What ‘R’ You Prattling on About?
By Corey McCloskey, Customer Response Team Representative
Over the last few months, I’ve penned blogs on specific energy-efficient products included in Cedarglen’s Energuide 80 Package, and last week I summed up the changes Alberta’s new energy code requirements are bringing to our industry. As I look back upon my latest composition with fondness, I came to realize there are more ‘R’s in our energy efficiency specs than you’d hear at a pirate convention, and it’s entirely possible you have no idea what an R-value is. And that’s OK!
While a pirate’s favourite letter is actually the ‘C’, for our purposes, the letter of the day is ‘R’. R-value is a numerical representation of the thermal resistance rating of a specific material or assembly of materials, such as a wall, and is calculated using the following equation:
How’s your algebra these days? Translated into English, R is a ratio, derived from the degree difference in temperature across an insulator and the heat flux, which consists of heat transfer per unit area per unit of time ), when the material thickness is nominalized to its thermal conductivity, under uniform conditions.
Helpful, right? I’d be flat out lying if I said I knew that before I wrote this blog, but the Internet is a wonderful tool. Let’s try this: the higher the value of R, the better the insulator it is. That’s better! If you’ve ever seen a bag of fiberglass insulation, you may have already been introduced to this concept. A bag of R-12 batt insulation is meant for a 2x4 wall, and a bag of R-20 for a 2x6 wall. Wider wall, thicker material, better insulator. It’s that easy!
You may have also seen RSI used, as well, which is simply R-value Système International, also known as the way the rest of the world measures stuff, our American friends, notwithstanding. When converted from Imperial to SI, these R-values are reduced 5.67 times, but mean exactly the same thing, so it’s important to know which language you’re speaking.
Let’s bring it back around to your Cedarglen home. Last week, I included a sample performance modelling comparison report, which illustrated the way we would achieve energy code compliance, based on the performance-based path; if you missed it, it gives a great comparison between prescriptive and performance compliance paths for the entire home. Since R-values are the flavour of the week, I’ve created a table of my very own, which illustrates specifically those values, and puts them up against Cedarglen’s spec package.
|9.36 Prescriptive, No HRV & Effective Values||9.36 Performance, Active HRV, Nominal Values||Cedarglen Homes Spec (Includes Active HRV), Nominal Values|
|Wall/Rim Joist Insulation||R-17.49 RSI-3.08||R-20||R-20|
|Attic Insulation||R-59.22 RSI-10.43||R-40||R-60|
|Foundation Wall Insulation||R-19.65 RSI-3.46||R-12||R-20|
What did we discover about R-values earlier in this blog? Bigger numbers = better insulation, that’s what, and we’re bigger where it counts. You pay for heating and cooling, and more of your money stays right where it belongs, inside your Cedarglen home. Oh, and our windows have an extra pane of glass, we’re more efficient at heating the air and water in your home, and our building envelope details are superior. We could talk about that now, or we could wait…
Tune in next week!
Have a great weekend,