Solving an attic mold problem with proper venting

Q. I need major help. I have always read your column, but now it's my turn to ask for help from someone I can totally trust.

I had an attic fan replaced a couple of weeks ago and while the installer was working I climbed the ladder to check the attic and saw a lot of black patches on the sheathing of the roof and around the nails; also on both sides of the wall of the attic. I had a mold remedial person come out and give me a quote. My question is what is the correct process and how can I find somebody I can trust?

I live in the Northwest suburbs of Chicago: Hoffman Estates. Sorry I have no photos to share with you.

My house is 30 years old. The guy said the plywood on one side has a hole and that is causing the moisture, but this has always been there all these years (I am the original owner).

A. If you used the attic fan during the winter to ventilate the roof, it may have contributed to the moisture condition responsible for the mold. Very seldom, if ever, is there enough net free ventilation area (NFVA) in attic vents to satisfy the CFM requirements of attic fans, so the fans rob the conditioned spaces of warm, moist air through many cracks and crevasses found in most construction. This moisture condenses on the cold roof sheathing and gable walls.

If you used the fan solely to cool the attic during the summer, and didn't thoroughly weatherstrip and insulate any access to the attic, the same warm, moist air converted into the attic by means of what is known as the stack effect.

There may also be other convective paths from the living spaces into the attic, such as recessed ceiling lights, bathroom and kitchen fans, etc.

There is usually no need to have costly remediation performed to remove mold. Closing all convective paths, not using the attic fan in the winter (or better, removing it) and providing natural ventilation by means of continuous soffit and ridge venting should dry up any living organisms in the moldy patches. The black patches may remain or peel off as they dry up, but they will have become inactive as the relative humidity (RH) in the attic drops and the moisture content of the framing members and the sheathing dries up.

The ridge vent must be externally baffled to direct any wind over its top in order to prevent most rain and snow penetration. A very popular one is Shinglevent II; there are others, but this has been my favorite for decades.

Soffit vents should be continuous and not added piecemeal along the soffits in order to provide what is called an air wash in all rafter spaces. And a free flow of air must be provided between the soffits and the ridge.

You didn't say where the plywood is missing; is it on the roof sheathing or one of the gables? How big is the hole and do you know why it's there? My guess is that the hole is on a gable wall that may have had a gable vent, which was removed if new siding was installed.

Whatever the reason for it, it is not what is causing the excess moisture in the attic since it is covered with roofing material or siding.

Q. Our home is 100 years old and the front door is very grungy. How can this be cleaned without harming the wood? There is a storm door in front of it and a covered porch. We usually use the back door and don't see this often, but now that we are retired and use the porch more I see this often and it is driving me crazy.

A. I assume you are referring to the greenish material I see on the trim of the door panels on your photos.

It looks like a sort of mold that developed on these horizontal moldings over the years, perhaps from condensation as seasonal temperatures fluctuated.

Try cleaning these surfaces with Milsek Furniture Polish & Multi-Purpose Cleaner. I have received many comments from readers about its magic.

Go to Milsek's website: www.milsek.com. Click on "Where to Find" and enter your ZIP code.

Be sure to read and follow Milsek's directions to use it properly. Do the entire door on both sides and consider a regular maintenance program. It may take several applications, considering the build up I see in one photo.

Q. We now have an exterior bump out that extends into our patio area. This was intended as a fireplace by the builder in a suburban track home. We do not need the fireplace as we added a family room with fireplace in 2003. It is unsightly and uses a lot of real estate on our patio. We have had a few contractors look at it and each has his own idea; all are concerned with keeping a pitch for drainage. Removing it is not a good solution as the floor joists extend through this bump out.

There is a concrete footing around the perimeter of the bump out. We would like to make this area useful and aesthetically more pleasing.

Originally we thought storage with seating; now we are thinking a step type shelf and seating area with the shelf creating a back rest. Perhaps the shelf area could be used for some storage.

It is located outside of our eating area. There is a kitchen to the south and family room to the north. Can you think of some options to convert this area into useful and visually pleasing space?

A. Thank you for sending photos. This is an interesting bump out; it is so low and just below two windows, and outside your eating area.

Since it has a concrete foundation and the floor joists extend though this bump out, I am assuming it has been considered as part of the living space and it is insulated.

Would you consider removing its slanted roof (an experienced contractor should be able to remove it whole for reuse on the suggested new construction), cutting open the wall above and building up the bump-out walls, reusing the windows and making the space part of the eating area?

Or, better yet, making it into a sunroom? It could be made into a greenhouse with glass shelves supporting plants that are improving the air quality. Of course this is assuming that the orientation is right for a sun space.

My confusion lies in the fact that one of your photos shows an angular shot of the right side of the bump out and you indicate that it is facing east. However, the shadow made by the sun seems to indicate that the long side of the bump out is facing east, not the right sidewall, which would mean that the left side of the bump out is facing south.

If this is correct, the sun pace would bring you morning sunlight, but not be too ideal for solar gain.

This may be more of a project than you are willing to contemplate, but that's the best I can come up with.

• Henri de Marne, a former remodeling contractor turned columnist and consultant, is the author of "About the House with Henri de Marne" (Upper Access Publishing). He continues to take questions from readers for this column and his website, www.henridemarne.com. Email questions to aboutthehouse@gmavt.net.