I had a home built last year and we have one bedroom that is 6-10 degrees colder than the rest of the rooms in the house when its cold outside.
The heat is radiant and the system has temperature gauges on the manifolds which tell me what the temperature of the water is going out and coming back. I have reflective bubble insulation between the floor joists and the water is coming back only 2-3 degrees colder than when it leaves. I have three zones and this zone is our main living area, two spare bedrooms and the bathroom. The bath is between the two spare bedrooms and the same radiant tubes heat all three. The bath is warm, one of the bedrooms is warm, but the other is cold. I have had additional insulation put in over the bedroom and have installed aluminum plates around the perimeter to increase the heat output into the floor. This room is on a corner, as is the other spare bedroom, however this room had an additional 8 feet of exterior wall over the other spare room. I have been told that is why it is cold. It also has northwesterly exposure which I am also told is adding to the problem.
So my question is, will an additional exterior wall, even if it is only 8' long, as well as northwesterly exposure, make a bedroom 6 - 10 degrees colder? The heat is getting there, it just isn't keeping that room as warm as it should be.