Is A Vented or Unvented Attic Best in Florida?

Photo by Dillon Kydd on Unsplash

Heat rises. And when you live in an already naturally hot climate like Florida, all the warmth and humidity can accumulate in the highest points of your home, such as your attic. Maybe you need some ventilation up there, but you’re undecided. Is a vented or unvented attic best for a Florida home?

Both vented and unvented attics can be energy efficient, but vented attics tend to have issues with moisture development while unvented attics don’t. Unvented attics cost about twice what vented attics do, though, so you’ll need a bigger budget!

In this article, we’ll discuss vented and unvented attics in detail, including their differences as well as their pros and cons. By the time you’re done reading, you’ll be able to decide whether a vented or unvented attic will be better for keeping your Florida home cool.

The thermal boundary for a gable roof can be located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic
The thermal boundary for a gable roof can be located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic. Source: Building America Solution Center

Vented and Unvented Attics: How Are They Different?

Let’s start by delving into the features, pricing, and pros and cons of vented and unvented attics, respectively. Seeing the differences between the two types should make your decision easier.

Vented Attics

A vented attic is one in which the attic is insulated yet the vents introduce outside air. This may seem counterintuitive, but it’s the key to energy efficiency in vented attics. When the Florida temps finally come down somewhat in the winter, the cool outdoor air that’s let into the attic through the vents will make the attic cooler as well.

This is more beneficial in homes that have harsh winters with snow, where the vents prevent a weather phenomenon known as ice damming. With ice damming, the snow that accumulates on the roof of a home melts as it slides off the roof, then re-freezes by the time it hits the gutters.

But vented attics have advantages in warmer weather as well. Since the room has airflow, the warm air trapped in the attic can exit the vents. This limits roof moisture, which can prolong the life of your home’s shingles.

Many homes are built with vented attics, and yours might be one of them. If your Florida home by chance does not have these vents and you’d like to get them installed, how much would they cost? According to HomeAdvisor, installation is $300 to $650, including both materials and labor.

The vents themselves can be as low as $10 up to $500 apiece.

Here are the pros of a vented attic:

  • Can protect your roof against ice and moisture damage.
  • Relatively inexpensive to get installed.
  • Your home might already have the requisite vents.

These are some downsides of vented attics to think about:

  • Florida homeowners don’t need any ice or snow protection.
  • Moisture accumulation has still been known to happen, even with vented attics.
  • The temperature of the attic will be closer to the outdoor temperature, which means you likely shouldn’t use your attic for storage. It will be too hot!
Photo of houses in a subdivision with a yellow arrow pointing out an exterior attic vent to highlight the difference between a vented or unvented attic.
It’s easy to identify a vented attic from the exterior of a home.

Unvented Attics

Unvented attics, as the name suggests, do not have vents. Also referred to as conditioned attics, these attics are insulated using spray foam or another insulating material. All gaps and openings in an unvented attic are sealed as well.

Not only are unvented attics known for their energy efficiency, but their temperature is much more consistent. You don’t have to deal with the constant weather fluctuations as you would with a vented attic, since outdoor air never gets in.

This can safeguard ductwork for traditional HVAC systems that might have been installed in or around your attic. Unvented attics can also ward off ice dams much like vented attics can (although again, ice dams aren’t typically a concern of Florida homeowners).

Attic insulation costs are around $1,700 to $2,100, notes HomeAdvisor, which translates to about $1 to $7 a square foot. Spray foam insulation prices are even higher, between $2 and $5 a square foot, which brings the project tally to somewhere in the ballpark of $1,300 to $3,800.

Let’s examine the pros and cons of an unvented attic, beginning with the pros:

  • Spray foam has a high R-value for energy efficiency, especially closed-cell spray foam.
  • Even better at preventing roof moisture accumulation.
  • They too can block out ice dams.

Here are some potential issues with an unvented attic that you should know:

  • More expensive than a vented attic.
  • No need for ice dam protection in Florida.
  • Could void your shingles warranty since some contractors believe spray foam insulation causes shingles to overheat and curl (it doesn’t).

Do You Need a Vented or Unvented Attic in Florida?

Now that you’re familiar with the terms, it’s decision-making time. Is a vented or unvented attic the better choice for your Florida home? To answer that question, let’s look at issues such as cost, longevity, temperature maintenance, and more to see which type of attic is superior.

For Convenience – Either

As we discussed earlier, many homes already have vents installed. If your Florida home does, then it’s energy-efficient without you having to put in any further effort. Just make sure you have adequate insulation on the attic floor, to keep your air conditioning where you can enjoy it. You might have to repair or replace your vents at some point down the road, of course.

Unvented attics can be convenient, too. After all, if the attic in your Florida home does not have vents, then why go through the trouble to get them installed? Spray foam insulation can last for upwards of 30 years when applied around roofs, says spray foam company Spray Foam Insulation NYC. This is quite a long shelf life, so to speak.

With no clear winner in this category, if you want a more energy-efficient Florida home right away, you’re better off sticking with vents if you have them in your attic or using spray foam in a ventless attic.

For Cost-Savings – Vented Attics

Homeowners are usually on a budget. You’d probably prefer not to spend too much money to regulate the temperature of your attic and make it eco-friendlier. Vented attics cost less money to install.

To recap the earlier sections, vented attic installation–which includes materials and labor–is $300 to $650. Spray foam insulation for a conditioned attic costs $1,300 to $3,800, which is more than twice the cost.

For Moisture Resistance – Unvented Attics

Although both vented and unvented attics alike promise moisture resistance, only one follows through with that promise. Perhaps it’s due to the temperature fluctuations in a vented attic, but moisture can accumulate within the vented system. If this moisture spreads, it can damage the roof, necessitating costly repairs.

An unvented attic does not develop moisture. This system is reliable enough that it can house electronic equipment like HVAC units.

For Temperature Retention – Either

The temperature retention between a vented or unvented attic could be a much bigger deciding factor. But this is Florida we’re talking about. Winters in Florida are very mild, compared to the rest of the country.

While a vented attic would usually be very cold in the winter and warmer in the summer as outdoor air passes through, the temperature of your vented attic in a Florida home would be warm pretty much the whole year through.

That consistency matches the temperature regulation you get with an unvented attic. However, since unvented attics don’t allow outside air in, spending time in them would be more comfortable. If you used your attic for recreation, you’d be able to stand being up there with an unvented system, since it would be less hot. You wouldn’t be able to say the same about a vented attic system.

Conclusion

Vented attics allow outdoor air to enter through the vents, and insulation can make this option energy efficient.

Unvented attics feature spray foam and seals to maintain the indoor temperature of the home in the attic.

We hope the information in this article has helped you decide between  a vented or unvented attic for your Florida home!

Erin Shine

Erin Shine

Founder | Attainable Home

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