 W

hether you’re worried about saving a few dollars or saving the environment, there are many ways to go about it when 

2019 issue, Samantha Sawyer discussed solar panels, energy  we’re going to focus on insulation, particularly a system that is becoming more common: continuous insulation (CI).

 energy in or out of a building, so your home stays the temperature you want, and you don’t lose the heat or cool air you’re paying for. The most common insulation in residential construction is   seen in the attic. Fiberglass batt, or batt, insulation is installed in the space between the structural components in the wall, roof, or ceiling.

Measuring R Values

Insulation is commonly measured in R Value. The higher the R value of a material the better insulated a structure is. For houses, R values can range between R-2 for an uninsulated wall to upwards  assembly. While you may install R-13 insulation in a wall or R-30 in a roof, the R value of that assembly, even when you add small increases in insulation from interior  is less than the advertised value of the insulation itself.

The decrease in R value is not false advertising; it’s due to a phenomenon known as thermal

bridging. Air, both hot and cold, is always looking for the easiest way to

travel. Instead of going through thick insulation, it will funnel through openings in the structural parts of the wall where there is less resistance.

The structural components act as  the insulation, funneling energy from your toasty living room to the cold exterior and causing you to pay more to heat your house. In a wood-framed wall, for example, with R-13 batt insulation the effective R value of a wall is closer to R-10.8.

What Is Continuous 

Continuous Insulation (CI) is a layer  substantially reduce thermal bridging  Installed continuously, typically on the exterior side of a wall behind cladding, it is only interrupted by fasteners, windows, and mechanical, electrical, or plumbing penetrations.

CI has been required since 2012 in steel-framed buildings and is frequently used to meet advanced standards, like the Evergreen Sustainable Design Standard (ESDS), Leadership in Energy and Environmental Design (LEED), and Passive House. It’s not necessarily required by code for most reclad projects, and sometimes it makes more

 conservation methods even where continuous insulation is prescriptive. But CI is an important strategy that should be considered as part of a comprehensive energy package for every energy upgrade project.

Looking At Case Studies

To understand the effect of adding continuous insulation to a condominium building, we created energy models for two condominium reclad projects in the Seattle area.

 story, property comprised of eight units with a ground-level garage. The other is a 4,800-square-foot, two-story  and no garage. Both buildings are wood-framed, have existing R12 batt insulation in the walls, and use electric baseboard heaters. Complete re-cladding is planned for both projects. We studied whether adding continuous insulation on the exterior would be a good investment.

Cost savings are typically evaluated against two parameters: payback period and a savings to investment ratio (SIR). The payback period is calculated by dividing the estimated cost of the improvement by the expected annual savings. The result is the number of years it will hypothetically take to recoup the initial capital investment in the improvement.

The SIR is calculated by dividing the total cost savings over the expected service life of the improvement by the estimated initial cost. When the SIR is more than 1.0, the investment is

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