Should I Remove Old Attic Insulation Before I Spray Foam

Well should you? This question has been danced around for quite a few years now. Believe it or not many spray foam contractors either don’t know the answer to this question or don’t care. Mainly because it can be expensive and make you reconsider doing anything at all. Think of it like this, you called a few companies to come out and give you a quote on spray foaming your attic. The prices vary for the foam and they are doable, but then you notice the additional cost for removal. Wow! Now you are scratching your head thinking, “Well do I really need to remove the old insulation, or can it just stay?” At this point the guy trying to make a sale no matter what will try to persuade you not to do it just to get the job. But the truth is it takes someone with actual experience and understanding of the process to make a judgement call.

So here are the 3 options with removal.

  • Full Removal
  • Partial Removal
  • No Removal

Now that you know your options I’m going to give you 3 reasons why we would do a full removal and then break down why you can get away with partial removal in some cases as well as possibly not having to do removal at all. Remember every home is different for the most part, there is many factors that go into play to make to right call so hiring a company with experience and proper training is crucial.


  • To Prevent Moisture Issues

Think about how hot your attic gets as well as the dew point. If you decide to leave the old insulation on the attic floor after spray foaming the underside of the roof deck, the attic will be much cooler in the winter than if you removed the old insulation.

But one reason to put spray foam under your roof deck is to avoid having to air-seal your attic floor. With that said, the air in the attic is connected with the air inside your home. Meaning its more humid than outdoor air and more humid than common vented attic air.

But now after spray foam the attic isn’t vented to outdoors. The attic is now much warmer than outdoors in winter but significantly cooler than the living space if you leave the old insulation in the attic floor. That makes the surface of the spray foam colder, and most likely even below the dew point.

Removing the old insulation for the attic floor will solve this problem.

On a side note.  We need to think of spray foamed attics as conditioned attics. Once you regulate the air in your attic, this problem goes away, with or without the insulation in the attic floor. But most attics are not retro fitted by a a/c company after spray foam is installed.


  • To Guarantee a Good Seal

Spray foam insulation installed properly not only insulates a home but greatly reduces the air leakage from the home. The only way this can be done properly is making sure the installer can get into all those hard to access places where the attic was originally vented.

If you leave the existing insulation on the attic floor it can interfere with the install process and prevent the installer from properly sealing voids. In some cases, you can rake or fold back insulation with no problem that’s where the partial removal comes into play.


  • Improve Air Quality and Reduce Odors

Now that you understand the risks of moisture and how old insulation can cause issues with the application process, here is something else you need to take into consideration. Air quality and Odors. Does your home seem to always have dust everywhere no matter how many times a week you clean? What about smell, you updated everything in your home, but the old home smell just won’t seem to go away.

Believe it or not this is caused by that old insulation that’s laying on your attic floor. Yes, it all makes sense to you now. You just realized that insulation up there is just as old as the house. God only knows what they made that stuff out of years ago and we don’t even want to think how many rodents have come and gone. So if you aren’t concerned about the first two reason, this should push the vote.

Other things to take into consideration is that some building codes require the removal of old insulation. Also, many energy efficiency programs will help with the cost of having spray foam installed but require the removal to be done. You can check with Energy Star and most government programs for more information on assistance.

Again every home is different and in some cases removal might not be necessary. I’ve personally used all 3 options of no removal, partial removal and full removal. But those decisions were based of 10 plus years of hands on experience in the business.