Installing exterior rigid insulation to existing walls
I am looking to add exterior rigid insulation to an existing house that is located right at the border of Climate Zones 4 & 5. I have read many conflicting ideas about the proper way to construct the revised wall. The current wall construction is (from inside to out):
1/2 GWB
3 1/2″ studs w/ R-13 Batt Insulation
1/2″ OSB sheathing
house wrap
Wood siding
My plan is to remove the existing siding and house wrap (both are deteriorated) and resurface the wall as such (inside to out): PDF attached
1/2″ GWB
3 1/2″ studs w/ R-13 Batt Insulation
1/2″ OSB sheathing
1′ strips of 1 1/2″ Polyiso Rigid insulation between 2×4 studs running vertically
Tyvek Drain wrap
Aluminum siding
My other option is to put the furring outside the rigid insulation (which seems more common) but I still would like to use the drain wrap between the rigid insulation and furring.
Any thought, comments or suggestions?
Thanks
Andy
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Replies
It would be much easier, faster and more efficient if you apply the foam to the sheathing in full sheets and apply furring to the outside.
Andy,
It's always best to install rigid foam as a continuous layer (rather than cutting it up into rectangles and inserting the rectangles between furring strips). A continuous layer will perform better from a thermal perspective -- the resulting wall will have a higher R-value -- and will do a better job of reducing air leakage.
Moreover, installing the furring strips on the exterior side of a layer of continuous rigid foam gives you the benefit of a rainscreen gap.
For more information on these issues, see these two articles:
How to Install Rigid Foam Sheathing
All About Rainscreens