Heating to 18c is different than cooling to 20c. When it's hot you're typically wearing lighter cooler clothing and are more comfortable at hotter temperatures

Heating to 18c is different than cooling to 20c. When it's hot you're typically wearing lighter cooler clothing and are more comfortable at hotter temperatures. When heating it's the opposite, you're wearing warmer clothes and better suited to cold. Humidity also plays a big factor. In the southern US, most people have their AC set to between 23C and 25C during the summer and somewhere around 20C in the winter. In more arid regions the temperature settings creep up because you tend to feel cooler when it is dryer.