Can You Put Too Much Insulation In The Attic?

As concealed as insulation is in your attic walls and floorboards, the various associated benefits are much more visible. If you’re looking to install insulation or already have it in your home, you’re likely aware that the correct amount can improve year-round comfort and reduce your energy bills.

However, the key words here are “correct amount.” If your home is not appropriately insulated, you’ll have much more difficulty saving money and staying comfortable in both summer and winter seasons. It’s very possible for a home to be under-insulated. In fact, numerous homes across the United States have this very issue. Are you wondering if you can put too much insulation in an attic? In short, yes, it is possible for an attic to be over-insulated.

It’s incredibly common for homeowners to insulate areas of the attic that should not be. In addition to other concerns, too much insulation can reduce its functionality, hinder airflow, cause mold and mildew and eventually lead to wood rot.

The most common type of insulation for an attic is batt insulation, or sometimes referred to as “blanket” insulation. This type of insulation can be found in a number of R-values (its resistance to heat flow), depending on particular spaces. Generally, you’d fill 2-by-4 stud walls with R-13 insulation, 2-by-6 with R-19 and 2-by-10 ceilings and floorboards with R-30.

Some companies offer batt insulation that is considered to be high-density and is designed to provide high levels of insulation for smaller spaces. However, it’s important to keep in mind that you will not achieve a greater R-value by simply shoving more insulation into an area where that individual R-valued insulation is not formatted for. In this case, the attic can end up having too much insulation.

While we’re on the subject of placing the wrong insulation in improper areas, the same goes for areas with moisture. You should not put insulation in places where moisture is known to accumulate, it will shrink, not efficiently protect your home and could lead to mold and mildew growth.

Too much, or improperly placed insulation can hinder the air circulation in your attic. A suitable (generally R-30) insulation should be laid out along your attic floor but should not be placed in the space where the rafters meet the top of the exterior joists and walls. To allow for ample air circulation, this area must be left open.

Drafts are necessary in your attic and stuffing this area full of insulation can be a breeding ground for mold, mildew and potentially even wood rot in the roof sheathing and rafters.

If you think your attic may be under-insulated, instead of placing it in the wall transition of the rafters, walls and joists, lay another layer over a current one.

What about if you’re not sure if your attic has enough insulation? Regardless of the type of insulation you have, one easy way to determine if you have enough is to examine the attic space. If the insulation is level with or below the floor joists (can you visibly see them?), you should add more. However, if you cannot see the floor joists because the insulation is concealing them, you likely have enough or may have too much.

For best results, you want your insulation to be evenly distributed throughout your attic. Though the exact amount needed may vary depending on the aforementioned factors, the ideal level for most attics is to insulate to R-38, or between 10 and 14 inches.

Believe it or not, a properly insulated attic can actually save you money. When your attic is not insulated, all the money that you pay to condition the air in your home simply goes up and out of your roof. According to the Environmental Protection Agency (EPA), the average homeowner saves 15% on heating and cooling costs with proper insulation of their attic, basement, rim joists, and crawl spaces. For most, this equates to a savings of about $200 per year.

Beyond that, a home that is well-insulated is generally more durable overall and more valuable when it comes to resell.

While it is more common for a home to be under insulated, it is possible to over insulate your attic. In fact, the amount of insulation required by building code is the minimum standard a home can be constructed with; it’s often never the appropriate amount. In some cases, homeowners and builders get overly ambitious and install more insulation than is necessary or even remotely effective.

Achieving the right amount of insulation in your attic is all about striking a balance between the up-front costs and the long-term energy savings and performance you can expect to enjoy from your insulation. Homes should be constructed with the area’s climate in mind and there is an ideal level of insulation for any given geographical region.

The law of ‘diminishing returns,’ as it relates to insulation, means that there is a point where you should stop insulating homes and start spending money on adding heat. Otherwise, you risk spending too much money on insulation and could potentially cause far more harm than good.

Related Questions

Can too much insulation cause mold?

Over insulation, in an attic or anywhere else in the home, can result in poor ventilation. This prevents the humid air from escaping can makes the area more prone to condensation. When you have condensation, you have a breeding ground for mold. So, yes, too much insulation can cause mold.

Can you install fiberglass insulation over blown-in insulation?

There is no issue with installing fiberglass batt insulation over top of existing blown-in insulation. However, make sure that you only use “unfaced insulation,” meaning there is no aluminum foil or paper facing the batts.For more insulation related knowledge, check out: “ How To Install Foam Board Insulation Under Siding” and “ How to Get Rid of Mice in Attic with Blown Insulation.”