Why Does the Type of Door Weatherstrip Matter?

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Weatherstripping for doors is NOT ancient technology.  The earliest of doors had none.  The door just rested against the stop of the frame as closely as possible and you hoped for the best.  Having a door at all was a big improvement over living in a cave.  We are so spoiled.  We take doors for granted and just assume that they have effective weather-strip.

The weatherstrip (or gasket) is by nature a flexible material that bridges the fixed frame that screws to the building and the swinging or sliding door sash or door leaf. It needs to prevent or minimize air and water infiltration without interfering too much with the operation of the door.  Swinging doors (single, French, bi-fold) all use compression gaskets while sliding doors use sliding or friction surface gaskets.  What material and how they integrate with the overall weather proofing strategy differ greatly.

Sliding gaskets need to offer enough force between the sash and frame to stop leaking but that force needs to overcome by the person opening or closing the door.  The tighter the sliding gasket is the harder the door is to operate.  Compression gaskets are generally better than sliding gaskets because they only touch the door in the final moments of it completely closing. There is no sliding friction to overcome, only enough force to slightly compress the weatherstrip to ensure continuous contact around the perimeter of the door/

Swing doors are the earliest door function and what we most often think of when the word door hits our brain.  My earliest memory of weatherstripping in my childhood home was the bronze spring gaskets nailed to the frame at the edge of the door leaf.  They were non-compression gaskets at the head and lock jamb and compressed only at the hinge jamb.  They were moderately effective but did leak at the corners where they came together and around the lock bolts.  Changing the weatherstrip position or plane from the edge of the door to the inside face of the door where it overlaps the small door stop allowed for the introduction of compression seals.  These seals could be sealed at the corners and didn’t require any force other than the friction of the hinges to move the door through its full travel.

Sliding gaskets include pile weather-strips which have a strip of dense “hairs” perpendicular to the door face.  The earliest versions have added a plastic film in the center to reduce air infiltration.  If they are designed with just the right length (slightly longer than the gap between sash and frame) a sweet spot of protection and minimal force can be reached. Rubber materials do not work well in sliding gaskets because they have huge coefficients of friction and would be more likely to tear than slide.  Again, modern times have introduced slick textured plastic coatings to foam sponge rubber to make what might be the best sliding gaskets. But the protection vs. operating force is a delicate balance.  German technology has created lift/slide door hardware where when the locking handle is turned 180˚ the heavy glass panel lifts about a quarter inch eliminating sliding gaskets altogether.  The down side is that operating the handle can become quite an effort not easily accomplished by the weak or aged.

Pile, rubber, and plastic coated foam gaskets all work well in compression settings.  There are even plastic coated magnetic gaskets like you would find on a refrigerator used sometimes.  2Fold™ doors are currently all swing doors with compression gaskets so we can offer the easiest operation with the best air and water resistance possible.

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