Attic Insulation Sins, The Top Mistakes Insulation Contractors and DIY’ers Make And How To Avoid Them

Insulation jobs are not as simple as blow-and-go and mistakes made or overlooked by insulation contractors can end up wasting a lot of your money with little benefits to show.  Here are 3 critical items that must be done for every insulation job to make sure the insulation is not compromised because when it comes to blowing insulation, the preparation is almost as important as the depth.

1. Air seal the attic. 

Two story homes and ranch style homes are particularly guilty of committing air sealing sins.  Air sealing is separating the attic from the conditioned house and you would think that the framers, drywallers and A/C contractors would know this when they build the house but surprisingly in most homes we find a lack of boundary between the attic and home.

​Often times there is no barrier between the attic and the house except for a piece of ¾” drywall that is all that is stopping the Arizona summer heat from entering the home.  Of course there should be a nice thick blanket of 12” of insulation on top of the drywall but no, during our attic inspections we often find these attic air sealing sins and need to air seal the home before we blow the insulation.  ​

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Why Is Air Sealing Necessary Before Blowing Insulation?

If you take away nothing else from this blog, know that insulation is not an air barrier.  What does that mean?  It means that attic insulation does not stop the air from passing through it, so even if you pile 24” of insulation in the attic, hot attic air will still pass through the insulation and get into the home.  Think of a sweater on a windy day, that sweater is still letting a ton of air through.  You need a wind breaker on top of your sweater to keep you warm just like your insulation needs an air barrier to be effective.  What qualifies as an air barrier?  Drywall does, as does foam board, plywood, and spray foam when installed continuously to seal the cavity air tight.  Don’t make the mistake of typical insulation contractors and blow-and-go and air seal your home before you insulate.  

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What needs to be air sealed?  

Soffits, wall chases, plant shelves, top plates, exhaust fans, boot to sheet rock gaps, thermostat wires, electrical wires and plumbing penetrations.  A home energy audit can help identify how leaky your home is and where the majority of leakage is coming from (it’s not your windows if you live in Arizona).

​2. Kneewalls Are Neglected. A kneewall is a vertical wall in your home that has a back side in the attic.  Kneewalls are a nice architectural feature that homeowners use the horizontal shelves as a place to hold decorations or they may be functional to change from a vaulted part of the house to a flat ceiling in a bedroom or office.  The fact is that kneewalls are also in the attic and just like the drywall ceiling, they need to be properly insulated. Many a times our thermal cameras will reveal how poorly insulated kneewalls are.  If the entire attic floor is well insulated but the kneewalls are bare, guess where the all the attic heat is going to enter your home through?  That’s right, your kneewalls.  Heat flows in the path of least resistance and having improperly insulated kneewalls will compromise the entire attic insulation.

3. Taking Care Of The Attic Hatch.  I love when insulation contractors throw a fiberglass batt across the attic hatch and call it good.  It’s like telling your kids to clean their room and you come back to see a half-ass job and them preoccupied with whatever they were doing before.  Nice try, but that’s a fail.  You want a permanent solution and our method is to glue a couple sheets of thick foam board to the attic hatch so the hatch is permanently insulated.  Or have you ever noticed how the insulation conveniently tapers down around the attic hatch because no one figured you could build a dam around the hatch and insulation right up to the hatch?  All interior attic hatches need to be insulated with foam board and have a dam built high enough so insulation can be the same depth right up to the attic hatch.

Honorable Mentions – Insulation Tips and Common Mistakes To Avoid

1. Protecting Non-IC Rated Canned Lights.  IC rated canned lights are common now but in homes built before 2000 typically did not have IC rated canned lights installed.  IC rated stands for “insulation contact” rated, meaning the canned light can have insulation in direct contact with it.  This is typically denoted by a engraves stamp on the top of the canned light.  Non-IC rated canned light cannot have insulation touching the light directly or it will overheat.  There is supposed to be a safety shut off built into the light but I have seen these fail before.  Before you insulate your home you need to check the canned lights to make sure they are IC rated.  If you find they are not IC rated, a protective “hat” should be built around the entire canned light assembly, including the thermocouple. 
2. Not Installing Baffles At The Bird Vents.  If you look on the side of your home where the roof comes down and see a set of 2” holes in the side eaves, these are to help ventilate the attic.  The problem with them comes when insulating your home, you need to install baffles at all the eaves to direct the airflow up the roof deck.  When baffles are not present, the wind will actually push the insulation back a couple feet, also called wind washing, leaving the attic bare at all the eaves.  By installing baffles, you can avoid wind washing.  

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What Insulation Upgrades Do Not Need To Be Done

This list includes common insulation misconceptions, upgrades that won’t save you money on your energy bills but they may or may not be beneficial in other ways.

1. Insulating The Garage.  Homeowners that come from cold climates are always surprised when they find no insulation above garages in Arizona.  This is because our temperature swings are not as extreme as cold climates.  By insulating the garage in Arizona, you won’t save any money on your energy bills but it will help keep your garage a couple degrees cooler. 
2. Insulating Interior Walls.  Insulating your interior walls also won’t save any money on your energy bills however it is an effective way to sound proof your rooms.  It’s the insulation on the exterior walls of your home that make the blanket that protects your home from the elements. 
3. Adding Too Much Insulation.  Yes, you can add too much insulation to your attic that is begins to increase the temperature of your attic.  I like adding a couple additional inches of cellulose insulation above Energy Star Standards to account for settling over time, but any additional amount is overkill.  You won’t save any more money by adding more insulation in your attic above Energy Star Standards.

​By doing these upgrades before you insulate your home, you’ll be sure to have a properly sealed and insulated home.

Find out more:

Does your attic insulation need to be removed?

How much does insulation cost?

SRP rebates for insulation.