How to Insulate an Attic
Determine your desired R-rating., Choose your insulation material., Prepare your attic., Collect your equipment., Be aware of irregularities., Install the vapor barrier.
Step-by-Step Guide
-
Step 1: Determine your desired R-rating.
The R-rating of insulation shows how effective it is; a higher R-rating is more effective.
There are two R-rating scales, one US customary and one metric; the US scale is
5.68 times the metric scale so it should be obvious which one is being used.
It's usually recommended that existing homes have their attics insulated to a rating of R-38 (US), which will typically require a layer of insulation 10–14 inches (25.4–35.6 cm) thick, depending on what type of insulation you use.
If you're adding on to existing insulation, use this rule of thumb to guide your work:
Once joists are level with, or slightly below, your level of insulation, the total should be adequate for an R-38 rating.
Less than that, and you'll probably need to add more.
Past a certain thickness, it may not be cost-effective to add more insulation even if you aren't sure your attic is at the R-38 level.
If your existing insulation is more than about 10 inches (25.4 cm) thick, it might not be worth the extra money. -
Step 2: Choose your insulation material.
There are a few different kinds of insulation available for your attic project.
Choose whichever option works best for you in terms of cost, ease of installation, and effectiveness.
Batting insulation comes in low, medium, and high-density batts.
The higher a bat's density, the less is required to reach your target R-rating.
Batting is convenient and can be rolled out easily into rectangular spaces.
Most batting is made of mineral wool or fiberglass, which requires protective gear to work with safely.
Safer batting made from recycled foam is also available, though.
Loose fill insulation comes in bags and is used to insulate odd corners or angles where batting insulation won't fit as well.
It can be hand-packed, but blowing it into place with a special machine makes it more even and complete. , Attic insulation is installed in the floor of the attic, so you'll need to do a few things to make the process straightforward.
Start by installing temporary lighting, such as clip lights, and laying a few sturdy boards along the joists to create a walkway.
If you're installing new insulation and there's no old insulation, check the drywall of the ceiling below the joists for a silver backing, called a vapor barrier.
If it doesn't have one, you'll need to purchase material for one yourself.
Polyethylene vapor barrier rolls are available at any home improvement store.
If you need to work during very hot weather, be sure to have water close at hand, and stay hydrated to avoid overheating.
Heat collects in attics; the temperature inside can be many degrees hotter than the temperature outside, in some cases.
Try to work in the early morning if you can. , You'll need standard safety equipment, plus materials, and all the tools required to install those materials.
At the very least, be sure you have the following:
Safety goggles and gloves A dust mask A flashlight A tape measure A staple gun , Be sure you know where chimneys, recessed lighting elements, and any other possible heat sources are ahead of time.
If you suspect your attic has air leaks, try to find and seal them with caulk, spray foam, or weather stripping before you begin. , If you need to, now is the time to install your polyethylene vapor barrier.
Cut it into sections that fit snugly into the spaces between the joists, and staple it to the drywall below with your staple gun.
Leave a few inches around every heat source.
Polyethylene can melt and burn.
Be sure to cut away a 3-inch space around any chimneys or other heat sources. -
Step 3: Prepare your attic.
-
Step 4: Collect your equipment.
-
Step 5: Be aware of irregularities.
-
Step 6: Install the vapor barrier.
Detailed Guide
The R-rating of insulation shows how effective it is; a higher R-rating is more effective.
There are two R-rating scales, one US customary and one metric; the US scale is
5.68 times the metric scale so it should be obvious which one is being used.
It's usually recommended that existing homes have their attics insulated to a rating of R-38 (US), which will typically require a layer of insulation 10–14 inches (25.4–35.6 cm) thick, depending on what type of insulation you use.
If you're adding on to existing insulation, use this rule of thumb to guide your work:
Once joists are level with, or slightly below, your level of insulation, the total should be adequate for an R-38 rating.
Less than that, and you'll probably need to add more.
Past a certain thickness, it may not be cost-effective to add more insulation even if you aren't sure your attic is at the R-38 level.
If your existing insulation is more than about 10 inches (25.4 cm) thick, it might not be worth the extra money.
There are a few different kinds of insulation available for your attic project.
Choose whichever option works best for you in terms of cost, ease of installation, and effectiveness.
Batting insulation comes in low, medium, and high-density batts.
The higher a bat's density, the less is required to reach your target R-rating.
Batting is convenient and can be rolled out easily into rectangular spaces.
Most batting is made of mineral wool or fiberglass, which requires protective gear to work with safely.
Safer batting made from recycled foam is also available, though.
Loose fill insulation comes in bags and is used to insulate odd corners or angles where batting insulation won't fit as well.
It can be hand-packed, but blowing it into place with a special machine makes it more even and complete. , Attic insulation is installed in the floor of the attic, so you'll need to do a few things to make the process straightforward.
Start by installing temporary lighting, such as clip lights, and laying a few sturdy boards along the joists to create a walkway.
If you're installing new insulation and there's no old insulation, check the drywall of the ceiling below the joists for a silver backing, called a vapor barrier.
If it doesn't have one, you'll need to purchase material for one yourself.
Polyethylene vapor barrier rolls are available at any home improvement store.
If you need to work during very hot weather, be sure to have water close at hand, and stay hydrated to avoid overheating.
Heat collects in attics; the temperature inside can be many degrees hotter than the temperature outside, in some cases.
Try to work in the early morning if you can. , You'll need standard safety equipment, plus materials, and all the tools required to install those materials.
At the very least, be sure you have the following:
Safety goggles and gloves A dust mask A flashlight A tape measure A staple gun , Be sure you know where chimneys, recessed lighting elements, and any other possible heat sources are ahead of time.
If you suspect your attic has air leaks, try to find and seal them with caulk, spray foam, or weather stripping before you begin. , If you need to, now is the time to install your polyethylene vapor barrier.
Cut it into sections that fit snugly into the spaces between the joists, and staple it to the drywall below with your staple gun.
Leave a few inches around every heat source.
Polyethylene can melt and burn.
Be sure to cut away a 3-inch space around any chimneys or other heat sources.
About the Author
Scott Wright
Scott Wright has dedicated 9 years to mastering lifestyle and practical guides. As a content creator, Scott focuses on providing actionable tips and step-by-step guides.
Rate This Guide
How helpful was this guide? Click to rate: