krista@veldarchitect.com

THE AGRITECT

A blog about all things rural and agritourism related

Baby, its warm inside! Cost-effective insulation


Tags: , , ,     Categories: Technical, VELD architect

In light of this cold snap, I thought I’d tell you a little about insulation and how to design and keep your house warm without breaking the bank!

roxul insulation in the stud space and cathedral ceiling

Most people know that r-value is how to measure the quantity of insulation in your walls and that affects how well insulated your house is. Did you know that there are many choices and combinations of insulation you can choose from?

The Ontario building code has been slowly increasing the energy and insulation requirements for all buildings. There are a number of options to choose from but the code minimum is around R22-25 in your walls and R40-50 in your roof (Zone 2). These can be accomplished in a variety of ways. using a variety of insulation in the stud space with or without some exterior continuous insulation. Remember that the code is the minimum required by law, it doesn’t mean it the best performing or the best value for your dollar. Passive house or low-every homes, often have R50+ in the walls and R80+ ion the roof! I always spec more insulation when possible to give you the best performance for your budget and goals.

You insulation choices used sing-ally or in-combination are as follows:

  • Fibreglass batt: this is the pink stuff your used to that makes you itchy to install. I never spec this as it doesn’t perform well over time and can mold if it ever gets wet. R-value of 2.2-2.7 per inch.
  • Mineral wool batt. This is my go-to insulation, as it will not mold! Just in case it ever got wet in the walls it won’t mold and contaminate your breathing air. It is the most cost effective and averages around R3.7-4.2 per inch(Therefore in a 6″ stud(actually 5.5″) you have 20.35-23.1 R-value. Note that this doesn’t quite meet the minimum code requirements.
  • Spray foam (open cell): Open cell spray foam is a good option for higher r-values in less space. At 3.7 per inch it performs very similar to mineral wool batt, but it does cost more. But it does reduce air leakage in the overall building!
  • Spray foam (closed cell): closed cell spray foam is great because it has a high r-value and it acts as an air barrier! (achieving goal #2 for building performance). It is more costly, but it seals your house really well, and is great for cathedral ceilings. It has an r-value of 6.5/inch. Therefore only 3.5 inches are required in your stud space to acheive code minimum. Of course you can add more for better performance! Be careful on your application of closed cell spray. It acts as a vapour barrier, so no poly barrier is required and dewpoint calculations should be done to ensure no damage to the wall in cold weather.
  • Expanded Polystyrene (EPS): This is often also call “bead board” and it is composed of small white beads. This product often comes with foil face adhered to it and is used for exterior continuous insulation. It is cost effective with a r-value of 3.85/inch. It does vary in performance with different temperature ranges. With the lower value it does take more space (depth) of wall to increase the insulation value, but for code minimums 2″ is usually sufficient.
  • Extruded polystyrene (XPS): One of the more expensive options it has a R-value of R5/inch, but if you need the added exterior insulation and you want to get more out of the space you have, it great. It can also act as an air and vapour barrier to eliminate the interior poly costs and increase air-tighness with the proper construction details. Caution: as it is a vapour barrier care must be taken to ensure no damage to wall when moisture enters it.
Spray foam, an ideal solution for cathedral ceilings

I mentioned continuous insulation earlier. Although an insulation material has a certain R-value, when combined with studs which are only R1.41 per inch, and make up approximately 10% of the wall area, your overall wall performance decreases in R-value because of these “thermal bridges” So although your insulation is R24, you overall wall assembly might only be R20. Therefore the Ontario Building Code has creates a term call continuous insulation (CI). meaning a layer of insulation that does not have any breaks in it. In the code not all options require CI, but I always recommend it as you will have a better performing wall. CI is usually a board insulation put on the outside of the studs. There are two choices for this material:

  • Expanded Polystyrene (EPS): This is often also call “bead board” and it is composed of small white beads. This product often comes with foil face adhered to it and is used for exterior continuous insulation. It is cost effective with a r-value of 3.85/inch. It does vary in performance with different temperature ranges. With the lower value it does take more space (depth) of wall to increase the insulation value, but for code minimums 2″ is usually sufficient.
  • Extruded polystyrene (XPS): This is the pink or blue boards. One of the more expensive options it has a R-value of R5/inch, but if you need the added exterior insulation and you want to get more out of the space you have, it great. It can also act as an air and vapour barrier to eliminate the interior poly costs and increase air-tightness with the proper construction details. Caution: as it is a vapour barrier care must be taken to ensure no damage to wall when moisture enters it in cold weather.
2-layers of XPS insulation for a total of R24 continuous insulation on a passive house

The combinations of wall types are endless and at VELD architect we will help you pick the best wall assembly for your budget, energy goals, and type of construction. We’ve looked at the various combinations and determined the cost per R-value of overall walls, the advantages and disadvantages of each and can help you pick the best wall assembly for your project. Contact us now to help you keep your house warm.

Insulation is important, but did you know that is only half the equation for keeping your house warm. Air leakage is the second most important factor, followed by windows and free heating! But we’ll save that for another post… stay tuned

If you can’t wait, you can check out the post about blower door tests and air tightness here.

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