Which insulation is safer, foil or wool?

Submitted by Peter on Fri, 2010-03-19 13:02

Which insulation is safer? Foil? Glass fibre wool? Natural wool?

Choices

There are lots of choices for insulation. Here is a quick summary.

Type	Description
Bricks	Bricks provide some insulation when dry. A single brick wall might not do much in winter because rain keeps it damp. Double brick with an air gap keeps the inner brick layer dry and insulating. The inner brick also acts as a heat bank to control internal temperature. Brick works well in houses with wide eaves to keep the rain off the outer layer of bricks. In warmer days during winter you let the daytime sun and warm air in to warm the brick walls then shut up the house at sunset and the warm bricks warm the air during the cold night. Double brick is especially useful for moderating temperature during Spring and Autumn when temperatures are all over the place. If you insulate double brick, you can place the insulation between the two layers of brick but make sure it does not stop air flow from removing moisture.
Cellulose fibre	Shredded paper. Same effect as the newspapers you pull over your body when you sleep in the park. Mice and rats make nests of shredded paper. Borax and boracic acid are added to kill insects, rodents, and retard fire. You spray it in until it is deep enough to provide the insulation depth you want. When it is damp or you walk over it, squashes down and you lose the insulation effect.
Expandable foil batts	These are one of the foil products killing people in Australia. The manufacturers laminate metallic foil, usually aluminium, over cardboard box material to make two or tree layer reflective foil sheets. They are flat during shipping and pop up into separate layers when installed. They crush back down if you step on them or lean against them. They are designed for use in ceilings, walls, and under floors. The metal conducts electricity which means they should never be used in ceilings, walls, or under floors.
Glasswool batts	Fibreglass. The glass is melted then spun like fairyfloss into a think layer then cut into batts. There may be a plastic or foil later each side. The manufacturers and installers have to wear masks to stop loose glass fibres going up their noses. Once installed it is totally safe and reliable. The foil coated wool go in the roof away from wiring and the plastic coated ones go on your ceiling.
Polyester batts	The same material used to make cheap pillows. You dig a hole in the ground, extract oil, make polyester, then squeeze it out as thin springy threads to make cheap clothing. If the threads jamb, you take the bunched up mess and stuff it in a pillow case. That was how plastic pillows were invented. Think of a polyester batt as a giant pillow. The polyester does not harm the installer and is cheaper, two reasons for people sneaking polyester in even if you ask for glasswool. Are they safe in your house? Hydrocarbons burn. Think of all the children who died from burning nightwear before the law was changed. If you settle for polyester, you want chemicals added to retard fire.
Polystyrene foam boards	Think of those cheap foam plastic boxes they use to pack fish at the market. Think of all those people who died when their caravans burst into toxic flames. You are thinking of polystyrene foam. The foam can be squeezed into gaps between brick walls but then it stops moisture escaping and you end up with damp wall problems.
Reflective foil laminate	Metallic foil, usually aluminium, laminated to paper provide strength and sometimes to glasswool to provide insulation against conducted heat. Reflective foils only work if they can reflect the heat back through an air gap so there is no conduction, making reflective foil almost useless in every situation where it is used. The only real effect of reflective foil on your roof is to stop water falling on your ceiling after the water splashes under the joins in your tiles. When you want real insulation, you need the foil laminated over glasswool. Reflective foil might have blue sprayed over one side to stop glare blinding installers during the installation. That blue coating reduces the insulation effect and is another reason why you use it with glasswool or use it only as a moisture barrier. In damp climates, near the coast, and anywhere tropical, the shiny metal surface will quickly erode to a dull useless grey. You might need a plastic coat to protect the metal despite the fact that the plastic will absorb heat and reduce the reflective insulation effect.
Reflective foil laminate with glasswool	This is honesty in action. Foil to stop moisture and glasswool to stop heat conduction.
Rockwool	The same as glasswool but made with melted volcanic rock. Slightly coarser making it denser and that might help with acoustic insulation. There is more variation between brands and models of batts than there is between rockwool and glasswool.
Wood	Wood has an insulating effect and multiple layers of wood can trap air to form insulation. If you have a tin work shed and it is too hot in summer or too cold in winter, you can line it with plaster or wood to provide some insulation. Wood has the advantage that you can easily bang in nails to hold tools. Your natural wood insulation becomes a natural wood storage area. Wood is not very good when wet so place a metallic foil glasswool laminate barrier under the wood to keep the wood dry and to boost the insulation effect when you use thin wood.
Wool	The natural fibre from sheep. It makes sense to use waste wool as insulation the same as we use waste down from duck nests to make doonas and eiderdowns. Wool is the slowest to burn of all the natural fibres and in most cases will smolder then go out. Wool roofing insulation will eventually burn after a build up of dust and leaves adds some cellulose to start the flame. If you have a tile roof, you want the tile roof lined with foil to keep out the dust and leaves. Vermin and insects love woll for nests. Some eat it for food. Use wool treated to resist insects and vermin.

