Need Exterior Insulation In Edmonton? Avoid Foil Faced Polyiso For These 3 Reasons
Some insulation products just don’t work in Edmonton’s unique climate.
Exterior insulation has absolutely exploded in popularity in the Edmonton area over the past few years. It makes total sense, too: with our “so cold your nostrils freeze” winters and our “fry an egg on the sidewalk” summers, Edmontonians have to deal with some pretty intense temperatures.
And when a homeowner in Edmonton is planning a siding renovation, it doesn’t cost all that much to add a layer of insulation before the new siding gets installed. And siding contractors sure don’t mind the chance to add to the projects price tag, either!
But installing exterior insulation isn’t as easy as just slapping up some foam panels and calling it good. There’s actually a whole bunch of building science that goes into selecting the right insulation products, and how to install them for the best long-term results.
And when you dig into the science, there’s some major red flags about one exterior insulation product in particular: foil-faced polyiso insulation panels.
Wait. What Even Is Foil-Faced Polyiso Insulation?
Simply put, foil-faced polyiso is a common type of exterior insulation that is frequently installed in Edmonton.
Polyiso is short for polyisocyanurate which is a very science-y sounding word, and I promise that you won’t have to read it again in this article. Unlike other foam based insulation products, when polyiso is manufactured, it comes out as a liquid. So it’s applied it to a backing material that gives it structure while it dries. Once it’s cured, its texture looks and feels similar to dried sprayfoam.
By far, the most common backing material used is foil. Manufacturers use foil because it’s reflective, so it can help with insulation value. They also use it because it’s light and cheap!
I really don’t know why, but foil-faced polyiso has become the default option for exterior insulation in Edmonton. All the siding suppliers have lots of stock on standard thicknesses, and it would be easy for anyone to go pick up a truckload of it today. So if you ask your contractor for exterior insulation and don’t specify the type, there’s a good chance you’ll get foil-faced polyiso.
But before you let your contractor install it, make sure you’re aware of these potential problems:
Problem #1: Declining R-Value Over Time
When it’s first manufactured, polyiso has the highest R-value of all exterior insulation products. In other words, it does the best job of stopping heat from leaving (or entering) your home.
But that “extra” R-value isn’t permanent! Over a period of 15-20 years, the R-value of polyiso drops back to about the same R-value as any other generic styrofoam product.
This is because polyiso gets its extra R-value from a mix of special gases that are pumped through it during manufacturing. Over time, these gases leak out of the polyiso insulation and are replaced with plain old air, which has a lower R-value. This process is called “off-gassing”.
When the off-gassing is complete, your polyiso insulation will still have an R-value. It just won’t be more than generic products, which are much cheaper to buy in the first place.
Problem #2: Lower R-Value During Edmonton Winters
Exterior insulation makes your home energy efficient year-round. And our clients love the way their insulation keeps them cool on Edmonton’s hottest summer days.
But let’s be real: when an Edmontonian is thinking about upgrading the insulation for their home, they’re thinking about keeping warm in the winter. And that’s where polyiso really falls short. Remember that special blend of gases that gives polyiso its extra R-value? Well, unfortunately they freeze when exposed to sub-zero temperatures. And when they’re frozen, the R-value of the entire panel plummets.
Unfortunately, I can’t tell you exactly how much the R-value drops because there’s no solid data out there. Since most product testing is paid for by the manufacturers themselves, they don’t really have an incentive to publish test data that exposes weaknesses in their insulation.
And because the true R-value loss will vary from project to project, it’s difficult to nail down exactly how much the impact will be. (For example, thicker layers of polyiso insulation don’t seem to suffer quite as much from cold temperatures as thinner layers.)
Sources that I’ve reviewed place the insulation loss between 25% on the low end and 50% on the high end. The truth probably lies somewhere in the middle.
(You might be wondering, if polyiso loses so much R-value in cold temperatures… why do they even bother making this product? The important thing to remember is just how few people live in climates as cold as ours. The combined 94 million people down south in California, Texas, and Florida don’t need to worry about freezing temperatures: they’re trying to FIGHT the warm air.! And polyiso works great for them.)
Problem #3: Water Vapour, Condensation, & Rot Damage
The problems we’ve discussed so far affect all polyiso insulation products, and they’re real issues. But with all that said, there is absolutely still a place in the market for polyiso. Blue Jay Exterior Renovations has installed Iko EnerAir (a fiberglass-faced polyiso insulation that has some breathability) in the past, and we will again in the future if the right situation comes up.
This next problem applies to all foil-faced (and plastic-faced) insulation products, whether they’re made from polyiso or something else. They create an external vapour barrier, which means they trap moisture vapour inside your walls.
You can try this experiment at home: fill a plastic bowl with warm water. Cover it with plastic wrap, and pop it into your freezer for 10 minutes. Then, take a look at the plastic wrap. You’ll see that a bunch of little water droplets have collected on the under side. If you run your hand across the plastic, you’ll find that it’s quite wet.
The warm air in your home has water vapour in it, just like the warm air in the bowl. And when that warm air moves through your wall and hits your foil-faced insulation, that vapour will turn from a gas to a liquid, and your walls will become wet.
And since foil-faced insulation products are completely air and vapour proof, your walls will have a really hard time drying out. Next stop? Rotten walls.
EnerSpan GPS Exterior Insulation: The Best Fit For Edmonton
So, if we can’t use foil-faced polyiso insulation, what’s a better choice? We should be looking for a product that:
● Comes with a good initial R-value, to make the investment of exterior insulation worthwhile
● Has a stable R-value that doesn’t decrease over time
● Doesn’t lose R-value when it gets cold outside (aka when you really want to have the best insulation possible in your walls)
● Is breathable, so your exterior walls stay healthy and dry for the long term
EnerSpan GPS insulation manufactured by PlastiFab checks all these boxes. EnerSpan’s R-Value of 4.7 per inch never goes down over time or due to temperature changes. And with a permeance rating of 5.2, EnerSpan qualifies as a semi-permeable material that allows moisture vapour to escape from your walls.
Want more information on the benefits of EnerSpan over foil-faced polyiso? We’ll be happy to fill you in on all the details.
Just call Blue Jay Exterior Renovations today at (780) 850-2602 for an in-depth consultation and a free quote on your project. We’re committed to helping you find the perfect exterior insulation solution for your home!