Direct vent fireplace fogged glass

What do you think is causing the inside of the glass on this direct vent fireplace to fog? Poor venting? Pilot was lit, it vents directly out the back to the exterior.

Thanks, Steve

fireplace fog.jpg

Water is in gas. The condensation is a by product of combustion. It will probably disappear when the burner is ignited.

Did you try the burner?

Yes, and it fired up. I did not run it long though. Were you gonna say after leaving it run a while the fog would go away?

Thanks, Steve

Yes, once the fireplace heats up the moisture should go away.

It’s more than moisture.

Be right back with great info for you.

Here you go:

There’s also a picture in the very first post in that thread.

Sometimes the link doesn’t work; tonight it did.

Yes, good info Russel. It may be that, however I’ve noted many fireplace glass fronts that cleared, what appeared to be moisture, after it was heated up. These were all pilot lighted units I’m talking about. I had one for years that acted that way and never damaged the glass. It always cleared.

They do clear up. I’ve never seen one that didn’t clear up. However, the damage from the sulfuric acid remains, even though it might, indeed, take years before the damage is noticeable. It depends on the quality of the gas and how often the fireplace is used.

I had a one-year-old house a couple of weeks ago that had a direct vent fireplace. When I flipped on the switch, the glass fogged up and the Client got upset. We let it burn awhile and I showed her the damage that had already been caused by the sulfuric acid. They have requested from the seller a new glass front for the fireplace. Our gas out here is pretty oogy.

Yes, that may be it.:wink:

I’ve heard that about more things than gas in CA. :mrgreen:

By the way, if anyone ever has an opportunity to attend a seminar by Dale Feb, one should jump at the opportunity. One will never look at, or think about, fireplaces and chimneys the same way again. They are eye-opening seminars.