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The purpose of insulation can be stated simply: It’s to keep the heat where you want it.
How Does Insulation Work?
Most insulating materials create “dead-air spaces.”
What you’re after is to keep the coldest air from getting in your house
at the bottom and to stop the warm air from getting out through the walls
or the top.
It’s important to keep the dead-air idea in mind. It’s like the down jackets worn in northern climates. They will keep the body warmer than layers of solid clothing. Good heat conductors are poor insulators. For example, a stone outer wall is low in insulation value. The same can be said for brick and concrete. Sheet metal (for the so-called tin roof), single-pane glass, stucco, and roofing shingles all fall into the same category: very little insulation value.
Lumber, composition board, and earth-walls have some insulation value, but the real winners are the expanded glass and mineral fibers you can buy as fiberglass, newspaper products like cellulose, or rigid foam boards.
Crumpled paper and dry straw can serve that air-trapping purpose but are a fire hazard and should never be used. Dry paper can catch fire even when it is encased in a tightly sealed box made of steel 1/ thick.
Thorough insulation of your attic, walls, and floor can save up to 50 percent on the winter fuel bills, so we’re talking about the major item in this business of saving energy. The best thing about this undertaking is that every step is profit. Even if you don’t accomplish everything, each insulation area checked off on your list will be a money saver.
Start Insulating at the Top
The attic is one of the best places to save money if your insulation is skimpy or nonexistent.
Let’s say your attic is a completely unusable space under a truss roof and isn’t insulated. You have two alternatives: blankets of fiberglass or bags of loose fill. If possible, select the loose fill so that the rafters can be completely covered. In this way, you will minimize the bypasses created by the wood rafters. However, if the space is easy to get at and the spacing of the rafters is a standard 16 or 24 inches, fiberglass batts or rolls are a definite option. Again, the insulation will be more effective if it overlaps the rafters.
If what you’re up against is a crawling job with a lot of irregular spaces, choose the bags of loose material. You may be able to rent an insulation blower. This machine will enable you to pack more insulation into each cavity. The most common loose fill is cellulose, which is made from recycled news papers and contains boron as a fire retardant.
Many attic insulation jobs can easily be do-it-yourself tasks. However, if you are also planning to insulate your walls with blown cellulose, you will probably need to hire a contractor.
How Much Insulation Do You Need?
The amount of insulation required depends on the severity of your winters, how you heat your home, and how much you can fit into the area you want to insulate. You will probably want R-38, which is equivalent to about 12 inches of insulation, in your attic.
What Else to Know before You Insulate
Don’t forget about the vapor barrier. Standard insulation rolls and batts have a vapor barrier on one side. The vapor barrier should face the heated living space. With loose fill, put down 6-mil polyethylene before installing the insulation, unless the spaces are so irregular or inaccessible that such a placement is impossible.
Be sure to place insulation out far enough to cover the top of the outer wall. At the same time, be sure you don’t block the vents under the eaves, if there are any That may mean putting a piece of scrap wood or cardboard at each end of each run of loose fill to avoid plugging necessary ventilation.
In all likelihood you’ll be running into light fixtures and a maze of wires up there. Unless the fixture is labeled “IC,” be sure that it isn’t accidentally covered during installation. Provide a minimum 3-inch clearance around the light fixtures by baffling with fiberglass batts on end. Insulation should never be in contact with bare wires. If you have any bare wires, call the electrician immediately.
The loose fill is fire resistant and can be in contact with the boxes that hold electrical connections. With batts and blankets, be sure that any paper coverings are peeled back or cut off to at least 3 inches away from any electrical junctions or fixtures.
Let’s say that you have an unfinished attic, but the floor is already in place. If you’re not going to use the attic, and there’s no reason at all to heat it, now or in the future, your best bet will be to put insulation between the ceiling of your living space and the attic floor. If you want to do it yourself, you will need to take up the floor and put insulation between the exposed floor joists. Then you can put the floor back down again so the attic can be used as unheated storage space. You may want to get a contractor to install the insulation. The con tractor will need to remove several boards, but will then be able to blow the insulation the length of the joists.
