Do You Need To Vent A Metal Roof?
Metal roofs have been used to top barns, country-style homes, and buildings across the U.S. since the 1700s. However, the metal roofs of today are nothing like the familiar tin roof of years past.
With the use of modern technology, metal roofs now come in a variety of shades, colors and many styles are almost indistinguishable from other traditional roofing materials. Metal roofs are very popular among homeowners for their durability, longer lifespan and energy efficiency.
The question becomes: Do you need to vent a metal roof? While metal roofs do not come with any particular condensation concerns or ventilation needs, good ventilation is important in any home. Installing an effective ventilation system will properly protect and optimize your metal roof.
While they are a desirable alternative to more conventional roof coverings, they are significantly more costly. With an investment that is close to two or three times the price of asphalt shingles and other traditional materials, it’s important that it’s protected. In this article, we’ll explain why it’s important to vent your metal roof, as well as the benefits you can get from doing this.
Why Good Ventilation Is Important
Roof venting is a great way to release hot air and moisture from your attic and the upper levels of your home. Let’s examine the reasons why you may want to consider installing a vent on your metal roof.
During the summer months, ventilation helps to remove excess heat from your attic, effectively reducing air conditioning costs. In the past experts have suggested that reflective, or “cool roofs” are a great way to keep heat out of your attic.
While this is still the case, studies have shown that good ventilation that removes heat quickly is just as effective, if not more, at energy efficiency in the home.
If you live in the north or experience harsher winter months, installing good attic ventilation can help to prevent winter ice dams. When warm air from your lower living areas reach the roof deck, this causes the snow to melt resulting in ice dams.
The melting snow will cascade down the roof, freeze over the home’s overhangs and cause hazardous and destructive ice dams. These ice dams have the potential of forcing melted snow into your home.
With proper attic ventilation, you can keep the attic the same temperature as the outside and prevent the snow on your roof from melting and forming dangerous ice dams.
There’s no doubting that a large amount of moisture is produced daily in the living space of your home. Whether it’s generated by your houseplants, running your showers, doing laundry, cooking or ventless stoves, the moisture originates in the living area and travels upward.
If you don’t have a reliable vapor barrier, this moisture will end up in your attic. Once in your attic, the warm, moist air will condense when it reaches a cool surface. This resulting condensation will create a very unhealthy environment in your attic.
Because of condensation, your attic will be prone to mildew, mold and other biological growth. However, an attic that has been well-ventilated will keep your attic’s insulation dry, prevent moisture and increase effectiveness.
Ventilating Your Metal Roof
During the heat of the summer, the metal of your roof can become scorching hot and without proper ventilation in your attic, humidity and heat will accumulate beneath the roofing. This buildup of warmth can shorten the lifespan of your metal roof, reduce energy efficiency and warp the rafters.
Ventilation options for metal roofs are mostly the same as other traditional roofing systems, with some added considerations.
Understanding Metal Roof Ventilation
The need for roof ventilation stems from the scientific understanding that heat rises. The hot air and warm moisture that accumulates beneath the metal requires an escape route on the top of the roof and intake vents at the base.
A continuous natural draft is created from the air rising and exiting through dedicated escape vents. With nothing blocking the airflow between the exit and intake vents, you can achieve effect metal roof ventilation.
The most common place to install intake vents is beneath the roof eaves within the soffit. The soffit is the lowest area of your roof and refers to the material where the gutters and fascia are affixed to the wall.
The most reliable method of installing intake vents into the soffit is by measuring and cutting holes into the soffit board. These holes are then covered with louvered vent panels. The number of vents that your roof requires will depend on the overall surface area of your metal roof.
Keep in mind that on most new constructions, builders install a soffit that is perforated. This allows for a continuous intake vent already in place along the entire stretch of the soffit.
Ridge vents are a very efficient way to achieve good attic ventilation, allow air to flow naturally through the building and are also becoming increasingly popular among homeowners with metal roofs. Ridge vents are mounted at the roof’s ridgeline.
They are installed continuously along the entire stretch of the roof so that moist, hot air can escape from the attic along the complete ridge. Ridge venting is also an excellent option for finished attics. Airflow enters through the intake vents in the soffit and is transported up through the rafter spaces and exists through the vents at the roof’s peak.
To install, an opening is cut along the roof’s peak and the ridge vent is mounted over the opening. Metal ridge caps are then used on top of the vent for the air to escape and when installed properly, are virtually unnoticeable.
Another option for effective ventilation with a metal roof is to use gable vents. One of the main draws of metal roofing is the uninterrupted stretch of metal from the gutter to the top of the roof and prevents leaking. However, the thought of having to cut into the metal to install an exhaust vent is often frowned upon.
That’s where gable vents come in as they are a great choice for homeowners who don’t want to have to slice into their metal room. But, this venting system is not suitable for all homes.
Gable venting involves the use of at least two vents that are mounted just below the peak of the roof but as high as possible and in opposing wall gables. If you have an attic that is unfinished, installing gable venting is effective, low-cost, and very easy.
The Cost To Vent A Metal Roof
For labor and materials, you are looking at paying about $300 to $650 for venting your metal roof. This is quite cheap compared to other types of roofing. However, you can take it a step further and save some money by doing this yourself. Yes, it’s a very involved process but if you have the skill necessary, then you are looking at paying about $150 to $300 in materials.
But, if you prefer to hire a professional, then that’s fine too. It’s a good idea to call around to several stores to see what each charges, and what their fees include. For instance, some professionals don’t include clean up in their quotes. Or, they don’t include the cost of materials.
Will A Metal Roof Cause Mold If It Is Not Vented?
Metal roofing is great for locations that have mold issues, particularly humid weather. However, if you install the metal roof over an existing asphalt shingle roof, this can cause more damage than what was occurring in the first place. The metal roof will harness the humidity, allowing the mold spores to grow quicker within the asphalt. So, as long as you don’t install your metal roof over an existing asphalt roof, everything should be good to go!
Do you need to insulate under a metal roof?
Yes, if you have a metal roof you should add a layer of insulation underneath. This can help manage condensation and retain heat in the winter. Since metal is intuitively a better heat conductor than wood, good insulation will help your home stay cool in the summer and warm in the winter.
Can you install a metal roof on top of shingles?
As long as local building codes allow for it, you can install a metal roof over an already existing roof. Consult the local building codes to find out if you can install it without removing any of the old shingles.
Are there any problems associated with metal roofs?
One of the most common issues with metal roofing is corrosion. If your metal roof is made of galvalume or galvanized steel, it has the potential for rust and corrosion if any damage occurs to the water-resistant coating.
Wrapping It Up
While the existence of a metal roof doesn’t require that you make any special considerations in regards to ventilation, every home should have good attic ventilation regardless of roofing material.
Whether you choose to install ridge or gable venting, proper ventilation is vital to maintaining durability, optimizing energy savings and ensuring a long lifespan for your metal roof.
Jessica considers herself a home improvement and design enthusiast. She grew up surrounded by constant home improvement projects and owes most of what she knows to helping her dad renovate her childhood home. Being a Los Angeles resident, Jessica spends a lot of her time looking for her next DIY project and sharing her love for home design.
More by Jessica Stone