Ventilation last month … insulation this month! They are two entirely separate systems in an attic, and they must both be done right to work the most efficiently together. I saw this recently in a home I inspected in which a loving helpful son installed the blown-in insulation in his dad’s older house … at first glance, the new insulation looked great, then I saw that he totally ruined the flow of ventilation in the house by covering up all the intake vents in the soffit.
Insulation is a comfort and energy efficiency issue. I lived in a pier and beam house many years ago that was built in the 1920’s that had zero insulation in the walls or under the flooring, and the attic had only 3”-4” of insulation. My energy bills were outrageous compared to the house I live in today.
The insulation in a brand new house can look like a freshly fallen snow blanket after a night of a foot of snowfall … it’s beautiful! And on the other hand, the insulation in an attic can be a extreme and even hazardous mess with settled insulation filled with trash, debris, and all kinds of junk. Insulation in an attic will settle over time and what was once a foot of insulation will be much less depth of insulation and thus, the R-value has decreased.
The older the house, the more disarray and disheveled the attic will usually be. Air-conditioning technicians, electricians, plumbers, cable or satellite technicians, remodelers, and others will mess up the insulation and leave their trash in the attic. Then there are older house that originally had a cedar shingle roof installed that has been removed and replaced with roof decking and a composition roof. The roofer doesn’t clean the attic with all the trash that falls in the insulation. The attic will still be filled many years later with all the trash and debris from the cedar shingle roof. The older house attic can be a total disaster that is not only inefficient and even dangerous!
If you live in a newer home, it’s likely that the insulation and ventilation are in pretty good shape. On the other hand, if you live in an older home, it’s likely the insulation needs some vast improvement. This could really be a LONG article about different insulation types, R-value, how much to buy, installation tips, sealing leaks, and more, but there’s not enough room with articles like this. If you’re going to attack the insulation issue your attic, please do your homework. And be careful moving around and working in your attic!
So how do you know if the attic insulation is in good shape? How deep is it (12” of insulation provides about a R-30 value) and does it look fresh or a mess? Are there baffles installed for the ventilation intake in the soffit area or is the ventilation intake covered with insulation?
Here’s a brief account of the attic story of the 1976-built house I lived in to illustrate some principles of what you can do to improve your attic insulation. The attic was worse than a dangerous disaster with cedar shingle debris, disheveled, missing, and low insulation, unsecured 2 x 6 boards and broken Masonite siding used for walking across the ceiling joists, old wiring from previous phone and cable services, exposed wire splices, no insulation under the 1 x 4 boards on which the HVAC equipment was installed, and even an old 16’ panel to the garage door in an area of the attic on the other side of the HVAC equipment (why that was up there, I have no idea!). There was zero insulation under the HVAC equipment, and when the old furnace and HVAC equipment was removed, I went into “attic mode” to get the attic insulation and more in efficient and functional condition. It’s dirty sweaty work and worth the result when you’re finished, and you should only have to do it once.
I filled large trash bags with old wood shingles and trash, carefully took down the old garage door panel, removed all the dormant wiring no longer in use, and removed all the broken siding. I removed the wood slats that were under the HVAC equipment. I then reused the blown-in insulation by moving it with a large dust pan to other areas. I installed new batted insulation between the ceiling joists that I had emptied. I also added new blown-in insulation over the old blown-in insulation to increase the R-value. I then constructed a new platform where the new HVAC equipment was to be installed and cut ¾” plywood as needed as a walkway from the attic stairs to the HVAC equipment platform. It took me less than one day, and I was dirty and sweaty. The attic was transformed, functional, and more efficient. Our home was more comfortable, enjoyable, and safe for the remaining 10 years we lived in that home.
It’s not rocket science to do all the above. If you look at the entire situation in front of you, plan out what you need, you can do it! And you can hire a qualified handyman to do all the work. Be insulated well my friend!
There’s no getting around it: If your house is in a cold climate, keeping it warm in winter is expensive. The Department of Energy predicts that prices for natural gas and heating oil will rise again this winter compared with last—and that’s after a year in which heating-oil prices rose sharply in most parts of the country.
Sure, you can dial down the thermostat and get used to wearing bulky sweaters indoors to cut costs. But if you’ve got an unfinished attic, giving it proper insulation is one of the simplest ways to keep a lid on your heating bill this season. “It’s a DIY project you can tackle in a weekend, and the savings you’ll get add up every year,” says TOH general contractor Tom Silva. The Department of Energy estimates that a properly insulated attic can shave 10 to 50 percent off your heating bill. And it works the opposite way for warm climates; in summer, it helps stabilize your house’s indoor temps to keep cooling needs in check.
