Would you keep all the windows open with the heat on in your car?

Bet you didn’t know you are heating and cooling a wind tunnel!

Certainly the biggest contributors to moisture in the attic are breakdowns in the building envelope. (Of course I am assuming that water is not getting in from outside the envelope–like a leaking roof) These compromises also make the building less efficient and will empty your wallet more as you attempt to heat and cool your home/tunnel.

air bypasses To understand this problem, it is helpful to think of one’s house like a Tupperware container. Clearly if we leave the lid a little bit ajar (like an attic access that is not weather-stripped), or start drilling holes in the bottom, sides and top, the container will no longer do its job–or at least less efficiently—relative to the number of holes, the size of the holes and where they are located.

Of course, if the holes are so the snake (or whatever else the kid catches) does not die, that is another matter.  It is still important to keep the lid on though.

There are other factors–but let’s keep it simple for today.

We can build the most super-insulated house in the world but if we don’t control air movement in and out of the building our efforts at insulating can be wasted.

One of the most common, obvious, everyday sort of “by-passes” that I see in homes is dampers in fireplaces that are left open. These chimneys will pull conditioned air from the home 24/7–with an occasional pause for atmospheric inversions that can happen. The screen on the fireplace filling up with lint is the first clue that this is happening. Even closed dampers in most cases will not stop this movement entirely.

Eliminating open flame solid fuel appliances altogether is a good idea in the context of building more energy efficient homes.

I have heard people argue that this natural draft is a good way to exchange the air in the home–without a mechanical fan. The truth is that this works–but at much greater cost than running a simple exhaust fan periodically. It is the 24/7 aspect of the chimney that makes it a problem, as it vents conditioned air that we are also paying for. On a windy day the venting might be much more than on a still day. We need “control” over this air exchange if we are truly going to control energy use as well as maintain a healthy indoor environment.

I want to stress that this is a LOT more complicated than I am willing to address here. For example rates of ventilation will not always guarantee good indoor air quality. While outside air is generally of better quality than indoor air, that is not always the case and in some areas of the country, outside air is becoming worse every day. At some point the political aspects of outdoor air quality will be forced to reconcile with the private aspects of indoor air quality. Some will argue that if you want “quality” drinking water you had better be prepared to solid-block-carbon-filter the water where it comes into your home. The same thing is perhaps coming for the air we are bringing into our homes.

Welcome to the 21st Century.

Back to air by-pass issues.

As previously mentioned, the attic access hatch is a common by-pass but the list is almost endless. Here is a partial list of some common breaches: plumbing pipes running through walls and ceilings, can-lights, HVAC equipment/ductwork in attics, crawl space hatches at the interior of the home, wiring holes in top and bottom plates of walls, chimneys, b-vents, improper framing techniques, skylights, pull down stairs, drop ceilings, exhaust fans etc.

“Stack effect” is something else that affects our homes.

Stack effect is relative to temperature/pressure differences. It is relative to the fact that warm air is buoyant. It is further driven by the lowering of pressures inside the home which then allows for air to be pushed into the lower levels of the home (from outdoors and/or crawl spaces). The taller the home, the more pressure differential as the buoyant air moves to the exterior (attic) of the home, bringing with it the moisture in the air. The colder the outdoor environment and the taller the building the more that hot air will be trying to get into the roof structure or outdoors to get to that cold. Perhaps the perfect storm is to have a leaky floor system over a vented crawl space in conjunction with serious breaches in the attic floor.

In this scenario you can think of your poor heating system as attempting to heat a wind tunnel. You will have to be willing to throw a whole bunch of energy at this wind tunnel in order to feel comfortable in your home.

In a very well sealed home there will be less stratification of temperatures and less “driving” of the stack effect–even when doors at the lower level are opened. Opening and closing windows on upper and lower levels in conjunction with each other is a way to manually control stack effect to change the air in the home. This is not rocket science, but can be as expensive as rockets.

