Retrofit Is In

May 01, 2011
May/June 2011
A version of this article appears in the May/June 2011 issue of Home Energy Magazine.
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It’s easy to talk about building new houses that are energy efficient. When you build from the ground up, you can do anything—the thickest insulation, the best sealants, the most efficient furnace; but what about older houses? Is it possible to take a house built 100 years ago—when insulation, if it existed at all, consisted of wadded-up newspapers—and make it as energy efficient as a brand-new dwelling?

Greg Pedrick is a project manager at the New York State Energy Research and Development Authority (NYSERDA), a state organization that invests in hundreds of green energy-related projects. The Albany-based organization is a public-benefit corporation that works to encourage green technologies and building practices. One of the unique aspects of NYSERDA, compared to clean-energy incentive programs offered by other states, is that it heavily promotes research and development programs around the state to encourage new types of clean-energy technology.

Three years into his NYSERDA job, Pedrick had been working with new-home builders to promote his ideas on home air sealing and insulation. But this was upstate New York—there just weren’t that many new homes being built.



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But there were plenty of old homes. “A lot, probably 70%, were built before the 1980s, when insulation became common,” says Pedrick. “So there’s a lot more opportunity to work with existing stock.”

So began a bold idea. What if NYSERDA began to work with a bunch of contractors, and showed them some innovative ideas on retrofitting old homes to be more energy efficient, healthier, and more comfortable to live in? Perhaps what they learned from this experiment could encourage contractors all over the state to offer this service to homeowners. 

Begin Extreme Retrofit

In early 2010, NYSERDA introduced the deep-energy retrofit concept in a classroom training targeted to the employees of insulation-contracting companies located around the state. When the teams learned about new insulation technologies and ideas for sealing and installation, NYSERDA requested bids from the groups that participated and hired two contractors to begin the work on four houses chosen beforehand as good retrofit candidates. Each contractor was awarded one house to work on, and when that project was completed each one did a second house.

The houses were located in the heart of upstate New York, where frigid, windy winters are the rule. Three were in the Rust Belt city of Utica, and one was in nearby Rome, home to a now-closed Air Force base and the 1999 Woodstock concert. What followed was a basement-to-attic retrofit that turned four drafty, chilly houses into four models of energy efficiency.

In the basement, insulating foam with a moisture barrier was added to the walls of each house. A dense insulation that could withstand foot traffic was added to the floor, and 3 x 5 sheets of Dura Rock were installed on top of it. The insulation was connected to the upper walls to ensure that no air could get in.

In the main part of the house, the exterior siding was removed down to the sheathing. A new air barrier and 4 inches of rigid insulation were added, with appropriate moisture barriers, before the homes were resided. High-efficiency windows were installed if existing windows were in poor condition, and casings were built out to match the new, thicker exterior.

In two houses the roof was removed, and the roof deck was topped with 4 inches of rigid insulation. The roof was then replaced with corrugated metal sheets. In the other two houses, a flash coat of foam and blown-in cellulose insulation was added to the attic after it was thoroughly cleaned of any old insulation.

Existing mechanical systems were removed and replaced with significantly scaled down systems. The new systems supply domestic hot water and space heating through a tankless hot-water unit and a small furnace equipped with a fan coil. An air-to-air heat exchanger was also installed in each house. This allows fresh air being pulled into the house to be warmed or cooled by the used air being vented out.

Measured Site Energy Consumption Before and After Retrofit
Measured Site Energy Consumption Before and After RetrofitFigure 1. The four retrofitted houses realized an average 76% reduction in the ACH50 calculations. The tighter houses use less energy.

Performance, Performance, Performance

Utility bills were used to evaluate the energy performance improvements. Therm usage, which reflects space and water heating, and electrical usage were compared before and after the retrofit for each of the four retrofitted houses (see Figure 1). In addition, blower door tests were performed before and after the retrofits to gauge the improvements in air leakage. The four retrofitted houses realized an average 76% reduction in the ACH50 calculations. These calculations reflect the amount of air leakage in the building envelope.

In some cases, the amount of air moving through the house during a blower door test was 6 times lower than it was before the retrofit. And the size of the required heating system was reduced from 250,000 Btu per hour to 45,000 Btu per hour in some houses. Air quality was also improved, thanks to a forced-air system that circulates fresh air regularly throughout the house, and to the elimination of the unlined chimneys that typically vent atmospheric heating appliances.

As with many projects by NYSERDA, the cost of this project is an investment in learning new ways to make homes more energy efficient. As the contractors gained experience working on the projects, they worked faster, and so the cost of labor went down. However, the work was expensive—an average cost of $76,900 per house. These costs may drop considerably when retrofit projects like this become more common, contractors become more experienced, and materials can be purchased in bulk.

“We learned a lot,” says Gary Edwards, project manager at Kalex Energy Company of Utica. Thanks to what they learned, the Kalex team significantly cut the time it took them to complete the job from the first house they worked on to the second. For example, removing the siding and installing the thermal air barrier took Kalex five and one-half days on the first house, but only two days on the second one.

For homeowners, some of the tricks learned in this retrofit could be used in smaller doses when it makes sense to do so. For instance, if you were already planning to have your roof replaced, it would make sense to have the foam added to the deck first. If you’re having siding replaced, foam could be added to the exterior walls at relatively low cost. Or a particularly drafty basement could have insulation added. Each piece of work reduces the amount of air passing through the house, and also reduces the amount of energy consumed.

“This was an experiment, and the homes were my lab,” says Pedrick. “Based on the results we’ve seen so far, I would say it was a success. The next step is to determine how to bring the costs down and create a market that can adopt this strategy.”

Alan Wechsler is a communications specialist for NYSERDA.

>> learn more

To learn more about NYSERDA’s advanced buildings programs, go to www.nyserda.org/advancedbuildings.

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