Drafts, humidity and radiant (+ conductive) heat.

What you experience, and what determines your level of thermal comfort, is how quickly your body loses heat to the environment. Your body is constantly producing heat in the process of staying alive and has to get rid of it, but it doesn't want to lose heat too quickly either - if it does, that's when you feel cold.

The (average) temperature of the air around you is a major influence in all this, but it's far from the only one.

Let's start with drafts. Recall that I said that your body is dumping heat to its surroundings. This includes the air directly near your body. As a result, this air heats up. Now, if the air is relatively still (doesn't move much), then this results in a kind of blanket of warmer air forming around your body over time, which slows down your body's heat loss. On the other hand, if the air is moving, then the air warmed by your body gets blown away and replaced with cooler air. As a result, you will feel colder, even though the average temperature in the room is the same. So, one possibility is that your parents' house could be more prone to drafts. This could be simply because of things like gaps in the construction that let outside air in (e.g. gaps around doors or windows), but another possibility is poor insulation. Cold floors, walls and windows cause air to cool down and sink. The sinking air causes other air to move in to take its place, and thus a thermal draft is born. Whatever the cause, these drafts will make you feel colder, even if you measure the same temperature on a thermometer.

Next up, humidity. This is a pretty simple one. Humid air has a larger capacity to absorb heat than dry air. So, humid cold air will sap heat away from your body faster than dry cold air of the same temperature (on the other hand, humid air will make it harder for your body to cool down in a hot environment - so high humidity is always bad for thermal comfort). If your parents’ place is more humid, then it will feel colder at 14°C than your own house does.

Finally, there’s the effect of radiant heat. All warm things (i.e. warmer than absolute 0) radiate heat in the infrared spectrum, including walls, windows, floors and furniture. Your body absorbs this radiant heat. So, the more radiant heat you receive from your surroundings, the warmer you will feel. This, by the way, is also why you feel warmer when the radiators are on, versus when they are off, even if the temperature of the room is the same. Why does this matter? Well, the temperature that your thermostat or thermometer measures is the air temperature in the room. Mostly, everything in the room will be at that same temperature. However, walls, floors and windows might be quite a bit colder, especially if (again) you have poor insulation (and/or if you have many walls with the outside, rather than walls with neighboring houses or apartments). So even if the air temperature is 14°C, if your walls, floors and windows are all at (say) 9°C, that means you receive less radiant heat from them than if they were at 12°C or even 14°C. In short, your parents might have colder walls, floors and windows than you do at home, and so you are receiving less heat from your surroundings there.

This latter point is exacerbated if you are in direct contact with these cold surfaces, which is mainly a problem with cold floors. In that case the issue isn’t just a lack radiant heat – you’ll also be losing heat through conductive heat transfer.

(On a final note, I'm surprised that 14°C would ever feel warm and comfortable to you. That seems very chilly to me even in a well-insulated house. )