This paper presents nanofluid convective heat transfer and viscosity measurements, and evaluates how they perform heating buildings in cold regions. Nanofluids contain suspended metallic nanoparticles, which increases the thermal conductivity of the base fluid by a substantial amount. The heat transfer coefficient of nanofluids increases with volume concentration. To determine how nanofluid heat transfer characteristics enhance as volume concentration is increased; experiments were performed on copper oxide, aluminum oxide and silicon dioxide nanofluids, each in an ethylene glycol and water mixture. Calculations were performed for conventional finned-tube heat exchangers used in buildings in cold regions. The analysis shows that using nanofluids in heat exchangers could reduce volumetric and mass flow rates, and result in an overall pumping power savings. Nanofluids necessitate smaller heating systems, which are capable of delivering the same amount of thermal energy as larger heating systems using base fluids, but are less expensive; this lowers the initial equipment cost excluding nanofluid cost. This will also reduce environmental pollutants because smaller heating units use less power, and the heat transfer unit has less liquid and material waste to discard at the end of its life cycle. (C) 2009 Elsevier Ltd. All rights reserved.