How to Insulate

Insulation is just like any other project. And for small jobs it can even be a DIY project. But let me start with the warnings first on why you should consider a Contractor;

  1. It is surprising how inexpensive they can do the job, they pay much less for the materials and are much faster than most of us would be.
  2. They know what steps need to occur and in what order.
  3. It is a dirty job, often in hot attics or other tight spaces.
  4. The insulation at the big box store is often not what you should be using. The best option is friction fit batts, these will likely have to be special ordered at a big box store. Definitely don’t get the plastic wrapped stuff, you’ll struggle to get a grade one install with it.

Whether you hire a contractor or tackle this your self, knowing what needs to happen is critical. If you are talking to an insulation contractor, let them know you expect grade one installation and plan on third party certification from an Energy Auditor, HES Assessor or HERS Rater. The difference in performance for insulation that is not grade one can be as much as 75% for the same insulation purchased.

The map below shows the recommended R-values for each region of the country. Here in Birmingham we are zone 3 and as of 2017 our codes for new homes are similar to these recommendations.

What is R-Value? Simply an object’s ability to resist the flow of heat. The higher the R-Value the better it resists the flow of heat.


How much insulation does it take to get an R-value? Take a look at the next image to see:


So what do you do with this information for your plan. First consider what you can practically get to. Walls are generally not worth opening up to add a few points of R-value. But consider a foam board under siding if it is going to be replaced. The one type of wall we will address is Attic Knee Walls; they’re so bad, they desire their own write-up. Cathedral ceilings is another area we can’t do much with, without ripping apart your home. Most cathedral ceilings we see only have R-19 with no deck vents or R-13 with deck vents. Honestly I’d take the R-13 with deck vents. So the improvement for Cathedral ceilings would be to seal the bottom and top where accessible (allowing the deck vent to still function).

So all we are left with is ceilings and floors. Your biggest bang for your buck is ceilings, with proper air sealing and deck venting, additional attic insulation can make a huge comfort and energy savings impact. Your next opportunity is floors. Though not spelled out here, the rim joist is the key component of floors. Then again with proper air sealing and installation insulation can be very effective under your floor.

The following three videos from NAIMA show (1) what to look for when planning for insulation, (2) how to insulate, and finally (3) what to look for to a get Grade I Install.

For more great information visit The Insulation Institute.