Recently, we’ve seen and heard a number of folks claim that shipping Passivhaus windows from Europe isn’t the ‘sustainable’ solution – but we’ve never seen any data to really back that up. People seem to assume that local always equals more sustainable. But is this necessarily the case? 
We weren’t so sure, especially after crunching the numbers through PHPP on a potential Passivhaus in the Northwest. Our realization during this task was that certain European windows allowed us to achieve Passivhaus with significantly less insulation than any North American window could. This really didn’t seem that odd to us, as high performance windows being developed in Europe are pretty superior to here in North America, and the quality of glazing overseas is fairly stunning as well – high solar heat gain coefficients (SHGCs), low U-values and superior visible transmittance (VT). What follows are some quick, back of the napkin calculations that make the argument that shipping high performance windows from Europe might actually save CO2. A lot of CO2.
In addition to the baseline model with European windows and glass, we ran three North American windows with high SHGC triple pane glazing through PHPP and then adjusted the amount of insulation needed to achieve the Passivhaus standard. We’ve taken the approach that the client wouldn’t want anything to change. Therefore, window size and orientation, building assemblies, etc. remain as intended, and we’re merely adding EPS insulation as needed.
First, we need to determine a few things…
Shipping weight of windows
448 sf x 6.13 lbs/sf = 2746.24 lbs (1.25 tons)
Envelope areas
Wall area = 3,302 sf
Slab area = 1,360 sf
Roof area = 1,360 sf
EPS foam CO2 (4’x8’x1” EPS type IX insulfoam)
5.33 lbs x 5.5 lbs CO2/lb= 29.3 lbs CO2 per sheet
Freight CO2 rates
Sea = 0.0887 lbs CO2 per ton-mile
Truck = 0.3725 lbs CO2 per ton-mile
Baseline Model w/ European window
Our baseline is the as-designed building.
Window: Internorm Varion
Glazing: Glastroesch (0.64 SHGC, 0.105 U-value, 0.73 VT)
Specific space heat demand: 4.74kBTU/ft²a
EPS insulation at envelope assemblies
3” EPS at wall
4” EPS at roof
6” EPS at slab
Baseline Shipping CO2
Trucked from factory in Lannach (AT) to Rotterdam (700 miles), shipped from Rotterdam to Portland (8,685 nautical miles/9,988 miles)
700 miles * 0.3725 * 1.25 tons = 326 lbs CO2
9,988 *1.25*0.0887 = 1,107.5 lbs CO2
Total Baseline CO2 = 1,433.5 lbs
Option A: Serious Windows
Window: Serious Window 925 series
Glazing: Serious 9 (0.47 SHGC, 0.107 U-value, 0.45 VT)
Specific space heat demand: 6.68kBTU/ft²a.
In order to achieve the standard (ultimately coming in at 4.68kBTU/ft²a), more insulation is needed.
EPS insulation at envelope assemblies
Add 2” EPS to wall = 6,048 lbs CO2
Add 2” EPS to roof = 2,490 lbsCO2
Add 5” EPS to slab = 6,225 lbsCO2
Serious Windows Shipping CO2
Trucked from factory in Longmont, Colorado (1,285 miles)
0.3725 *1,285 miles * 1.25 tons = 561.5 lbs CO2
Total Serious Windows CO2 = 15,324.5 lbs
Option B: Thermotech Windows
Window: Thermotech fiberglass
Glazing: 322 Gain #3#5 (0.61 SHGC, 0.16 U-value, 0.63 VT)
Specific space heat demand: 6.22kBTU/ft²a.
In order to achieve the standard (ultimately coming in at 4.72kBTU/ft²a), more insulation is needed.
EPS insulation at envelope assemblies
Add 1” EPS to wall = 3,024 lbs CO2
Add 4” EPS to roof = 4,980 lbs CO2
Add 4” EPS to slab = 4,980 lbs CO2
Thermotech Windows Shipping CO2
Thermotech windows are manufactured in beautiful Ottawa, Ontario (2,642 miles)
0.3725 *2,642 miles * 1.25 tons = 1,230 lbs CO2
Total Thermotech Windows CO2= 14,214 lbs
Lastly, the local option – it’s always greener to go local, right? Let’s take a look…
Option C: Cascadia Windows
Window: Cascadia fiberglass frame
Glazing: Cardinal 179 LoE#2#5 (.57 SHGC, 0.17 U-value, 0.69 VT)
Specific space heat demand: 6.78kBTU/ft²a.
In order to achieve the standard (ultimately coming in at 4.71kBTU/ft²a), more insulation is needed.
EPS insulation at envelope assemblies
Add 2” EPS to wall = 3,024 lbs CO2
Add 4” EPS to roof = 4,980 lbs CO2
Add 5” EPS to slab = 6,225 lbs CO2
Cascadia Windows Shipping CO2
Cascadia windows are manufactured just across the border in Langley, BC (294 miles)
0.3725 *294 miles * 1.25 tons = 137 lbs CO2
Total Cascadia Windows CO2 = 14,366 lbs
This was shocking to us, as we expected the numbers to be significantly closer. Of course, the locally manufactured windows had the lowest transportation CO2 production – that only makes sense. However, the superior frames and glazing from Europe require significantly less insulation in the envelope. This definitely seems backwards and goes against conventional wisdom, but in this instance, shipping windows from Europe saves CO2 – a whole lot of CO2. In fact, with an average of 14,634 lbs CO2 for the three North American options, the European windows can save six tons of CO2 emissions. That is not insignificant, and something to keep in mind if North American manufacturers don’t think that developing high performance glazing is a worthwhile venture.
We realize that a more sustainable wall assembly would probably be utilized in most situations, rather than stacking on more EPS, but we wanted an apples to apples comparison between the windows from a performance standpoint. Regardless, the North American windows would all require several inches of EPS in the slab. Production of just one inch of EPS in the slab emits 1,245 lbs of CO2, which is almost equal to the CO2 emissions of importing the European windows. Additionally, the Internorm window is a clad wood window, which as architects we’re more drawn to versus fiberglass. I’m not aware of any wood window produced locally that comes close to Passivhaus standards. And here in the gray and gloomy winters of the Northwest, windows with a higher VT, such as the Glastroesch, are definitely a great bonus.
We’re definitely interested in any thoughts/critiques readers may have on this one.
When we ran across the AI Passivhaus 
brute force collaborative 