In a perfect world, you’d hire an energy auditor to tell you exactly how much protection you’re getting from the few inches of attic insulation you may already have and to pinpoint things like air leaks that you can seal to make sure your insulation will do its job well. But if you can’t afford to shell out a few hundred bucks for this service, never fear: We’ve rounded up all the most important know-how about attic insulation products, prep work, and installation right here. Keep reading for the details.
Why? Because the simplest and cheapest way to insulate an attic is to add material to the floor. But if the floor is covered in plywood, you can’t stuff enough insulation beneath it to do the job sufficiently—not even in warm climates. Plan to pull up the flooring and layer new insulation on top of the old. With the floor gone, you’ll have to find a spot elsewhere for stashing those off-season clothes and that holiday decor.
For DIY attic insulation, you’ve basically got two choices: loose fill or batt (the common term for blanket insulation). Both can be added to uninsulated attics or layered over existing material. Once you’ve decided which type is best for you, examine the material options and prices to home in on the right product. Always check labels for specifics on whatever you buy.
Loose fill
Insulation fibers are packaged in bags and blown in place to the desired depth and density using special machinery you can rent from a home center. You can pour the fill in place and spread it manually, but the process is much more labor-intensive and the results won’t be nearly as good.
It works best for:
Attics with irregular or nonstandard joist spacing
Attics with lots of obstructions and penetrations to work around
Attics where there is existing insulation to be topped, since it fills
gaps and joints well
Low-clearance attics with limited headroom for maneuvering
during installation
DIYers who want to get the job done quickly and are comfortable
working with power equipment
Material options:
Fiberglass
$$$
R-value per inch: 2.2–2.7
Made of: Recycled glass or sand that’s melted and spun into fibers
Bottom line: Lighter in weight than cellulose or mineral wool, but it settles more than those materials, so you’ve got to put in a thicker layer to get the protection you need.
Cellulose
$$$
R-value per inch: 3.2–3.8
Made of: Fibers from recycled post-consumer paper that are treated for insect and fire resistance
Bottom line: The most common blown-in material used, but it can rot and grow moldy if exposed to moisture.
Mineral wool
$$$
R-value per inch: 3.0–3.3
Made of: Fibers from rock or recycled slag from blast furnaces
Bottom line: Offers natural fire resistance, but costs more than other loose-fill materials.
This flexible insulation material is most often packaged in rolls that come in various thicknesses and standard widths, usually 16 inches and 24 inches, to fit between joists or studs in a house’s framing. They come with or without a paper or foil facing that acts as a vapor barrier. You add one or more layers to achieve the desired level of insulation.
They work best for:
- Attics with standard joist spacing, especially those with no insulation
- Attics with few obstructions or penetrations to work around
- Attics with sufficient headroom for maneuvering during installation
- DIYers who don’t mind cutting the material to fit around obstructions
Material Options:
Fiberglass
$$$
R-value per inch: 2.9–4.3
Made of: Recycled glass or sand that’s melted and spun into fibers
Bottom line: Commonly used and inexpensive, but fibers can irritate lungs and skin (though less so than in years past, thanks to better manufacturing), and it’s less effective at blocking airflow than other materials.
Cellulose
$$$
R-value per inch: 3.7–3.8
Made of: Fibers from recycled post-consumer paper that are treated for insect and fire resistance.
Bottom line: Won’t irritate lungs or skin, but the product is made by a limited number of manufacturers.
Mineral wool
$$$
R-value per inch: 3.0–3.3
Made of: Fibers from rock or recycled slag from blast furnaces
Bottom line: It’s naturally fire resistant, but the product is more expensive than others.
Cotton
$$$
R-value per inch: 3.7–3.8
Made of: Fibers from recycled denim cloth
Bottom line: Blocks airflow and sound transmission, but the material is more expensive than others.
Size Up Your Existing Insulation (and Get Rid of The Bad Stuff)
Determine Your Target R-value
The Department of Energy recommends these minimum R-values for unfinished, unconditioned attics. The numbers are based on your house’s location and climate zone.
Check for Rebates and Credits in Your Region
Most federal tax credits for weatherizing your house and boosting its energy efficiency expired in 2011. But your state’s energy office or local utility may offer product rebates, discounts, or other financial incentives for insulating.
