Cardinal Glass Window Specs
I just took delivery of my windows, and they were installed. They look great.
On my southern facing windows, I had ordered triple pane, argon with high solar heat gain. When ordering, I had asked who was the glass supplier, and we had chosen the 1-3/8″ cardinal 180/clear/180 glass. The specs of the glass are SHGC 0.56, U-value 0.13. https://www.cardinalcorp.com/technology/reference/loe-performance-stats/ I have this on my bill of sale with the supplier and through e-mail confirmation while i was stating that i wanted the high heat gain.
The windows were delivered to site, and the label is noted as having the 272/clear/180 glass. The Cardinal glass technical specs are SHGC 0.37, U-value 0.13. I wasn’t overly happy about this, however after speaking with my hvac designer, he suggested that the glass I received was better overall, granted it may lead to slightly more energy use in winter, it should make things more comfortable in summer (even with 36″ overhangs we still have some solar contact at the bottom). The reduction in wintertime solar heat gain will be marginal, and given that there is some oversizing to my minisplits, he suggested not to change. To quote him, he said “their mistake is your gain”.
I still pressed the window supplier for the energy ratings.
They have since provided me with the energy ratings, which have come back from the NRCAN data base as: SHGC 0.28, U-factor 0.17. A double negative compared to what i thought the specs of the new glazing would be.
To summaruize:
Ordered: SHGC 0.56 Ufactor 0.13
Received: SHGC 0.28 U-factor 0.17
Now, compared to the the window i spec’d one could argue that this glazing allows 50% less solar heat to enter the house (bad in winter, good in summer), and 25% more heat loss (bad in any season).
The windows in question are all in the living/dining/kitchen area, where we are comfortable in the summer with temps around 75-76F, but prefer our bedroom down around 70-72F for sleeping. This is a single level house, very well insulated, and planning to be very air tight. Stratification won’t be a big deal. In winter we had always hoped that the sun would shine on the living area of the house would warm up during the day and allow me to coast through most of the night before the mini-split kicks in .
I also would have to have to re-glaze and pull apart the joints on these brand new windows..
Thoughts? Advice?
Thanks,
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Replies
Are the Cardinal specs glass only and the window specs for the whole window?
Stephen is undoubtedly right. Here are the Cardinal glass-only specs which match Ryan's numbers https://www.cardinalcorp.com/technology/reference/loe-performance-stats/
The final number has got to be the whole window spec.
Ryan,
You're not alone. Many builders in cold climates, seeking high-solar-gain glazing, have been stymied by window manufacturers who either (a) refuse to supply high-solar-gain glazing, or (b) screw up the order.
A thorough analysis of the pluses and minuses would require energy modeling, and the results would depend on factors we don't know, including the width of the roof overhangs, the vertical distance from the tops of the windows to the soffits, and the area of the south-facing glazing.
Clearly, though, the cost of remedying this error should be the entire responsibility of the window supplier. Even if every window has to be removed and new windows have to be installed, the paperwork says that the cost of this work should not be your responsibility.
Whole window spec i understand and can live with, but would the frame reduce the solar heat gain coefficient that much? The energy star stats are from NRCAN for this window with this glazing do not specify the window size used for certification. Presumably, the larger the window, the closer to the cardinal specs the numbers would be. The windows are fixed with awning above, total window size is 42"w x 78" height. The awnings are 42w x 21h, and the fixed panes below are 42w x 57h, which is a good size window, and the frame to glass ratio is much lower than the awning window above.
So if they tell me it is 272, clear, 180 glass, then the SHGC of the glass should still be equivalent to the cardinal spec sheet (0.37 in my case), and obviously a SHGC of 0.00 for the frames, which on an area of window basis would reduce the total SHGC.
Similarly, the glass is 0.13 u-value, but the frames are not as well insulating, thus the total u-value increases for the window, but the glass component is still per the cardinal specs.
Ryan, window frames can reduce the U-value that much. If your house is reasonably well insulated and air-sealed, though, the financial impact of the lower-SHGC windows could likely be measured in tens of dollars per year. (As opposed to hundreds, or more or less.) I would try to hold the manufacturer accountable for the mistake, but unless going for Passive House certification, I wouldn't want to deal with the headache of replacing all of those windows.