You can add insulation to the roof deck, seal the attic and then actively condition it (temp and humidity) to anything you want, including less than your interior. Ie, a sealed conditioned attic with turned-down heating/cooling.
Cold Rooms, Walls, and Floors
If you find that a few of the rooms in your house are colder than the others, or if the ceiling and interior walls are cool when you touch them, it is a sign of improper insulation.
Back to the original question, the cheapest way to heat an attic would be if there is living space under the attic. Simply cut out holes (between the joists) in the attic floor in each area you want heat and a corresponding hole in the living space below. Connect the two with a short piece of duct.
If you're concerned about attic temperature control, a specific attic temperature range should help. Make sure your attic is no colder than 60 degrees Fahrenheit and no warmer than 10 degrees above the outside temperature.
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.
If your attic temperature is consistently hitting 130 degrees or hotter, damage to your home and a high utility bill is very likely. You can keep a thermometer in your attic to check – it doesn't have to be an expensive one and will give you a better idea of how hot things really are.
Adding insulation to the attic is generally a moderately difficult do-it-yourself (DIY) project, but the benefits can be substantial. If you are doing a major home renovation project, now may be a great time to tackle this project too.
Hot air rises, just like your energy bill will do if your attic is poorly insulated. A poorly insulated attic can result in 25% heat loss in fall and winter—that's 25 percent of your average heating costs going toward energy that won't even heat your home.
Should You Insulate the Attic Floor or Roof Deck? If you are looking for an insulation upgrade that you can see (on your energy bill) and feel (in a home that is more comfortable), we recommend insulating the attic floor, and using radiant barriers on the roof deck.
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.
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.
Insulate The Attic
Aside from insulating your attic pipes, the best thing to do is to insulate your entire attic. A frozen pipe in the attic can affect the entire water line throughout the house, so insulating the attic will come a long way in keeping the home safe and warm.
If you plan on converting your attic into livable space, such as an additional bedroom or a recreation room, adding heating and cooling to it can be worthwhile. Even if you do not plan on using your attic for living, you might still want to do something to better control the temperatures and humidity levels up there.
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.
While it may seem like the more insulation you have, the more energy-efficient your home will be, you do not want to insulate both the attic floor and ceiling. Insulating the floor and the ceiling would create a separate and conditioned environment, especially if you air-sealed your attic.
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.
Ventilate The Attic Space
How else can you keep the attic cool? Remember the cool attic trifecta: radiant barrier, insulation, and attic ventilation. A complete ventilation system consists of exhaust vents, intake vents, and solar attic fans. Proper ventilation improves airflow and air circulation within your house.
Baseboard heaters will probably be your #1 go-to for heating your attic. Not only are these out of the way and efficient, but they are also very safe and cool to the touch.
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.
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.
On a 100-degree day, an attic can reach temperatures of 170 degrees or more due to the radiant heat effect.
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.