Anyone understand r-value math?

[Zero Knievel]

Trying to determine how efficient/effective the house windows are.  Outside temp 26 F.  Indoor air temp 69 F.  Inside glass pane 51.9 F.  Outside glass pane 34.3 F.  From what I know, double pane windows usually have an r-value of 1-2 on average.

[DBLXX]

 

[Zero Knievel]

Wrong “r value.”

[DBLXX]

Nope, that’s the one. 

[superhawk996]

4 hours ago, DBLXX said:

Nope, that’s the one. 

Being that it maxes out at 1 and insulation R value goes way above that, it appears that the R value of your video is about 0.

 

Mike, I don't know if this will answer your question, but it has a better chance: https://en.wikipedia.org/wiki/R-value_(insulation)

[Zero Knievel]

I know what r-value means, but how does one determine it from just temperature readings…if it’s possible?  Most of the math is way over my head.  I was hoping there was a calculator that could guesstimate r-value based on inputting the outside and inside surface temp of a material or structure.

[SwampNut]

17 minutes ago, Zero Knievel said:

I know what r-value means, but how does one determine it from just temperature readings…if it’s possible?  Most of the math is way over my head.  I was hoping there was a calculator that could guesstimate r-value based on inputting the outside and inside surface temp of a material or structure.

 

Outside of a controlled lab environment, no way to do this reliably.  You'd have to factor in all sorts of other things like air movement, and reliably read one square meter.  I think our insulation could use improvement for summer heat, so I'll rent/buy a FLIR to scan the whole house.  Then put it on the quadcopter to scan the roof.  

 

 

 

[superhawk996]

23 hours ago, Zero Knievel said:

I know what r-value means, but how does one determine it from just temperature readings…if it’s possible?  Most of the math is way over my head.  I was hoping there was a calculator that could guesstimate r-value based on inputting the outside and inside surface temp of a material or structure.

Beyond what Carlos said, accurately measuring the temp of glass seems impossible to do with household equipment.

[XXitanium]

Glass temp?? Tape a generic thermometer to the glass with one of those clear lightweight plastic grocery salad containers. You will get close.

 

https://bim.rockwool.com/rvalue/

 

U-value is the inverse of r-value.

 

 

[XXitanium]

...daylight - solar gain will throw off that value.

[lordzarkon]

tape some cardboard on the outside to keep the sun from affecting readings

[superhawk996]

The cardboard will insulate and throw off the reading.  Just do it on the shady side of the house or at night.

[XXitanium]

...at night best.

 

The cardboard is a good idea. You could check the difference at night fr fun.

 

...cardboard just big enough to keep the sun off the plastic container and not insulate the whole window. 

 

Really light weight so mass is less of an effect.

[XXitanium]

...by-the-way, we want pictures.

[SwampNut]

"I'll take 'how to get random results in science' for $800 Alex!"

 

[XXitanium]

On 2/5/2022 at 5:21 AM, Zero Knievel said:

Trying to determine how efficient/effective the house windows are.  

...not the whole house.

[XXitanium]

On 2/5/2022 at 5:21 AM, Zero Knievel said:

Outside temp 26 F.  Indoor air temp 69 F.  Inside glass pane 51.9 F.  Outside glass pane 34.3 F.  From what I know, double pane windows usually have an r-value of 1-2 on average.

That can be modeled with the right software.

[XXitanium]

Oh yeah, measure it in the center of the glass.

 

https://www.allweatherwindows.com/the-pros/architect/glass-performance-chart/

 

[XXitanium]

....and if you'd like a more expensive option for testing.

 

https://www.greenteg.com/gO-Measurement/

 

[XXitanium]

....nerdier guys than me.

 

https://sustainability.stackexchange.com/questions/358/how-can-i-determine-the-u-value-or-r-value-of-my-existing-double-glazing-syste

 

[XXitanium]

We went with pleated insulating blinds.

On 2/5/2022 at 5:21 AM, Zero Knievel said:

 Outside glass pane 34.3 F.  

...how did you "attain" that number please?

[Zero Knievel]

Took temperature from inside then went out on the porch and took the outside one.  Both with one of those laser thermometers.

[XXitanium]

On 2/13/2022 at 3:03 PM, Zero Knievel said:

...Both with one of those laser thermometers.

 

 

https://www.slantfin.com/slantfin-heat-loss-calculator/

 

https://www.doityourself.com/stry/hot-topics-hot-water-baseboard-heaters