Alternatively, let’s suppose the attic space is going to be used as a workshop or for some other purpose that requires heating. Then you’ll want to insulate the roof.
If your roof beams are on 24-inch centers, there will be standard 6-inch fiberglass batts that will fit for insulating the roof. Make sure that air for ventilation can flow between your insulation and roof sheathing. If yours is an older house you may not have those standard spacings, in which case you’ll have to cut batts to fit, or buy sheets of polystyrene foam board and cut to fit. If you use the polystyrene foam board, the way to buy is by “R” numbers. In general, these panels have high insulation value for their thickness. Again, try to insulate to R-38 if possible.
A word of caution: These foam-board panels release deadly toxic fumes if there is a fire in your home. They should be covered with Sheetrock to minimize that danger and meet most fire codes.
Some added notes on attics:
— When you’re working in an attic, be sure you have sturdy boards to walk on and an extension light to help you see what you’re doing. When walking on the floor joists, it only takes one slip to send you to the hospital, because that ceiling under you won’t support you and you’ll fall right through.
— Be careful at all times to steer clear of the roofing nails that are sticking through.
— The end walls can be hazardous because the nails that secure the outer siding are almost certainly sticking through. If your house has any years on it at all, those nails are dirty and rusty and likely candidates for giving you a serious infection. If you do get a puncture wound in the attic, don’t mess around with it. Get to a doctor right away.
— Before you begin insulating, check the exposed roof areas for stains and discolorations on the wood. They indicate the presence of moisture. Be sure to find the source of moisture and assess its importance. For example, the moisture may originate from a bathroom that vents to the attic. Be sure to extend this vent to the outside. It may be due to a leaky roof. You could have a mess on your hands if you don’t consider moisture as you weatherize your home. Wet insulation is ineffective and may damage your home by holding moisture and causing rot.
— Before insulating you should seal any places where warm air can enter your attic from your living space. Chimney channels, pipe and stack penetrations, holes made for wires and cables, and partition walls are areas you need to check.
When you insulate your attic, make sure that any moisture that gets into your attic is whisked to the outdoors before it can condense in your insulation or on your roof. This is the purpose of ventilation. Usually a combination of high vents and low vents is best to insure that there is adequate air flow to move the moisture effectively. Vents can be installed in the gables, eaves, or roof.
I know it seems strange to intentionally allow cold air to come into your attic, but it’s better than the damage that moisture can cause. If you have a vapor barrier in place, then you will need about half as much ventilation as when there is no vapor barrier. The rule of thumb is that for every 150 square feet of attic space without a vapor barrier, or 300 square feet with a vapor barrier, you will need approximately 1 square foot of “net free area” of ventilation.
If an exhaust fan in your bathroom is venting into the attic, make sure that the air is ducted from the attic to the outside through the eaves or roof. This will help prevent warm moist air from condensing in the cold attic space where it may cause moisture problems.
Are you planning on converting your attic to living space? Perhaps the attic rooms will be able to heat themselves in the winter with what naturally rises from the house beneath, unless the attic floor is well insulated. Running heating ducts to the attic may be unnecessary.
If you expand your living space into attic rooms, avoid running water pipes up there if you can. If there are no water pipes, the rooms can be closed off when not in use, with no danger of pipes freezing and breaking.
If you have an unheated attic with flooring for storage, then there’s a place for that worn carpeting when you redo the living room. Put it down on the attic floor. It may not look wonderful, but who cares? It will add a measure of insulation, and you’ll be able to enjoy the luxury of wall-to-wall carpeting in the attic!
Check the door to your unheated attic and any other unheated area in the house. That door should be treated like a door to the outside: closed whenever possible and weather-stripped if needed. You can also insulate the back of this door with vinyl-backed fiberglass wrap.
When you plan to open extra rooms in the attic, be sure to include the cost of Thermopane windows or storm windows in your estimates, or the project may wind up costing you a lot more in the long run. The heat loss through attic windows can be greater because it is windier so high up.
