Getting Adequate Attic Insulation
Attics and Basements, Green Home, Heating and Cooling, Insulation, Interior by Danny Lipford
No matter where you live in the U.S., homeowners are struggling more than ever before to find the balance between being comfortable inside their homes and keeping energy bills smaller than their mortgage payment. This struggle has taken center stage as the cost of energy rose dramatically this fall and December has already produced lower-than-average temperatures to date. Although turning down your thermostat will help at first, the ultimate in energy savings is to keep the heat you’ve paid to produce within your walls as long as possible. That makes adding insulation one of the single most effective ways to save on heating costs.
In almost any climate, if you can see the tops of your attic floor joists when you venture up there, you’ll need to add more insulation. As a minimum, most home in the U.S. should have between R22 and R49 in the attic – that’s about 7 inches to nearly 12 inches. But take the time to go to the Department of Energy’s Website to get an exact minimum for where you live. The DOE Website has a wealth of easy-to-access information about saving energy that is practical and accurate.
To determine if you need more insulation, measure what’s in place with a ruler or tape measure. When you do the measuring, make sure you have plenty of light to work because you will have to walk exclusively on the top edge of the joists—let your foot slip in between where the insulation is and you will end up breaking through the drywall or plaster ceiling in the room below.
Once you determine how much insulation you have and then the amount you need, it is easy enough to install additional amounts over existing insulation yourself. There are quite a number of insulations types including rigid foams, sprayed-in foams, mineral wool, and natural products like cottons and wools, but most attics in the U.S. are insulated with either fiberglass or cellulose:
Fiberglass
Fiberglass insulation comes in rolls or batts and is formed at a particular width and thickness to fit between studs in walls or joists in attics. Each thickness represents an R-rating standard (for instance, R-19 is 5-1/2 thick for use with 2×6 wall studs or attic/floor joists).
Blown Fiberglass
This is fiberglass in a loose form that can be blown by a professional installer through a hose to whatever level is desired.
Cellulose
Cellulose is a paper-based insulation (much of it recycled newsprint) treated with fire retardant that is also blown into attics or walls with a large, vacuum-like machine.
Which material you use is less important than making sure you have enough insulation for your climate. All of the insulation types above do a good job, and you do not need to stay with the form that is in your attic now when adding more. Here are some tips that will help you add more insulation:
- If you are using fiberglass insulation in batt or roll form, make sure the insulation is unfaced—that means no kraft paper or foil facing on either side.
- Wear a long-sleeve shirt, long pants, gloves, eye protection, and a dust mask.
- If you’re using roll or batt fiberglass insulation, lay it perpendicular to the joists so it does not compress the existing insulation below it and creates a blanket with fewer areas where air can leak through from below.
- Don’t cover can (recessed) lights unless they are rated for contact with insulation. If using loose (blown) insulation, build a small enclosure with hardware cloth or plywood to keep the insulation away from lights and exhaust fans.
- Use cardboard or rigid-foam baffles to keep soffit vents from being blocked by insulation where the rafters rest on the outside walls. Encouraging this cold air circulation above the insulation will help exhaust moist warm air leaking from the living space below. If it can’t find a way out, it can condense and begin to rot the roof sheathing.
- Fill all cracks between the living area and the attic with caulk or expanding foam. This includes areas where plumbing vent pipes, flues, electrical wiring, and vent fans, and light fixtures poke through into the attic. Sealing these voids helps defeat the “chimney effect” that draws cold air in at the base of the house and exhausts warm air (that you’ve already paid to heat) out into the attic floor (the ceiling of the top-most living area of the house) at a furious pace.
- If you are insulating walls or uninsulated joists, fill the cavity completely with insulation.
- Don’t overly compress the insulation—it’s most effective in a fluffy state.
- Split or cut insulation when you run into electrical wiring across the stud or joist bay.
- In walls and floors, staple faced batts every 8- to 12- inches.
11 Comments on “Getting Adequate Attic Insulation”
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June 21st, 2007 at 2:24 pm
Dan, I missed most of the info on the solar attic fan. Is it on your wab sight? Please advise! Jeff
Nicholas Roussos Says:June 21st, 2007 at 2:34 pm
Jeff,
Don’t worry. If you missed something on a show, you can now view the last 5 episodes online, commercial-free. (Note: the current week’s episode won’t appear online until the following week.)
Full Episodes of Today’s Homeowner®
June 26th, 2007 at 6:42 am
I love your show – just bought my first house and you are better than a handyman any day! I really want to get my attic insulated this summer…I am having a baby in a month or so. Can you please direct me to a good how to resource for installing additional cellulose insulation over existing bats in my attic. Most of what I find online is ilke reading another language!
Thanks!
Jamie
Allen Says:June 28th, 2007 at 8:14 am
Jamie, it’s easy to have additional cellulose blown over existing batts. In fact, you can often find the insulation and the blower at your home improvement store. Sometimes, if you purchase a specified amount of the insulation, they’ll let you use the blower at no charge. At eight months pregnant, though, just make sure someone else does the work! It’s as easy as point and shoot. Geez, I sound like a commercial for the Salad Shooter….
June 29th, 2007 at 6:02 pm
does the insulation come in batts.
thanks!
dylan
June 29th, 2007 at 6:04 pm
allen you should look through the attic
before installing fiberglass insulation.
June 29th, 2007 at 6:07 pm
do not squish the insulation in it has to
be fluffy so the air gets trapped in the
fiberglass blankets.
January 24th, 2008 at 2:37 pm
Venting of attic or under roof space does NOT avoid condensation. When the roof gets down to dew point temperature, any humidity allowed thru ceiling insulation WILL condense on that cold surface. Soffit and ridge vents will NOT vent out humidity when surfaces are as cold as dew point!
March 16th, 2008 at 10:18 pm
Why should attic insulation batts be unfaced? Is condensation the issue? How hard is it to get fiberglass unfaced ceiling batts?
The inspector for our home purchase said we could benefit by putting 4″ roll insulation on top of blown insulation in our ceiling, but I am assuming batts will work fine as the space is barely enough to use rolls.
That for the half of the house that has a ceiling space. The other half is a cathedral ceiling. Any ideas there? It was built in 1982.
Thanks.
Roadrage
October 1st, 2008 at 9:26 pm
please help me I’m female senior citizen I live in Detroit Michigan please recommend someone to insulate my attic Thank you
November 17th, 2008 at 5:47 pm
I have papertype blown in insulation. There is no roof vents, only 2 soffits open and no baffle and don’t know if the 2 soffits have vent protection. There are very small vents on both corners of attic. I have been told there is not enough ventilation and could get mold and roof and beam rot.
The pulldown to access the attic is not protected. Can you help me as soon as possible so that I can contact the contractor and get the problem solved before it really gets cold up here in New York. I’m an elderly widow and I need your expert advise to do something now. Thank you for helping me. I enjoy watching you on the weather channel. Mrs. Marion Pringle