How much insulation do I need in the attic of my Seattle home?

I was asked to write a 200-300 word response to the question, “How much insulation do I need in the attic of my Seattle home?” This comes in at 298 words. I had to keep editing it down so if I had my own way it would have more information, but this is all the words that would fit the space!

Getting Started
As a homeowner you might wonder where do I start with this whole attic insulation project? What type of insulation should I use? How much do I need?

In Seattle it is recommended that your total insulation obtain a factor of R-38 to R-49 (38 if you are using oil or gas or a heat pump with forced air heating, 49 if you are using electric heat like a baseboard or forced air register). The “R” means a measure of insulating power or “ability to resist the flow of heat”.

Attic insulation for the Do-It-Yourselfer
You can choose between roll out insulation (batts can be made of fiberglass of cotton from recycled denim), or “blown in” insulation, which is loose (cellulose, fiberglass, or rock wool) and can be purchased by the bag.

To know how much to add determine how much you currently have. Each inch in depth of your current insulation corresponds to an R factor depending on the material it is made of. Multiply the factor number to the number of inches in depth currently in place, and then make up the difference to reach 38-49 with new insulation.

How do I calculate how much I need?
1) Measure the length and width of your attic space in “feet”
2) Multiply those two numbers together to get the total “square feet”
3) Then you just need to buy enough material to cover the whole attic!
*Be sure to check the label for batt width (if you have joists), and R-value for the material.

If your attic is constructed so there isn’t enough space or access to put in the full amount you calculated, just add insulation where you can. Be sure to wear eye protection, gloves, and long sleeves! And maybe get some help!

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