Can A House Be Over-Insulated?

Whether you’re building a new home or reinsulating the one you’ve got, you may be wondering if there’s such a thing as too much insulation. Is insulation where you should be investing your money? If you over-insulate your house, will there be any side effects or consequences?

South Central Services has insulated hundreds of new and existing homes around Greencastle, Pennsylvania. We get this question a lot, and we get it: you want to make sure you’re making the right investment. The good news is that our team works to understand building science and home energy efficiency. So, we know what it means for a house to have too much insulation.

By the end of this article, you’ll understand:

• What it really means for a home to be over-insulated
• What the real risk of over-insulating a home is
• Whether or not you should worry about over-insulating your home

Don't have time to read right now? Check out everything you need to know at a glance.

There Is No Harm In Insulating A Home Well.

Too much insulation is never going to cause problems in a home. Making a house “too tight” or “over-insulated” does not translate to issues in your energy efficiency, air quality, energy costs, or home comfort.

Too much insulation will not make your home hot in the summer and cold in the winter. Too much insulation will not increase energy costs or prevent you from circulating clean air inside.

While there is no harm in insulating your home well, there is also no reason to over-insulate a house. What you want from your insulation is efficiency and performance.

The Best Amount Of Insulation Has A Good Return On Investment.

So, what is the right amount of insulation for a house? Where do you draw the line between a well-insulated home and an over-insulated home?

The goal of insulation is to support the conditioning of your home. The right amount of insulation will make heating and cooling your house less expensive. The best insulation will also keep your home comfortable during more extreme seasons of the year.

If you spend $4,000 on repairing your crawl space with spray foam and recoup that investment through lower energy costs over five years, then that was a worthwhile investment.

Moving from minimal insulation to premium insulation will make a dramatic difference on your energy bills, allowing you to recover that investment cost over time.

The Right Amount Of Insulation Depends On Climate Zone & Project Type.

But how much insulation do you actually need? The amount of insulation that is right for your home depends on your climate zone and where you are insulating.

Homes in our climate zone have to consider vapor barriers for some exterior walls, while other climate zones don’t have that concern at all.

An attic application needs more insulation than a basement or crawl space. These are different areas of the home that influence their need for insulation.

A popular claim is that 2 inches of spray foam insulation is adequate for any area of a home. In reality, the appropriate depth of foam depends on where the foam is being sprayed.

Basement and crawl spaces can insulate well with only 2 inches of closed cell spray foam, due to the fact that the temperature differences that wall will generally see won’t exceed 30 degrees Fahrenheit.

However, an attic receives direct radiant heat from the sun. Different assemblies have significantly different temperature ranges, making the “right” amount of insulation different for every application.

Too Much Insulation Means Diminishing Returns On Investment.

Installing too much insulation isn’t going to cause problems for your home. The real problem of over-insulating a house is financial in nature.

When you upgrade the insulation in an attic from nothing to a premium, airtight seal, there will be considerable changes in energy costs. Making the thermal envelope of the home tighter and better insulated delivers a great return on investment.

Initially, when you start upgrading your insulation, you will get a significant ROI. Eventually, that ROI will drop off. The performance change becomes minimal after a certain point.

Once you’ve achieved a decently high insulation performance, it will start to cost more than you can recoup to seal your thermal envelope completely.

We would say a house is over-insulated when the homeowner can no longer reasonably recoup their investment cost through lower energy bills. When your ROI drops off, your home is insulated enough.

A House Can Be Under-Insulated.

You can technically have a house with no insulation at all. You can still heat and cool a home without any insulation. It simply takes more energy to condition a house without insulation. The BTUs needed to heat and cool an uninsulated home are very high.

As you add insulation, the BTUs required to condition the home drop. This is where the change in your energy costs also comes along. Eventually, you will reach a point where the BTUs required for a home don’t change by adding more insulation.

Our recommendation is always to address insulation first. Once your home is properly insulated and your BTUs cannot be reduced further for a reasonable investment cost, you can examine your HVAC system.

The Bottom Line About The Amount Of Insulation In A Home

A home with too much insulation cannot recoup the insulation investment cost through lower energy bills. Over-insulating a house has no negative impact on energy usage, comfort, or air quality.

We don’t recommend over-insulating a home because it is not a wise financial decision. However, we will always recommend the right amount of insulation that delivers a dramatic ROI, a more comfortable home, and better air quality.

Now that you understand what it means for a home to be over-insulated, your next step is to:

• Estimate the cost of a spray foam insulation upgrade for your home
• Learn the best way to insulate a new construction home
• Compare spray foam insulation to fiberglass batts