Exhausting! The building codes have limits.

Seems like this dryer vent is a “cut-and-dryer” case of what were they thimkin?!

As anyone that regularly reads my posts knows–I love standing seam metal roofs. Inspecting them is difficult if they are steep, but because a fair amount of skill is necessary to install them, they usually don’t have a lot of issues that are not going to be apparent from the eaves–assuming you can get to the eaves. I was able to get to the eaves at two locations on this duplex, and overall the roof looked great.

The pitch is 7/12–not an exactly friendly pitch for an asphalt roof–and certainly not for a steel roof. A slippery slide at the playground is not much steeper than this–some are less steep. Add to that, that it was raining at the time of inspection, guaranteed that I would not be venturing onto the roof. From the eave I did note one thing on this 5 year old home.

The dryer exhaust cap.

How is anyone going to do routine maintenance on this vent cap? While the installation meets code requirements, I still find the installation seriously lacking.

Even with the best filter/screens in dryers, these caps will eventually plug with lint. Cleaning at least a couple of times a year is typically necessary–but at least there was no screen in this cap like is so often the case.

The “close-up” of the cap shows a fair amount of lint building up inside the cap–who can tell whether the flap opens properly or not?

I have no clue as to a viable solution to this problem, when the dryer is not located on an outside wall of the home–but surely some solution is warranted. If no other route for the exhaust can be found, then establishing a maintenance program with someone trained and qualified to be on this type of roof a couple of times a year may be warranted.

Perhaps it is time to make an adjustment to the codes–and/or good sense.

By Charles Buell, Real Estate Inspections in Seattle

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Log homes and energy efficiency

On a recent road trip around the State of Washington, we stayed at a motel constructed of older style Pan Abode buildings built sometime in the late 50’s. 

The structures seemed in remarkably good condition for their age, but the stresses on these structures are perhaps not what they would be in a wetter area of the state–like west of the mountains–in the Seattle area.  The structures seemed well suited to their hot and dry climate.

What I found interesting was the insulating ability of the 4″ thick walls–or their lack of ability would perhaps be more accurate.

This first picture is of the exterior wall.  The red rectangle corresponds to an area at the interior that will be discussed below.

Pan-abode type building

This next picture is what the wall structure looks like.  You can see the double tongue and group shape with the wall being approximately 4″ thick.

Pan-abode type wall structure

On the interior, with thermal camera, the wall and pillow temperatures show in the next two pictures.

Thermal image Thermal image

In this next picture we see the wall with the pillows moved away from the wall to reveal how the wall was “insulated” by the pillows.  The wall, heated up by the direct sun shining on it at the exterior, could not give up its heat to the interior as readily as the other areas of the wall. Thermal imageThermal image

My understanding is that modern Pan Abode structures are a double-wall type of construction that allows for the installation of insulation inside the walls.  This would certainly be required by modern energy codes for both heating and cooling. 

Regardless, these pictures demonstrate very well how poor 4″ of wood is as insulation (about R-4).  By themselves, it would take exceptionally large logs to meet modern energy efficiency standards.

By Charles Buell, Real Estate Inspections in Seattle

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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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