How much hotter is an attic than the outside temperature? (2023)

How much hotter is attic than outside?

Note excessive heat – if it's 90 degrees outside, the attic temperature shouldn't be more than 110 degrees. More often than not, attic temperatures will be in excess of 125 degrees on a 90 degree day. This will overwork your air conditioning equipment, run up your utility bill and shorten the life of your roof.

An unventilated attic can reach 150 degrees in the heat of summer -- 50 degrees higher than it should be. An overheated attic can bake asphalt shingles on the roof and cause them to deteriorate.

Step one: Ventilation

Thanks to the radiant heat affect, attic temperatures on a 100-degree day can reach 170 degrees or more.

Attics can reach temperatures of 150 to 160 degrees F during a summer day, although outside air temperatures are only 95 to 97 degrees F.

Your attic is a cold zone – that means that it should be the same temperature as the outside air. By letting heat escape freely from your home into the attic, and having cool air from the outside meet in the middle you may have a problem.

The laws of thermodynamics dictate that heat naturally rises, which means your attic is the last stop for hot and warm air in your house. Your attic also rests right under your roof, which means on hot summer days the heat is going to radiate through the shingles and collect in your attic, creating a lot of hot air.

In fact, nearly 40% of the heat in your home is lost through the attic. Without proper insulation in the attic floor, you will find that rooms in the upper levels of a home will become colder quicker, making for a long, uncomfortable winter.

More specifically, for our area, most systems are designed to lower your indoor temperature about 20^°F from the outdoors. So, on days when it's 100^°F outside, and your system is running at its peak efficiency, your indoor temperature will likely never maintain a level lower than about 80^°F.

This increase in temperature at the top of your house results from the sun's rays blasting the roof surface. It will transfer the heat right into your living spaces unless it's impeded by insulation, a radiant barrier and/or an attic fan providing ventilation.

Can a hot attic catch fire?

Electrical overloads that overheat in attic insulation and other parts of the home are responsible for approximately 43% of all residential attic fires. Another common cause of attic fires is heating. Studies show that around 5% of attic fires are started when home heating systems malfunction.

An attic with balanced ventilation can be expected to have a temperature 15-20 degrees higher than the outdoor temperature peak of day. If it's 100 degrees in Texas at 5 pm, the attic can be 115-120 degrees.

First, attic temperatures that put Death Valley to shame, in the 140-150-160-degree range, add lots more “heat load” to your system through your ceiling area, making it harder to cool your home. For most homes, this ceiling area is one of the largest factors in your home comfort, as well as equipment size.

If your attic is too cold, it probably lacks sufficient protection from outside temperatures. According to the U.S. Department of Energy (DOE), the average unimproved attic has just R-19 insulation – the insulation value of a five and a half inch thick fiberglass batt.

One of the most obvious culprits of a chilly attic is poor insulation, especially in older homes. Improperly installed or deteriorated attic insulation can lead to a massive loss of warm air in the winter, and cool air in the summer. To maintain a comfortable temperature in your home, invest in new insulation.

There are several benefits to opening the loft hatch to cool down a house. Firstly, it allows cooler air to circulate throughout the house, which can help to cool it down. Secondly, it can help to improve the air quality in the house by allowing fresh air to circulate.

The Windows

If your home has a lot of windows, then these are a primary source of heat transference in summer. Especially windows facing east and west, which will get the most direct sunlight hitting them.

The biggest area for heat loss in most homes are drafts within in the walls, windows and doors. It's typical for these spots to be less noticeable than you'd think they would be. Just a single 1/8 inch gap under a standard 36-inch wide door will leak just as much cold heat out as an almost 2.5 inch hole through a wall.

How do most attic fires start?

Electrical malfunction is the leading cause of residential building attic fires (43 percent), followed by natural fires (16 percent). A third of all residential building attic fires spread to involve the entire building. Only 2 percent extend beyond the building to adjacent properties.

5% of Your Home's Lost Heat is Through Ceilings

A small portion of your home's heat is lost through your ceiling. If you get a home energy audit and find that much of your heat is escaping through the ceiling and into the attic, it may be time to test and see how much insulation you have, and how much you need.

