Door gaps are a primary source of unwanted air exchange between a home’s interior and the outside environment, allowing conditioned air to escape and unconditioned air to enter. Sealing these leaks is a straightforward process that significantly improves interior comfort by eliminating drafts. Mitigating this air infiltration reduces the workload on heating and cooling systems, resulting in lower energy consumption and utility costs. The initial step is to accurately locate and assess the specific areas where air is moving through the door assembly.
Locating and Assessing Gaps
Identifying air leaks requires more than a simple visual inspection, as even small gaps allow a substantial amount of air to pass through. A highly effective method is the smoke test, which uses a lit incense stick or a smoke pencil moved slowly along the door frame and bottom. If the smoke stream wavers or is drawn toward the gap, this confirms the presence and direction of an air current.
Another simple diagnostic tool is the light test, which involves standing inside a darkened room and checking the perimeter of the closed door for any visible streaks of daylight. Any spot where light penetrates the seal is an uncontrolled air pathway that needs to be addressed. For the gap beneath the door, a dollar bill test can be performed by closing the door onto the bill. If the bill slides out with little resistance, the gap is too large and the seal is insufficient.
Sealing the Door Frame
The vertical sides, or jambs, and the top header of the door frame are sealed with flexible weatherstripping that compresses when the door is closed. Closed-cell foam tape is a common option, which has an adhesive backing and works well for small to medium gaps. For gaps that vary in size, tubular vinyl or rubber weatherstripping, often called a bulb seal, offers a durable, resilient barrier that maintains a tight seal through repeated use.
A less visible option is the V-strip or tension seal, made from a thin strip of plastic or metal folded into a “V” shape. This material is installed discreetly into the corner of the door stop, and the tension pushes against the door face to create a firm, long-lasting seal. Before installation, the surface must be thoroughly cleaned with an appropriate solvent to ensure proper adhesion. The weatherstripping should be cut precisely and installed to make continuous contact with the door without creating excessive resistance.
Addressing the Door Bottom and Threshold
The gap beneath the door is often the largest source of air leakage and requires more robust hardware than the flexible seals used on the frame. Door sweeps are strips of metal, plastic, or vinyl that hold a seal made of materials like neoprene, silicone, or nylon bristles. These sweeps are surface-mounted to the door bottom and are designed to glide just above or lightly touch the threshold as the door operates, blocking air flow and preventing debris.
A more comprehensive solution is the door shoe, which is a U-shaped or L-shaped piece of metal that wraps around the entire bottom edge of the door. This hardware contains a durable vinyl or rubber insert that creates a continuous seal against the threshold. This offers increased protection against moisture and air infiltration compared to a simple surface sweep.
In some cases, the threshold itself may need to be adjusted or replaced to ensure it meets the door bottom mechanism correctly. A threshold with an adjustable riser allows the homeowner to fine-tune the height. This guarantees a tight compression seal against the door sweep or shoe when the door is fully closed.