Energy savings is important when it comes to saving money, and many home improvements can generate substantial energy savings that lower utility bills (or stabilize usage as Technology Driving Up Utility Bills). When we think about saving energy at home, most people assume we're talking about things inside the house.
This article instead, talks about the barriers or envelopes that separate a home's interior from the outside, and the benefits they provide – energy savings, an airtight home that's more comfortable and fewer problems due to water penetration.
Energy Savings from An Envelope?
Wikipedia defines an envelope as “… a common packaging item, usually made of thin flat material. It is designed to contain a flat object, such as a letter or card.” While a house envelope isn't flat, the concept of a house envelope fits because your home is surrounded (packaged) by materials that protect it, similar to security or waterproof envelopes. There aren't any envelopes or boxes big enough to hold a house, so house envelopes are fabricated around the house as it's being built.
- The thermal envelope – delivers energy savings by reducing the amount of air exchanges between your home's interior and the outdoors. The thermal envelope is the pink area shown above as we don't typically heat our attics, basements or the garage.
- The building envelope – illustrated by the gray border, wraps a house to keep water out, preventing water damage and related problems. The building envelope because of the materials used, also contribute to energy savings.
Many Layers for Energy Savings
Unlike the envelopes we use to mail letters, your house envelope will last many years and it's likely you'll either replace or add a layer like more insulation, to gain even more energy savings. The envelopes are made of multi
- Drywall – is the interior finish you paint. It hides the framing and everything inside the walls – electrical wires, plumbing, insulation, etc. In older homes, this layer might be made of plaster and the wood slats to support it.ple layers of building materials, each with a specific job so to help you understand the layers, let's put our Superwoman glasses on and look through a wall in your house:
- Framing – provides the structure for your home, from the foundation up to the roof plus interior walls that define your rooms.
- A vapor barrier – is typically found on one side of your insulation. The paper (asphalt adhesive) stops water vapor from passing through to the insulation, where mold might grow.
- Insulation – is a key component of your thermal envelope, providing the most energy savings. It reduces the flow of heat from warm to cool areas and your home may use multiple forms of insulation.
- An air barrier – typically combines sheathing (plywood or OSB) and either building paper, house wrap, or rigid board insulation. New green sheathing products offer integrated sheathing with a weather-resistive barrier to save labor as only the seams need to be taped versus wrapping the entire house with a vapor barrier like Tyvek.
- Siding is the final external finish, keeping everything inside dry and some new siding materials integrate insulation for added energy savings. Where there are openings for windows and doors, flashing provides added protection at the seams.
|This article covered the layers that make up your home's envelope. Each layer must be installed properly, i.e. the seams sealed where one material meets another, to get maximum energy savings, water and air tightness. The materials to seal these seams will vary, i.e. flashing goes under the siding and over the tops of windows and doors while caulking is used to fill the cracks where the siding butts up to doors and windows.|
Hopefully this explanation of the layers making up your exterior walls, will help you understand why home repairs can be so challenging. There are many materials and layers involved, with each contributing to energy savings and making your home air and water tight.