What happens if there is not enough insulation in the attic?

Author: Maryjane Hettinger  |  Last update: Tuesday, June 3, 2025

Heating and cooling systems work hard to keep the home at the desired temperature. When a home has inadequate insulation in the attic, a lot of air is lost through the roof. Energy bills skyrocket, and it's impossible to keep the temperature in the house regulated.

What happens if you don't have enough insulation in your attic?

As energy efficiency moves to the forefront of priorities for homeowners and buyers, attic insulation has become increasingly important. Homes that lack adequate insulation in attics are at risk for a range of expensive and irreversible impacts like water damage and heat or cold air loss.

How to tell if your attic needs more insulation?

No matter what kind of insulation you currently have in your attic, one quick way to determine if you need more is to look across the span of your attic. If your insulation is just level with or below your floor joists (i.e., you can easily see your joists), you should add more.

Does adding extra insulation in the attic help?

Savings in Energy and Money

By adding insulation in your attic, you can maintain the desired temperature throughout your home much better. Combined with attic air sealing, it can also help to alleviate the formation of dangerous ice dams in the winter.

How much heat is lost through an uninsulated attic?

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.

Roofing How you can you tell if you don't have enough attic insulation

Should you insulate an unheated attic?

The purpose of insulation that lays along the ceiling joists (the attic floor) is to keep the home's rooms cool in summer and warm in winter. The walls and ceiling of an unfinished attic do not need to be insulated, but it's important to have vents in the roof. A finished attic is treated like any room in the home.

How much will attic insulation reduce my heating bill?

On average, you can save up to 20% on your home's heating and cooling costs or up to 10% on its total energy costs by adding insulation to attics, floors, crawl spaces, and accessible basement rim joists, and by reducing unwanted air leaks all around your house.

Where should you not put insulation in the attic?

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.

Is it possible to put too much insulation in your attic?

While over-insulated attics aren't as common as under-insulated attics, it is possible to put so much insulation in your attic that it has a negative impact.

How much does it cost to add insulation to an attic?

Attic insulation costs anywhere from $1,680 to $3,125, depending on the size of your attic and the material used. On average, most homeowners shell out around $2,380. These costs include the insulation materials and installation by a professional.

Can you put new insulation over old insulation in the attic?

In many cases you can add new insulation on top of old insulation, unless the old insulation is wet, mouldy, or vermiculite. If the old insulation is dry but appears to have previously been wet, you should look for the cause and repair the problem.

How do I know if my attic insulation is bad?

How Do I Know My Attic Insulation Should Be Replaced?
  1. Indoor Drafts and Temperature Swings. Does the temperature on the second floor of your house swing dramatically? ...
  2. Water Damage. ...
  3. Rising Energy Bills. ...
  4. Pest and Animal Infestation or Dirty Insulation. ...
  5. Bad Odors and Allergy Symptoms.

What is the most cost effective way to insulate an attic?

Fiberglass Batt and Roll Insulation

This insulation comes in pre-cut batts or long rolls, making it easy to fit between the framing members, like joists and trusses, in your attic. Fiberglass insulation is good at resisting heat flow and it's relatively inexpensive compared to other materials.

Is blowing in insulation in attic a good idea?

Blown-in attic insulation is one of the most effective ways to enhance your home's thermal performance and reduce energy bills.

What happens if you have poor insulation?

The lack of insulation in homes can lead to condensation and mould growth, creating unhealthy living environments and potentially causing structural damage. Insulation slows the movement of heat through the walls, roof, and floors, maintaining a more consistent indoor temperature.

Does attic insulation help with AC?

Attic insulation reduces your AC unit's energy usage, making it more cost-effective to cool your home during the summer.

What is the lifespan of attic insulation?

Conclusion. Attic insulation can last 80 to 100 years, though it loses its energy efficiency benefits with time. Certified attic specialists' professional advice is to upgrade it every 15 years to ensure that it is still performing the job.

Is it okay to cover attic insulation with plywood?

Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.

Is it worth adding more insulation to my attic?

With an average savings of 15%, a family of four could save $924.58 each year after installing new insulation in their attic. An extra $900 a year to spend on groceries, clothes, or school supplies would make an enormous difference for working families.

What is the rule for attic insulation?

Insulation is graded by its R-value—the higher the R-value, the greater the insulating power. If you live in a mild climate, your attic should have a minimum grade of R-38, or about 13–14 inches of insulation. If you live in a colder climate, R-49 is the minimum recommendation, or about 16–18 inches of insulation.

What happens if you don't insulate attic?

Uninsulated attics can cause major temperature fluctuations at home. In most cases, rooms on the upper floor will have significantly different temperatures from those on the lower floor. It becomes particularly problematic during the winter and summer when you need your home's indoor temperature to be comfortable.

Is it better to insulate a ceiling or roof?

The answer to these issues may be adding insulation, but that still leaves the question of where to apply additional thermal protection to see the most benefit. While both ceiling and roof insulation will increase your home's resistance to outside temperatures, insulating the ceiling should be your priority.

Can you have too much insulation in your attic?

Yes, it is possible to put too much insulation in a loft or attic.

Does blown in insulation save money?

Reduced Heating and Cooling Costs: By maintaining a more consistent indoor temperature, blown insulation can reduce the need for heating in the winter and cooling in the summer, potentially slashing your energy bills by up to 20-30%.

Does attic insulation help electric bill?

EPA estimates that homeowners can save an average of 15% on heating and cooling costs (or an average of 11% on total energy costs) by air sealing their homes and adding insulation in attics, floors over crawl spaces and basements.

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