Dear Barry,

My question involves the popular but unwise practice of closing the foundation vents around a home. Many homeowners and maintenance people do this in the belief that they are conserving heat during winter. Instead, they are causing serious building damage and heath problems. As a heating contractor, I often find blocked vents, and too many hardware stores sell products specifically made for closing the vents. You’ve addressed this subject in the past, but the practice remains widespread. Could you please advise your readers to let the subfloor areas beneath their homes breathe? – Chad

Dear Chad,

Closure of subarea vents is definitely a widespread problem. As a means of winterizing a home, it misses the entire purpose and intent of ventilating the crawlspace. Winter is when ground moisture most commonly occurs under a building. It is the time of year when vents are most needed to prevent dampness, condensation, and resultant moisture damage. Closing the vents wrongly assumes that there is a need to retain heat in the subarea. Instead, heat should be retained within the dwelling by installing insulation in the floor framing. The subarea needs to be dry, not warm.

The key points in a nutshell are these:

1. The building code requires cross ventilation of a subfloor space beneath a building, with openings equaling at least one square foot per 150 square feet of floor area. Exceptions are allowed when a vapor barrier is installed on the ground surface or when mechanical ventilation is provided. These requirements are found in section 1202.3 of the International Building Code, section R409 of the International Residential Code, and section 2306.7 of the Uniform Building Code.

2. Insufficient ventilation can cause moisture condensation, resulting in fungus infection, dryrot damage, rusted hardware and mold infestation. With mold as a consideration, we are therefore concerned with health safety as well as structural damage.

3. Insufficient ventilation can also violate combustion air requirements for fuel burning equipment, such as furnaces.

Surprisingly, some builders entirely overlook this common requirement, and municipal building inspectors occasionally fail to notice the omission. But most homes are properly vented, and owners are strongly advised to keep these vents open at all times.

Dear Barry,

My gray shingle roof is about 10 years old and is gradually turning green, kind of like there’s a fungus on it. What can I do to clean it and prevent worse damage? – Judy

Dear Judy,

Roof surfaces that receive little or no sun exposure are prone to grow a thin layer of algae. This commonly occurs on northern exposures or where roofs are shaded by tall trees. Typically, algae does not adversely affect the condition of the shingles, therefore, removing it is not essential to maintaining the integrity of the roof. However, if restoring the original color of the shingles is desired for cosmetic reasons, you can try washing the roof with a watered down solution of algaecide, such as would be used for swimming pools. But no guaranty of satisfactory results can be made without first inspecting the roof.

For questions please visit Barry at


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