Insulate the Walls
If yours is an older home that has never been insulated, find out whether the walls can be insulated. If you need insulation, it’s easiest for a contractor to blow cellulose into the walls from the outside. The contractor will remove enough of the siding to drill a hole through the wall or clapboard. Then he will insert a hose through which cellulose will be densely packed in the wall cavity.
If you are planning to replace your present insulation or your interior walls or windows, the easiest way to insulate is to install fiberglass batts from the interior. You can remove the indoor side of the outer walls and start insulating. In an older home, you will probably have wallpaper, then plaster, then wooden lath strips, then paper, then — I hate to tell you. Inside the walls will be the dust of the centuries, augmented by whatever the mice have left behind. Have a shovel, broom, and vacuum cleaner handy. Old lead paint could be present and should be addressed at this time.
When you get into the wall you may discover that the vertical studs aren’t spaced evenly, so standard insulation won’t fit. You may also find braces between the studs. Those are fire- breaks. They tend to slow down a fire that might otherwise run up through the walls unchecked.
When the outer wall is exposed, caulk all the gaps to the exterior. This will keep cold air from coming inside. Next, fit in the insulation as best you can, first filling in all the cracks around doors and windows. Be sure to wear protective clothing including a mask, long sleeves, goggles, and gloves. The vapor barrier should be on the warm side of the wall. If there isn’t a vapor barrier on the insulation you are using, then a sheet of 4-mi! polyethylene is needed. Take care not to puncture or tear the plastic because this will diminish its effectiveness.
If yours is a newer home and not insulated, the process of redoing the walls may not be as difficult. You may even be able to salvage some of the panels of Sheetrock if you are very careful when taking them down.
A final thought.
When there is any amount of insulation material to install, you’ll do well to buy one super-tool. It’s the staple gun. There’s really no easy way to install batts or blankets of insulation without a staple gun. It’s also just about essential for handling polyethylene sheets. Keep it around the house when the insulating chores are completed. You’ll find yourself using it for lots of chores, and it’s indispensable if you get into reupholstering a favorite chair.
Insulating in the Basement
It’s sometimes a bit more complicated to figure out the best approach to insulating the basement.
Do you have an unheated basement that is used only for storage and utilities? Then you should consider insulating the basement ceiling. In effect, this is insulating the floor of your first story. After you insulate, your first floor will feel warmer and more comfortable.
Fiberglass batts are the easiest bet. Before you rush out to buy, measure. If the floor joists are spaced on 16-inch or 24-inch centers, you’re in luck, because those are the standard widths for batts or rolls of insulation. The standard length for batts is 6 feet, so you can figure how many batts you’re going to need for the under-floor area you’re working with. The insulation should be installed flush to the ceiling to minimize air or moisture flow between the insulation and the ceiling.
Standard insulation rolls and batts have a vapor barrier on one side. Again, you want that vapor barrier to be facing the warmth, which means that in an under-floor installation the vapor barrier goes up. However, it is really difficult to get an effective and continuous vapor barrier. An equally important consideration is keeping the fiberglass fibers covered with a fire-rated material.
If you have a problem keeping the insulation in place, roll out the insulation and then tack up lengths of wire mesh or chicken wire. Metal stays are often used for this task.
A word of caution. Right now the basement may be unintentionally heated from the heating system and pipes. That under-floor insulation, if you do your job right, may leave the cellar colder. That’s okay, unless there are water pipes running through the cold area. The cold water pipes may need to be wrapped to prevent freezing, and the hot water pipes should be wrapped to avoid chilling the water you are paying to heat. If you have a boiler or forced-air furnace in that space you’re making colder, you will definitely need to insulate the heating pipes or heating ducts leading from the furnace.
Before insulating the heating ducts (the supply side only), check the seams between sections of both supply and return ducts to be sure they are tight. If you have any doubts, use mastic or reinforced foil duct tape. Ironically, standard duct tape is not suitable for this task. Seal the joints between sections of insulation with high-temperature vinyl tape.
High-temperature closed-cell foam for hot-water base board heating systems usually comes in sections 6 feet long. This foam is available for any diameter of heating-system pipe. For steam-heating systems, various sizes of high- temperature fiberglass sleeve insulation are available.
