Tuesday, January 2, 2018

Glazing Surface Temperature

Glazing Surface Temperature

DISCLAIMER: This is for informational purposes only, I only own an IR Camera and I am NOT a certified thermographer. I know enough to be dangerous, and that is about it!

Here is my attempt at figuring out the glazing surface temperature at Rochester Passive House. I did 2 different scenario's.
                 1) Full Solar Gain - South facing window
                 2) No Solar Gain - Breezeway (north) door glass

Here were my test parameters:
                                         Full Solar Gain:                                 No Solar Gain:
                                 

The difficulty with finding an actual glazing surface temperature is glass tends to reflect quite a bit, so you are not reading the glass temperature, but the temperature of what is reflecting on the glass.

You can see my reflection in this IR Photo. 

To get closer to an actual glass surface temperature I took a scrap piece of paper, and covered half with black electrical tape, and covered the other half with 2 layers of painters tape. I taped this square to near the center of glass and let it sit there for a while. I am going to assume the paper will become the same temperature as the glass.

This is the paper I taped to the glass. I needed to make sure the paper was completely opaque. I used black electric tape for half, and 2 layers of painters tape for the other half. According to FLIR electrical tape has an emissivity of about 0.95. The painters tape is not as shiny (lower emissivity) but I wasn't sure if how the black tape would show a hotter temperature with the solar gain. 

Here is the Solar Gain Photo:
You can see, the black tape is hotter than the painters tape. But both of them are in the 103-106F range. The hottest temperature is not centered in on the black tape because of the angle the sun is hitting the exterior glass.
I have 2 images for the shaded glass
This one was taken roughly 1.5 ft away at a slight angle. It is roughly 65F
This one was taken about 6" away, but you can see how varied it is, there is quite a bit of reflection going on - but the average temperature is about 62 F

Because I was going in and out of the breezeway multiple times, the breezeway door and interior walls may be a few degrees cooler than normal. I took an IR photo of the interior wall, next to the breezeway door and it was 65F. I didn't post it because it is just an orange square - nothing really to see. 

Summary:
IN WINTER EXTERIOR CONDITIONS
Glazing Surface Temperature of South Windows in full sun = 100-105F
Glazing Surface Temperature of Windows in full shade = 60-65F - within 7F of indoor air temperature.

 Someday I am going to do this with an Energy Star Window and compare. 

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