Fire safe

Wool from sheep, glasswool, and foil do not burn. Everything else is risk once a fire starts. You can treat thinks with chemicals but the chemicals can be dangerous, can lose their effectiveness, and can have a limited protection time. Choose stuff that does not burn.

All insulation insulates making them dangerous over anything hot. Downlights are the only common dangerous hot thing in the average house roof. In Australia people have died in house fires resulting from the current federal government's rush into insulating houses using unqualified people mass installing a mixture of cheap untested material and the occasional tested material but installed in an unapproved way. Replace downlights with a better design or cover them with something that will keep the insulation away and allow the heat from the downlights to vent up into the roof. If you keep your downlights, replace the hot incandescent element with cooler LED elements now then OLED panels when OLED panels drop to a reasonable price. The transformers may also burst into flames given the cheap poor quality imports in common use. Make sure transformers are above the ceiling insulation and, when you use celullose and other burnable junk, there is a metal plate between the transformer and the firetrap to spread the heat or mount the transformer on a bracket away from the bonfire material.

Are you spraying a shredded or foamed bonfire material? The spray can go into hot water services, wiring connection points, and fan motors leading to more fires. You want everything properly sealed before spraying. Use brightly coloured paper sheets and masking tape to cover air vents. Remove after spraying.

The last reason for a fire is an electrical short caused by foil. Foil should line the roof but not touch the ceiling because your wiring runs across the ceiling. The ideal is to line your ceiling with glasswool and have all the wiring run along beams above the insulation where the wiring can be easily tracked and inspected. If you are adding insulation batts after the wiring, place markers where you have lights and other connections. Get glasswool batts with a plastic top layer then draw the wiring on the plastic later with a big marker pen.

Electrical safety

You do not want to die. The people working in your roof usually have the same idea. Think roof-foil-moisture-barrier, ceiling-wiring-heat-glasswool-insulation. Done.

Formaldehyde

Formaldehyde is a preservative and carcinogen used in, among other things, some building materials including foam insulation. There are strict limits on the use of formaldehyde in Australia but not in China. When the current Australian federal government decided to subsidise insulation of homes without any regard for safety, they let China flood the Australian market with cheap insulation containing massive amounts of formaldehyde. The installers will get the brain, nose, and other cancers. You will probably be safe because the carcinogen will waft away through the vents in your roof.

You have vents in your roof. (Perhaps you should check.) If the vents were blocked by the installers, the fumes could travel down the gaps in the walls then enter your home through the vents in your walls. Roof ventilation is good because it reduces moisture buildup and, in the case of materials from China, remove the chemical fumes.

Insulation is not alone in the carcinogen stakes. Newspapers are reporting cases of clothing and all sorts of other things from China containing dangerous levels of formaldehyde.

R value

Insulation effectiveness is measured by an R value. R3 means the insulation is three times better than no insulation. Insulation varies from R2 up to R6. In New Zealand the government recommends R2.9 as the minimum for their North Island, the equivalent of the southern half of NSW in Australia, and R3.3 as the minimum for their South Island, the equivalent of Victoria and Tasmania in Australia. They suggest R3.3 for the higher elevations in the North Island.

My house is 200 metres above sea level and our area is 2 to 3 degrees cooler than the areas near sea level. The higher up you are, the more insulation you need. I suggest about r0.5 for every few hundred metres. If sea level is supposed to be R3 territory where you live and you are 200 or 300 metres up, use R3.5.

The ocean dampens down temperature changes. Inland you need more insulation because of the bigger extremes of temperature. When a city slicker tries to sell you R3, look at R4.

Blanket or segment?

You can buy glasswool batt insulation to fit between the wooden joists holding up your ceiling or a blanket to go over the top of the joists. The New Zealand government subsidises roof insulation in an intelligent manor, better than the current mafia in the Australian Federal government. NZ says a blanket of R3.3, the South Island requirement, is equal to batts of R4.

The first problem with blankets is they hide wiring, connectors, and the joists making work in the roof dangerous. The second problem is the number of times trades people will step through the ceiling because they cannot see the joists. Plus you have to rip up the blankets every time you work on the ceiling. Plus the blanket over the joist will be squashed down when you walk in the roof, making that part of the blanket less effective. Unless you are placing all your wiring above the ceiling and doing a lot of other unusual things, use batts instead of blankets and get the extra thickness.

The blanket style is a better choice when hung down walls or across roof joists under tiles because the blanket is self supporting.

Reduce carbon

Insulating the ceiling of an average Australian house reduces carbon production by nearly 2 tonnes per year. There are lower estimates out there but they were made before people started buying air conditioners big time. Modern homes have bigger areas of glass and very little is double glazed. If you are building a new home or rebuilding, use insulation and double glazing.

Do you have a home on a slope with an open area under the house? You need insulation under the floor. See UnlevelHome.com for details.

Conclusion

Lay glasswool across your ceiling for thermal insulation and use foil as a moisture barrier under your tiles. Everything has it's place. Those are the safe places for foil and wool.