At an inspection a while back I had one of the most egregious examples of a home with a functional wind tunnel. The defect was created when part of the forced air heating system was removed. If you could zoom in on this picture, you would be able to see the furnishings in the room below. There were three of these vents into the attic. The missing insulation around the vent is not even consequential in relation to this breach.

Closet vent open to attic

Closet vent open to attic

Sealing these air by-passes, even in older inefficient homes, can drastically reduce heating and cooling costs. Remember , heat tries to get to cold and high pressure moves to areas of lower pressure. So if the attic is really hot in the summer and we are cooling the home we have made the job of the AC unit all the more difficult. Better sealed homes accounts for why the size of heating and cooling systems have halved since the 40’s–remember—back when oil was free?

Sealing and eliminating all kinds of air by-passes is perhaps the most important thing we need to do in making our houses more energy efficient. Insulation alone will not do it and in fact in many cases will only filter the air as the air moves through it. This is especially true of fiberglass insulation–even 18 inches of it. All air by-passes must be found and sealed (or otherwise eliminated) prior to insulating. Choosing types of insulation that are in themselves good air barriers is also recommended.

By Charles Buell, Real Estate Inspections in Seattle

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A case of better late than never!

A case of, “Let’s embarrass the home inspector!”

Some stories are worth telling even if it does have to come at one’s own expense.

Years ago, we remodeled our kitchen.  In the process, the range was relocated to the other side of the kitchen.  This meant that the old vent pipe from the range hood had to be abandoned.  The pipe was disconnected at the ceiling in a space above the stairs behind where the hood used to be.



I stuffed the pipe with insulation (or at least I would like to assume I did) figuring that the pipe and roof cap would get removed when the roof was replaced.

At some point I noticed there was a lot of dust collecting around the edges of the cabinet door to this space above the stairs.


I knew what the dust meant and more or less ignored it figuring the vent was still functioning a bit–air moving through the insulation.

In the context of the recent window replacement project, I had some work to do on the roof and decided that I would get rid of the old vent cap and pipe in the process.


When I pulled off the roof cap and looked down the pipe I was surprised to see—nothing!  No insulation in the pipe.  This pipe had been acting like a chimney since the kitchen was remodeled.   Aaaarrrrgggghhhh!

It is by-passes like this that can amount to higher energy costs and work against the huge amounts of insulation that had been added to the attic space.  It is really no different than leaving the damper open on your fireplace.  The dust in the screen of the old cap is testament to how it has been cleaning the air as I attempted to heat up all outdoors.


You too can look for the signs of these types of air by-passes, and eliminate them to improve the energy efficiency and comfort of your home.  Here is a partial list of indicators.  Look for dust and discoloration like that in the picture above, around:entryway doors, windows, fireplace screens, attic access hatches, crawl space hatches, ceiling light fixtures, light switches, receptacles, along baseboards, along the run of stairs, around the edges of floor registers, skylights, or anywhere else where air sealing has not been complete.

I guess it is a case of better late than never.

By Charles Buell, Real Estate Inspections in Seattle

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Grateful for the wind in my face!

One of my recent posts, More Attic Ventilation Is Not Going To Help, was about excessive moisture in an attic due to breaches in the air barrier between the indoors and the attic space.

As that post discussed, these by-passes can be obvious or hidden. There are often multiple breaches in the same home and some may be easy to find and other may be very difficult to fine. When I find these breaches I point them out and recommend that proper repairs be made. These breaches, if not a problem now, may become a problem in the future.

The picture below is an example of an obvious breach in the connection of the ceiling heat register to the insulated duct in the attic. The picture is looking down at the insulation and the pink insulation is part of the wrap that goes around the heat duct that runs to the ceiling register.

It was pretty easy to find because the heating system was running and this little hole in the insulation was blowing air in my face as I climbed through the access hatch into the attic.


If the heating system had not been running, I like to think I would not have just thought it was a mouse hole.

The truth is though—it does not look at all like a mouse hole because there is no trail.

I’m just grateful for the wind in my face.

By Charles Buell, Real Estate Inspections in Seattle

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