Signs of Over-Insulation in Your Home and Tips for Finding the Right Balance

Houses in regions that experience four seasons or experience extreme temperatures need some form of insulation. Wall and roof insulation make up the building envelope that prevents heat loss in winter and heat gain in summer. Now, electricity prices in Kansas City might be 8% less than the national average (a little over 10¢/kWh). Still, any opportunity to save is always welcome.

This is the motivation behind most home insulation DIYs. Residents use spray foam insulation to beat the extreme summer and winter temperatures in Kansas City. The goal is to reduce energy consumption and costs by ensuring reinforcing their house’s insulation instead of turning the air conditioning or heater on 24/7.

Reversing Under-Insulation

One of the most common problems of home insulation is under-insulation. It can come in any of these forms:

  • Gaps in the walls
  • Gaps in the soffits and tray ceiling
  • Uneven or lumpy coverage
  • Misplaced insulation (not inserted in the “building envelope”)
  • Contracting and pulling away from framing (can result from improper application or incorrect mixing of spray foam insulation)

These being the most-talked-about home insulation problems, people with basic knowledge about building envelopes assume that laying the insulation on thick is the right thing to do.

Their assumption is partially correct: every additional inch of insulation increases energy savings. If you consider the cost of installation, however, the extra thickness also reduces the savings per inch. But there’s an even bigger problem: DIY installations that are unsupervised by insulation specialists can go wrong in so many ways.

Too Much In the Wrong Places

Insulation being added

Too much of a good thing cancels the expected benefits, and nothing can be more accurate when it comes to home insulation.

Here’s a rule of thumb: over-insulation exists where ventilation doesn’t. This explains why home builders and contractors say there’s no such thing as over-insulation. What they truly mean is it’s okay to go a little over the Goldilocks zone when insulating attics and walls as long as the house is adequately ventilated. If not, the house will be too “tight” for comfort, and its air toxicity and fire risks can even increase.

Over-insulation can happen by:

  • Covering the hollow where the rafters and the tops of the exterior walls and joist meet – This space is crucial for ventilating the roof. It should, therefore, be left open. Some homes protect this space by installing rafter vents, but others don’t use the hardware and leave the attic mostly bare. Many make the mistake of filling the gap with insulation, thinking that doing so will prevent air leaks and increase their house’s energy efficiency.
  • Insulating between rafters – The rafters are part of the house’s passive ventilation system (doesn’t require energy to work), and packing them with insulation defeats their purpose. Rafters should be left open if the floor is insulated. Likewise, you may insulate between the rafters if there is none on the floor. These rules apply specifically to spray foam insulation.
  • Insulating the conditioned space of unfinished attics – An unfinished attic is an extra space that’s uninhabitable as is. It has exposed beams for a floor and bare rafters: unconditioned spaces that make up the building envelope where insulating material should be installed. Some houses, however, have unfinished attics with conditioned spaces. These areas are not part of the envelope and therefore don’t need insulation. Inexperienced installation companies that fail to locate the envelope could end up insulating the conditioned spaces (and wasting much of the homeowner’s money).

Over-insulation, therefore, is not about the excess of spray foam, fiberglass batting, or loose fill. It means having insulation in areas where there should be none.

Possible indicators of over-insulation are if your attic is inexplicably hot, there are signs of mildew on the floors, corners, and rafters in your attic, and there’s moisture in random spots all over your house (these will be discussed in further detail in the next section).

Another way to find out if a house is too tight is to measure its air exchange rate. Find a roofing professional who can measure the ACH or air changes per hour. The ASHRAE Standard, which indicates the ideal ventilation and indoor air quality in residential buildings, says that the ideal ventilation for homes is 0.35 ACH at 15 cubic feet of air per minute (cfm) per person, or higher (this means three air changes for every hour with the air moving at 15cfm).

The ideal ACH is flexible, however, and may change depending on the following:

  • The size of the house
  • The number of combustion appliances (burns fuel) inside
  • The efficiency of the exhaust systems in the kitchen and bathrooms
  • The moisture levels indoors

If these don’t sound familiar, schedule a consultation with a roofing insulation expert like A+ Insulation. We can answer your questions about ventilation and determine the ideal air exchange rate for your house.

The Consequences of Over-Insulation


Now that you’re aware of over-insulation and how it hinders ventilation, it’s time to learn why it’s important to avoid the former and ensure the latter.

Over-insulation can create health risks and cause structural defects in a building:

  • Poor indoor air quality – The lack of ventilation means the indoor air that gets increasingly stale and polluted (e.g., mixing with fumes from cooking and fuel-burning appliances) have nowhere to escape. Even if fresh air comes through open windows or doors, the air flows will still be problematic without a properly functioning vent.
  • Uncomfortable indoor temperature – Warm and humid air that forms from heat-generating appliances would naturally rise to the ceiling. Ideally, the warm air would pass through the ceiling floor and out the roof vent. With the roof vents blocked, however, the warm air will be trapped inside the attic. This is a big problem in summer as the trapped air will make the attic so warm, the heat might radiate back to the house.
  • Damaged roofing – An over-heated attic during the summer can cause premature damage to the roof over it. Extreme heat can weaken the wood framing and cause the shingles to warp. In winter, the warm, moist air that rises will condense as it hits cold surfaces in and around the attic. If the moisture seeps into the wood framing, it can lead to premature rotting. As the winter progresses and the temperature drops, the trapped moisture will enter into a cycle of freezing and melting. This can cause the roof deck to swell unevenly and reduce its stability and load capacity.
  • Mold growth – Another consequence of moisture formation is mildew and mold growth. What’s worse is that warm air can enter wherever there’s a vent: through the building envelope, beneath the soffits, through the plumbing, and crannies for electrical wiring. Water could pool where you least expect it and mold can grow if left unnoticed. Mold is, of course, a health hazard. It can trigger allergic reactions like itchiness, red eyes, sneezing, runny nose, and other respiratory issues.

How to Correct Over-Insulation

If you suspect your house is over-insulated, the remedy is simple: check if your soffit dormers, rafter vents, and ridge vents are indeed blocked, whether by insulating material or debris. Remove the blockage and take note of the locations of your roof vents moving forward.

In the process of removing insulating materials from your attic and envelope, sections that should be left behind might be inadvertently affected. You can touch-up your insulation with polyurethane spray foam as it is very easy to work with. It expands and fills empty spaces, giving you full coverage no matter how jagged or uneven the edges of your existing insulation panels are.

You only need to have insulation installed correctly once, and you’ll be set for years. Over-insulation is supposed to be easy to avoid. When it’s time to upgrade or touch up old insulating materials, all installers would have to do is follow the layout of the original insulation.

Solve Over-Insulation By Trusting Experienced Home Insulation Installers

You can get this type of spray foam insulation and have it installed expertly in your home through A+ Insulation. Our installation specialists are certified and expertly trained to be the best people for the job. We’re proud of our hard-earned reputation as professionals who are courteous, friendly, honest, and will always deliver quality work.

We are a licensed, bonded, and insured insulation company that specializes in polyurethane spray foam. We serve customers from Kansas City and over 30 other cities and neighborhoods in Missouri.

A+ Insulation is an Angie’s List Super Service Awardee and a part of the IBP Family of Companies. Choosing us to insulate your home will be worth every penny and second of your time.

Get in touch with A+ Insulation and get a free, no-obligation inspection and cost estimate for your home.