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Since I had today off there was time to spend on yet another heating efficiency project: insulating the attic hatch. In my case it is a small 18" by 24" opening in an upstairs closet. Nothing more than a rectangular hole with a piece of plywood sitting on top of the trim. I chose to attack it as described at energysavers.gov (http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11400) with one modification. I did use 4" of solid foam insulation held in place with construction adhesive. But since I have lots of window film lying around from my other recent project (http://www.cleanmpg.com/forums/showthread.php?t=35813), and since we almost never need to squeeze up there, I decided to forgo the weather stripping and seal it tight with the plastic. It was an easy job that took little more than an hour and well under $10 in materials.

http://www.cleanmpg.com/photos/data/500/Attic_Hatch.JPG

So here's the part that got me all excited. As soon as I sealed the film over the hatch it became apparent how real this problem is. Take a look:
http://www.cleanmpg.com/photos/data/500/Chimney_Effect.JPG

I put a little piece of tape in place to make it easier to see the clearance between the film and the straight edge that I placed across the frame. Look at that deflection! This is warm air trying desperately to get out of the bedroom and into my cold attic. There won't be a cold draft in this area even if there is a major heat loss problem. All of the warm air is going up and cold air is being sucked in through gaps in other areas of the home (like the basement, or the leaky windows I haven't made storms for yet).

The more you know...

Hi Tim:

Thanks for the pic!

My oldest son came to me over the weekend and apologized for being so hard headed when we had this discussion years ago. He said he saw the chimney effect in action on Myth Busters with a real fire in the fire place and it was drawing cold air in from every nook and cranny from anywhere into the house while sucking the warm air in the house up the chimney. Thus we have used our fireplace on low level gas just twice in the 16-years I have lived here ;)

Great to see that you sealed the opening and hopefully the aesthetics are not too bad so as to keep your wife happy?

Wayne

So far I haven't managed to do anything that offend's my wife's aesthetic sensibilities. This particular area is in a place nobody (including us) ever looks, so no big deal. It's not like I've gone to town with a pallet of Thermax on the interior walls. Yet ;)