Dual pane window infrared….normal?
Greetings all,
We’ve just finished building a home along the So Cal coast, and are surprised at how cold the house is. As a longtime follower of this site and others, I was diligent about air sealing (10 cases of caulk, 25+ cans of foam) and ended up re-doing at least 1/3 of our insulation myself because the subcontractor was so sloppy.
Any by “cold” I mean the temp will say 74-75F, but it feels like 65F the moment the FAU shuts off. We’re going to do a blower door test soon. I’ve walked around with a FLIR and while our (many) IC recessed lights are clearly offenders (10F colder than the room), I don’t see any large likely air leaks or cold areas.
That brings me to glass. I’ve attached an IR pic of a window. Interior temp was 72F, outside temp was 50F, center of glass 65F, and the edges were mid 50F range. Is this normal?
Thanks for any insight.
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Replies
What is the outside temperature. Windows will run colder than the room depending on their quality
Oh, and my Cardinal glass with the interior coating will reflect your own temperature back at you
thermal camera gives a nice heat signature of your reflection
50F outside.
They're Cardinal glass as well.
Ok missed that, I don't trust your thermometer. seems unlikely that there would be that kind of temperature when there is that little Delta T
[Edit]
Just checked my windows
The worst 30+ year old glass had edge of glass numbers about 49 degrees
It is 20 degrees out thermostat set to 69
Interior surfaces[walls floor] read 65-67 degrees
That or image looks pretty normal to me. The frame is cold because of thermal bridging, the glass is cooler than the walls because of lower R value.
If you want to measure the surface temperature of the glass, an IR thermometer won’t give accurate results because of the reflective solution. The solution is to put a piece of masking tape on the glass, then measure the temperature of the tape.
Bill
Hmm. Besides the FLIR IR, the only other tool I have is a thermal spotlight that can only tell you if what's in its read area is 5F cooler or warmer than a base reading. I do have a Thermapen, but I don't think I can go stabbing the wood!
The FLIR does show the center glass about what you'd expect? 7F below room temp, +15F vs outside. Edges not so much at ~20F below room? Last night, with the shades down, I was shocked how cold it was between the shades and window.
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Who is the window manufacturer?
Do you know what coating you have on the glass?
Do you have a surface 4 coating?
Everybody's focusing on the glass. What is the frame material? I'm guessing metal without a thermal break.
Good point. A solid wood frame might also show up pretty "cold" on the IR scan, if the wall is really well insulated.
Bill
That's a very good point.
I see no way it is normal to have only a 5 degree temperature difference between outside air temp and inside frame temp. I was seeing a near 40 degree difference. Metal edge spacers, 3/16 gap thermopane.
Try putting a piece of masking tape on the glass, then measure the temperature of the tape. The tape will be the same temperature of the surface of the glass, but won't have the issue of trying to read the temperature of the shiny glass directly with an IR device. You'll probably find a big difference in your readings this way.
Bill
I have done this in the past, it is a small difference, except with inside coating
Unless there is an air leak at the edge of glass, it is virtually impossible to have a 5 degree difference. The camera is not accurate
Scan looks normal to me. Center of glass has lower U / higher R than around edge where spacer and Frame are much better conductors of heat and will appear (are) cooler when it's cool outside. Note the FLIR is not a thermometer, it just measures total IR received and somebody has programmed it to read out in oF. Lots of assumptions have to be made re Emissivity of target surface, temps of surroundings which contribute some IR to measurement depending on Reflectivity of surface etc. etc >>> shooting a wall is a very different proposition vs a window, probable errors, so the a.m. idea of shooting a piece of applied tape sounds good, or use a quick contact thermocouple (oral?) under an insulator pad.
As to how the house feels like 65 when it is 74-75, just as a thought do you have lots of windows? When yes, as mentioned above re the glass being partially IR reflective of your IR image, your physical body will feel colder standing in front of windows that are not all that cold just from the radiant heat losses from your body increasing due to the nearby lower surface temp of (large) windows. Assumes of course they're not triples, where the inner glass is closer to room temp. That's why folks report triples' comfort factor much higher. Energy consumption will tell you about the improved R value, but how you feel sitting next to them is next level better. ... Not helpful, but close the curtains?