Clothes dryer vent totally blocked with water (C) Daniel Friedman Clothes Dryer Exhaust Vent Termination / Screens
Dryer vent terminations at walls or rooftops

  • CLOTHES DRYER WALL VENT SCREENS - CONTENTS: Clothes Dryer Vent Duct termination screens or closure devices used at exterior walls or rooftops. Outside dryer vent termination back-draft dampers are required to keep out drafts and animals but the outlet must not be screened - a feature that collects lint.
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Clothes dryer exhaust vent termination at walls or rooftops:

Clothes dryer vents should terminate outdoors and should be screened enough to prevent entry by animals as well as to minimize cold back-drafting when the dryer is not in operation.

This article describes problems with lint-clogging at the dryer vent screen and suggests regular inspection & cleaning and perhaps installation of clog-resistant dryer vent terminating devices that reduce lint clogging. (They do not completely prevent lint clogging.)

At the top of this page: a sidewalk-level commercial dryer vent in San Miguel de Allende, Guanajuato. This dryer vent is not so easy to clean and is clog-prone.

This article series describes good practices for clothes dryer vent installation, lint traps, wall vents, filters, and screens. We include a list of clothes dryer fire safety hazards and other clothes dryer installation or maintenance mistakes that are either unsafe or that interfere with effective, economical dryer operation. We discuss types of dryer vent ducting and dryer vent doors or opening protection devices

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Clothes Dryer Exterior Wall Termination, Covers, Shields & Rooftop Dryer Vent Warnings

Exterior wall clothes dryer vent termination: check the exterior wall dryer vent screen monthly for lint blockage.

Lint blockage and clogging often occurs right at this screen, causing longer dryer operating times and possibly overheating. In addition some dryer vent terminations and covers, particularly those that rely on a flapper that is opened by the moving exhaust air, can become stuck in the open position, inviting dangerous vent line clogging by entering birds or insects.

Rooftop clothes dryer vent (C) Daniel Friedman

Our clothes dryer vent photos below illustrate lint clogging at an exterior dryer wall vent after six months' of usage. These pictures show why it is so important to inspect and clear lint from the dryer wall vent at least every few months. Because this was a brand new dryer vent installation, the rate of dryer vent system lint accumulation is unambiguous. The laundry and clothes dryer system in this home was used by a family of four, including two young children for a period of just six months.

Rooftop clothes dryer vent (C) Daniel Friedman

Below we illustrate our inspection of the interior of this six-month-old laundry dryer vent duct system. We removed the outer screen on this vent as that would allow more lint to blow freely to the outdoors and would slow the system clogging rate. The screen was unsafe.

Below I'm inspecting the vent termination louvers for free movement.

Rooftop clothes dryer vent (C) Daniel Friedman

Watch out: do not leave off the dryer wall vent louvered-rodent cover itself: doing so invites birds or rodents to nest in the duct system, leading to unsanitary conditions, vent blockage, and fire risk. I mean do not leave a simple round vent opening with no closing mechanism or you invite animals inside the vent system.

Clothes dryer vent protective louver-screen at the exterior wall (C) Daniel Friedman

Above: I am removing the plastic grille that leads to clogging of the dryer vent system.

Rooftop clothes dryer vent (C) Daniel Friedman

Above you can see six months of lint accumulation - rather light - in a brand new, solid metal 4" clothes dryer vent system that began with no blockage but that apparently was not checked nor cleaned during six months of use.

Below: We inspected this dryer exhaust vent terminal covering with the dryer running on a chilly night, giving a good view of the freely-opening louvers as well as a large billowing cloud of moisture condensing from the hot humid dryer exhaust air.

Dryer exhaust open and working on a cold night in Poughkeepsie (C) Daniel Friedman

Rooftop Clothes Dryer Vents Also Clog & May Be Blocked by Snow or Ice

Rooftop clothes dryer vent (C) Daniel Friedman

Our photos just above and below illustrate our investigation of a lint-clogged rooftop clothes dryer vent located on a low slope roof in New York. Below you see years of lint accumulation in the dryer vent duct on this home.

Lint-clogged rooftop dryer vent duct (C) Daniel Friedman

This 20+ year old clothes dryer vent system had become totally blocked with lint (a fire hazard as discuss below) and of course the cost to operate the clothes dryer was multiplied by the long run-time necessary because there was no functional exhaust of hot moist air. A symptom of the trouble was that the owners noticed that the clothes dryer was really hot at the end of a dryer cycle.

Rooftop clothes dryer vent (C) Daniel Friedman

Equally poor design of this clothes dryer vent system was its installation on a nearly flat roof in a climate where winter snow cover could completely cover and block the vent even if its internal ducting were not already clogged by lint.

Below: the same roof where this clothes dryer vent is installed is shown covered in nearly a meter of snow. No clothes dryer can melt its way through so much deep snow: the dryer vent will be initially blocked by snow, and when the dryer is operated the result may be a rooftop clothes dryer vent that is further blocked by ice from melted snow or even a dryer vent that blocks open and allows melting snow to enter the building.

This rooftop dryer vent design is more likely to cause a dryer fire than to put out the fire by melting rooftop snow.

Shoveling deep snow off of a flat roof in Poughkeepsie (C) Daniel Friedman

Watch out: as you can see above, such deep snow will completely block a rooftop clothes dryer exhaust vent.

Air-Operated Exterior Clothes Dryer Wall Vents Avoid Lint Clogging

Air operated clothes dryer wall vents may be a way to avoid these dryer fire hazard and high energy cost troubles.

Air-Operated Exterior Wall Vents for clothes dryer vent lines are available at hardware stores, building suppliers, and from some online sources.

These devices use a movable plastic cylinder that lifts to permit venting of the laundry dryer exhaust when the dryer is operating. The opening is not screened when the vent is open, so lint clogging is practically eliminated. When the dryer stops operating the plastic cylinder returns to its closed position. [1]

Air operated clothes dryer wall vents may be a way to avoid clothes dryer fire hazard and high energy cost troubles.

Dundas dryer vent draft blocker

The Dundas "Draft Blocker" dryer vent shown above and the Lambro Dryer Vent that is operated by dryer air pressure (shown below) are designed to prevent back-drafting of cold outdoor air into the building through the clothes dryer exhaust vent termination or cover. Such back-drafts can occur when the dryer is not in use.

Dryer vent from Lambro

Watch out: as we point out at CLOTHES DRYER FIRE HAZARD WARNINGS some of these dryer vent terminations and screens can be invaded by small animals, and even these wide-opening clothes dryer vents need periodic inspection and lint cleaning.

Also see CLOTHES DRYER VENTING FAQs for more about dryer vents that resist lint clogging, and about use (or recommendations against using) supplemental lint filters in dryer vent and duct systems.

Fire Hazards from Clogged or Improperly-Installed Clothes Dryer Vents



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