Wall Contruction, Temp At Each Layer

[jack2525]

Hi All,

I have a wall that i have calculated the u-vlaue for but i now need to find the temperarure at each of the layers that build up to make the wall. I have the internal and external temperatures and the resistances of the components that build up to make it. Is there any kind of formula?

Cheers

 

[IRstuff]

It's just a series resistance problem. The total series thermal resistance and the overall delta temperature gives you the power per unit area. Then you simply run that power through each layer.

TTFN

 

[jack2525]

Ok thank you,

So my calc will look like this

R1+R2+R3+R4+R5

=Rt (Toal Series Resistance)

My delta T is 23c

Rt / delta t = power per unit

Resistance of layer / power per unit = Temp at that layer!?

 

[DickRussell]

Almost there. R=1/U, and the resistances to heat flow are additive, and q/A (the power/area) = U*dT = dT/R. From the power, which is the same rate through each component of the wall, dT(for component)=power/r(for component). Expressed differently, the fraction of the overall dT through each component is (1/r)/sum(1/r).

If you are doing this for a house design, bear in mind that what the insulation nominal R values are and what you actually get in service vary considerably. Without good air barrier installation, a cold windy day can cut an R-19 nominal value in half. Then there is thermal bridging through all that wood connecting inside to outside, anywhere from 12 to 18% of the total wall area. But there are plenty of sites with good info on good wall design for thermal efficiency.