A poorly insulated attic is easily one of the top 3 things I find in just about every home where I perform a home inspection in Louisville, KY. I’d be willing to bet it’s like that in lots of other areas of the country as well. So I decided that when I finally got around to fixing my own home’s insulation in the attic, I would write a DIY guide for it. A properly insulated attic is one of the easiest and highest ROI (return on investment) things you can do to your home. Most folks can recoup their cost in as little as a year or two. So the faster you muster up the get-up-and-go to get this knocked out, the better off you’ll be.
This DIY guide explains step-by-step how to insulate your attic properly. We’ll cover the different types of insulation you can use, the prep work you need to do before adding the insulation, and everything in between. As with all things concerning a home, no guide or list can be all-inclusive, so this should be read with the understanding that you may not be able to follow it verbatim, but it should cover the topic for the vast majority of you. As always, feel free to give me a shout if you are unsure or have questions about your process. I’m here to help. You can tweet me @inspectorben, or You can email me here.
UPDATE: Below is a list of frequently asked questions about insulating your attic. You’ll want to read the whole process to fully understand how to insulate your attic space properly, but this FAQ will get you started.
If you are curious about the energy savings, here is a copy of my utility bills a year later after finishing my attic. I cut my usage for the month nearly in half. If this doesn’t motivate you to get your home fixed, what will?!?
Can you install cellulose insulation over old fiberglass insulation?
Yes. It will not cause any problems to mix the two types. The most important step is to air seal your attic before you install the new insulation.
Does cellulose insulation create an air barrier?
Once cellulose insulation reaches a certain depth in the attic, it can act as an effective are barrier and slow down the movement of air between the living space and the attic.
Is rolled insulation better than blown-in insulation?
No. Rolled batt insulation creates gaps in your coverage after it has been installed. Blown-in insulation is a much better choice for attics as the small pieces will fill those small areas.
What is the best type of insulation to use in my attic?
While every application has its own challenges, cellulose insulation is one of the most common found in modern construction due to its R-Value per inch and air sealing capabilities at higher depths.
Can you have too much insulation in your attic?
No. In general, the deeper the insulation levels the better off you will be. However, you must make sure you are not blocking off your attic ventilation for moisture removal.
Insulation Material Options – Why blown In Insulation is the best option
There are many choices available for you when it comes to attic insulation. Let’s take a quick look at the most popular ones, and discuss the pros and cons of each type.
Prepping Your Attic for New Insulation
Much like a quality paint job, the prep work is vital to a quality end product when it comes to insulating your attic. Let’s look at each step and I’ll explain what you need to do and why, in order to make your new insulation perform as well as it can.
I had about 50 hours of prep work in my attic before I even ordered my insulation from Lowe’s. While your time will vary, you need to put forth the effort if you want to reap the full benefits of your new attic insulation. Does it suck spending so much time to get things ready? Yep, sure does. You know what else sucks? Spending all that extra money every month on heating and cooling, and not being comfortable in your home. That sucks even more in my book.
Let’s look at the prep work that I needed to do in my home. Most of this will apply to you, so be sure you do not skip these steps if you want the best possible results with your new attic insulation.
Installation Time – Rally the Troops
So you’ve worked your tail off getting things ready for the new insulation and now it’s time to install that new blanket of love.
The delivery of my materials arrived at about 9am on a cloudy, rainy Saturday morning. The online calculator from Lowe’s website said that I needed 138 bags of cellulose insulation to reach my desired depth of 20″. That seemed a bit excessive to me, so I rolled the dice and ordered 125. The truck pulled up and dropped off the blower machine, and four pallets of insulation. Below are my tips for install day. It’s all downhill from here…Kinda.
Grand Total in Cost
Here is the breakdown for the total cost of the project.
We started around 9am the morning the materials were delivered, and I climbed down from the attic at about 1:30pm, only stopping to grab some water or change my dust mask. Clearly, your time will vary, but I would think just about any home could be finished in a day. As long as you’ve got everything prepped, and enough material to do the job, once you start the machine it is all downhill from there. Let’s look at the total cost of the job for my house. Remember: I added about 14-16″ of blown-in cellulose, installed a baffle system all around the perimeter of the attic with foam board, extended my B-Vent for the gas appliance, insulated my knee walls with 6″ of rigid foam board and air sealed my ceiling plane with fire-rated can foam.
- 125 bricks of cellulose. The cost per brick is about $10.00. However, Lowe’s has bulk pricing on this when you buy more than 100 bricks. That brought my total to $7.00 per brick. I ended up returning 18, so my total cost on the cellulose insulation itself was about $750.00.
- The 1/2 foam board used to make my baffles (or insulation dams) was $10.00 a sheet. I used 12 sheets for a total of $120.00
- The wood for the catwalk I had left over from another project, so I consider that old money and a freebie. If you had to buy this stuff I’d budget about $200.00
- I used two full sheets of 2″ rigid foam to insulate the walls. It’s $27.00 a sheet for a total of $54.00
- I ended up using about 5 cans of the Great Stuff Pro Foam. This is about $12.00 a can. You could save a bunch here by using caulk to do most of your air sealing, but the foam is so much faster it was worth the extra cost. Spray Foam – $60.00
- A couple of new short sections and an elbow of B-Vent for my flue pipe. $100.00
This brings my total to around $1300.00 in materials.
Not bad for a job that would likely cost around $3-5k if you hired a pro. I called 3 local insulation contractors in Louisville and tried to gauge what it would cost to have this done, air sealing and all, and none of them would even give me a price. All said it was a “waste of time” to do all the extra prep work I was asking for. This tells me that the “pros” don’t want to spend the time to do things correctly. They can make more money by just blowing in a new layer of insulation and running off to the next gig. If you decide that this job is more than you want to tackle, be sure and gauge your contractor by the prep work in this guide. If they are not willing to do things correctly, I’d advise you to move on and find a new insulation contractor.
Now, through the magic of video editing, you can watch my 5-hour job in 3 minutes. Thanks for reading, and if I can help in any way please give me a shout! Stay warm!
More How-To Guides for Insulating and Air sealing your home
Don’t forget to implement my other guides on your home as well.