Common Attic Insulation Mistakes and Why You Should Use a Professional

Your attic does more than providing storage space for your stuff. It’s also designed to protect your home from the elements: cold, heat, and humidity.

But for your attic to do its job, you need proper attic insulation.

The trick, of course, is doing it right. Insulation is a skilled trade, and it takes time and practice for a safe and effective insulation installation. Without expert help from an insulation contractor, it’s easy to make costly or even potentially hazardous errors.

Don’t waste time and energy. Read on to avoid the five most common DIY attic insulation mistakes.

What Insulation Is and How It Works

First things first: how does insulation work? To answer this question, you’ll first need to understand how heat flows. 

Heat circulates in three different ways: conduction, convection, and radiation. 

  • Conduction is the way heat transmits through materials.
  • Convection is the way heat circulates through liquids and gases.
  • Radiant heat, also known as thermal radiation, heats anything solid in its path, which then absorbs the energy. For example, this is how the sun warms the earth.

Insulation works by slowing conductive heat flow through the walls of your home. To a lesser extent, it also slows convective heat, which is the flow of heat through the air. 

Proper home insulation can save you up to 20% on heating and cooling costs while keeping you comfortable year-round.1 And the appropriate amount of attic insulation results in less wear and tear on your HVAC unit.

Insulation Through the Seasons

Regardless of the mechanism, heat flows from warmer to cooler air until there is no longer a temperature difference between the two. 

  • In the winter – During this time, you should be preparing your attic for the cold. Heat will flow from the heated interior spaces of your home to adjacent colder spaces such as the garage, unheated attic, basement, and outdoors. To maintain interior comfort, your home’s heating system should replace the heat lost in the winter.
  • During the summer In warmer months, heat flows from the warmer outdoors to the inside. The heat gained in the summer must be removed by the cooling system.

Properly insulating your home will decrease the amount of air needed to be replaced by your home’s HVAC system by providing an effective resistance to the flow of heat, which will result in energy savings and dollar savings.

Proper attic insulation  can also prevent:

  • Gradual damage to your home caused by heat and moisture
  • Water or condensation from seeping in and eroding the walls.
  • Excess summer heat that can cause shingles to swell and break.

Now, you understand all of the benefits and you’re ready to insulate your attic.  So what are the common attic insulation mistakes to avoid?

Mistake #1: Using Incorrect Materials

The first step to a proper insulation job is choosing the right material. Insulation comes in many different forms:2 

  • Fiberglass
  • Cellulose
  • Rock and slag wool
  • Natural fibers
  • Foam boards
  • Reflective foils
  • Polyurethane
  • Vermiculite and perlite
  • Cementitious foam
  • Phenolic foam
  • Urea-formaldehyde foam

To choose the best insulation for your home, you’ll need to consider where you want or need to install the material, the indoor air quality, life cycle costs, recycled content, and ease of installation.3

Most people use fiberglass batt insulation for their attics because it’s affordable and relatively easy to install. With this type of insulation, you must pay close attention to the R-value: its ability to resist heat flow.1 The higher the R-value, the greater the effectiveness. The R-value is determined by the thickness and density of the insulating material, as well as temperature, aging, compression, and moisture content.3

The amount of insulation or R-value you will need depends on: 

  • The climate where your home is located
  • The type of heating and cooling system in your home
  • The part of the house you’re insulating

For example, the R-value required for an attic in Zone 1, which includes the southern tip of Florida, Hawaii, Guam, Puerto Rico, and the Virgin Islands, is R30-R49. 

However, for an attic in Zone 5, which includes Massachusetts, Rhode Island, and Connecticut, R49-R60 is needed. 

To determine exactly what is required for your home, consult an insulation contractor.

Mistake #2: Neglecting to Seal Air Leaks

Insulation is a protective barrier that slows the rate at which heat enters or leaves your home.

But the insulation that you use is only half of the equation.

To prevent air movement between unconditioned and conditioned spaces, you’ll also need to seal:

  • Outer walls
  • Windows
  • Doors
  • Floors

Over time, air and thermal leaks can seriously impact your home’s air quality by allowing in pollutants such as dust, dirt, mold, and mildew. Insulating your attic can prevent these pollutants from entering the interior spaces of your home, allowing your family to breathe easier.

