Do you know where your dryer vent cap is?

While I could get to the location in the picture to inspect the roof and the dryer vent cap on this two story house, it took my 26 foot ladder (fully extended with just a few inches of the ladder above the gutter) to do so.

Poor Dryer Vent Location

Poor Dryer Vent Location

I know inspectors that do not go on roofs like this–let alone homeowners.

Why do the building codes allow such locations for dryer vents?

Because, the codes are “minimum” standards.

Why do builders install them at these locations?

Because, it is the easiest place to get the duct to, and it meets code.  Do we really expect more of them?

The codes defer to manufacturers installation instructions and of course the manufacturer advises installers to follow applicable codes.  Most, if not all, manufacturers have no restrictions on location of the vent cap at the exterior–only that there be one (along with guidelines as to length, materials etc.).

Best practices would have the builder run the vent to a location where it could be monitored and more easily maintained by the homeowner.

Instead, the builder taking the easier and cheaper route might result in additional costs to the homeowner to have someone qualified to be on the roof assess and maintain the vent cap 2 or 3 times a year.

Until some homeowner gets killed trying to clean a vent at a location, or the house burns down because they were not able to clean it, the codes are not likely to change.

Of course perhaps a sport-climber may buy the house.

By Charles Buell, Real Estate Inspections in Seattle

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A Forest of Vent Caps!

How many vent caps can you count on this roof? ventforest

The vent cap, front and center, in the picture, is the vent cap for a bathroom exhaust fan.  This picture captures perhaps 70% of the total number of such caps on this condo building roof.  Since I don’t inspect from a helicopter I could not get a picture of all of them.  I also was only really interested in the 6 involved with my unit of this condo building.  When I climbed over the edge of this roof and into this forest of vent caps, I marveled at how cool and how wrong they looked.

I occasionally see this type of cap used as a vent cap, but to find an entire building’s vents terminated this way–in relatively new construction–threw me for a loop.

For a long time now–since at least 1991 in Washington State–it has been required that all exhaust fans terminate at the exterior of the building at a cap with a back-draft damper.

Here is what the code that was in place at the time these vents were installed said: “Outdoor air intakes and exhausts shall have automatic or gravity dampers that close when the ventilation system is not operating.” (Underlining is mine)

NONE of these caps have back-draft dampers.  None of these caps have screens to keep out insects and birds.  I count 33, “for-sure-and-a-couple-of-maybe,” vent pipes in the picture–how many can you see?

Every one of these vent caps is actually a little chimney.  Cold air can drop into the pipes leading to condensation inside the pipes.  They also have no screens to keep out vermin–so insects and birds might think they are nice places to call home.

Because they are little chimneys, they also “act” like chimneys.  In other words as wind blows by the caps it will put the chimney under negative pressure.  This can pull open the dampers that are built into the fan units–drawing warm air out of the building in the winter and conditioned air out in the summer.

It begs a question.vents2

How does this get by the jurisdictional inspectors?  This was no cracker box structure either.  It was a very high end Condo building that paid the big bucks for a PVC roof system and many other similar expensive upgrades throughout the building–inside and out.


By Charles Buell, Real Estate Inspections in Seattle


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Your Seattle Home Inspector vents about venting!


Today’s post is about the various exhaust vents in your home.

There are a multitude of exhaust vents in most homes.  At this point I am not going to discuss combustion appliance vents/chimneys.  This post is about bathroom, laundry, kitchen, dryer, and whole house exhaust vents—-mechanical type vents—-and specifically—-just the vent caps for this equipment.

Because of their importance in helping control humidity levels and indoor air quality it is critical in modern homes that these vents be maintained as functional as possible.  While it is important for all aspects of these mechanical ventilation fans to be properly maintained, today I am only going to talk about the exterior cap.

All exhaust fans should be vented to the exterior of the home at a cap with a back-draft damper. 

These caps can be on the side walls of your home or on the roof and sometimes even on the soffits (although soffit determination should be avoided if at all possible).

I recommend that you turn on all of your exhaust fans and walk around the exterior of your home and make sure that the flaps are opening properly.  If they are on your roof you may need to use binoculars.  Wasps and other critters like to build their nests in these caps and the winter time is a good time to make sure nests and other debris is not present.  But be careful, stinging insects may be present.  Wasp’s nests can fill the cap so that the vent flap will not open.  Remember too—-roofs can be DANGEROUS places so make sure whoever maintains the caps knows what they are doing.

Caps can suffer mechanical damage to the point that they will not open properly and screens can become clogged with lint and debris.  If the flap moves freely by hand but no air is coming out when the fan is running or the damper does not open when the fan is running—–have the venting fixed by a qualified person—-it may be venting warm moist air into areas that could cause damage to the home.

vent cap

Badly damaged exhaust vent cap

vent cap

Clogged vent cap for a dryer

These exhaust fans should never terminate in crawl spaces or attics or at roof and soffit vent screens.  Especially problematic are the types of terminations in the next two pictures.

Bathroom exhaust fan terminated at screened hole in bird-blocking

Bathroom exhaust fan terminated at screened hole in bird-blocking

vent cap

Screened and metal louvers are not a proper vent termination

Obviously—unless you are creating a bird house—-the flap must be able to close by gravity if you are going to keep cold air and vermin out of the ductwork.

vent cap

Landing platform for birds

Many of these vent caps come with screens and/or protective grilles—and most of these screens are required by the building codes.  While these screens may prevent small birds and mice from building nests in them, they are of questionable value in my opinion.  But since they are required by the codes we must make sure they are maintained free of debris and vermin.  Properly screened vents actually will promote wasps because they are protected from other vermin behind the screens and if the screens had smaller openings they would clog up even more quickly.

vent caps

Wasps nest in a vent cap

Because screens are required in the caps of range hood vents, we must be especially vigilant in maintaining the screens in these caps clean.  Depending on cooking habits these screens are prone to plugging with grease and lint, creating a fire hazard.

vent cap

Very clogged screen on a kitchen range hood vent cap

Screens also should NEVER be installed on dryer vents because when they become clogged, the lint represents a fire hazard, and it will take forever to dry your laundry—-wasting a lot of energy.

vent cap

Clogged dryer vent cap

Louver type vent caps often don’t operate well, the flaps sometimes don’t fully open and sometimes they become warped by the sun—-when installed on the sunny side of the home.  I prefer single flap type caps for most vents.  Most louver type caps also do not meet the requirement for there to be a screen—when they are used at locations that require a screen.

vent cap

Damaged louver type vent cap

Here is a list of some of the many things that can be wrong, or go wrong, with just this single component of your exhaust vent systems.

  1. Missing
  2. Wrong type
  3. Mechanical damage
  4. Disconnected
  5. Blocked with lint/debris
  6. Blocked by nests (wasps and other vermin)
  7. Damper painted shut
  8. Too close to the ground
  9. Not attached
  10. Not sealed to prevent moisture and vermin entry to the home
  11. Vent flap stuck open
  12. Vent flap stuck closed
  13. Vent screens/grilles  in caps that should not be screened
  14. Missing back draft damper
  15. Damaged back draft damper
  16. Damaged louvers
  17. Missing louvers
  18. Installed at wrong angle—damper won’t stay closed

I am done venting now.


By Charles Buell, Real Estate Inspections in Seattle

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