How to Shop for Insulation

By Vernon Trollinger, October 3, 2017, Energy Efficiency, Home Improvement

While most homeowners love their homes, not every home is perfect. There are one or two things the homeowner would like to change, such as an outdated bathtub for a new walk-in shower or updating the look of their kitchen. And then there’s occasional “uh-oh” of the unexpected repair. In our How to Shop for Home Improvement Projects series, we’re going to identify several projects and some of the ins and outs of what you can expect.

How to Shop for Insulation | Bounce Energy Blog

How to Shop for Insulation

One of the most cost-effective home improvements is to air seal and add insulation to your attic. Not only does this reduce your energy usage and lower your monthly heating and cooling bills, but that savings can often pay for itself in just a few years. According to the DOE’s Home Energy Saver (HES), a 1800 sq. ft house in Ft. Worth that upgrades its R9/3” of insulation to R49/14” of insulation in the attic can save $315 a year (or more) on heating and cooling. With the expected cost running between $176 to $725 for the insulation (and around $2430 for labor ) payback time is roughly 8 years. It can also pay for itself when you go to sell your home. A recent study showed that fiberglass insulation recouped its cost by adding 107% value to the home.

Where to Start

Begin by planning the installation:

  • Since you’ll be in the attic, weather is a factor. The best time of year for attic projects is when temperatures are moderate and cool. While that’s usually in the spring or fall in northern states, for Texas, that usually gives you from November to March.
  • Take enough time. An attic insulation install can be completed in a weekend. Wear comfortable clothing, use good quality dust masks and wear eye protection, especially if you are adding insulation on top of an existing layer. Pace yourself. If you start getting too warm, take a break and drink plenty of fluids. Also, remember that the area where you come out of the attic will tend to get covered in dust as well. In that case, it’s a good idea to put a drop cloth on the floor and move items like clothing or bedding well out of the way.
  • Air seal the attic first. By sealing any gaps and holes where air from the living space below can escape up into the attic, the more effective the insulation will be. After all, having a thick blanket of insulation in place isn’t going to save much energy if you have a 2’ x 2’ hole in your ceiling that lets all your conditioned air escape into your attic.
  • Build insulation dams for soffit venting, chimneys, and attic doors. An insulation dam prevents the insulation from blocking soffits, touching hot surfaces, or falling down into the living space.
  • Figure out the square footage of your attic. You’ll need this measurement to help you decide what kind of insulation you’ll use and to figure out how much it will cost you. For example, let’s say you’re going to increase your attic insulation from R9 to about R47. If you use 12” thick 16” x 48” batts, you’ll be able to calculate pretty easily how many you’ll need to fill up a 1800 sq. ft. area. In this case, we take attic’s 1800 sq. ft divided by the sq. footage per batt (or bag) and that equals the number of batts (or bags). That’s around 29 batts. In the case of blown fiberglass or cellulose, you’ll need to factor in the thickness because you’ll be blowing in loose material. Fortunately, many home centers feature insulation calculators to help you figure this out. Manufacturers usually state on their packaging the number of bags per 1,000 square feet for a particular R-value.
  • Figure out how you’re going to get the insulation into the attic. Some attic entrances can be pretty narrow —less than 16 inches wide. That’s going to spell trouble if you’re trying to shove a bulky, fat package up through narrow opening. Figure out ahead of time what will work best for your situation. If you’re using an insulation blower, you’ll want to position the machine where it will be convenient to operate without making too much of a mess to the home’s living area.

How to Shop for Insulation | Bounce Energy Blog

What Insulation Types Should You Consider?

There are three main types of insulation currently in use: blown, rolls/batts, and sprayed foam. Each has their benefits, conveniences, and their costs. However, you don’t necessarily need to choose one or the other as all three can be used together.

  • Blown fiberglass uses loose fiberglass insulation fibers. Blown cellulose is made from recycled newspaper with borate added to increase its resistance to fire and insects. Cellulose also tends to cost less than fiberglass insulation, including both rolls and batts. Be advised that depending where you buy the insulation, the store may or may not offer use of the their insulation blower for free. If not, then you’ll have to add the cost of that rental into the overall cost of the insulation. While using the blower, you’ll need to be mindful of the insulation depth. A good trick here is know the thickness or depth and then draw a depth mark on several vertical truss supports in your attic. One drawback to blown cellulose insulation is that if it isn’t done right, it may settle over time and loose some of its R-rating. Another problem is that your attic’s framing must be sturdy enough to support all the insulation because cellulose weighs roughly three times as much per square foot than loose fiberglass.
  • Fiberglass rolls or batt insulation might be more convenient to handle and the installation may go quicker with less mess —however— for it to be really effective the insulation layers must be installed perpendicular to each other. For example, the first lies between ceiling joist and runs width-wise across the attic floor. The next layer would then be laid on top but running lengthwise across the attic floor. Add to this that the fiberglass rolls or batts need to be packed tightly together side by side to prevent as much heat loss as possible. To be sure, fiberglass rolls and batts don’t provide as thorough a covering as blown fiberglass or cellulose but it works well enough to be effective.

How to Shop for Insulation | Bounce Energy Blog

  • Spray foam insulation can combine both air sealing and insulation. Combine that with higher R-value per inch, ranging from R-3.5 for open-cell to R-6.5 for closed-cell, and that makes spray foam generally more efficient. Open-cell foam is vapor semi-permeable and is best used where water vapor should be allowed to move through. Closed-cell is vapor semi-impermeable and should be used where water vapor should not be allowed to move through. Even though foam has been used for years, choosing the wrong foam for the job can still cause headaches for both installer and homeowners.

Currently, one trend is to convert the attic to a conditioned space by sealing off attic venting and applying foam to the underside of the roof decking. It’s a good idea for Texas homes where the HVAC system is situated in the attic. Bringing the HVAC system “inside” the house helps it work more efficiently. It’s also a fairly expensive project due to the cost of the foam.

Spray foam is about two to three times as expensive as blown or rolled insulation. It’s best to go with a professional because spray foam requires a little more experience in mixing the foam agents as well as good technique to make sure it’s applied properly. It also requires protective clothing and a face mask due to foam spattering. One other caution is that climate and proper application.

For home owners who want to take advantage of foam but not the entire expense, one economical hybrid approach is to spray the attic floor with 2 inches of foam to completely air seal the attic floor. After the foam cures, the attic floor is then covered to the right depth with blown cellulose insulation. This way, you get spray foam’s full air sealing benefits and the lower cost of blown cellulose.

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About 

A native of Wyomissing Hills, PA, Vernon Trollinger studied writing and film at the University of Iowa, later earning his MA in writing there as well. Following a decade of digging in CRM archaeology, he now writes about green energy technology, home energy efficiency, DIY projects, the natural gas industry, and the electrical grid.

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