July 9, 2012

Insulating Our Row House

Like a lot of kids, I grew up in an un-insulated old house with an attic crawl space.

In warm weather, the roof gets sizzling hot during the day and radiates the heat into our living spaces at night. We spent many summer nights falling asleep with our heads lolling out the window to catch a breeze, listening to the Northern Katydid song for comfort. Unlike a lot of kids, my parents were EDUCATORS! So - I learned - the reason I woke up sweltering, brown bangs plastered to my forehead in clumps, was because of the magic of 'radiant heat' and 'thermal gain'. ISN'T SCIENCE INTERESTING?

The magic of science is happening in our house.

There are two steps to the insulation process. First, air sealing. Second, actual insulation. We're 1/2 through insulation and about 3/4 of the way done with air sealing. I am my parents' daughter, so you know what's coming, right? EDUCATION about AIR SEALING!

All air has moisture in it, and moisture has a dew point. The dew point is the condition below which water droplets begin to condense and dew forms.  Think of the back of your toilet on a hot day: hot air hits cold porcelain surface. Voila. Dew.

So, if you've got 50% humidity at 70 degrees, that same volume of air, when cooled to 40 degrees will condensate. In an attic space in the winter, you have a cold roof. If any moist air hits that cold surface, the moisture will condensate. Why do you care of condensation? You care because it can lead to mold.  If no moist air gets into that interstitial space, you don't have a problem because there's nothing to condensate. If you air seal perfectly. Air sealing also stops the movement of air that you've spent good money to heat or cool. If you can stop air from moving, it's not going to take the warmth (or cool) out with it.

To save money, Mr. Man is air-sealing our attic himself. The back half of the house was easy - BECAUSE WE TORE DOWN ALL THE CEILINGS in the back half of the house.

The front half of the house is a little trickier to air seal because we did NOT tear down all the ceilings. Mr. Man has air sealed about 3/4 of our 'attic' by crawling around on his belly patching any holes in the 3 chimneys and blowing air sealing foam from a giant can into the space between the furring strip on the exterior wall and the attic ceiling.  He's got a little more to do, then we're ready to insulate. Which is good, because it's hot up in here. AGAIN.


  1. WHAT a process! Thanks for the interesting post...and the science lesson!

  2. We were pretty amped up about insulating our house, too. We went with a sprayfoam. I guess we'll need to wait for winter to see how that worked out though... fingers crossed!

  3. Your husband is my hero...he goes where no man really wants to go..or woman for that matter. I hope it all goes smoothly because it sounds like a really not fun thing to do. Plus no one gets to see a pretty finish...but I guess they, and more importantly, you will sure feel it. Good luck!

  4. Good for you. This is a big project. We beefed up the insulation in our attic, but our house isn't as old as yours, so it was just a matter of blowing new cellulose into the space. We did spray foam in the basement--after opening all of the walls and ceilings. It definitely makes it easier to work, but putting it all back afterwards is not the most fun!

  5. Good luck with the project. It looks like a lot of work!


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