Hot Roof Vs. Ventilated Roof

Hot Roof Insulation

• A roof is "hot" when no ventilation exists to allow air to move through the attic space of the home and out into the environment. Insulation in the home's attic becomes critical when a home has a sealed roof. Without proper insulation, a roof lacking ventilation can trap air in the home's attic or crawlspace. Over time, this causes water vapor to form, which can promote bacterial growth and lead to wood rot. During winter, a sealed roof with inadequate insulation can encourage the accumulation of snow and ice, forming a thick layer over the roof. Water then accumulates under the roof shingles and pours into the rest of the building.

Ventilated Roof Alternatives

• A ventilated roof does not require insulation in the attic or crawl space to prevent the accumulation of water vapor. While the attic requires no insulation at the roof, the bottom floor still has insulation to protect the rest of the home from cold air. During summer, a ventilated roof can help keep a home cool by allowing hot air from the home's living spaces to escape. According to the website for This Old House, attic ventilation is also popular in cold climates because it allows warm air to escape the attic and discourages the formation of damaging water vapor.

Manufacturer's Building Requirements

• The type of roof installed on a home often depends on the requirements of the home builder and any product warranty stipulations. For example, according to This Old House's website, a building contractor using asphalt shingles on a roof must install ventilation into the structure to comply with manufacture warranty requirements. Considering how the choice of building materials will affect the structure of a home is important if the owner does not want restrictions on material choices and building options.

Climate Variety Problems

• Th wide variety of climates and seasons across the United States makes it difficult to choose a hot or ventilated roof. A ventilated roof may provide airflow benefits during the cold months, but the conditions that would require a ventilated roof don't occur in all areas of the country. Conversely, a hot roof works well in warmer climates because it preserves the temperature inside the structure, but can be useless in a colder climate if the insulation is substandard.