Building Budget Design materials

Hello again I have another doubt about the Budget Building Design from section 11 of ASHRAE 90.7 – 2007. When you choice of materials for the , Budget Building Design, the Table 11.3.1 says that they should have the same heat capacity from the proposed building but have the U-factor required in Table 5.5 . So, to create the Budget Building Design I'm changing the reference parameters of the proposed building materials in order to maintain their heat capacity and modify only the U-factor. This is a correct procedure to make the building of reference? Thanks for the attention