SKOKIE, Ill.—Homeowners and builders are increasing recognizing that concrete homes are more energy efficient and can save money. However, these cost savings can begin before turning on the home’s furnace or air conditioner.
The inherent energy-saving properties of insulated concrete walls can result in heating, ventilation and air conditioning (HVAC) equipment being downsized by as much as 15 to 40 percent in concrete homes in comparison to identical wood-frame homes. This provides a comfortable home with correspondingly smaller, less expensive heating and air conditioning units and lower bills.
Newly updated software published by the Portland Cement Association (PCA) allows builders to estimate heating and cooling system capacities for energy-efficient single-family concrete homes and take advantage of these savings.
Developed as part of a HUD-sponsored project, the software calculates the system capacities based on the house dimensions, construction materials, air infiltration, location (U.S. Mexico, and Canada) and thermostat set point. To account for the thermal mass imparted by concrete walls, this software uses hourly weather data for a typical year.
Current widely used HVAC-sizing methods such as Manuals J and the ASHRAE Load Calculation Method do not account for the thermal mass, high levels of insulation and/or low air infiltration of the insulated concrete walls. This omission, and the fact that many builders and HVAC contractors’ size HVAC equipment based on a “rule-of-thumb” developed for wood-framed homes that equate equipment size with square footage of living space, results an the installation of an inefficient HVAC system that is typically oversized.
An oversized HVAC unit will have a higher initial cost than a correctly sized system and will consume more energy than necessary. In addition, an oversized system will have a shortened “on” time, which can lead to larger temperature swings and reduced thermal comfort. Air conditioning systems with short “on” times do not remove enough moisture from the indoor environment, which can increase the probability of occupant respiratory problems.
The PCA software uses energy modeling software that is more representative of actual conditions in which the HVAC system will be operating.
MS Excel version 97 or later required for operation of the program. Available at www.cement.org/bookstore
Based in Skokie, Ill., the Portland Cement Association represents cement companies in the United States and Canada. It conducts market development, engineering, research, education, and public affairs programs. More information on PCA programs is available at www.cement.org