Caution: If you have steam pipes, check to see whether they are insulated with asbestos. If so, do not disturb this insulation without checking with your local health department to find out the regulations and procedures you must follow.
All you have underneath is a crawl space? Insulation will do a good job there, too. Choose a day when you are feeling calm and even tempered, and wear old clothes. An under- house crawl space will try your patience, skin your knuckles, and certainly leave you with bumps on your head and cob webs in your ears.
Plan one trip into the crawl space just for measuring. Do a good job and make notes. Then you can cut your materials outside instead of struggling with that part of the job while you’re flat on your back with spiders crawling into your collar and dust sifting into your eyes. Remember that in handling insulation such as fiberglass, you definitely must wear a mask over your nose and mouth to avoid breathing those tiny glass particles.
The materials you need are 4-mil polyethylene for a vapor barrier, R-19 fiberglass batts (the ones about 6 inches thick), and strips of wood for nailing. The boards to hold the batts in place can be scrap 1 x 2s or anything else that’s handy. All you want is something strong enough to keep the insulation positioned where you need it.
How did you get into that crawl space? Through a trapdoor, an entry hatch, or a ventilation opening? Be sure any outer entry is closed tightly, weather stripped, and insulated as much as possible, or some of your effort will have been in vain.
It is important to put a layer of polyethylene on the ground to keep moisture from getting into the insulation, especially with dirt floors.
Chances are that there are some pipes leading to the kitchen sink going up an outside wall in the crawl space, and maybe some other water pipes as well. Before you leave, be sure they are well wrapped against the cold. The pipes through the crawl space may not have frozen in other years, but now that under-floor area will be colder.
The security of those exposed water pipes is doubly important if the pipes are PVC (polyvinyl chloride) or another plastic. The plastic pipes aren’t as likely to burst as copper or galvanized pipes, but they are difficult to thaw if they are blocked with ice because you can’t use either blowtorch heat or electric resistance treatment on them.
Ventilation in the crawl space is important to avoid wood rot and mildew problems. However, ventilation is tricky in basements and crawl spaces. Think about which is more humid — the inside or outside — and ventilate accordingly to keep moisture from building up.
On the other hand, let’s say you have a basement area that is used for a variety of purposes that require it to be heated, like laundry areas, play areas, and indoor gardening efforts. Then insulating the walls is the task at hand, and it’s easy, even if the existing walls are poured concrete or cinder blocks. As usual, make sure you seal all the gaps first!
On the interior of your outside walls, you’ll be building another facing wall with 2 x 4s. The bottom plate will just sit on the concrete floor, not nailed to anything. The top plate can be nailed to the floor joists above it, then the vertical studs should be cut to fit snugly, or slightly force-fit, to be sure the whole works is going to stay in place.
Insulation made to fit on 24-inch centers, R-11 (about 3½ inches thick), will do well, so your vertical studs must be positioned accordingly. This isn’t a bearing wall holding up house weight, so your construction can be simple.
Install the insulation from the top down to at least where the frost line is expected to be. In colder areas, that may mean running the insulation all the way down to the floor. The vapor barrier on the insulation panels should be facing the room. If the batts or rolls you buy don’t have a vapor barrier, sheets of 4-mil polyethylene should be installed over the insulation after it is put in place. A continuous vapor barrier is most effective.
Cover the insulated wall with whatever suits your fancy, taking into account that cellars can be damp. Sheetrock or gypsum board can be quickly ruined if there is water on the floor, and so can plywood, unless it is exterior construction grade, which is expensive. Inexpensive wood paneling is a good bet.
If floor water may be a problem, you can run almost any kind of wallboard down to about 6 inches from the floor, then cover the gap with a board molding of 8-inch planks. Don’t run the wallboard down to the floor, or it will act like a wick and draw water up to ruin your wall.
Above your new wall, between the floor joists and at both ends, will be exposed areas where insulation is needed. Place it vertically to meet the floor above and also across the top of your new wall. This won’t be the most beautiful thing you’ve ever had in your house, but it is practical, and you won’t see it at all when you finally get around to putting in a ceiling.
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