Q: We had a new roof with ridge vents and attic vents installed on our 14-year-old house. The old roof had no roof or ridge vents —...

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Q: We had a new roof with ridge vents and attic vents installed on our 14-year-old house. The old roof had no roof or ridge vents — only lots of under-eave vents.

Several neighbors use wood-burning fireplaces, and one occasionally uses a smoker and open fire bowl in his backyard. The wood smoke comes in our roof vents and attic, then is pulled (by forced-air furnace) down into the living area through recessed can lights and vents. The house fills with smoke. My husband plugged the eave vents on that side of the house. This did not help.

We also had a new air conditioner and furnace installed. However, only lukewarm air comes from the heat vents. On cold mornings, it may take an hour or more for the heat to rise from 63 to 69 degrees.

To complicate matters, attached to the furnace is an air-filtration system with a fresh-air intake and its own blower.

I don’t know if this is relevant, but no smoke is coming out of the heater vents.

Another thing: Smoke comes in through the recessed lights when I turn the downdraft stove vent on.

I’m asthmatic and feeling helpless. What can we do?

A: Ask your neighbors to voluntarily reduce the amount of smoke produced while explaining your health condition, and what is happening with the house. Goodwill hopefully will result in an end to your discomfort. The open fire may or may not be legal. If the initial friendly discussion with the neighbors is not effective, contact Puget Sound Clean Air Agency (www.pscleanair.org or 800-552-3565) and let them determine the lawfulness of the neighbor’s outdoor burning.

Now regarding the house itself: You have negative pressure inside the building shell that is pulling air inside. Negative pressurization strong enough to pull smoke in through every gap is the result of an imbalance between the hot and cold side of the furnace; in other words, you have a disconnected heat duct somewhere. The dislodged duct is probably in the crawlspace.

You probably also have cold-air returns in the attic that are partly disconnected. The older roof venting simply masked the problem, whereas the new well-vented roof allows the smoke to enter.

When you turn on the downdraft fan, the dryer or any other fan that vents outside, you make the smoke problem worse, since you are increasing the negative pressurization inside the house. If you opened windows and doors, you would see less smoke. The fact that it takes an hour for the heat to rise in the morning simply proves my hypothesis about a disconnected heat duct. It’s also possible that an entire plenum or feeder pipe may have come loose.

To make matters worse, your fresh-air system is pulling air directly from the exterior, and may be wired incorrectly so it runs 24/7, which would result in this problem occurring constantly, not just when the furnace comes on.

You need to get a heating contractor familiar with air-movement problems to carefully analyze the entire heating and cooling system, paying particular attention to the ducts and fresh-air intake system. Correcting the pressurization, duct and fresh-air intake issues should eliminate the smoke problem for the most part. Sealing large gaps around lights would be another good step to take.

If you don’t get results, then you will need to have a “blower door” test done. This is a specific test that is performed with the house pressurized or depressurized, then each air-moving appliance is activated and air leaks found with a smoke pencil. That will be expensive but will find the exact problem.

Darrell Hay is a local home inspector and manages several rental properties. Send home-maintenance questions to dhay@seattletimes.com. Sorry, no personal replies. More columns at www.seattletimes.com/columnists.