I am currently building a SIP home and I am undecided on whether or not to go with a vented or ventless gas fireplace. I know that a vented fireplace would obviously be better for air quality, but I hate the idea of boring an 8" hole in the wall after I have gone through so much trouble making it tight. Its almost like buying a prius and drilling a hole in the gas tank Ive been getting mixed reviews from fireplace retailers. Some say that I MUST go vented, while others say I should just go ventless and just open a window when its in use. The perfect solution to this would be a vented fireplace that had some sort of insulated baffle that would close when the fireplace was off. Does such a fire place exist? Does anyone have first hand experience with a gas fireplace in a sip home whether it be vented or non vented?

Be sure to read the operating instructions before you purchase a ventless fireplace.  Some have a restriction on how many minutes they can be used in a twenty-four hour period.

I would not normally recommend the use of vent-free gas fireplaces. Problems with them in years past have left a bad taste, so to speak. They may be OK for warming up a romantic atmosphere, but not for warming up homes.
You should be able to find a good quality direct vent unit with outside air source and sealed doors that would be relatively efficient.

The combustion air for the fireplace has to come from somewhere. If you have a vent-free fireplace, then it's coming from the room air, which must be replaced with outside air. The combustion air for the direct-vent fireplace comes in the vent. Given the choice, I'd rather have the direct-vent since now I'm not relying on the mechanical ventilation (or the natural infiltration) to provide the combustion air. Deliberately adding infiltration to supply the fireplace would also seem to defeat the purpose of building a tight house.

You also may need a lot of infiltration/ventilation to provide enough oxygen for the fireplace. If it's in a small room you may need more air changes just to feed the fireplace. If you don't supply combustion air, the O2 sensor will kick in an shut off the fireplace.

Bottom line, cold air is going to come in somewhere. I think that it's better that it come in only to the fireplace.

I wanted a fireplace in my mountain SIP home for both looks and heat. I wanted a fireplace with glass doors that would force air through a heat exchanger to minimize heat loss from the house up the chimney. I placed the fan and fresh air inlet outside to bring fresh air from outside through the heat exchanger out the top of the fireplace, and let the cooler house air go into the bottom of the fireplace for the fire. After the fire gets going, I close the glass fireplace doors, close down the bottom inlet vents for the fire, and the thermostat turns the fan on. So, I’m bringing in fresh air, heating it, slightly pressurizing the air in the house making sure I don’t have any back drafts back down the chimney. Works like a charm.

Steve
GrandCountySIPs.com

I am building a home near Durango and am using a sealed, DV fireplace. No cold air comes into the room, no heated air goes out--self balancing. A sophisticated solution utilizing your ERV/HRV might be worth pursuing. I am using a fail safe approach. Air in, exhaust out.

I would NEVER sell or install a 'vent free' fireplace in anyone's home, no matter what. There are too many negative issues related to VF fireplaces. Some states do not allow the use of them (at least that was the case a couple years ago).

Of the Mfg's that offer vent free products, they STRONGLY advise the retailers (I've been to the dealers meetings) to "educate your customers" who might buy VF products. There is a serious risk - especially for elderly and infants and shut-ins.

So what if the original purchaser of the VF sells his home? The unsuspecting new home buyers (victims of the "acceptible levels" of carbon monoxide) may actually try to heat their home in the winter with the windows actually shut! (who wouldn't?)

MOLD is the next big problem to contend with if you want to live with a VF fireplace. Burning propane gives off water vapor! Lots of it! (Thats why the HVAC installers of gas furnaces must plumb the unit to the ground to discharge the water).

Indoor air quality seems to be such an important topic in new construction. I can't understand anyone tollerating the CO2 and water vapor.

Also, what if the FP gets 'out of adjustment'? The sooting I have seen with gas fireplaces which have either been altered by owner, or installed improper, or faulty parts, or,... Black soot associated with a direct vent FP is at least confined to the inside of the fireplace.  A VF FP will put black soot all over your ceilings and walls (slowly, gradually, so that it goes unnnoticed until serious damage already occurs before you can do anything about it.

"Vent free fireplaces are fine, if you don't mind living inside a chimney". Thats what I tell my customers to get them to re-think their ideas on VF.

If you Google "vent free fireplaces indoor air quality" you will likely find arguements supporting both sides of the issue. However, just because some people report having no problems "so far" Many people have had LOTs of problems.

Maybe I'm comeing off as a biased, one sided jerk, but I refuse to sell a vent free to one of my customers as I do not want to be connected to the inevitable problems that will likely come up. Even though it may be tempting to cash in on some extra sales, not worth it!

As others have stated, vent free is a safe way to vent the 'combustion by products' to the exterior of your home, as well as provide the combustion air for the fireplace.

Good luck with the project!

Mark

After having had a house for 30 years with a wood-burning fireplace (converted to gas logs) I took an entirely different approach to the fireplace in my new SIPS house -- 5400 sf single floor w/walk-out basement; 4100 sf is conditioned air with WF ghp in Florence, AL.
Fireplace design model considerations:
1. Wood burning was out, never again to have one of those filthy things.
2. Cost of "wantabee" fireplace and cabinetry was $10,000 -- gas logs or electric
3. Wanted back-up heat source ---- installed a 15KW natural gas powered generator ($4500)
4. Bought a 50" flat screen TV for nicely designed cabinetry ($1100)
5. Bought a $10 DVD from Amazon.com of wood burning fireplaces, with music, and crackling log sounds. ($10)
6. When I get tired of looking at the fireplace, I flip the switch & watch the ball game or the races.
7. Many visitors have commented they feel warmer after watching the DVD for 15 minutes. Like Agassi said in the camera commercial, "Image is everything".
8. No holes in the wall, no gas smell, and no sorry looking flames from gas logs.
Now I have heat from my ghp powered by a generator during black outs and I can watch my fireplace -- end of story.

Note: Alton Keown was my mentor on this house and it turned out to be the house of our dreams. Thanks Alton.

Gene