Posted by: Scott McCullough | October 2, 2011

Serious Field Trip

The 2011 NESEA (Northeast Sustainable Energy Association) Open House event was yesterday.  Jess and I drove out to Sanbornton to visit the San Bani School where construction was nearing completion on an addition to the school.

The one item  we were most interested in were the windows manufactured by Serious Energy,  These windows are made in Boulder Colorado and are known for their energy efficiency.  Serious Windows has four basic window series that offer a range of cost, R-Value, and solar heat gain coefficient, with 525 being at the low end of the scale, followed by 725, 925, and 1125.  At the San Bani School the 525 Series were used, all of the windows were sliders, with the exception of a few fixed units.

We are strongly considering using Serious Windows for our house, and this is the first chance we have had to see them in person.  Several months ago we received prices from three different window manufacturers: Serious, Thermotech and Fibertec.  Serious was slightly higher in price than the other two manufacturers, but also offered the most design flexibility.  We have quite a few windows that are 8 feet in height, and Serious was the only manufacturer that was able to make that sized unit.  It’s mostly for that reason we are leaning towards Serious.  Though one reservation I had was the visible light transmittance, or the idea of the window looking tinted.  The image above shows this window having a VT of 0.42.  According to several articles I’ve read, including this one from Martin Holladay at Green Building Advisor, 0.40 is probably the lowest VT number we would want to go without the view starting to look tinted.  Looking at this window I could sense a tint, but nothing that would be noticeable without looking for it.  Maybe not the best day to judge since it was raining.

On a typical American made window such as Marvin you would see U-Values in the 0.30 or higher range.  This window has a 0.20 U-Value, the 725 series we are looking at for our house have U-Values ranging from 0.14 to 0.19.  The primary reason Serious is able to get such low U-Values is because of their triple glazing, that uses a thin film at the inner layer rather than glass.  The solar heat gain coefficient is also important, Serious has glass with a SHGC as high as 0.49 which we would use on the south side of our house.

On the second floor of the Sant Bani School was a radiant slab floor, something that we are likely doing for our first floor surface.  They used a 1 1/2″ thick concrete slab with pex tubing installed over a layer of ice and water shield over the plywood sub-floor.  We had been planning on doing a 2″ slab but are happy to see that it can be done thinner, as it will save on material cost.

The NESEA Open House is a great event, and we met some local contractors who spoke our language when it came to energy efficiency which was reassuring.  Hopefully next year we will be ready to add our own house to the list of projects that people can visit.


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