Our crews have been in plenty of attics where it's super-hot, I mean we're talking 140- to 150-degrees or more. I've even seen situations where the wood trusses are so hot to the touch you wouldn't be able to hold them for very long. If there are metal ducts in the attic, you can actually burn yourself.
Ideally, the attic temperature should be close to the outside temperature, give or take 10 to 20 degrees. If your attic temperature is getting to 130 degrees or hotter, you can expect to see damage to your home. An attic can easily surpass this target in warm climates, getting as high as 160 degrees in the summer.
The reason for this is that the average person can touch a 140°F surface for up to five seconds without sustaining irreversible burn damage. Telcordia GR-63 for telecommunications appliances categorizes contact surfaces by material types –metal and nonmetals, shown below.
By improving ventilation in your home's attic, installing an attic fan can help reduce moisture and even lower the temperature within your entire house.
Heating and air conditioning systems, often placed near the top of the house, work really hard to keep us comfortable. These essential systems can occasionally overheat and catch fire. The danger is more severe in the summer when your attic is already really hot.
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.
Hot attics steal away capacity from your system, which robs efficiency and wreaks havoc on your comfort. Utility bills soar, while air quality plummets. Your system runs much longer, and works way, way harder than it needs to, which results in a lot more wear & tear, plus greater frequency of breakdowns.
Why are attic fans not used anymore? Due to inefficiencies in relying on existing attic vents for air intake, attic fans have lost popularity. These vents often aren't designed for this purpose, resulting in inadequate replacement air supply.
Install electric ventilators and attic fans, which remove hot air from an attic. They have thermostats that turn the fan on at a recommended preset temperature of 100-110 degrees. Alternatively, install passive vents such as gable, soffit and ridge vents, which are openings in the roof that allow hot air to escape.
During the summer heat, you'll notice that running your attic fan will keep the rest of your home more comfortable. If you've ever been up in your attic during a hot summer day without your attic fan running, you'll know that attics can become extremely hot because they trap heat.
Live Science writes that most humans can endure about 10 minutes in 140–degree heat before suffering from hyperthermia, a lethal form of which is the aforementioned heat stroke.
Most adults will suffer third-degree burns if exposed to 150 degree water for two seconds. Burns will also occur with a six-second exposure to 140 degree water or with a thirty second exposure to 130 degree water. Even if the temperature is 120 degrees, a five minute exposure could result in third-degree burns.
140-degree water scalds in just one second. It takes four minutes for 120-degree water to scald. Safe bathing temperature is 100 degrees, cooler for infants or elderly.
Heat rises to the top of the house and gets trapped under the roof. Roof windows also mean plenty of sun throughout the day. All this can cause an uncomfortable attic temperature, especially during hotter months.
As you know, cold air settles and hot air rises. Opening your automatic garage door will let cool air and a draft in; opening your attic access panel will draw that air into the attic and help to push the hot air up there and out through the roof vents, assuming you have proper attic ventilation.
Rafter vents should be placed in your attic ceiling in between the rafters at the point where your attic ceiling meets your attic floor. Once they are in place, you can then place the batts or blankets, or blow insulation, right out to the very edge of the attic floor.
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.
Contact a professional to add extra vents and a roof exhaust to enhance the natural circulation of air throughout your home and reduce the temperature in your attic. For a more active way of easily reducing the heat in your attic, a solar fan is ideal.
If your goal is to help keep your home cool, adding a radiant barrier to the insulation in your attic can make a big difference. Radiant barriers are made of reflective foil sheeting. It is added to the walls of an attic to help reflect heat away instead of absorbing it into the space.
If the evenings are cooler, you can try turning the attic cooling fan off until the morning, but if you notice your HVAC system begins to struggle to keep your home comfortable, you may want to keep running the attic fan overnight.
There are several strategies you can employ to cool down your attic, including insulation upgrades, ventilation improvements, and the use of attic fans or air conditioning. Each of these solutions addresses a different aspect of the problem: Insulation upgrades can prevent heat from seeping into your home.
If you had to choose just one—and your attic has a great need for ventilation—an attic fan is your best bet. Attic fans in the $300 to $400 range can move upwards of 5,000 CFM. For lower capacity ventilation at a steep cost savings, a ridge vent might be your best choice.
Thanks to the radiant heat affect, attic temperatures on a 100-degree day can reach 170 degrees or more.
Does insulation make your house hotter? "Insulating homes has very little, if any, impact on the risk of overheating," said Professor Kevin Lomas from Loughborough University, who led the largest national study so far into overheating in homes.