First Aid for the Ailing House: Soffit vents not for bathroom ventilation

Q: I recently read a column of yours regarding venting through a soffit, and I had a related question. My master bath has a stand-up shower with a light in it, but the bath fan is approximately 13 feet away from the shower and the bathroom gets steamy, therefore condensing on the upper walls near the shower. I was thinking of installing another bath fan outside of the shower doors (how far from the doors?) to alleviate some of the steam and condensation. I would like to just duct this new fan to the soffit, which is only a few feet away, and question if some sort of connection is required between the flex duct and vented soffit. I looked in the attic, and the other bath fan is already ducted with a flex duct to the soffit, but the flex line is just laying on top of the vented soffit. Should I install some kind of termination through the soffit, or is it OK just to lay the fan duct on top of the vented soffit? My dryer on the second floor also is vented to the soffit but just lays on top of it. — Harrison City

A: The builder really messed up. Soffit vents are an inlet for air to ventilate an attic. Any fan venting through soffits is only introducing its contents -- warm, moist air -- into the attic, which is the last thing you want to do. Regardless of whether or not the duct is laying flat in the soffit or terminated through it, the outcome is the same. Bathroom and kitchen fans should be vented through gable walls, as I have mentioned many times before. Place the new fan as close to the shower as possible. A simple solution is to keep the bathroom door open after showering; this would dissipate the moisture a lot faster.

CHIMNEY POINTING

Q: I'm a senior female living alone and need help with a problem. I live in a ranch-style house. I have natural-gas heating, water and dryer. My chimney has not been pointed for a few years. I would appreciate any information you could provide on who should do the work or whether my handyman should do it. And if so, what materials would he need? The bricks look as if there is dried-out mortar between some of them; otherwise, it appears OK. What do you think? I love your book and have gifted it to several people. — Burlington, Vt.

A: I am not sure what you mean by dried-out mortar. If some pieces have fallen out, the chimney should be tuck-pointed to prevent further damage from freezing, which could cause the bricks to spall. If your handyman is experienced with this type of work -- and with walking safely on roofs -- you can have him do the repair. Otherwise, a mason or chimneysweep is an alternative. You may also ask whoever will take care of the repair to coat the chimney with a clear siloxane-based sealant to protect the bricks and mortar. It can be purchased at a masonry-supply house such as Trowel Trades in Colchester, Vt.

Venting attics — Charles Buell Inspections Inc

I have blogged about this particular issue in the past.  This defect is not common in New Construction.  It usually occurs in homes that have been re-roofed.  I am talking about compromised attic venting due to “opposing” systems being installed.

Older gable roofed homes typically had gable vents.  Historically, as we came to understand how venting works, and came to understand the problems associated with inadequately vented attics and roof structures, we moved away from the use of gable vents.  Gable venting relies on movement through the vents from one end of the attic to the other to change the air in the attic—and hopefully to carry any moisture that has entered the attic with it.  While in some cases this can be adequate, it often left areas of the attic “under-ventilated” due to poor circulation.  This system was also subject to poor venting depending on the house’s orientation to the prevailing wind direction.

The next approach was to have soffit vents that circulated air up to roof vents located near the ridge of the roof.  This was better but could still be affected by wind direction and in some cases the vents could be buried in snow drifting across the ridge.

By far the best method of venting the attic space is to have soffit vents that work in conjunction with continuous type ridge vents.  As wind moves across the ridge from any direction it acts to pull air out of the attic. I discussed this principle previously in, Ridge Vents–venting of roofs and attics .

So how does improper venting happen in New Construction?

It is easier to see how it happens in old.  For example:  the gable vents are already there—-and no one thinks to cover them up.  The roof vents are already there—-and it is easier to put another roof vent over the hole than it is to patch the hole and then properly patch the roof.  Perhaps the framers were just used to cutting the holes but the roofers where trying to do better?  Lack of communication perhaps?  Whatever the reasons, it shows a serious flaw in someone’s understanding of basic building science.  The following picture, from inside the attic, shows how the air is likely to flow to the continuous-type roof vent—-pulling little air from the soffit vents.

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