There are many types of insulations. The goal is to reduce the movement of the heat from warm to cold. For most homes built today the standard is fibglass insulation.
 
Fibreglass is actually spun glass fibers. They are placed together and hold air in one place to prevent it from moving and cooling. Fibreglass comes in various thicknesses, widths and manufacturers. Most friction fitted batts are rated at about an R-value of 3.5 per inch.

Therefore a 5.5 inch thick batt is R-20. This is somewhat deceiving since there are other factors that affect a wall.

If you build with the studs placed on 16-inch centers, you will have a solid piece of lumber on top and bottom of the wall as well as at every stud.

Solid lumber has an R-value of between 1 and 1.25 per inch, so an average 2X6 stud is about R-6. If you calculate that you have this R-6 in about 30 per cent of the wall, the effective R-value is reduced to about R-15.8. When the studs are moved to 24 inches on center, the values increase a little to about R-17.5.

That however is only a portion of the reason for insulation to not be as affective as it could be.

Let me explain it this way. If you put on a nice heavy knit sweater in the winter because you are cold, many times it keeps you too warm if you are just wearing it around the house.

Fibreglass insulation is much the same as that sweater. What happens though when you go outside and the wind is blowing? If you don't have a jacket or something under the sweater you freeze! The sweater will not keep you warm.

In technical terms we call this wind washing.

Fibreglass insulation has very poor insulating value if the wind can pass through it, just like that sweater. Therefore, if you want to ensure that your insulation does its job, you need to stop the air from passing through it.

How can this be accomplished? How much warmer would you be if you took a large plastic garbage bag, cut wholes fro your arms and head and put it on over the sweater? You would find that you were once again very warm, even if the wind is blowing. However, you will begin to sweat, which will cause you to get wet.

That is uncomfortable for you, but if this happens to the insulation in your walls, they will also have other issues. Consequently you need to stop the air, but let things breath or dry as well.

Sort of like if you were to wear Gortex© clothing.

Fibreglass insulation will be cold if air can pass through. Now we can look at alternatives.

Blown-in fibreglass has the same issues as batt, plus its R-values are only about R-2.5 per inch.

Cellulose is another insulation that works well since it is a denser material, therefore allowing less air to pass through it. They are less affected by wind washing. It provides a slightly better R-value of about 3.8 per inch.  A material that has been around for over 50 years believe it or not, is now catching on in residential construction is a foam spray called polyurethane. This material provides very high insulation values per inch, plus stops air.

Its advantage also is it is sprayed into place wet and dries within 30 minutes.

Solid insulations can be used on exteriors.

One example is Styrofoam. This is a polystyrene foam sheet. It has an R-value of 5 per inch. When used on a wall, you can remove the exterior sheathing and replace it with Styrofoam Cladmate.

This may allow you to reduce the size of the studs from 2X6 to 2X4. If you apply 2 inch Styrofoam sheathing it provides an R-10, plus the 2X4 wall of R-12 (effective R-9.6). The advantages are no loss from air movement, and no solid lumber in contact with the exterior.

The cost of materials is usually a determining factor for many. The better a product performs, the more it costs. You will have to decide whether you want to upgrade to save money.

Do a simple analysis. If you can save $50 per month, and you multiply that by 12 months, you will save $600 in a year. What is the cost of the material versus the extra cost for heating?  NHS

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Darrell Paul, Building Consultant, has dedicated his entire career to the residential building industry. He is president of Building Science Resources, is a director with the Professional Home Builders Institute of Alberta (PHBIA) and is an accomplished speaker/presenter in addition to instructing home building and building science courses with SAIT.