Saturday, July 07, 2007

Concrete Momentum, and Panic

Momentum is the force that gets difficult projects done and keeps people from changing their minds. It breathes life into all sorts of undertakings ("Relationships are like sharks, they need to keep moving forward to stay alive. What we have here is a dead shark." --Woody Allen in "Annie Hall.")

This project ("Chartier Hermitage") has been in the works for a couple years now, and almost got built last Fall, but it lost steam when we couldn't resolve some key issues. The biggest decision was how to build and insulate the concrete walls. Concrete has essentially no insulating value of its own (although it acts as a thermal mass, like a stucco wall), and there a few ways to keep out the cold:

  • Conventional insulation on the inside--frame a wall against the inside concrete surface and fill the openings with your favorite insulation material.
  • Insulated concrete forms--the concrete is poured between forms made of a rigid Styrofoam sandwich. Called "ICFs" in the trade.
  • The "Thermomass" approach--another sandwich, but the reverse of ICFs. Concrete makes up the bread, and Styrofoam insulation is the filling. The two concrete walls are held together by plastic ties that don't conduct heat.

You guessed it, we're going for the third approach. This means that there can be a bare concrete wall on both the inside and outside, so the structural material is also the finished surface. ICFs force you to add another couple of layers to the wall on both sides, This has a lot of appeal for modernists, and, given that I'm paying a ton of money for this T-Mass approach, you're gonna see every inch of that concrete.

It also creates its own set of concerns:

  1. Not many foundation contractors have experience with this technology.
  2. It's a proprietary technology, so there's no price or product competition
  3. It's therefore not cheap. How much "not cheap" is difficult to say, because of #1, not many people do this. We couldn't get a true apples-to-apples comparison to the conventional approach because we couldn't find two T-mass foundation guys. So, while this project is in southern Wisconsin, our concrete guy is coming from Minnesota.
  4. The finish of a concrete wall is somewhat of a crapshoot. You can clean the forms so they shine, use the right release agent, spec the concrete recipe precisely and use fancy admixtures, but there's no guarantee that it'll come out the way you wanted.

Hence the panic. We start pouring in 10 days; until then, I'll be dreaming about concrete...

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