I've heard this phone call before - "Air blows in the hall, but the door is tight." Door weatherstripping is something that gets looser over time, and can admit air.
The weatherstripping is an important part of the energy efficiency of any door. And window!
The door itself is insulated metal, or insulated vinyl, or even wood, which is a good insulator. And any surrounding windows will be double pane and be pretty efficient.
But the weak spot is the weatherstripping.
This is a thermal image of the bottom of the front door.
It is very interesting because the warmest temperature is about 70F.
Yet the weather outside is sunny and 28F.
Imagine how hot that space under the door is in July!!
Why is it so warm under the door? Because it is 10am and the sun is shining directly onto the front door. The door weatherstripping is weak.
There is no storm door, so the area is heating up from the direct sunlight. But with a gap this large imagine how much heat is escaping when the sun is not on the door! Remember, heat seeks cold, AND MOVES TOWARD IT. With a gap this large, and when it's very cold outside, it would feel like cold air is literally blowing in from under the front door.
Yet, when facing the door, this gap is not visible. The thermal camera shows it quite well though.
Sweeping the rest of the house I was able to show them similar situations with other doors where the same area under the door was cold.
A storm door outside the front door would enhance the energy characteristics of the space dramatically. That space of dead air between the two doors is a great energy seal. And controls the sun's heat!
My recommendation: sometimes the simple answer is THE answer. If you feel air moving, there is a reason! It may not be obvious to the naked eye, but would be to a thermal camera. So call a thermographer. And remember, the side benefit is that all thermographers are really cute.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560