Just because the outdoor temperature is above 100, the Ideal temperature to set your AC unit to doesn't change — it's 78 degrees. Higher temperatures in the home are to be expected when the weather is hotter than usual, but your thermostat can still be set the same as if it were a lower temperature outside.

What Is An Unhealthy Room Temperature? For babies, pets, and the elderly, or for those who suffer from respiratory, lung, or heart disease, anything below 68 degrees and anything above 74 degrees for a prolonged period of time can cause serious health concerns.

They recommend that when it's 90 degrees outside, you should try setting your air conditioning thermostat at 80 degrees or higher.

Reasons for Attic Overheating

In many buildings, finished and unfinished attics serve as that highest point. Hot air rises, heat builds up in the attic, and so the attic overheats.

Roofing in Hot Weather

As a general rule, heat can pose a danger to roofing technicians when temperatures climb above 90 degrees. The heat index, which reflects both the temperature and the humidity, means that temperatures below 90 degrees can be dangerous, too.

Staying cool while roofing can be a challenge. Demand for roofers is high in the summer; so roofing professionals often have to work the hottest days and without shade.

Roof temperatures can be anywhere from 5 to 20 degrees warmer than the temperature on the ground.

The ideal attic temperature should be no less than 60 degrees in the winter and no more than 10 to 20 degrees above the outdoor temperature in the summer. If your attic temperature climbs above 130 degrees, you may start running into issues with your energy bill, as well as the integrity of your roof.

Is it OK to store clothes in a hot attic?

Remember, clothing items you truly care about must ideally never go into the attic, since heat is a concern here. Moreover, attics are particularly sensitive to harsh environmental conditions, dust, mites etc. An attic is hard to seal, due to ventilation issues.

Pre-melted candles probably aren't what you have in mind, but that's what you could end up with if they're stored in the attic. Candles will melt in the heat, and the wax can potentially get on anything else in the storage container with them.

If it is well sealed, using a fan at one end of the attic to draw fresh air from the other end will certainly reduce the temperature in the attic. Reducing the temperature of the surface of the ceiling below lowers the air conditioning load and does save air conditioning money.

Attic dust can contain various harmful toxins and pollutants. These can include everything from lead and asbestos fibers to mold spores and bacteria. Inhaling these particles can cause various health problems, including respiratory issues, allergy symptoms, and skin irritation if you come in direct contact.

The answer is yes. Attic fans lower your air conditioning bill by removing the heat at the top of the house. They can also help cool the second floor, and in fact, they even prevent moisture from building up beneath your roof.

The short answer, yes, insulating the attic is an effective way to keep your home cooler during the summer months. While it's a given that the insulation in your attic will keep the home warmer during the winter, it isn't immediately obvious that insulation can also help to keep the home comfortable during the summer.

This increase in temperature at the top of your house results from the sun's rays blasting the roof surface. It will transfer the heat right into your living spaces unless it's impeded by insulation, a radiant barrier and/or an attic fan providing ventilation.

The Department of Energy estimates that a properly insulated attic can shave 10 to 50 percent off your heating bill. And it works the opposite way for warm climates; in summer, it helps stabilize your house's indoor temps to keep cooling needs in check.

Electrical overloads that overheat in attic insulation and other parts of the home are responsible for approximately 43% of all residential attic fires. Another common cause of attic fires is heating. Studies show that around 5% of attic fires are started when home heating systems malfunction.

Is a hot attic dangerous? In the summer, attics can reach temperatures of 140 degrees and higher. This type of heat build-up can be dangerous because it can damage your roof and any items you have stored in the attic. Excessive heat can also be dangerous if you have things electrical wiring running through your attic.

What should be the temperature difference between inside and outside?

Some experts suggest keeping about a 15- to 20-degree difference between the outside temperature and the air inside.

A properly insulated attic can benefit your home in many ways, beside just keeping the home at a comfortable temperature year round. The short answer, yes, insulating the attic is an effective way to keep your home cooler during the summer months.

It is possible to over-insulate your house so much that it can't breathe. The whole point of home insulation is to tightly seal your home's interior. But if it becomes too tightly sealed with too many layers of insulation, moisture can get trapped inside those layers. That's when mold starts to grow.