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Advice for improving attic and exterior insulation.

Sofiane | Posted in Energy Efficiency and Durability on

Background :

My wife and i recently purchased a 2800 sq ft  built two story home built in 1989 near Ottawa, climate zone 6. It has a thick brick veneer exterior and mostly all windows are facing east and west. We’ve noticed some of the rooms feel rather cold in winter and wanted to improve the efficiency of the home.

We had an energy audit done and blower door test done with an ACH of 3.12.

Our exterior walls are 2×6 with fiberglass batt insulation and we have, being in Canada, a polyethylene vapor barrier prior to the gypsum wall.
Our attic is presently insulated with R-35 fiberglass blow in insulation. We have some HVAC ducts in the attic as our pulsed air system was retroffited. The furnace and most of the HVAC ducts are in the conditioned space.

We need to redo our roofing this year and thought about using this as a chance to uprade the insulation and reduce air infiltration by:

Removing the blow in insulation
Air sealing the attic – I am looking for what would be the best option as I am rather confused on this end.
Adding insulation to get to R-60
Changing asphalt roof shingles for a metal roof.

Would that make sense?
What could and should we do about the ducts? Would burying them in insulation be safe in our climate zone? 

The harder parts is what to do to add insulation to the exterior? 

I was thinking of using about 2 inches of koolthem +  0.5 of eps to get a staggered installation + rainscreen and reinstall the brick veneer. Ideally, I would do it in sections as doing the 4 sides at once would be on the expensive side.  If we could do that, it would make the entire process more bearable. Or does it only make sense on an insulation standpoint if we do it all in one go?

Thank you for your help,


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  1. user-723121 | | #1

    I would follow through on adding additional insulation to the attic. 3.12 ACH50 is not bad but I would hire an energy rater to do a pressure test to identify attic leakage areas. Make sure you have air chutes in every rafter space high enough to extend beyond the additional blown insulation. You likely have a poly vapor barrier on the ceiling so air leakage will be limited to wall intersections, plumbing and electrical penetrations. Removal of the existing attic insulation is not always needed to air seal attic bypasses, they can be located and foamed as is. I would build airtight enclosures around any attic ductwork and add the appropriate amount of insulation over them.

    To upgrade the wall as you describe it is not money well spent, windows the same way. Concentrate on other areas, foundation walls and accessible rim joist areas, work on making the ceiling very airtight and highly insulated.

  2. Sofiane | | #2

    Hi Doug,

    Thanks for your reply, it’s quite helpful!

    I have a few follow up questions :

    Does it make sense to insulate from the exterior to reduce thermal bridging on the joists or is the added expense not worth? In the case of exterior + interior insulation of the joist, should I avoid foam on the inside part?

    As for the windows, would your remark regarding the cost effectiveness apply to windows that already need to be changed?

  3. Peter Yost | | #3

    Hi Sofiane -

    Connecting the air control layer (barrier) of your exterior walls to your attic/roof air control layer is key especially in cold climates. So in your work, connecting the retrofit of your walls and attic/roof is important. If you move your insulation/air sealing from your ceiling to your roof line, and you can apply the "chainsaw" retrofit approach ( , connecting your air control layers is easy, and now all of your HVAC is in conditioned space.


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