Insulation--Warm Inside and Out

With colder weather approaching we are giving more consideration to heating our homes now, and to keeping ourselves warm. This week we are going to look at insulation, to see what the numbers mean and understand how it works.

Let’s look at heat, and see how it works. Heat moves via three modes: conduction, convection and radiation. Conduction is you touching something hot directly. Convection involves a medium such as air or water, and heat is carried from one place to another by that medium, such as the warm air coming out of your register. Radiation is how the earth is warmed by the heat of the sun even though there is no air or other medium to carry the heat directly to us through space. The inside of your furnace employs all three of these methods to get the heat to where you want it.

Under the laws of thermodynamics, heat flows “downhill”, or it goes from a hot area to a cooler area. In winter, the outside of your home is cold, and you want the inside to stay warm, so you need a furnace or heater to generate heat inside your home. This heat tries to escape through all the exterior walls and surfaces of your home. Insulation slows this process down and allows your home to stay comfortable. What kind and how much insulation you have will dictate how fast this process is, and how much your furnace has to work to keep your home comfortable. As well, heat rises, so to retain that heat within your home you need more insulation in the ceiling than in the walls.

Most of us are familiar with home insulation, in the form of the pink batts (the 15 X48 in. panels) and the Styrofoam panels, and we have a vague idea about the R number, in which more is better. What does this number mean? It refers to the rate at which heat flows through a certain thickness of material; because it is a reciprocal, a higher number is better than a lower number. It originated before metric units existed so it is based on BTUs (British Thermal Units, a way of measuring the quantity of heat) per inch per time unit. Europe uses a U value, in which lower is better.

Insulation works by trapping many tiny pockets of air within a structure of some kind. These pockets are separated from each other and each acts as barrier to the transmission of heat. Fibreglass, Styrofoam and blown cellulose all share this property. The foamed urethane that you can spray into the cracks around windows starts as a liquid but as the polymer forms and hardens it gives off carbon dioxide gas which becomes trapped in tiny cells, giving the insulation value. Another key property of insulation is its non-flammability. Fibreglass is non-flammable, and blue and pink Styrofoam is treated to be non-flammable. White Styrofoam, also called beadboard, has to be covered with a non-flammable layer, often plasterboard, to meet building codes. Blown cellulose is made from waste newsprint and is treated with chemicals called borates to resist mould, rodent damage and to reduce its flammability.

Fibreglass insulation is made from glass in the same way as cotton candy. It is heated to melting and spun through fine holes to make fibres. These fibres are collected and formed into batts and treated with a non-flammable resin to holds them together. Interestingly, FG insulation can use recycled glass, including coloured glass, which is often difficult to recycle. Some brands contain up to 90% recycled glass.

In the post-war building boom of the 50s and 60s, energy costs were not a consideration and thousands of homes were built with 4” cavity walls with minimal thought given to insulation. As energy costs rose in the 70s we began to see more attention paid to this area, and better methods of insulation and stricter codes came into effect. Today most new homes have 6” walls with a minimum R12 and often R20, and higher in the ceilings. Many of those older homes have been successfully retro-fitted with improved insulation to lower the heating costs.

Choosing the right insulation can be a bit daunting. As far as strict efficiency goes, pink or blue Styrofoam boards have the highest R-value per inch, about 5, with fibreglass and cellulose about R3.5 per inch. This however does not factor in cost and ease of use, which are major considerations, especially in retro-fitting an existing building.

An effective method of insulating windows is to use transparent shrink film, held in place by double-sided tape and tightened with a hair dryer. This traps a layer of still air in front of the window and lessens dramatically the amount of heat that escapes through the window, as well as blocking drafts around the window. Your home fix-it store has economical kits to do this.

With warmer summers now common, many of our homes are air-conditioned. The same principles apply as in winter, except the heat is trying to go the other way. Your air conditioner is removing heat that makes its way into the building, or is generated inside. That is why you turn off unnecessary lights and use the microwave instead of the stove when you are running the AC, and a well-insulated home is easier to air-condition as well as heat.

Canadians have an intuitive feel for insulation, and we must do a better job of minimising our consumption of energy. If we apply insulation carefully, to make best use of its properties, we can make significant progress towards energy conservation and save money as well.

