Tag: rainscreen

Energy Efficiency starts from within

1″ exterior eps (vapor permeable) continuous insulation beginning to be installed
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FOUNDATION: we used 6″ core Insulated Concrete Forms (LOGIX brand) for the foundation.  The sub slab insulation was state-of-the-art 2lb spray foam — we are able to fully seal all plumbing, electrical conduit and other penetrations with this form of sub slab insulation.  This is one of the most important aspects of creating an energy efficient heated slab: allow the slab to heat the home with every calorie possible, and not the earth beneath it.  Also, this form of sub slab insulation provides a complete and continuous radon and vapor barrier,
WALL ASSEMBLY:  This home demonstrates a vapor-permeable wall assembly – meaning that the wall is designed to allow water vapor to pass through all of its assemblies.  We are trying to achieve the tightest assembly possible, while using a system of materials that encourage vapor transmission — air tight, ventilated right and walls that can breathe.   First off,  the house was sheeted with plywood instead of osb because plywood has a greater perm rating (allows water vapor to pass through it to a greater degree) than osb.  We used SIGA sheeting tape to air seal the plywood seams.  Our primary insulation on the walls is wet-blown cellulose, which of course is breathable and also provides an insulation material that completely fills whatever shape each bay provides.  IN certain areas, like behind the fireplace for example, where it would have been difficult to execute the job properly with cellulose, we apply a combination of 2lb and 4 lb spray foam.  Window and exterior door perimeters and all exterior wall penetrations are spray foamed to seal them properly.  Electrical outlet boxes on exterior walls will be caulked as necessary to seal them up.  On the interior side of our exterior walls we have applied Certainteed’s MemBrain, which provides a continuous air barrier on the interior plane of the wall assembly, while allowing water vapor to pass through it.  Actually, this incredible material’s permeability changes with the seasons, keeping the moisture out in the winter months, while allowing the wall assembly to dry out during the warmer months.  On the outside of the building, we applied tyvek house wrap, taped the seams and we will soon be applying a 1″ layer of continuous insulation (C.I.)  This C.I. will be, of course, vapor permeable, allowing water vapor to be drawn through the wall toward the exterior.  To further encourage the drawing of moisture outward, we will be creating a “rainscreen” — a 3/4″ to1.5″ air gap between the siding and the C.I. that will allow air to travel vertically in the space between the siding and C.I. — air will be introduced low in the siding and exhausted high, utilizing a thermal-siphon effect.
ATTICS and CEILINGS: For some of the roof assembles in this home, it was not practical or possible to properly vent them.  For these areas, we used a hybrid 2lb and 4lb spray foam application to air seal and insulate — these dead spaces will be thereby conditioned.  For the other attics, we extensively air sealed the weakest links in our assembly with spray foam: drywall seams, wall to ceiling connections, ceiling penetrations (light cans — all LED of course; smoke detectors, light recepticles etc), truss heal to plate connections — this is the number one source of leaky assemblies, gable end wall plate edges.  On top of the air sealed drywall, we have blown in an R-60 of cellulose and in each of the attic accesses (this house has 4) we built special spray foam lids that will provide an excellent air and thermal break at each of these notorious weaknesses.

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All in all, this home is sure to perform at a very high level.  The HRV will handle energy efficient, calculated and filtered air exchanges for the entire home — we will be targeting a ACH of .3 or, simply put, all of the air inside this home will be exchanged completely approximately every 3 hours and 20 minutes.
WINDOWS and EXTERIOR DOORS: we are using Glo European’s A5 product.  They are truly amazing! Triple-paned windows with thermally broken frames and sashes.  It was below 20 degrees outside, we were at around 65 degrees in the home and when i put my hand on the largest pane of glass in the house, which also happens to be north-facing, it actually felt warm to the touch.  Any budget that can allow for these windows should absolutely incorporate them.