Thursday, June 30, 2016


Now that everything that goes inside the wall cavities has been installed, it is time to fill those cavities with insulation.  We used several different types of cavity insulation in addition to the rigid EPS insulation that was installed on the exterior walls during framing.  The highest performance readily available type of insulation is closed-cell spray foam.  It provides over R6 per inch of thickness and also does a good job of air sealing.  However, it is the most expensive and also has environmental impacts due to the materials used in its manufacture.  Therefore, we used closed cell spray foam selectively in a few places where its properties would help the most.  Cellulose insulation is the most affordable and environmentally friendly common insulation product, so we used cellulose for the hangar/garage walls and for the attic spaces.  Cellulose is not recommended for basement walls.  Also, our insulation contractor was not comfortable installing cellulose in the walls that have exterior rigid foam.  Therefore, fiberglass insulation is used in the basement and exterior walls.

Closed cell spray foam is used in the rim joist areas and on top of the wall top plates in the attic.   Over the top plates, it is used for its air sealing capabilities.  The air barrier of the ceiling is a polyethylene sheet.  The air barrier at the walls is the OSB sheathing.  The spray foam connects these layers to one another to avoid air leakage between components.  The ceiling air barrier gets interrupted at interior walls, so spray foam is applied over the top plates of the interior walls to connect the ceilings of adjacent rooms and prevent air leakage through interior walls.  Some of the spray foam is applied before drywall installation and some of it will be done later.

Some rooms have vaulted ceilings.  In these rooms, access to the outside top plates will be difficult after the ceiling drywall is installed.  To get spray foam on these top plates, a piece of poly sheeting is installed and held in position by a temporary piece of OSB while the foam is applied.  The OSB gets removed before drywall is installed.  The grey baffles provide an air pathway from the soffit vents to the attic after the insulation gets installed.  Notice on the right of the picture, the spray foam installer had to create a psuedo top plate using some fiberglass batts in order to have a surface to spray against.

In the rim joists, the spray foam reduces heat leakage via the top surface of the concrete wall.  The air sealing properties also supplement the peal and stick air barrier on the outside of the rim joist to prevent air leakage.

The framed exterior walls in the basement are insulated with unfaced fiberglass batts.  The rigid EPS between these framed walls and the cement wall keeps the cavities warm enough to prevent condensation.

In the hangar and garage, cellulose is installed in the walls using the damp-spray method.  Enough water is added to the cellulose to make it stick.  Most of that water dries before the drywall is installed.  It can continue to dry later because the drywall and the OSB on the outside have some vapor permeability.
The insulation contractor was uncomfortable using damp-spray cellulose for the house walls because the rigid foam on the outside would prevent any drying toward the outside.  So, we used a blown-in fiberglass method.  Fabric is stapled to the studs.  Then, fiberglass is blown into each stud bay through holes in the fabric.

This picture of our stairwell shows the blown-in fiberglass process.  On the first floor, the fabric has been installed but the insulation has not yet been blown in.  On the second floor, the insulation material has been blown in.  When the drywall is installed, the fiberglass will get compressed.

This is the master bedroom with the walls and ceiling insulated.  For some reason, the contractor decided to staple a layer of polyethylene on the walls after blowing in the fiberglass.  That was removed before the drywall got installed.

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