Corbett delivered this 1-hour keynote address for Earth Week in Illinois.
To book Corbett for an entertaining and inspiring presentation for your event, visit:
http://buildingperformanceworkshop.com/about/keynotespeaker
Corbett’s Keynote Address: THE MUSIC IN BUILDING CONTROL
April 30th, 2013 by corbettTesting Carbon Monoxide Air Free: When and Why
April 30th, 2013 by corbettDear Corbett:
In measuring the carbon monoxide from my parents’ stove (fuel source=propane), I set the oven to 400ºF, and took the measurement at 375ºF. The resultant measurements were CO=58 and CO air free=198.
I understand from class that CO air free should be used for the stove, but there is a huge difference between the two results, is this normal??? I mean they almost cover the entire BPI standard (either it’s all good or we should replace the thing). Your insight would be appreciated. Thank you!
Jerad W.
PS- Miss you guys and your enthusiasm.
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Dear Jerad-
Aw shucks, we miss you around here too! Great advanced question!
First off, let’s discuss what carbon monoxide (CO) “Air Free” means. If you were to subtract all the excess oxygen that’s diluting the carbon monoxide’s concentration, the result would be what we see in the Air Free reading (or µ CO reading on a Testo device).
Now you’re thinking: but there IS oxygen in there, diluting the gases, so why are we pretending there’s not?
In the case of an oven, for most people most of the time, the combustion gases will spill into the house to the tune of 100%. A professional chef knows the range exhaust hood should be on continually, but your average homeowner only uses it when they burn something. So if ALL of the carbon monoxide is coming into the home, it would be nice to know exactly how much we’re talking about.
Now for the oxygen itself: there’s generally always leftover oxygen (O2) in combustion gases (even though technically it would be ‘perfectly efficient’ combustion if all the O2 were used up), but in water heaters and furnaces the oxygen percentage is around 5-10%. The air that you’re breathing right now contains 20.8% oxygen.
SO HERE’S THE KICKER: When you test the oven, check out the oxygen percentage as well as the CO parts per million, and if your O2 percentage is 15-20%, that’s a very diluted reading you’re taking, because there’s simply SO MUCH AIR coming out of the vent sleeve. In that case, grab the CO Air Free reading and you’ll know exactly how much carbon monoxide is actually going to be breathed by all of us while you’re making us meatloaf.
My rule of thumb: if the oxygen is over 14% I always use the carbon monoxide air free measurement, which will be considerably higher than the diluted measurement.
Happy testing!
Corbett
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Corbett Lunsford, Founder of the Building Performance Workshop
Teresa Lopez of Green Energy Money interviewed on the Building Performance Podcast
April 25th, 2013 by corbett
Today we talk with Teresa Lopez of Green Energy Money about the future revolution of high performance home mortgages and the current problems that plague the financial system.
Don Stevens of Panasonic/ASHRAE on the Building Performance Podcast
March 5th, 2013 by corbettToday we talk again with Don Stevens, National Research & Development Manager at Panasonic Eco-Solutions, about the history of ASHRAE 62.2 residential ventilation standard, and the upcoming changes in 62.2-2013.
Blower Door Testing from a Sliding Glass Door
February 15th, 2013 by corbett
Ever found yourself without any good exterior door options during a home energy audit? Setting up a blower door test in a sliding glass door is certainly not ideal, but it is possible, and to make it less intimidating I’ll share with you my technique for getting accurate blower door results from this slider.
First, you should know that you have 3 size limitations in sliders:
- The blower door frame must fit
- The center brace must fit
- The blower door fan must fit
First, fit the frame into the inner track (nearest the interior)- if you install it in the outer track, you usually won’t be able to reach the knobs and locking cams. You’ll notice that the frame’s rubber edge presses up against the sharp metal frame of the slider- that’s why you don’t tighten the knobs yet. Get the frame approximately fitted, then back the size down a notch, so you can remove it and install the shroud.
Once you’ve covered the frame with the nylon shroud, make sure, as always, that you place your reference hose outside, away and off-axis from the fan’s flow. Then install the shrouded frame, and expand the frame to fit firmly into the sharp metal frame (again, on the inner track).
Now for the fun part. Your center brace will likely not fit into the frame like it usually does. You’ll have to create an interesting geometry; remember that the purpose of the center brace is twofold:
- To create lateral tension, keeping the long sides of the frame in full contact with the jamb
- To suspend the fan
Hook the ends of the center brace into the slots, as horizontally as you can. The hooks themselves may not catch, but if you get enough lateral tension, they should at least be embedded in the frame slots. The weight of the fan will ensure the center brace stays put vertically as well.
Before you install the fan, you’ll need to put the final touches on your blower door’s air seal. I use duct mask, but you could use masking tape instead. It’s important that the tape seals from the metal of the slider frame to the metal of the blower door frame. Don’t seal to the shroud- peel back the nylon to adhere to the frame by disconnecting the velcro and folding the shroud edge up as small as possible.
And lastly, don’t forget the meeting rail! You’ll need to tape the two ’sashes’ of the sliding door together to prohibit air leakage between them.
Voila, you’re ready to make love to your client’s home!
