Step 1. List the R-values of the building materials and compute the overall thermal conductance of the home

Let’s say we want to design a way to heat and cool a house in Iowa City, IA using renewable energy.  For a simple analysis we will say that the house is a 1 story, 2-bedroom, 1000 square foot home.  The design will be planned around the goal of maintaining an interior temperature of 70 ⁰F.  We will assume that there is no basement, and therefore we will not consider heat flow in or out of the bottom of the house(adiabatic).  We will also assume the overall dimensions of the house are as follows: base of the house is 25 ft x 40 ft and the walls are 8 feet tall.  Next, we assumed that windows in the house can be neglected. The ceiling and the four exterior walls will be modeled using the same R-values as those used for a wood construction wall.  This is a valid assumption because a typical R-value for a ceiling is usually between 10 and 15 (hr*ft^2*F)/BTU . Below is a figure that shows the generic components of a wall along with their specific R-value and the R-value of the wall assembly as a whole. [39]

As shown in the figure, the total one wall assembly R-value is 13.31 (hr*ft^2*F)/BTU. When we set R₁=R₂=R₃=R₄=R₅=13.31, find the area of the exterior walls to be 1040 ft² and the area of the ceiling to be 1000 ft², we can then find the overall thermal (UA) conductance of the home. UA = (1/13.31)(5)(25*40+2*8*40+2*8*25) = 766.4 Btu/(hrF)