Window Decision
We have chosen our windows. If you remember earlier posts about our criteria for windows (April Update and Window Shopping), you’ll know that we were looking for low U-values (more insulation), high SHGC values (more heat from the sun), and low dollar values (more money in our wallets). We found 2 out of 3.
AccurateDorwin (based in Winnipeg, Canada) is going to make us windows with two different types of glazing. Our south facing casement windows will have a 0.24 U-value and 0.47 SHGC. All other windows will have a 0.20 U-value and a 0.44 SHGC. The fixed window units are the most efficient with a 0.18 U-value. All values are whole window values.
Serious came in second. They make a casement with a 0.17 U-value with 0.33 SHGC (whole window values). Much better U-value but a fairly low SHGC value. And you have to ship them all the way from California and they are not cheap. Plus they use a different technology that can add reflections inside the window, limiting it visibility.
In contrast, the Marvin Integrity All Ultrex windows (our fall-back comparison) are difficult to compare because they only publish center of glass U-values which are always better then the whole window values. Their stated center of glass U-value is 0.25 with a SHGC value of 0.41. Remember, the whole window average is going to be less efficient than center of glass.
We have about 170 sf of glazing area, thats roughly 11% of our conditioned floor area. We added sun shades on the south elevation to block the sun in the mid to late summer.
I’m not sure what the energy guys found, but by my rough calculations, the south facing windows will contribute roughly half of our heating needs in the winter. That includes a bunch of estimates for solar intensity (average sunny days and cloudy days throughout the winter months) and solar heat gain factors (BTU/h-ft2) for our latitude (from the ASHRAE Handbook of Fundamentals).
We’re paying roughly $5k more for windows than if we used our comparison windows, but I’m betting that the extra efficiency will pay for itself. I just don’t want to think about the length of that payback period.
Categories
- Air sealing 13
- Appliances & Fixtures 4
- Art 3
- Award 4
- Bathroom 8
- Batteries 1
- Decor 5
- Design 10
- Electrical 5
- Energy Calculations 13
- Energy Monitors 4
- Farm 1
- Finance 1
- Flooring 3
- Foundation 9
- Framing 8
- Heating 9
- House 7
- Insulation 8
- Kitchen 6
- Landscaping 3
- Lessons Learned 1
- Performance 60
- Plumbing 10
- Porch 5
- Radon 1
- Rainwater catchment 3
- Research / study 1
- Roof 7
- Septic / Waste water 2
- Sheetrock 6
- Siding 9
- Site Work 22
- Smart home 1
- Solar 64
- Solar Obsessed 10
- Stairs 2
- Surveying 3
- Ventilation 8
- Weather 1
- Windows & Doors 14
- plug-in 3
Archive
- Jan 2021 1
- Dec 2020 2
- May 2020 1
- Jan 2020 1
- May 2019 1
- Jan 2019 3
- Sep 2018 2
- Aug 2018 2
- Jan 2018 1
- Oct 2017 2
- Apr 2017 1
- Jan 2017 1
- Oct 2016 2
- Aug 2016 1
- Apr 2016 2
- Jan 2016 2
- Nov 2015 2
- Oct 2015 1
- Jul 2015 1
- May 2015 1
- Apr 2015 1
- Jan 2015 1
- Dec 2014 1
- Nov 2014 2
- Oct 2014 4
- Sep 2014 2
- Aug 2014 1
- Jul 2014 1
- Mar 2014 3
- Feb 2014 2
- Jan 2014 2
- Nov 2013 1
- Oct 2013 1
- Sep 2013 1
- Jul 2013 3
- Apr 2013 3
- Jan 2013 3
- Dec 2012 2
- Nov 2012 3
- Oct 2012 1
- Sep 2012 3
- Aug 2012 3
- Jul 2012 2
- Jun 2012 1
- May 2012 3
- Apr 2012 2
- Mar 2012 4
- Feb 2012 4
- Jan 2012 5
- Dec 2011 4
- Nov 2011 9
- Oct 2011 10
- Sep 2011 9
- Aug 2011 6
- Jul 2011 6
- Jun 2011 12
- May 2011 8
- Apr 2011 4
- Mar 2011 5
- Jan 2011 6
- Dec 2010 9
- Nov 2010 3
- Oct 2010 4
- Sep 2010 6
- Aug 2010 8
- Jul 2010 6
- Jun 2010 3
- May 2010 3
- Apr 2010 1
- Mar 2010 3
- Feb 2010 3
- Dec 2009 1
- Jun 2009 1
- May 2009 1
- Feb 2009 1
- Dec 2008 1
- Nov 2008 1
- Jun 2008 1