How Much to Buy
Measure your attic’s square footage. For loose fill, read labels; each bag lists the required depths for a range of R-values and the number of bags needed to cover 1,000 square feet at those depths. For batts or rolls, calculate the number based on the width and length of the product you’re using. In either case, get an extra bag or roll—you really don’t want to run out when you’re almost done putting it in.
The Number One Prep Step: Seal Air Leaks
Gaps in the attic or between the lower floors and the attic will let heated (or cooled) air escape to the great, unconditioned outdoors, making any insulation you add essentially useless. (Find a diagram of common air leaks here.) Here’s a quick primer on fixing draft-prone spots.
- Around attic windows: Use canned, minimally-expanding spray foam (DAPtex Plus Window & Door Foam Sealant, $6.40 for 16 ounces; amazon.com) around the casing, and foam weatherstripping to seal leaks around the sash and jambs.
- Around pipes, wires, exhaust fans, and ducts: Gaps of ¼ inch or less can be sealed with fire-blocking caulk (3M Fire Block Sealant, $6.57 for 10.1 ounces; homedepot.com); seal larger ones up to ½ inch with fire-blocking spray foam (Great Stuff Fireblock Insulating Foam Sealant, $15.99 for 16 ounces; amazon.com).
- Around chimneys and flues: Use metal flashing sealed with high-temperature caulk (SUPERBOND Silicone Sealant, $7.90 for 13 ounces; grainger.com) or furnace cement (Oatey High Heat Furnace Cement, about $21 per half gallon; amazon.com.
Other Key Prep Steps Before You Insulate
Knock these to-dos off your list to ensure that your insulation will last for years and keep conditioned air where it belongs: inside your house.
- Fix roof leaks. Water is insulation’s enemy. It creates a breeding ground for mold and mildew and ruins the air-trapping pockets that block heat flow. Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be.
- Box out light fixtures. Unless you’re using mineral-wool insulation or your fixtures are rated safe for contact with any type of insulation, don’t allow the material to touch or cover recessed cans or lights from the floor below—it’s a fire hazard. Use hardware cloth, metal flashing, or scrap plywood to create a safety gap of at least 3 inches all around fixtures.
- Direct all exhaust fans and vents to the exterior. Though it’s against building code to vent any kind of exhaust to an attic space, many home builders have gotten away with this shortcut. Correct that mistake so that humid exhaust air doesn’t get trapped in your insulation and ruin it.
Here’s how to get the job done without discomfort or injury:
- Wear a dust mask, goggles, work gloves, a long-sleeve shirt, and long pants to protect your lungs, eyes, and skin from fibers.
- Don’t stand on the joists. If you lose your balance, you could crash through the ceiling. Use a piece of plywood or a couple of sturdy, wide boards as a standing surface, and move them around as you work. They must span at least three joists for stability.
- Illuminate dark corners of the attic using portable battery-operated lanterns or clip-on workshop lights.
Preserve The Attic’s Airflow
Covering up the soffit vents with loose fill or batts, which can happen if you stuff insulation along the eaves, is a huge no-no. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams, and the material will block that flow. For the same reason, insulation shouldn’t touch the roof’s underside. Staple plastic or foam baffles to the roof sheathing, near the eaves, to keep the material away.
1. Work from the perimeter of the attic toward the door or hatch so that you don’t trample all over the insulation you just put in.
2. Always cover the tops of the ceiling joists to make sure the insulation is deep enough to reach your target R-value and to prevent thermal bridging, the heat loss that occurs through the wood framing.
3. Shower thoroughly after you’re done for the day to remove fibers from your skin, and launder your work clothes after one wearing.
For loose fill
- Fasten blocking around the hatch or door to allow the material to be installed around this area without escaping.
- Make sure the fill’s depth is uniform across the attic. To make it easy to eyeball how level the material is as you blow it in, screw depth guides to joists throughout the space.
- To get the target R-value from the product you chose, use the number of bags your calculations showed that you needed to insulate your attic—never fewer. If you’ve reached your target depth but still have a few bags left over, keep adding the material at an even depth throughout the space until all the bags your calculations called for are empty.
- To help the material achieve the right density as you install it, hold the blower hose parallel to the floor and the floor joists. Blow in the fill between and over the joists rather than across them.