Choose the right product depending on the type of air leak:1

  • Caulk, expanding foam, or weather-stripping can fill smaller holes and cracks
  • Plywood, drywall, or rigid foam insulation are ideal for covering larger holes
  • Sheet metal and high-temperature caulk can close gaps around furnace flues and chimneys

Mistake #3: Blocking Air Flow

Ventilation is important in an attic. It’s critical to know where to seal gaps but also which places need to remain uncovered, as you don’t want to obstruct airflow. 

Many homes have soffits or eave vents that are designed to allow air to pass through the attic. This airflow prevents humidity issues and also extends the life of the roof.

Make sure not to cover these vents with insulation in order to prevent condensation and mold growth, which can destroy the effectiveness of the insulation and cause health problems.

Mistake #4: Pulling Out Old Insulation

Many homeowners begin by immediately removing old insulation. While this would seem like the logical thing to do, it can make a huge mess and may not ultimately be necessary.

Conversely, if the insulation is soiled with mold or mildew, or rodent droppings, and then carried through the house, it can expose family members to these toxins.

Before you begin pulling out what’s already there, it’s important to keep a few things in mind:

  • The age of your home – In the 1950s and 60s, asbestos was commonly used in insulation. Asbestos is fine if left alone, but if agitated, the fibers released into the air can be extremely hazardous, especially if inhaled. Be sure to do your research and take the proper precautions to protect yourself and your family members.
  • Assess existing materials – If there’s no asbestos risk, then the old insulation in your home may not need to be removed. Layers of insulation work in a similar fashion as layers of a blanket. You might just need to add some new insulation on top of the old layer to attain the appropriate R-value for your climate.
  • Condition of old insulation – If there is evidence of moisture damage, such as from a roof leak, mold, or rodent activity, then the existing insulation should definitely be removed. Be sure to check each section thoroughly and replace it as needed.

Mistake #5: Overstuffing

When it comes to insulation, you might guess that the more you have, the better. 

But in reality, there can be too much of a good thing.

Fiberglass insulation is exactly that—glass that is blown into fibers.3 It has an almost magical quality to keep spaces warm in the winter and cool in the summer. But fiberglass insulation works by catching air between the layers of spun glass. If you pack too much into any given section, the air pockets will compress and the insulation won’t be as effective.

Mistake #6: Not Enough Material

The most common mistake when installing attic insulation is not being thorough enough.

It might sound easy to put up a few batts of insulation, but doing the job right takes time and precision. 

For a successful insulation installation , you should:

  • Take appropriate measurements and install just the right amount.
  • Cut the fiberglass to fit around any bracing, ducts, electrical, wiring, and pipes.
  • Wear the proper protective gear. Fit batts or rolls snugly together to avoid gaps or spacing.
  • Work it around any obstacles or tight corners.
  • Keep it at least 3 inches away from any recessed lighting fixtures to avoid excess heat or fire.4

You may also want to install rafter vents at the soffits to prevent the insulation from covering the attic ventilation and allowing moisture to build up.

Want to Avoid Mistakes? Call in Attic Construction. 

Proper insulation can lower your energy bills and keep your home cozy all year long—but unfortunately, these common mistakes can lead to everything from icy-cold winters to health hazards.

The best way to prevent insulation mistakes in the attic is to use a professional. 

Whether you’re unsure if your existing attic insulation needs to be replaced, questioning what R-value is needed for your climate, find yourself wondering how an attic fan works, or wanting to prevent your family from being exposed to any hazardous materials, consult Attic Construction.

Our experts will take care of the process from start to finish, ensuring your home is as comfortable and efficient as possible. Get in touch for a free consultation to make sure the job gets done right the first time.

Attic Construction is a well-established and reputable company that has been providing attic insulation services in different areas from San Diego, Phoenix and Orange County. So if you are searching for San Diego insulation installation or Phoenix insulation removal, we are just a call away! Don’t take our word for it though, schedule a free inspection, and we’ll show you!


  1. U.S. Environmental Protection Agency. “Seal and Insulate with Energy Star.”
  2. U.S. Department of Energy. “Insulation Materials.”
  3. U.S. Department of Energy. “Energy Saver–Insulation.”
  4. DIY Network. “How to Install Fiberglass Insulation.”

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