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

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Reducing the need for air conditioning

Grape arbor sun protectionHow long have we been building houses?  A lot longer than we have been air conditioning houses.

Well we have certainly done things to keep warmer and dryer for thousands if not 100’s of thousands of years–but we have also done things to keep them cooler as well.

As a designer/builder for most of my adult working life, I have marveled at how ignorant we are of how to accomplish keeping warm, dry and cool.

We now have air conditioning systems that allow us to live in places where not too long ago it would have been considered uninhabitable–or at least inhospitable.

We have long had the knowledge to mitigate the use of air conditioning to some degree and yet we simply choose to turn down the knob on the thermostat.

Today I just want to talk about a few “passive” things that can be done to greatly decrease the use of actual mechanical air conditioners.

First and most important is house design and orientation. Obviously if we build a house and make all the south facing walls floor-to-ceiling glass, with no roof overhangs, we can expect to find ourselves inside a solar heated oven. Just providing a roof overhang to prevent the sun from hitting the windows directly can go a long way to turn the oven down a bit. By eliminating ground and other surfaces that might reflect the sun’s rays into the home can also be an improvement.

Even these Native Americans made an attempt at basic principles

Of course reducing the amount of glass itself will make the most difference because then the walls themselves can be better insulated. This brings us to the huge topic of insulation in general. There is nothing like highly effective insulation in the walls and ceilings to keep the heat out of the house. This is not as simple as it may seem because heat is always attempting to move to cold and make balance. When it is 95 degrees outside, all that hot air is just hungry to gobble up our pathetic little bubble of coolness. So our air conditioners have to work their butts off to maintain that bubble of coolness.

While today I do not want to go into how I think houses should be built to eliminate the need for air conditioners altogether in many areas, I want to talk about ways we can deal with adverse conditions in our older homes in passive ways. While these things will not reduce your need for air conditioning in some areas it may greatly reduce the amount they may have to run. It may mean in some hot humid areas you might have to add a dehumidifier to make up for what the AC used to do.

The short story in all of this is to insulate your house as much as practical and use good air sealing type insulation–anything longer and we are into the full fledged novel.

One of the most important things you can do, if you live in an area where the nighttime temperature drops even 20 degrees between daytime and nighttime, is to change the air in the home and lower the thermal loading that has built up in the home during the day. The house is then closed up during the day to keep the nighttime cooling in and then the process simply repeats itself. In an average size house, even a simple window fan in a window on one side of the house and a window open on the opposite side of the house can accomplish this goal.

I cannot stress the importance of roof overhangs to keep the sun out, but in older homes that is not likely going to be possible.

In my own house, built in the early 30’s, the overhangs are insufficient to keep the south facing windows from overheating the house in the summer. So a simple thing I have done is to shade the windows with a grape arbor–the one plant now creates shading of most of my south facing windows and makes an amazing difference, and of course provides grapes in the fall.

Grape arbor sun protection

While we certainly do not get as hot as lots of areas of the country, my house certainly never needs any mechanical air conditioning. The attic has a ton of cellulose fiber insulation, the walls have minimal insulation limited by the 2×4 wall thickness, and we put a fan in an east window at night and open up a west window–on those occasional really hot days.

Before the days of the grape arbor, we use to have to do the fan approach a lot more.

If you have a house with a basement, you can open up a basement window (as the path to the upper fan in the window) and get the benefit of the cooler basement to improve the cooling of the interior space during the nighttime. Accessing the constant ground temperature is another thing that can have a huge impact on minimizing the mechanical cooling needs of the home.

A huge number of homes across America could benefit from this passive approach to improving house comfort and energy efficiency.

By Charles Buell, Real Estate Inspections in Seattle

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The Cat House & Home Inspection Protocol

 Just walking around a home–looking at it from a distance–I can often tell what might be in store for me on the interior.  Home inspectors will usually take this “macro-view” of the home prior to getting up close and personal with the “micro-view.”  It is a very important part of the home inspection protocol to utilize both of these views of the home–and all the spaces in between.

Crawl spaces

At a recent inspection, as I headed around the back side of the home, I took the following picture.

Cats in the crawl space

I suspected the home probably had a crawl space even though I was told it did not–supposedly built on a slab.

As I saw Kitty-Kitty sticking his head out of the crawl space hatch I knew what this meant–there was indeed a crawl space as I suspected.

Well it could have also meant that this was just the access well and that there was a door behind Kitty-Kitty and he was just hanging out in the access well.

But I knew what this meant.  There was in  fact no cover at all and the crawl space was where Kitty-Kitty lived.  The best I could hope for was that Kitty-Kitty had not turned the crawl space into a latrine and that he would be amenable to my checking out his digs.

As it turned out, not only was he amendable–so was his partner.

cats in the crawl space

Neither one even minded me snapping a few pictures–in fact one never even seemed to wake up.

I was also grateful that their digs was still a crawl space–instead of a litter-box.

Crawl spaces are perfect environments for cats.  They are dark, there is a high likelihood of mobile food, and they can do what cats do.

By Charles Buell, Real Estate Inspections in Seattle

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