Why Exterior Insulation Will Save You Money

Today’s guest post is from Skylar Bowker, who has been helping homeowners modernize the look of their home while saving them money through EIFS (that’s External Insulation Finishing Systems, kids) renovations for over 5 years.  And just what are EIFS, and how can they help you save money?  Let’s find out!

Take it away, Skylar!


Living in regions of North America necessitates that your home be somehow insulated from frigid outdoor temperatures in the northern winters, or the scalding heat of southern summers. This form of insulation has taken many forms over the decades (and even centuries) depending on location – wool and animal hides in the settlement days, newspapers towards the late 1800’s, and batt/cellulose insulation in the 1900’s.

Each advancement in materials and technology making homes a little more comfortable for it’s occupants. It wasn’t until the cost of heating and cooling a home become a growing issue due to rising energy prices that making the absolute most of insulation became a nationwide (even global) concern.

While building professionals and architects who attend conventions and training seminars understand why and how exterior insulation is a worthwhile alternative (or addition) to between-the-stud insulation, it’s time that you (the public) become educated and jump on board.

Insulation Continuity
One of the primary reasons that exterior insulation is so effective is because it is continuous. Between-the-stud insulation, which has become so standard, fails in two aspects:

First it is discontinuous at the studs which creates an area that is uninsulated. Studs can make up as much as 5%-10% of a wall surface, meaning that a wall filled with R-10 insulation can actually have a true R-value around 9. Additionally, if it is metal studs in the wall a thermal bridge is created – a material through which heat can be rapidly transferred from one area to another.

The second problem is that batt insulation is not airtight. There are hundreds of tiny air spaces between batts and between a batt and a stud. Unlike discontinuous insulation however, airflow has a huge affect on overall R-value. An area as much as 2% of the wall that allows air flow can reduce R-value by upwards of 60%, bringing your wall filled with R-10 down to R-4. This is why a room with an improperly sealed window or door is so much colder than other rooms.

(Note: Spray-foam insulation between the studs in lieu of batt insulation does an excellent job at eliminating gaps through which air can escape, but is unfortunately not standard just yet.)

Compound the two problems and your actual R-value can be as low as R-3 even though you used R-10 batt insulation in your walls.

Exterior insulation solves both of these problems in one fell swoop. By placing the insulation on the exterior of the sheathing, you are able to butt the edges of the insulation (typically a rigid form like EPS or XPS) directly up against one another, covering 100% of the wall surface. By butting the insulation up against one another and covering the insulation with a material you are also able to eliminate air flow and the problem associated with it.

That’s the theory anyway. In the real world a continuous weather barrier is typically placed between the outside of the sheathing and the exterior insulation to act as the true barrier to airflow. This is often a necessary step anyways to create a drainage plane for condensation to drain out from behind the insulation. While not perfect, this method maintains 90%-95% of the insulation’s R-value.

Weather Barrier and drainage
While the topic deserves an entire textbook and is still widely misunderstood, the position of the insulation (whether on the interior or exterior of the wall sheathing) will affect the location of the “dew point” and therefore the optimal placement of a weather and vapor barrier.

The dew point is the temperate at which humidity condenses to form water, and is important to manage in order to prevent moist conditions that are ideal for mold growth within a wall. In cold climates, placing the insulation on the exterior of the wall causes this dew point to be located on the exterior of the wall, thereby preventing water from forming between the wood studs and sheathing.

This again affects where you want to place a barrier to prevent moisture from traveling from one location to another. Over the past few decades the standard practice was to place poly on the inside of the wall, between the studs and the drywall, but as the insulation was moved to the outside of the wall, it became important to also place this barrier on the outside of the sheathing to prevent moisture from becoming trapped.

Varying thickness
Another benefit to exterior insulation is that you are not limited by the thickness of insulation that you can use. With traditional between-the-stud insulation you can only go as thick as the studs are, which are made as small as reasonably possible to preserve interior floor space.

Exterior insulation is typically between 1.5″ to 2.5″ in residential construction, but can go up to 5″ to 6″ if required (though this more common on commercial and institutional buildings). At 2.5″, EPS will provide an R-value of roughly 9.
Note: some municipalities require a permit if you will be adding more than 3″ of insulation to exterior of your home.

Government Programs
Various Government energy-efficiency programs have sprung up in the U.S. and Canada that will refund some of the cost associated with renovating a home with exterior insulation. These programs usually require an initial audit by an inspector beforehand to evaluate present conditions, and a final inspection afterward to examine what alterations were made.

In Ontario (Canada) for example, a homeowner can get a rebate of up to $3,750 for adding R-9 insulation to their exterior walls. That means that for a home that cost $12,000 to renovate with exterior insulation, almost a third of the cost was immediately regained through a check from the Government and the balance was likely to be gained through lowered energy bills over just a decade.

Some of the programs have expired, but it’s worth keeping your ears open for them being re-implemented. With society becoming more and more energy conscious, it’s likely the programs will be re-implemented in some form or another.

So, what does it all mean?
I was talking to an older gentleman a few years back who had recently covered his decaying bricks with EIFS (Exterior Insulation Finish Systems), a wall system that integrates continuous insulation with a continuous weather barrier and a beautiful exterior finish. When the power went out on a 5 degree Fahrenheit day in his neighborhood the previous winter, he told me that the interior temperature of the home didn’t drop more than 5 degrees over an 18 hour period. Aside from saving him potentially hundreds of dollars a year in heating and cooling costs, he was able to comfortably ride out a power outtage in his renovated 1930’s home that left his neighbors freezing, some of whom were even forced to go to a local community center to keep warm.

The point is that whether you’re living in a 1930’s home that didn’t originally have insulation, or are building a brand new home, adding exterior insulation is among the most cost effective ways to reduce heat lost (or gained depending on your part of the country), and in doing so, reduce your heating and cooling bills. Looking into Government rebates that may be available can help you recoup your investment quicker, but as an investment in your home – you just can’t do better.

To get in contact with multiple EIFS contractors to obtain a reasonable quote for a well-done job, visit us at: Stucco Toronto.


Thanks, Skylar!



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