Columbus Roofing: Article About Unvented Roof Construction
Unvented roofs are a relatively new and sometimes controversial construction method. They are becoming more common as modern technology allows for more tightly sealed home construction. They do offer several advantages over traditional vented roofs, especially when it comes to energy efficiency. The recent trend toward sustainable and green construction methods is also a factor in the rising popularity of unvented roofing. Columbus roofing contractors can walk homeowners through the viability of using this new design on their home.
To work effectively, unvented roofs must be installed on structures that meet certain criteria. First, the building envelope must be exceptionally tight and encompass the entire structure to the roofline. The easiest way to accomplish this is through the use of spray foam insulation. Second, there must be sufficient vapor barriers installed to prevent moisture from penetrating the conditioned space. Third, the building must be capable of holding enough air pressure to offset the stack effect caused by hot air in the attic forcing its way out through penetrations in the building envelope. Spray foam also helps with this problem, but extra care must be taken to make sure all possible leaks are plugged.
When done properly, an unvented roof does offer homeowners some significant advantages over traditional vented roofs.
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The most noticeable one is a more comfortable climate inside the home. A tightly sealed house contains the conditioned air better. In addition, having the attic included within the building envelope eliminates the need for insulated ductwork and takes some of the workload off of the HVAC units. This in turn leads to lower heating and cooling bills.
The tight construction and vapor barriers also keep moist air out of the home. Without moisture entering through vents, condensation on vents and other cool surfaces is greatly decreased. This can prevent damage to the insulation and protect against mold in less used areas like the attic.
The attic may see more use as well. By including it within the building envelope, homeowners gain an extra space that can easily be finished into additional living space. Even if the attic in question is not large enough for a full room, it is still extra climate controlled storage space. With conditioned storage homeowners don't need to worry about heat or moisture damaging their possessions.
There are some concerns when using this design as well though. Asphalt shingle manufacturers warn that unvented roofs can decrease the service life of their product due to the greater exposure to heat the shingles suffer versus going with a traditional design. So far, it also appears that unvented roofs are more prone to ice dams forming in colder climates.