Analysis of the Concrete Masonry Unit (CMU) Mass Wall Effectiveness of the 2015 International Energy Conservation Code (IECC) for a Single-Family Residence in Illinois State, USA

Abstract

Purpose: Illinois State accepted the 2015 International Energy Conservation Code (IECC) with amendments as State Energy Code to establish minimum design and construction requirements for energy efficiency of the buildings. In the 2015 IECC, mass wall credits are allowed to use to maintain the thermal performance of building's exterior walls while reducing the R-value based on the insulation strategies of mass walls. This paper investigates the effectiveness of mass wall according to the 2015 IECC for a single-family residence in Illinois State, USA. Method: Three climate locations (northern, central and southern locations) in Illinois were selected. Next, the general characteristics of the house including the floor area, construction type, thermal characteristics of the building envelope, an efficiency of the HVAC and DHW system were decided and modeled based on the survey data. Then, different wall types as specified in the IECC 2015 were incorporated into the simulation models. Next, simulations were performed to study the effects resulted by the wall types and different climates using the BEopt building energy simulation program. Lastly, the electricity (kWh/year) and gas consumptions (MBtu/year and kWh/year) of each simulation were converted to energy costs. Results: The following observations are found: 1) cooling and heating energy use were almost the same owing to the thermal mass effect of the code-specified envelope characteristics; 2) CMU walls with integral insulation strategies, which are not compatible with the 2015 IECC, show the highest heating, cooling energy and annualized utility bills ; 3) there are larger variations in heating energy use than cooling energy use; 4) utility bills are increased as moving from southern to northern region.