Where does your bath exhaust vent terminate?

It used to be a very common practice to terminate bath exhaust vents at the screened bird-blocking of the roof overhang. Everyone has likely seen bird-blocking, but perhaps you did not know what you were looking at.

Bird-blocks are essential components of the roof/attic ventilation system, and shows between the ends of the roof trusses or rafters at the roof overhang. These vents are where air enters the attic and travels to the roof vents or ridge vents. Also, as their name implies they fill the space between the rafters/trusses to keep the birds out of the attic as well as provide a path for ventilation.  I think the blocking also gets its name from stick-built type roof structures where the rafters had a “bird’s mouth cut in the rafter to sit flat on the wall top plate.  So this blocking was between the bird’s mouths of the rafters.  So they are either a “description” or a “function”—maybe both.

It probably does not hurt the ventilation of the attic too much to “borrow” one of these openings for the termination of an exhaust fan, but it can have some serious unintended consequences.

Let’s assume for example that the vent is indeed going to blow air out the hole of the bird-blocking. If the pipe is butted tightly up against the blocking it will likely work pretty well. However, this warm moist air is being blown into an area that is typically under negative pressure. In other words a lot of this warm moist air is being blown into a space where it is likely going to be sucked right back into the attic.

Another problem we have to consider is that all of this exhausted air has a lot of dust and lint in it. In a relatively short period of time the screen in the bird-blocking is going to plug with lint and then the exhaust fan will stop moving air from the bathroom. This will lead to moisture issues in the bathroom as well as the whole home. The odors we usually appreciate being vented out of the bathroom as quickly as possible will also “linger.”

It is for these reasons that an exhaust cap with a back-draft damper is necessary, and that it be located such that the air being exhausted is not going to be sucked right back into a space we don’t want it. We want to have control over the maintenance of the exhaust system as well as where the air ends up.

As you can see in the following picture the vent screen is completely blocked with lint.

Plugged vent screen

I slid the pipe over 3” just so you could see what happens when the exhaust is installed in this manner. There is a small area at the center of the lint where the screen is visible but this is only so because the pipe scraped off the lint when I slid the pipe over.

Often these vents are buried in insulation and you only get a hint this method has been used by the amount of fungal growth on the soffit at the exterior or on the roof sheathing in the attic.

vent at soffit

When the fan in the bathroom will not hold a piece of tissue paper up against it, this is sometimes the reason why–and it is certainly an indication the fan is not venting properly regardless.

By Charles Buell, Real Estate Inspections in Seattle

If you enjoyed this post, and would like to get notices of new posts to my blog, please subscribe via email in the little box to the right. I promise NO spamming of your email! 🙂

What is a little missing insulation between friends?

Sometimes it is the little things that get you.

However, these little things can end up costing you a lot of money over time.

At a recent inspection I had a house where the insulation details were not well thought out.  Without going into a discussion about the “type” of insulation, lets just discuss in the simplest of terms how the system was working—or not working as the case might be. 

The following sketch shows how the walls are insulated up to the ceiling and then the roof plane itself is insulated.  What got missed was the wall between the roof and the ceiling.  This space above the ceiling is essentially “conditioned” space and the short wall between has to be insulated to have continuous insulation around the conditioned space.

This next picture shows what that un-insulated area looks like with thermal imaging from the exterior.  However this is a space between the second floor and the main floor ceiling.

Going back to the original drawing, here is an exterior view of that un-insulated space—as seen by thermal imaging.  The un-insulated areas appear warmer (the white-yellow areas)

The same areas of the above picture as seen from the inside of the attic space with the un-insulated areas appearing “cooler” (the black areas).

These areas will need to be well-insulated to prevent wasting of energy that increases both heating and cooling loads of the home. 

The fiberglass insulation should be encapsulated, and for more information about that:  All Fiberglass Insulation Must be Encapsulated.

 By Charles Buell, Real Estate Inspections in Seattle

If you enjoyed this post, and would like to get notices of new posts to my blog, please subscribe via email in the little box to the right. I promise NO spamming of your email! 🙂

When designers don’t put on their thinking caps.

I often find instances where it would appear that designers have lost their thinking caps or never had one to begin with.

largecondo1Take this 6 story building for example.  There are probably a hundred condo units in this building and every unit has a dryer.  All these dryers have to terminate at the exterior of the building somewhere.  The top units can likely pretty satisfactorily be vented through the roof for ease of maintenance/inspection (they were not however).  Even the second floor vents can likely be fairly easily and safely maintained by ladder from the ground.

But what about the floor levels in between?  These vents are going to be 30, 40, 50 or 60 feet off the ground!  It some areas they are even further off the ground due to the slope of the site.  While it is common for Condo Associations to have a maintenance schedule for maintaining these termination points, one has to wonder just how cleaning and maintenance gets done.  Even renting a cherry picker a couple of times a year would get expensive on a building this size.  It is amazing to me that building codes would even allow the vents to terminate where maintenance would be so difficult.

In this next picture I have circled some of the dryer vent locations that would be extremely difficult to maintain.

largecondo2

To add insult to injury all of the dryer vent terminations on this building had screens installed over the vents.  Even if this was a good idea (It is not and is in fact not allowed) it would only increase the number of times they would need to be inspected/cleaned due to the presence of the screens.

As you can see in the following picture some of the screens—this one 40 feet off the ground—is partially blocked with lint consistent with inadequate maintenance.

So all of this begs the question, “Why weren’t the vents terminated at locations where they could be easily maintained at virtually not cost?”  This could have been easily accomplished by terminating the vents at all the deck locations around the building—as some of them were.

Given that dryer fires are one of the most common types of fires in residential construction, it makes sense to have more sense as to where these vents terminate.

This stuff is not rocket science and yet we try to make it so at times.

 

By Charles Buell, Real Estate Inspections in Seattle

If you enjoyed this post, and would like to get notices of new posts to my blog, please subscribe via email in the little box to the right. I promise NO spamming of your email! 🙂