Today's ramblings are about the insulation encapsulating Casa Tortuga. Insulation is one of the main components of a passive house. For the uninitiated, the amount of insulation we have in this house is a real head shaker. More often than not, folks will look at us in disbelief when the subject comes up and you can see them mentally calculating the expense of all that over insulation and then...well...they shake their head some more.
You be the judge. Here's what has gone into insulating this house...
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| 14" (35.5cm) of XPS under the slab. That's an R-value of 70. |
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| 1" (2.5cm) of foil-faced polyiso/XPS between the stud wall and the concrete foundation wall. This is the layer that gives us the continuous air-tight envelope, bottom to top. |
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| 1" (2.5cm) foil-faced polyiso, making its way to the ceiling of the upper level. This layer also serves as our vapour barrier. |
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| The air-tight envelope is completed with the installation of 1" (2.5cm) polyiso on the ceiling of the upper level. |
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| On the inside of the 1" (2.5cm) polyiso is 6" (15cm) of Roxul mineral wool insulation. |
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| On the outside of the concrete foundation, 2 layers of EPS Styrofoam equal to 10.5" (26.6cm) is installed. Also, note the 16" (40.6cm) deep I-joist cavities above the styrofoamed concrete foundation. |
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| Those 16" (40.6cm) deep I-joists, installed all around the house above the concrete foundation wall, get filled with dense-pack cellulose. The wall system is now around R-72 (Roxul/polyiso/concrete/EPS) to R-90 (Roxul/polyiso/cellulose) when the Roxul, polyiso and cellulose components are added together. |
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| Last but not least, 28" (71cm) of blown-in cellulose in the attic completes the passive house insulation. R-value here is around 80. |
Well...are you shaking your head yet? Laid out in pictures like this it does seem a bit over the top. But the fact that the heat pump rarely gets past the ultra low setting on a cloudy day here in the winter makes it all worthwhile.
I will say the lack of a conventional heating system makes for a very comfortable living environment. You may know what it's like with the drier winter air and the forced-air heating...how you feel like you're drying up from the inside out, the chapped lips, the parched mouth, the itchy dry skin. Well...that doesn't happen here. Just one of the perks of insane amounts of insulation.
Gotta love it!
More later,
Mimi
