https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/ Building science knowledge, HVAC design, & fun Thu, 16 Sep 2021 21:20:01 +0000 hourly 1 https://wordpress.org/?v=6.6.2 https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1108 Mon, 27 Oct 2014 22:41:44 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1108 @Savanna, if the water heater
@Savanna, if the water heater is “atmospheric” (e.g., not sealed combustion) and is installed inside the building envelope, it *must* have exterior venting, typically installed in a nearby wall. You can tell it’s an atmospheric water heater if the flue is metal and there’s a big gap between the top of the water heater and the flue collar. 
 
You can find the details in the installation manual (available online), but in general, a high and low vent are required if closet has a solid door. The vents are sized according to the BTU capacity of the burner. If closet has louvered door and adjoining space is over a certain size, or the water heater is located in a large room, a smaller single vent is acceptable.

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1107 Thu, 31 Jul 2014 20:01:34 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1107 Allison, I know that. I have
Allison, I know that. I have two graduate degrees. I studied this subject due to having been exposed to chronic low levels of carbon monoxide for several years. This needs further study. Retrospective studies that include subdivisions that were built with tight insulation and gas atmospheric water heaters and furnaces exhaused to the same chimney would tell the story. Also, gas stoves with no outside vent that blow the exhaust back into your face while cooking could be included. Good luck to you and your family.

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1106 Thu, 31 Jul 2014 19:41:41 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1106 Gloria: A
Gloria: A fundamental principle of science is that correlation does not prove causality. Otherwise, one could just as well say that the dwindling numbers of pirates on the open sea is responsible for the rise in global temperatures.

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1105 Thu, 31 Jul 2014 19:33:37 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1105 I believe this is a cause of
I believe this is a cause of the epidemic increase in autism spectrum disorder and dementia we are experiencing in this country. The increase coincides with the movement to seal up our homes.

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1104 Tue, 29 Jul 2014 01:56:45 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1104 Tom D: Not
Tom D: Not so fast. The only way what Dr. Austin says can be true is if the furnace is more efficient when burning warm air than cold air. Further, it would have to save exactly as much energy as is lost by the additional runtime of the furnace due to the higher heating load from infiltration. But how could that be true for every type of furnace, with blowers that have different efficiencies and duct systems that are all over the map? And looking at the combustion process, the amount of oxygen in denser cold air would have more of an impact than the kinetic energy of those oxygen molecules.  
 
I’m not sure what Dr. Austin was thinking there. I guess he thought physics was different in 1976 than it is today.

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1103 Mon, 28 Jul 2014 23:26:25 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1103 “Your energy bills will
“Your energy bills will be higher as a result.” Not true! Some infiltration, with humidity change, & draftiness, that’s all. According to Dr. LG Austin, Penn State: “from a heat balance point of view, it’s immaterial where the cold air enters, through a window crack, or through a venting pipe…” citation: http://www.popsci.com/archive-viewer?id=xAEAAAAAMBAJ&pg;=119&query;=outside%20combustion%20air%20%20flue%20%20balance It’s all chemical engineering, not physics!

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1102 Sun, 13 Apr 2014 12:18:37 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1102 Information pointed me in
Information pointed me in right direction. Water heater in attic, and noticed corrosion. Discovered vent had been displaced, so reattached. The roof was replaced a couple years ago and with it grates (term?) that replaced the older round roof ventilation (which seems less effective). There is a large caged open area above the porch that is suppose to facilitate air flow. Now that I’ve reattached the water heater vent, I also put a regular house fan up there (not pointed at the heater) but a bit behind and adjacent, blowing toward the porch (from attic). So far I’ve not read anything whether it’s a good idea or counter productive. Advice? Thanks, Rj

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1101 Tue, 11 Dec 2012 07:45:07 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1101 Related to this, has anyone
Related to this, has anyone done a thorough study of the use of all the primitive ‘traps’ added to thwart the undesired inflow of cold air in the combustible air ducts when the furnace/ water heaters are off? I would expect the stack effect is going to pull cold air in, anyway, without a more sophisticated fan-linked system, but am particularly curious as to how the traps are supposed to work, and if they’re really based on sound principles? P-traps work in water vents because water is held in the low portion, but that affects incoming air; I can’t see how a layer of cold air can effectively keep air from flowing freely.

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1100 Sat, 12 Feb 2011 06:28:39 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1100 David, you make some good
David, you make some good points, as always. Although combustion safety is the main concern of this post, when you’re looking at alternatives, it’s important to consider other factors, such as efficiency.  
 
I totally agree that the furnace and water heater are too close to each other here (my condo, no less). Even worse, I didn’t show you the dryer that’s in the same room with them. This arrangement is unfortunately all too common, especially in older housing like my 40 year old condo. The only thing that saves us is the 30+ ACH50 infiltration rate. It’s kinda hard to backdraft a water heater with that much air leakage. That’s why I haven’t done the air sealing yet that I’d love to do.

]]> https://www.energyvanguard.com/blog/3-problems-with-atmospheric-combustion-inside-the-building-envelope/#comment-1099 Sat, 12 Feb 2011 05:22:25 +0000 http://energyvanguard.flywheelsites.com/?blog_post=3-problems-with-atmospheric-combustion-inside-the-building-envelope#comment-1099 Where I live, water heaters
Where I live, water heaters are typically installed in the garage. In hot climates, this is actually more efficient than inside the envelope. Anyone who has studied EF ratings knows that the water heaters with the highest EF’s are atmospheric (non-condensing). 
 
In mixed climates, garage is probably a wash in terms of efficiency (especially if garage is insulated), with all the savings on the front end.  
 
In cold climates, sealed combustion begins to look attractive.  
 
One caveat: whether you put an atmospheric water heater in a garage, attic, basement, crawl, or combustion closet, do NOT install furnace or air handler nearby. That tight return side plenum may not always be so tight. In any case, the HVAC belongs inside the envelope in all climate zones. 
 
BTW: your top picture violates the proximity principle. And I’m ashamed to say, ditto in my previous home.

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