More on U values

It's just dawned on me that I already have a 'hot-box': My own home will work perfectly for the purpose. Both front door and back door have almost equal areas of Low-E Superspacer double glazing, insulated wood panels, and solid wood stiles and rails. Daily observations of inside and outside air and surface temperatures should build up a useful database of thermal gradients from which to calculate some correlations (not absolute, but indicative, nevertheless). Not exactly laboratory conditions, but the facility of being able to take multiple frequent observations is a great benefit. I am starting from the assumption that the temperature gradient is directly related to the thermal conductivity of the material or assembly. The steeper the gradient, the lower the conductivity (ie the better the insulation value). This morning, the empirical measurements (the only ones I have until my IR thermometer arrives) tells me that the steepest gradient is in the wood. Am I wrong? We shall see! If I am, then at least I will have a better understanding of the issue if I can see the figures.