Precast Sandwich Wall Panels - Where to Get Differential Interior/Exterior Surface Temperatures

[KootK]

I'm attempting to design some composite wall panels and one of my parameters is the differential temperature between the interior and exterior of the wall. For the life of me, all I can find thus far is:

1) The blurb shown below from the PCI manual which would seem to imply that things might be worse that 40F for common, interior wall panels and;

2) Examples, every one of which seems to choose 40F as the target value without justification.

So my question is this: is there a tractable way to figure out what the temperature differential should be? Some tabulated data someplace? Or is everybody just rolling with the 40F differential without digging any deeper into it? I've no doubt that a building envelope consultant would be able to work this out somehow but those expertise are not available on most of these kinds of projects.

 

[WARose]

If I was worried, I've relied on NOAA a lot of times for that data like that (in the USA). You can find record temps real fast.

PCI use to give maximum seasonal climate change maps. Looking in the 5th edition of PCI's handbook, it is on p.3-86.

 

[KootK]

Thanks WARose. The PCI manual still has max seasonal climate change maps. Unfortunately, that is quite different from the differential temperatures between exterior and interior surfaces. Ditto for NOAA.

 

[WARose]

Seems to me like a pretty straight forward calculation. (Famous last words. ) That is assuming you have the thermal properties of all materials involved.

 

[IRstuff]

It's not a completely random choice. Say the interior temperature is 75F, then that delta allows for 115F roof temperature. I could imagine that there might be cases where that delta is more like 50F, say in Yuma, with the interior A/C running at full blast. Note that most A/Cs have a minimum output air temperature of around 58F, so the actual room air must be higher than that, so the coldest practical temperature for inhabited spaces is probably no colder than around 70F.

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[WARose]

I think the worse temperature differential I've seen was a freezer room in Phoenix. On the outside, the tilt-up panels were hitting about 150 F. (Don't know what it was on the inside.)

But sounds like Kootk is trying to figure the drop in the layer(s) of concrete. (Which makes it a conduction problem if he just can't run with a outrageous guess/drop.)

 

[IRstuff]

NCDC has databases for temperatures in most parts of the world.

https://www.ncdc.noaa.gov/cdo-web/

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[Brad805]

If in Calgary, it will be greater than that in the winter months. -40deg C is possible, and interior tends to be 20deg C if climate controlled office space. As for actual surface temperatures during the summer, I doubt you will find tables due to the variables that affect that (shade, surrounding buildings, exposure, location..). A flir camera is great for this kind of question if so inclined, and they are not that expensive anymore. If you are designing a very slender wall panel it is a good thing to consider. We looked at one where they did not, and owners tend not to like their mezzanines to separate from their exterior walls 1"+- at certain times of the year.

 

[DBronson]

KK:

There's a program that can calculate the temp differentials called Wufi. It's a product of the Oak Ridge National Lab and the Fraunhofer institute. I believe there's a free version of the program that could probably do what you need. Bear in mind that the moisture and thermal regimes interact - temperature differentials alone won't tell the whole story. Wufi can deal with this. You might call ORNL and explain your problem. They probably have the data you're looking for.

Link

Regards,
DB

 

[KootK]

Thanks for the recommendations all. I was hoping for a table of recommended values for various occupancies, panel layups, and geographical locations. No such luck though. Based on this thread and my real world resources, there are but two options:

1) Do some kind of legitimate thermal analyis or:

2) Take the 40F and roll out like Optimus Prime.

For what it's worth:

- Wisconsin
- Boiler room with garage doors
- Non-comp 3/4/7 layup.

 

[KootK]

But sounds like Kootk is trying to figure the drop in the layer(s) of concrete.

Differential is enough here. Thanks for your contributions.

 

[XR250]

Wait, Boiler Room in Wisconsin? Seems like 100 deg or more would be more realistic.
I am assuming sandwich panels have foam insulation as a layer?

 

[KootK]

I am assuming sandwich panels have foam insulation as a layer?

Yesir. 4" worth.

 

[TehMightyEngineer]

Wait, Boiler Room in Wisconsin? Seems like 100 deg or more would be more realistic.

I agree, the room is probably going to be 80°F and the exterior could be -10°F.

I'd say the assumed 40°F temperature differential is likely insufficient.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[KootK]

Yeah, even at the large delta the inward bow doesn't really hurt me on account of it running counter to the effects of the gravity loads.