How to install additional attic batt insulation

On today’s article about how to install additional attic batt insulation I’ll be talking about what’s the best equipment to use and how to use it, how to find out when too much insulation is too much and what tools you will need to pull this off at home. Attic batt insulation comes in handy when you’re trying to upgrade your insulation to the latest standard, which is R-49. Most old houses have an insulation with an R-19 value, depending on the area you live in your insulation might have a different R-value. Using an insulation calculator would be best in this situation so you know which R-value you’ll have to achieve.

Attic insulation necessary equipment

When working with batt insulation, some form of protection equipment is necessary because of possible attic insulation dangers and because taking extra safety measures is always recommended. So, what you’ll need in this case are a long sleeved shirt, gloves, some form of eye protection and a dust mask - that’s it. Attic insulation doesn’t require too much protection but it is recommended you wear some, even if it comes in its basic form.

How much more insulation do I need ?

I’ve provided you with two simple to read graphics below, one is a state map and the other is a chart containing the recommended R-values for each zone ( marked with 1-6 on the map ).


Below you can see the chart for the recommended R-values for each zone.


Using some simple math we’re able to immediately calculate how much more insulation we’ll be needing, using this simple formula ( take into consideration this formula only works for batt insulation ).

Let’s say we’d like to achieve an R-value of 49 using only batt insulation ( which has an average R-value of 3.2 ), the way I’d do it would be like this:

49 / 3.2 = 15,31 ( the average thickness in centimeters of batt insulation )

15,31 / 2.5 = 6,1 inches. ( average thickness transformed into inches )

The result - we’ll need a thickness of 6.1″ to be able to achieve an R-49 using only batt insulation. Now, taking into consideration we’ll be using batt insulation over our existing insulation ( average R-value is 19 ) we’ll only need …

49-19 = 30; ( the difference between the two R-values )

30/3.2 = 9,375; ( dividing the difference with the average R-value of batt insulation )

9,375 / 2.5 = 3.75″. ( transforming it into inches )

So we’ll be needing an additional 3.75″ of batt insulation over our existing insulation - I hope this was pretty clear to everyone.

How do I install additional attic batt insulation ?

First make sure you’re going to use an unfaced batt ( one that comes without a foil layer ) so the insulation doesn’t trap even more moisture in the ceiling. Start laying the batts perpendicular to the joists and make sure they don’t compress the already existing insulation.

When laying the batts make sure not to cover can lights unless they are rated for contact with insulation and to use cardboard to keep soffit vents open. All the gaps and cracks between the living area and the attic should be filled using either caulk or expanding foam.

That’s it - it’s not rocket science. For any questions, feel free to contact me using the contact form at the top of the page.

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