when too much insulation is a bad thing..

windowguyJanuary 30, 2009

Gutted 1970's panel basement. Glued 2 inch rigid to concrete walls. R13 in joists above where foundation meets the walls. Framed and rock in front of that. Dricore subfloor. Also R13 in walls of laundry/mechanical area. the idea is that room can be cold while main basement area is warm.

1 month after installation my furnace shut down. Technician said it was a "pressure" code. checked hoses and pipes found no blocks. he thinks i made the room too airtight and it can't draw enough fresh air now (unit doesnt draw air from outside).

3 days ago my water heater stopped. error code was "vapor sensor" i know there was nothing in the area. in another forum a guy said the sensor trips sometimes because of bad air flow.

i didnt recall Holmes on Homes every saying too much insulation in the basement was a bad thing!

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I am finishing my basement in a similar fashion right now. My city is requiring combustion make air per 2003 IRC. Not sure what's involved just yet, but it sounds like you may need some make up air. I ordered the IRC this week, $65 on Amazon.

    Bookmark   January 30, 2009 at 12:59PM
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I keep mentioning providing replacement air when basement insulation questions come up. Be sure, too, to install CO detectors.

Be proud! You've obviously done a good job insulating and sealing.

    Bookmark   January 30, 2009 at 1:19PM
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Okay, my ignorance is going to show.. just how can I "make up some air for $65"?

    Bookmark   January 30, 2009 at 1:45PM
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The IRC (International Residential Code) book is $65. This gives the requirements for providing make up air. Your city may have a different version or Code, but you should check. Search online for make up air.

    Bookmark   January 30, 2009 at 1:50PM
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i just did some searching on a forum back in 2006.. i think what i need to do is cut a grill between the mechanical room and the main room. but jeez, that defeats my whole insulation job.. stinks. My mechanical room is pretty big.. i'd say 10X15 (laundry + workbench + sink). i can't believe there's not enough air in there.

but it had to have been that right? too much coincidence two appliances crapped out within 1 month of each other.

    Bookmark   January 30, 2009 at 1:55PM
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ughh.. now i know why the original door to the room was louvered. i replaced with solid core door for insulation. Crap! Can someone tell me if I put a 6X10 grill in the wall that might draw enough air? Or i can pull the Bats out of the joist area and really open up the air.. but all of this drops my insulation.

    Bookmark   January 30, 2009 at 2:06PM
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Here's a link for a rough calculation.

    Bookmark   January 30, 2009 at 2:10PM
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i just read that link and got very concerned about the C02 issue. If i have a "regular" C02 stand alone device and it doesnt alarm does that mean my levels are COMPLETELY safe? Of does the alarm only go off at fatal levels. (my wife has actually been complaining about dizziness lately). I think i'm going to go home and rip out all the bat insulation immediately.

    Bookmark   January 30, 2009 at 2:28PM
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very important.. both my furnace and water heater are power vent. not direct vent. Power vent.

    Bookmark   January 30, 2009 at 4:33PM
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Just having louvered doors may not provide enough supply air for the appliances. That's where HRV/ERVs come in. Before they were developed, in one house I built I had to provide a damper-controlled 8 inch air supply directly from the outside into the furnace room with a small heater at the outlet.

Power vents don't supply makeup air, they just ensure the exhaust of air. In a tightly sealed home, you will experience the effects of negative air pressure.

    Bookmark   January 30, 2009 at 5:20PM
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"i didnt recall Holmes on Homes every saying too much insulation in the basement was a bad thing!"

Because it is not?

It is not the insulation causing the problem, but the closing off of infiltration paths that was supplying combustion air.

While sealing up leaks is part of improving energy efficiency, it is not insulation per se causing the issue.

    Bookmark   February 1, 2009 at 1:04PM
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If the mechanical room has a common wall with the outside, you can vent through it..

    Bookmark   February 2, 2009 at 1:02PM
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Too much insulation can be a bad thing if it's too thick. But your problem is as the others have indicated, you've tightly sealed your home. A well sealed home may save energy but the trade off is the problem you are having as well as health issues caused by indoor air pollution. A healthy indoor environment requires a minimum of 4 complete air exchanges per day.

    Bookmark   February 2, 2009 at 11:06PM
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I would agree, insulation and combustion/makeup air are two different things.

On a related note, I prefer to keep the mechanicals inside the building envelope. The only reason I would insulate an interior wall would be for sound. Otherwise, you should plan on insulating the duct work.

    Bookmark   February 4, 2009 at 11:28AM
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If you're watching holmes on homes, are you in Canada? If so I think the rules about combustion air are specific, you do need a louvred door. I don't understand why you wanted to insulate the mechanical room, generally, even with HE units, they are going to warm the place, not cool it.

Does the furnace have a combustion air draw in? There will be an outside pipe that runs into the cold air return, that's not it, but a separate pipe that brings air in for the furnace, some he vents are a funnel shape outside, the part close to the wall draws air in, the other blows the combustion air out.

I've seen 'make up air' setups that appear to be a duct outside, with a cage over the end near the floor next to the furnace. That's probably the sort of thing you need.

    Bookmark   February 23, 2009 at 1:30PM
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