished.

That timing matters most where fireplaces are new. The Census puts 70.8% of homes in Harrisburg and 52.7% in Tea as built in 2000 or later, and its 2019 to 2023 survey already counts 145 Harrisburg homes and 164 Tea homes built in 2020 or later. A new home or a new insert is worth a look at the manual before the first long burn. If you are in Tea, our Tea page has more on the local housing.

Check this first

• Let it cool completely. Both Heat & Glo and Napoleon say not to clean the glass while it is hot.
• Clean only what your manual allows. On the Heat & Glo TRUE series the homeowner may only clean the outside of the glass, and glass removal is for a qualified service technician.
• No abrasives. Napoleon’s B36 manual rules out abrasive cleaners, razor blades and steel wool on the glass.
• Use an ammonia-free cleaner made for fireplace glass, as Napoleon specifies.
• Find your model. Heat & Glo says the rating plate is usually in the control area of the fireplace. A photo of it helps us bring the right gasket.

Why Sioux Falls glass fogs at start-up

A fireplace lit in a cold room starts with cold glass, and cold glass is where condensation forms. With a January normal high of 27.2 F at the airport, according to NOAA, many start-ups here begin that way. Napoleon’s manual also notes that sealing every vent joint avoids performance or condensation concerns in tightly constructed homes, particularly in cold climates. Fog that lingers well past warm-up, or water that runs, can point at the venting rather than the glass.

When a film means something else

A haze that comes back soon after a proper cleaning, or soot of any kind, can mean the burner, log placement or air mix is off, or the vent is not drawing as it should. Napoleon ties a blue, lazy, transparent flame to a vent blockage. We check the flame, the logs and the gas pressures before cleaning, so the cause gets fixed and not just the glass. See gas log repair, annual service and typical prices on our pricing page.