Flue Gases in attic

[Mike Schulz]

Codeman,

Inspected a ranch home today that had a direct vent fireplace. The exhaust hood on the exterior was up under the eave and was in compliance for distance to the perforated soffit. I turned on the fireplace and let it run the whole time I was there. When I went into the attic the smell about knocked you out from the flue gasses being sucked through the soffit. The builder was there and claims it is a energy star home and the that attic is sealed from habitable areas. He also claims the gases in the attic pose know risk and is allowed. It just doesn't sit well with me and I think it's a risk of leakage into the home.
Is there any code that says no gases in the attic?

[Jerry Peck - Codeman]

Hi Mike,

Is there any code that says no gases in the attic?

Sort of, yes, but there is no specific code which regulates the air quality in the attic.

That said, what you described would be a sure sign that the location of the direct vent exhaust hood on the exterior is not located where it should be located.

One thing to remember is that codes are minimum requirements for minimum levels of safety and operation which do not, and cannot, address all specific installation inconsistencies and specific problems.

As an example, if that vent is on the prevailing wind side of the house, the exhaust gases will be blown back toward the house, and, if an opening is located nearby, those exhaust gases will enter the opening(s).

The same applies for manufacturer's installation instructions: they were developed to establish a minimum level of minimum safety and operation and do not, cannot, address all peculiarities for every installation.

You found direct evidence that the exhaust gases are being blown back into the structure as the attic is part of the building. From this aspect and vantage point, the following code applies.

From the 2006 IRC. (underlining and bold are mine)
(applicable in general)
-> CHAPTER 15
- -> EXHAUST SYSTEMS
- - -> SECTION M1501
- - - -> GENERAL
- - - - -> M1501.1 Outdoor discharge. The air removed by every mechanical exhaust system shall be discharged to the outdoors. Air shall not be exhausted into an attic, soffit, ridge vent or crawl space. (Codeman's note: While not being exhausted "directly" into the attic, you found that, under the conditions present during your inspection, it was exhausting "indirectly" into the attic.)
- - - - - -> Exception: Whole-house ventilation-type attic fans that discharge into the attic space of dwelling units having private attics shall be permitted.

(applicable in general as direct vent systems are specialized mechanical draft systems)
-> CHAPTER 18
- -> CHIMNEYS AND VENTS
- - -> M1801.5 Mechanical draft systems. A mechanical draft system shall be used only with appliances listed and labeled for such use. Provisions shall be made to prevent the flow of fuel to the equipment when the draft system is not operating. Forced draft systems and all portions of induced draft systems under positive pressure during operation shall be designed and installed to prevent leakage of flue gases into a building. (Codeman's note: "shall be designed AND INSTALLED to prevent the leakage of flue gases into a building", your inspection found that THAT INSTALLATION, whether installed in accordance with the design or not, DID NOT PREVENT "leakage of flue gases into the building". Thus, THAT INSTALLATION *does not* meet the requirements of that code section.)

(applicable specifically as the appliance is a gas appliance)
-> CHAPTER 24
- -> FUEL GAS
- - -> SECTION G2408 (305)
- - - -> INSTALLATION
- - - - -> G2408.1 (305.1) General. Equipment and appliances shall be installed as required by the terms of their approval, in accordance with the conditions of listing, the manufacturer’s instructions and this code. Manufacturers’ installation instructions shall be available on the job site at the time of inspection. Where a code provision is less restrictive than the conditions of the listing of the equipment or appliance or the manufacturer’s installation instructions, the conditions of the listing and the manufacturer’s installation instructions shall apply. (Codeman's note: The opposite is also true, that when a code provision is more restrictive than the conditions of the listing, labeling, or installation instructions, the code shall apply.)
- - - - - -> Unlisted appliances approved in accordance with Section 2404.3 shall be limited to uses recommended by the manufacturer and shall be installed in accordance with the manufacturer’s instructions, the provisions of this code and the requirements determined by the code official.

(applicable specifically as this covers venting of gas appliances)
-> SECTION G2427 (503)
- -> VENTING OF EQUIPMENT
- - -> G2427.2.1 (503.2.3) Direct-vent appliances. Listed direct-vent appliances shall be installed in accordance with the manufacturer’s instructions and Section G2427.8, Item 3.
- - -> G2427.8 (503.8) Venting system termination location. The location of venting system terminations shall comply with the following (see Appendix C):
- - - -> 3. The vent terminal of a direct-vent appliance with an input of 10,000 Btu per hour (3 kW) or less shall be located at least 6 inches (152 mm) from any air opening into a building, and such an appliance with an input over 10,000 Btu per hour (3 kW) but not over 50,000 Btu per hour (14.7 kW) shall be installed with a 9-inch (230 mm) vent termination clearance, and an appliance with an input over 50,000 Btu/h (14.7 kW) shall have at least a 12-inch (305 mm) vent termination clearance. The bottom of the vent terminal and the air intake shall be located at least 12 inches (305 mm) above grade.

It just doesn't sit well with me and I think it's a risk of leakage into the home.

I agree.

Regardless how much effort has been put into sealing off the living space ceiling plane at the attic, trying to seal and stop *ALL* leakage is very difficult, additionally, there is air infiltration and exfiltration *through* various building materials, regardless of whether the material is sealed around or not.

The above risk is greatly increased if there is a second floor wall abutting this attic as now there are many more openings into the living space, such as at all receptacle and switch boxes, cable TV and phone cable entries, etc., the risk is so much greater with second floor walls present - leakage in around the sill plate, the top plate, the corners, you name it.

I've always found it interesting that a builder will claim, either verbally or through their advertisements, that they build "custom", "quality", or "luxury" homes, or whatever other phrase or term they use to imply or state the same thing, when something is shown to them that it is not working as it should, those same builders, with very rare exceptions, will dive to the bottom of the quickly sinking sand and try to stand on, and defend their construction on, *the minimum requirements of a minimum code*. So much for their * "custom", "quality", or "luxury" * construction stance.

Hopefully the information above will be helpful, some is generally so-so applicable, some is directly applicable.

Codeman

[Mike Schulz]

Jerry, just wanted to thank you for providing this wonderful site and for the timely replies.

[Jerry Peck - Codeman]

Mike,

Thank you, and please come back again.

Codeman