Home Building Envelope - Sealing & Insulation Methods

A building envelope is the invisible seal between the inside and the outside of a home or structure, or the barrier between conditioned and unconditioned space. A good one will maintain temperatures inside that are different (either hotter or cooler) from the outside, while shielding the occupants and even the building from moisture, air, and heat loss/gain. A solid, energy efficient building envelope will save substantial money on the cost of both heating and cooling your home.

Insulating spray foam by Great Stuff

There are a large number of ways a home can lose energy, but the good news is there are an equal number of places for you to shore up your building envelope. Caulking, sealing, and foaming up any kinds of gaps or cracks between the inside and outside is the first place to start. Windows and doors are susceptible to drafts, letting cooler air in during the winter and letting the same air escape during the summer months.

Roofing products have advanced in design to the point where they offer superior protection against heat loss, and the installation of radiant barriers can reflect heat back to ensure a cooler summer.

On the bottom of your home, the foundation or concrete slab can go a long way in making or breaking your overall building envelope. Filter fabrics and waterproof membranes can help this area by allowing water to drain away from your home or building while keeping moisture from penetrating the foundation of the building's envelope. And finally there are a bunch of green methods for conserving energy inside your home or building that don't involve any of the externally-facing surfaces. These involve tightly sealing any ductwork or plumbing, therefore saving on the fossil fuels needed to run your heating or air conditioning system.

Energy Saving Tips - Home Envelope Insulation By enforcing a tightly sealed and insulated building envelope, the average home can save between 5 and 40% of annual home energy costs, with the savings greater in houses located in colder climates.

Sealing the Foundation or Floor Slab

The bottom of your home is most susceptible to moisture since it's the part always touching the ground. During new construction, aggregate drainage layers made of gravel or coarse sand should be placed beneath the foundation to encourage good water flow away from the house. Geotextile filter fabrics can be added for additional protection against soil getting into the drainage layer. On the wet (bottom) side of a cement or concrete foundation, another layer of protection can be obtained by damproofing - an applied coating.

Waterproof membranes can be added to either the wet or dry side of a foundation. Such membrane systems include everything from sheets of asphalt & rubber to fluid-based to natural clay (usually bentonite) or cement-based applications.

Insulation of Walls & Wall Cavities

Recent advances to wall and wall cavity insulation techniques make this area a potential for huge energy savings. Celluose-based and spray foam insulation can be vastly superior to standard fiberglass products. Such materials minimize heat and moisture transfer past new levels of green efficiency. Composite wall panels also come pre-cast with foam already trapped beneath its layers, making for easy and no-mess installation.

Insulating Windows and Doors

Astounding amounts of heat loss occurs at the openings between your home and the outside world; more specifically the windows and doorways. Insulating glass windows can be purchased with a sealed air space trapped between panes, not only reducing heat transfer but also the transmission of sound. Coated, tinted, and laminated glass can come with low emissivity coatings that offer reflection or absorbtion of light radiation. Insulated window frames with double-caulked joints can be installed with spray polyurthane foam insulation to keep out drafts and water.

Exterior doors have traditionally used weatherstripping to keep out moisture and air transfer. Not only has the perimeter flashing and waterproofing membranes for standard doors been improved, but the construction of doors has advanced overall. Lighter, more durable exterior doors are better insulated, pre-filled and re-enforced with the latest insulation products. Jambs and frames are tighter and cleaner, and sustainable building includes Energy Star® efficient doors and windows that translate to big savings on utility bills.

Sealed Roofing Systems for Tight Building Envelopes

Each building's roof will be sloped differently, and green building methods exist for both steep-slope and low-slope types. Proper drainage goes a long way in preserving the integrity and lifespan of any roof, no matter how tightly sealed against water. Coverings should be based upon slope and shingle type, and these membranes can be both air and vapor retardant. Roofing membranes come in different thicknesses and breathability, depending upon the climate and type of weather the roof will see. Reflective asphalt shingles can also be positioned to deflect sunlight and help keep air conditioning bills low.

Inside the attic, adding layers of spray-foam or blown-in insulation could see tremendous heat retention in colder areas. Green cellulose is extremely energy efficient for this purpose, both well-insulating and great at blocking air. It's also a product made from recycled newspaper pulp that helps the environment. Pre-fab composite insulation boards can be installed in addition to this, or even a foil radiant barrier to guard against moisture and thermal transfer. Heat rises, and the colder a climate in which you live the more attention you should give to this top level of your building envelope.

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