Sunday, April 28, 2013

Walls and Windows

We have been busy thinking about the details of this structure.  About a year ago, Erica (our architect) and I were busy reading up about various wall systems and trying to pick the most energy efficient system that would fit in our budget.

We explored double-wall, cellulose filled walls, REMOTE walls, plain ol' 2x6 walls, ICFs, and somehow end up on on Structural Insulated Panels (SIPs).  Based on performance, construction time and costs, we decided to use 10" SIPs which will create a tight, well-insulated house (~R-38).  Because we are building with SIPs, which are manufactured out of state, many things have to be final when the plans are submitted to the Muni and to the SIPs manufacture.  Once the panels are ordered, windows placements are final and based on a window manufacture's specifications.  So, changing window sizes, placements, brand, etc, would cause problems, to say the least.
10" SIPS make thick walls and deep windows sills! - photo from Scott Homes

A house with super insulated walls probably ought to have pretty good windows. We have been looking for triple pane windows, with good performance numbers.  It is overwhelming how complicated window shopping can be.  Things to consider include, but are not limited to, the U value (opposite of an R value, so the lower the number the better),  Solar Heat Gain number (how much solar heat the window lets in), Visual Transmittance number (how much daylight comes through the glass),

There are plenty of aesthetic options too, that can affect performance as well.  Do you want wood/vinyl/fiberglass, aluminum clad or not, warm bar spacers for your simulated divided lights, internal or external divided light bars, and much, much more.

I think we have landed on a Kolbe, a window manufactured in Wisconsin and sold by a dealer in Fairbanks.  My builder seems supportive, but would prefer a local dealer. The dealer is planning to fly down here for the delivery, which is nice to know. Anyway, the other day I received my weirdest package to date: a window corner sample. It is sitting on my bookshelf along with exterior color samples.  I will return it to the dealer when we are done with it.
Kolbe window corner - aluminum clad exterior with pdls

Kolbe interior with square pdl option and square bead option
Performance wise, it is probably middle of the road for triple-pane windows.  There are some European windows have significantly better U/R values, but would cost as much plus the shipping from Europe to Alaska. There are some other American made windows with better U values and mirror heat glazing, but aesthetically cannot compare and the mirror heat glazing has some strong critics.

The Kolbe windows have all the aesthetic details we were looking for, including matching triple-pane doors.

Here are a few of the criteria I considered when choosing Kolbe over comprable windows (including Marvin and Loewen)

  • smaller divided lite muntins - ⅝”, ⅞”
  • square muntins
  • square glazing beads
  • warm edge spacer
  • pine interior available (we plan to paint the interior)
  • hidden pull down shades available
  • triple pane doors available
  • flat panel on doors (no raised panels on this house, inside or out)
  • low U values - .20/.18 fixed
  • triple pane
  • double argon
    1. Interior wood raised panel
    2. Interior wood flat panel
    3. Exterior extruded aluminum raised panel
    4. Exterior extruded aluminum flat panel
  • adjustable shgc for South side of house

I think they will look beautiful and they will perform significantly better than your average double-paned window.  It is one of the biggest single expenses we will have and it is a tough decision to make.  The research is done, so now I am going to cross my fingers and hope we love them when the are installed.

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