Do your exhaust vents terminate at your soffits?

The building codes specify that exhaust fans shall not terminate in the attic or soffits. While there are those that argue “at the soffits” is not the same as “through the soffits,” I think it pretty much amounts to the same thing.

The reasons we do not want to vent warm moist air into attics is well known and documented. It can lead to mold growth and other four letter words.

So what exactly does the code say:

M1501.1 Outdoor discharge. Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.

That seems straightforward enough, and since “aimed at the soffit” is still in the attic, my personal opinion is, when the code says “Shall not be exhausted into a …..soffit,” they are meaning “through the soffit” as well.

So let’s forget about the code, and let’s see if my opinion can be supported by building science.

Wow, do we really have to go to “science?”

What are the building conditions that would come into play to sort this all out? Typically, or at least most of the time, in a properly vented attic, the attic space is under negative pressure relative to the higher pressures at the soffits and at the ridge. Because of this, air is attempting to push its way into the negative air space to make balance–24/7. All air in the vicinity of the soffit vents is forcing its way into the vents.

Now lets place a bathroom exhaust fan vent right at the soffit vents.

We are exhausting warm, wet, buoyant air that it is already moving upward and increasing the pressure in the area of the soffits. This increase in pressure difference between the attic space and the soffits makes that warm wet air work even harder to get into the attic.

In this picture, you can see evidence of where corrections have been made of the four vents that terminated too close to the soffit. The opening have been covered over, and hopefully they now terminate properly through the roof.

The staining on the siding above the lower vents is consistent with the buoyancy of the air from the vents.

Staining above the soffit vents on the underside of the roof sheathing is consistent with the upper vent’s previous termination at the soffits.

I think the codes need to clean this up a bit and require minimum distances to vented soffits.  Any current guidelines are at best “vague.”

Until then we should resort to good sense.

Charles Buell, Real Estate Inspections in Seattle


The dark side of Carbon Monoxide Detectors

Carbon Monoxide detectors have been in the news a lot lately and with good reason. Given that the gas is colorless, odorless and can kill you while you sleep are all good enough reasons for me to pay attention. The building codes themselves require them, and in addition, many states have made laws requiring them.

There is a dark side to CO detectors that is not discussed very much however, and I have blogged about this issue with Carbon Monoxide Detectors in the past.carbon monoxide detector

This missing information can leave the consumer with a false sense of security.

Most of the CO detectors required by state laws and the building codes are quite good at detecting Carbon Monoxide in relatively acute doses. Acute doses are large levels of exposure over relatively short time periods. They are not very good at detecting Carbon Monoxide at chronic levels—low levels of exposure over longer periods of time.

In fact, the CO detectors required in your home are NOT ALLOWED to signal a problem at levels below 30ppm in order for them to obtain the UL listing necessary to meet the codes (UL 2034). It is interesting to note that most of these alarms are designed to sound at or below 70ppm within 60 to 240 minutes (I do not think that this information should make anyone feel protected).

There is a stream of emerging data (see HUD: Healthy Homes Issues: Carbon Monoxide) that there are health risks associated with low levels of CO exposure—levels below what is considered safe by the EPA. According to the EPA levels of CO below 9 ppm over an 8 hour period, or 35ppm for one hour are considered “safe.” Research is beginning to show that the elderly, the very young, the unborn and some other individuals experience negative physical, cognitive and emotional effects with exposures below these levels.

There is technology available for detecting low levels of CO. These devices do not meet UL 2034 and therefore cannot be “substituted” for the poorer performing listed devices but must instead be used as supplements to the required detectors.

One such device is the “Defender” CO detector. It is capable of detecting levels as low as 5 ppm for less than a minute. It has a wide range of sensitivities with different alarms and visual read-outs to display different levels of concern. These seem like a prudent device for any home. These devices also attempt to deal with the issue of when they have reached the end of their expected life. They come with a sealed in place battery so when the battery is dead you simply replace the whole device. I wonder how many regular detectors will continue to give their false sense of security long after the batteries are dead or when batteries are replaced when the units are well past their expected life.

Also keep in mind that there is no substitute for regular servicing of all combustion appliances in the home. Proper servicing is an essential part of any CO mitigation/detection system installed in the home.

By Charles Buell, Real Estate Inspections in Seattle

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When you do not know what your are doing…….

At first glance, this room looks pretty nice. The door looks nice. The transom looks nice. The hydronic floor looks nice. The painting looks nice–and I can even live with the yellow. Ok, yes, the receptacle at the right side of the door is a little “less than professional”—but still cosmetic.

The door from the house to the garage

The door from the house to the garage

There are a couple of hints that things may not be OK.

Can you see that little gap at the top of the door and the transom?

Can you see that there is absolutely no gap between the bottom of the door and the floor? Well, I admit—that is hard to see in the picture—so you will have to trust me on that one.

There is actually a WHOLE lot wrong with the door and the transom installation that is better seen from the other side of the door. When I tell you that there is a garage on the other side of this door a whole list of things should immediately occur to you—or at least to your home inspector.

Because of the garage we now know that it cannot be a flimsy interior door. It must be a solid wood fire-resistant door at least 1-3/8” thick, or a 20 minute fire-rated door.

Next is the glass. Typically glass is not allowed between the living space and the garage space. Of course there is “fire-rated” glass that you could use for such purposes but that would be extremely unusual in residential construction—and this certainly is not fire-rated glass.

To make matters worse—this is not a “door” at all. I realize it has a handle—but again if you look VERY close (this will require supper top secret military-grade photo-shop) you will see it has no hinges. Actually it has ½ hinges. The door halves are present but the jamb halves are not.

If you are now scratching your head as much as I was—let’s take a look at the installation from inside the garage. Of course we won’t be able to get into the garage through this door because, as we have already discussed, it ain’t a door.


The door from the garage to the house

The door from the garage to the house

That foam is probably not the correct type of foam for this application, so while it might stop some air movement, it is not really helping our fire-resistant assembly very much.

Now we can see why there is that little strip of light above the door on the room side. It is not really a transom after all.

And you thought it was going to be complicated?

Of course on the garage side we can now see that, in addition to all the problems with the “door,” the wood wall between the house and the garage is not covered with proper fire-resistant materials—typically ½” drywall.

But, it is not over yet. Now look and see what we have just to the left of the door in the previous picture.

The window from the garage to the house

The window from the garage to the house

Yup–another window—no fire-rated glass in this one either.

Someone is not going to be happy, when they find out all the work that there is still left to be done at this recent remodel—including verification of proper permits.

By Charles Buell, Real Estate Inspections in Seattle

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