I'm designing an oven and want to ensure that the insulation I specify has a low enough Thermal Conductivity (k) to resist excessive heat loss. I determine heat loss (Hout)with the following equation: Hout=A*U*(T1-T0). U is dependent on k (U=k/L). I omitted the heat transfer coefficient in calculating U to keep the calculation more conservative. My values are A=15.33m^2, T1=422K, T0=289K, L=0.041m so Hout(Watts)= 50000 * k. I am having difficulty determining the heat generated by the heating elements. I know the watt density is 1.24*10^4 W/m^2, and the bar dimensions (L=0.914m, W=0.038m, T=0.010m) with total surface area of 8.78*10^(-2)m^2. Am I okay to multiply watt density by the total element surface area to calculate the heat generated? Along with the previous question, is it acceptable to assume that all faces of the strip heating element have the same watt density? I have (4) of these heating elements, so this calculation yields 4390 W. then kmax=50000/4390 = 0.088 W/(m*K). I also calculated this with the Stefan Boltzmann Law. The Max Sheath Temperature of the elements is 673K, which after calculating the radiant exitance j* (j*=sigma*T^4), multiplied by element surface area and number of elements to find power yields 4085 W, or a kmax = 0.082 W/(m*K). The similar results give me confidence that I am on the right path, but am hoping someone can confirm this before I spend $2000 in building materials. Any and all help is appreciated!