For batts
- Always use unfaced batts, both when laying product for the first time and to prevent moisture from becoming trapped between new and old layers of insulation. You can buy them unfaced or simply remove the paper or foil backing.
- Place a new layer of unfaced batts perpendicular to the old layer, to cover any gaps in the lower layer. Adjoining batts should be butted snugly together, but not tight enough to compress them.
- Never lay heavier batts, such as cotton, over lighter ones, like fiberglass. You’ll compress the lower layer and reduce its effectiveness.
- Always cut batts to fit around obstructions and penetrations. Stuffing or cramming them around ducts, piping, and the like will compress the air-trapping pockets in the material, reducing its insulating properties.
- Don’t leave any gaps between batts and joists, obstructions, or abutting batts. Even narrow ones will let air escape. Instead, cut a thin strip of the insulation you’re using to size.
If you’re considering turning your attic into conditioned storage or living space, it’s worth changing tactics to insulate between the rafters and wall joists instead of the floor. You can use rigid foam panels, or do as Tom Silva does with nearly all houses these days: Hire a pro to install spray foam insulation (see Upgrades That Slash Energy Costs). Foam blocks airflow, needs no vapor barrier, and has a higher R-value per inch than loose fill or batts, so you’ll get more protection with less depth. With spray foam, unlike with loose fill or batts, you must cover the soffit vents (they aren’t needed to keep the roof cool). Then cover the foam with drywall as required for fire safety.
Last month, I wrote about the attic as a system of components and mentioned that the article could actually be written into a book with chapters expounding on each area in greater detail. 2017 was a DIY (“Do-It-Yourself”) year of articles, and I enjoy running into people who tell me they enjoy the articles or call me with a question. That’s rewarding! So for 2018, let’s break down the attic into a series of articles. I hope you find them helpful and will enjoy them as much as I enjoy writing them.
One of the most important components in the attic is something you can’t see, but you can certainly see and feel the results (or consequences) of it! On a recent inspection, the prospective buyer followed me up into the attic with a concern he had seen. He asked me what were all those holes “over there” around the edges of the attic space. Those holes are actually part of the all-important system of the air flow in the attic called ventilation, i.e., the action of moving air. Ventilation is a system of components, all sized and positioned to provide constant and balanced intake and exhaust of air. The lack of proper air flow or ventilation can produce short-term and long-term consequences.
There is a mathematical calculation for the amount of ventilation there should be flowing through the attic space. Different entities such as the International Residential Code (“IRC”), U.S. Housing Authority (“USHA”), International Building Code “(IBC”), and roofing materials manufacturer’s installation instructions have codes or required installation guidelines for the proper amount of attic ventilation. Proper attic ventilation consists of a balance between the air intake (in the eaves, soffits, and/or fascia of the structure) and the air exhaust (at or near the ridge of the roof). In no case, should the amount of exhaust ventilation exceed that of the amount of intake ventilation. Think about the air flow … air flow in at the lower part of the attic and then air flow out at the higher part of the attic. It’s that simple, and it needs to work right.
The IRC best calculation for optimal attic ventilation performance is to have 1 sq. ft. of ventilation for every 150 sq. ft. of attic floor space for a ratio of 1:150. You will also see acceptable calculations per the IRC up to 1:300 depending on different climate zones. For our area, you should have 1:150 ventilation in your attic.
Older homes in the Greater Houston area that were built with cedar shingles now usually have composition shingles installed. The original cedar shingles had a natural ventilation to them, and now those attics should be revised with additional vents to achieve an acceptable air flow. The most common mistake homeowners make when installing additional insulation is to block the holes at the soffit, thus starving the attic for air intake. There are many different kinds of vents for ventilation – ridge vents, static vents, turbine vents (“whirlybirds”), power vents, solar vents, gable vents, continuous soffit vents, whole house fans, and more.
In the summer, the natural air flow in a well-vented attic moves extremely hot air out of the attic. This protects the roof shingles from underneath from blistering and deteriorating more rapidly and removes moistures from the attic. By lowering the attic temperature, you can actually extend the life of the roof and save money on the expense of repairs, maintenance, and replacement. The insulation installed in the attic resists heat transfer into the interior of the home, thus the attic floor and interior ceilings will be cooler.
There is a free phone app called “Air Vent” you can use to calculate the ventilation in your own home. Shingles, HVAC equipment, water heaters and other items will last longer in a well-ventilated attic. A home with a properly ventilated attic will be healthier and more energy efficient. Be well ventilated my friends!
