When winter arrives and temperatures plunge, heat doesn't travel from an attic into the living quarters.  Instead, heated indoor air travels from the home into the attic, along with moisture.  If left unvented, moisture rising up through the house condenses in the attic, causing damage to studs, insulation, and other materials.  A vented attic allows moisture to escape.

Furnace-warmed air circulates through the house, picking up water vapor generated by activities such as cooking, bathing, and the washing of clothes and dishes -- as much as 2 to 4 gallons per family of four.  The use of humidifiers, common in many homes, provides an abundant and continual source of moisture.  Keep in mind also that the warmer the air is, the greater its capacity to hold moisture.

The problem is especially acute in homes with electric heating.  Most of these homes were built since the mid-1970's, using advanced insulation materials and methods.  As a result, most are "tight", allowing minimal infiltration of outside air.  In addition, electric heat sources do not require air for combustion, so another common source of outdoor air has been eliminated.  Problems arise when the warm, moist air from the living quarters moves toward the attic, where the air is cooler and drier.  That moist air is drawn to the attic in two ways.  The first is through a process called "vapor diffusion."  It's a process in which water vapor naturally travels from high-humidity conditions to low-humidity conditions -- for example, from the living quarters into the attic.  The force of vapor diffusion is so great that moisture even travels through building materials such as sheet rock.  Even vapor barriers cannot totally stop this process.

The second way moisture travels into an attic is by air moving through openings cut into a vapor barrier.  Such openings are commonly found, for example, at recessed ceiling boxes and attic entries.

The problems start when moist air hits cooler rafters, trusses and roof sheathing.  The moisture condenses as water droplets or frost.  Eventually, the condensation drips on the insulation below.  If too much water soaks into the insulation, its volume can be compressed and its effectiveness reduced.  The sequence of events that follows: greater heat loss leads to colder rooms, colder rooms lead to a great need for heat, great use of the furnace leads to higher energy bills.  As with heat buildup, moisture buildup has long-term effects.  That's because not all the condensing moisture drips into insulation.  The structural elements of the house absorb some, leading to wood rot and the deterioration of roofing materials.  Other moisture is likely to soak into the attic floor and eventually into ceiling materials, causing water stains and paint damage in the rooms below.

Although the problems of attic heat and moisture have different causes, they share a common solution; a high-efficiency ventilation system that allows a uniform flow of air to sweep the underside of the roof sheathing.  The system exchanges warm, moist air with cooler, drier air.  

In summary, even if your roof is new, without proper attic ventilation and insulation, you can still have moisture problems which could lead to roofing problems.  To preserve the life of your roofing material, attic ventilation and insulation are clearly an important component of your total roofing system.

If you wonder if your attic insulation and/or ventilation is protecting your roof, visit our website and schedule an appointment today: www.precisionroofingmi.com.

Dealing with the effects of Moisture Buildup in the Attic - Image 1

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