Plasticisers - Good or Bad?

PLASTICISERS – GOOD OR BAD?


A reader commented recently that she had heard that the plasticiser used in water bottles could be toxic and find its way into the water. This is a very timely question and one that I had considered but was unable to fit into my previous column. Let’s take a more detailed look at this complicated story.

First, what is a plasticiser? Many polymers contain additives to give them desirable properties such as colour, resistance to UV and heat (the enemies of polymers) and sometimes more or better flexibility. For example, we have seen the turquoise pipe made in Prescott for water pipes. It is made of polyvinyl chloride, or PVC, and is very hard. PVC is the same material that your swimming pool liner and your raincoat is made of, but they contain a plasticiser to make them flexible. So a plasticiser acts as a lubricant between the very large polymer molecules, enabling them to move against and past one another, and giving flexibility to the finished product. Sometimes plasticisers are added to make a polymer easier to process, such as in making wire insulation.

These plasticisers take many different chemical forms, depending on what polymer is being processed and what end-use is sought. A very common plasticiser is called dioctyl phthalate, or DOP for short… we won’t worry about the formula for now. DOP is used extensively in flexible PVC polymer, the kind consumers encounter frequently in waterproof clothing, pool liners and many other applications. DOP is considered safe… more about that in a moment. For food handling and packaging applications, plasticisers are based on citric acid, the most common of which is called tributyl citrate.

As I mentioned above, most plasticisers are used in PVC plastics. Water bottles are made of polyester plastic, or PET, and according to my research and to the manufacturers, do not contain plasticiser. Most common food-packaging polymers, such as polyethylene (milk bags), polypropylene (yogurt and ice cream containers) and polystyrene (clear clam-shell containers and foam plastic containers) are made without plasticisers. There is a catch, of course. When a polymer is made and all those tiny molecules are linked to make a large polymer molecule, not all the small molecules become incorporated into the polymer. This material, called monomer, may be soluble in the food, or may be volatile (evaporates) and this could be a cause of concern to some consumers.

I have read about claims that freezing a water bottle to keep your lunchbox cool and enjoying ice water at 3:00PM can increase the amount of plasticiser in the water. This is wrong on two counts – first, there are no plasticisers in water bottles, and second, in almost all physical and chemical processes, a lower temperature slows things down. Researching this in the 70s regarding plastic milk bags, we placed milk in bags at 35 deg. F., (fridge temperature), at 70 deg. F., (room temp) and at about 150 deg. F., (microwave temp). In every case more monomer (not plasticiser) migrated to the milk as the temperature increased, although none at a level thought to be harmful. So freezing your water bottle is not going to cause any health risk.

Now we get to an interesting component of this story. Some of this information and misinformation has been swirling around the Internet for a while, and as you know it can gain a life of its own. A thesis by a student at the University of Idaho claimed that chemicals were leached from water bottles into the water, and this was widely quoted. The problem is that this was not a peer-reviewed scientific study, one in which scientists familiar with the subject examine the work and determine if it was done to the highest technical standards A subsequent review of the student’s lab work revealed significant gaps and unacknowledged sources of error, yet the so-called study continues to be cited.

Back to DOP, the common plasticiser in PVC. In the chemical world, there are many chemicals that have been in common use for years. As knowledge and better testing advances, some of these are removed as we realise their harm, such as asbestos for insulation and phenol as a disinfectant. Others we substitute using a less harmful equivalent material, such as using HCFCs instead of the original fluorocarbons. With others we change the amount or the application as we refine our understanding of how they work. DOP comes in the latter category. It has no known connection to cancer or any adverse health effects, but it is being monitored to determine if it is being over-used and a better substitute can be used. This is a long-winded way of saying that medical science knows of no long term serious effects of exposure to DOP, but that doesn’t mean they don’t exist.

So where does all this leave us? Food packaging material is extensively tested under a variety of conditions, and is very safe. It has significant benefit to the consumer by keeping food clean, maintaining freshness and minimising waste. If you as a consumer are concerned, you can of course purchase your food fresh and have it wrapped in paper or polyethylene bags and wrap. My guess is that you will not see a difference.