Why Your Attic Is So Hot – and How to Cool It Down
No, you’re not imagining things.
It really is hotter up there than it is outside. So why is your attic so hot, and is there anything you can do about it?
Fortunately, there is. Maybe ventilation is the answer. But only in certain circumstances. Otherwise, you might make the oven up there even worse! And when I had my roof redone, I did something nobody seems to tell you about.
Keep reading, and I’ll share everything I know about why your attic is hot and what you can do to cool it down.
First, let me explain why your attic gets so hot.
Why Your Attic Gets So Hot
What happens to you when you stand out in the sun without any protection? You get really hot—and maybe a bad sunburn.
Your house gets really hot standing there in the sun as well. And if it doesn’t have any cover or protection like tall shade trees or a handy skyscraper beside it, all that heat might be building up inside.
If there is no means of escape for the radiant heat the sun is creating in your attic, it gets even hotter than it is outside. Up to 50 degrees F hotter.
Solutions to Cool Down an Attic That’s Too Hot
So what can you do to fix the problem? Thankfully, there are smart options. That means cranking your air conditioner and sending your utility bill sky high isn’t one of them.
1. Ventilate, ventilate, ventilate
You absolutely need to provide a means of escape for all that hot air. And fortunately, there are several ways to do it. And some of them are fairly inexpensive.
These are also called louvered vents, and of course, these only apply if you have a gable roof. These don’t have a fan mechanism and only offer passive ventilation of your attic.
Gable or louver vents are a means of passive ventilation.
To work effectively, they are installed in pairs. They work much like main floor windows at the front of the house and a window at the back of the house. On days with a nice breeze, you would get airflow throughout the house, with one window acting as an intake and the other as an exhaust.
Instead of a window, the louvered vents move air through the attic. They move hot air out of the attic.
Depending on size, gable vents cost about $25 and up but if you can’t install them yourself, you’ll also need to pay labor costs.
Ventilators / Attic Fans
If you’ve done any research on powered attic vents, you will have found there’s a great divide. Just as many are for them as there are against them. But there’s a good reason for that.
Research is key. You need to know your specific situation before deciding for or against powered attic vents.
Here’s what the National Renewable Energy Laboratory has to say. “Attic ventilation reduces attic temperature 10 to 25 degrees and slows the transfer of heat into the living space.”
But on the flip side, the Florida Solar Energy Center/University of Central Florida said, “attics with nominal natural ventilation and R-19 ceiling insulation do not need powered vent fans.”
What does that mean? If you have good insulation it’s going to reduce the effectiveness of a powered fan.
But wait, there’s another problem. If your attic isn’t air-sealed, there’s a good chance adding that fan will just suck out some of your air-conditioned air. Which clearly defeats the purpose.
So before you decide on a powered attic fan, make sure your home fits the following criteria.
|Go For an Attic Fan If . . .|
|Your attic insulation is less than R-19|
|Your attic floor has been completely air sealed|
|Soffit ventilation in excess of 336 square inches|
|Any HVAC equipment you have in the attic is well insulated and sealed|
But hold on before getting an attic fan if you meet the above criteria.
To put it simply, a powered attic vent is only going to help if you have insulation that has an R-value rating that’s too low.
Depending on your climate—anywhere that deals with hot or cold extremes—you should have adequate insulation in your attic.
The benefits of a well-insulated attic go beyond comfort. The Department of Energy states that says an attic that has been properly insulated could save you between 10 to 50 percent of your heating bill.
And yes, we’re talking about cooling your home not heating it. In the summer months, the reverse is true as well. Proper attic insulation will also help keep your indoor temps stable and reduce costs.
Attic Insulation Tips
As long as you can safely navigate around in your attic, insulating is something you can often do yourself.
Here are a few tips to get you started.
- Inspect any existing insulation
- Choose the right kind of insulation
- Seal air leaks
- Insulate your attic floor
Inspection. The first thing you want to do is find out how much insulation you already have up there. If you measure the depth of your existing insulation, you can determine the R-value.
R-value measures the resistance of heat transfer through the insulation.
|Insulation Type (R)||11||13||19||22||30||38|
Attics call for a maximum R-value of 60 depending on your climate zone. That’s about an 18-inch depth of settled fiberglass.
You also want to be sure your current attic insulation is safe. If your home was built before 1990, check for insulation that looks lightweight, grainy, and loose-looking that contains shiny flecks. It could be vermiculite with asbestos deposits.
Now determine your insulation target value.
Before adding your new insulation, seal all leaks. Leaks make all the insulation pointless.
- Spray foam around any attic windows
- Small gaps around pipes, fans, and ducts should be caulked
- Sealed metal flashing should be used around chimneys and flues
Finally, if you have a hot attic, stop using it as a storage space. The best way to insulate the attic is to add insulation to the floor. Which you can’t do if you have plywood down. And decades’ worth of junk you can’t bear to part with.
As a final insulation tip, don’t forget about access spots. Adding insulation everywhere and then leaving the access hatch, door, or pull-down ladder is a mistake.
For hatches or doors, cut a piece of rigid foam insulation the size of the door and attach it to the attic side. If it’s a door, add a sweep to it.
If you have a pull-down stair, you can find zippered, insulated tents that can help to keep things draft-free.
When It’s Time to Replace the Roof
This tip may not help you in the short term, but it will if you’re going to be replacing your roof anytime soon.
You’ve probably heard that dark colors absorb light and light colors reflect it. If you live in a hotter climate and you have an attic that retains a lot of heat, don’t create even more radiant heat by choosing a dark shingle.
If your attic is uninsulated and unvented, it really is an oven up there.
Just don’t be too quick to add power ventilation because under certain circumstances it won’t help. It might make things worse and ultimately cost you more in utilities.
If you have attic insulation that is at or above the recommended R-value for your climate zone, you should not add a powered attic fan if you’re attic is too hot. Instead, look for air leaks. Or insulate the attic floor.
You can also add passive vents such as gable or soffit vents if you don’t have them already.
If your insulation is below the recommendation for your area, you still shouldn’t be too quick to add powered ventilation. You should first address your lack of insulation.
Finally, if you’re going to be replacing your roof anytime soon, be sure to use light-colored shingles.
Hopefully, we’ve addressed some of your concerns and you found this article helpful. Why not check out our related links below?