Aug 06 2009

Deep Energy Retrofits: How to deal with the houses we live in

by Dan Clar | Montpelier Bridge, August 2009

After last year’s $4/gallon oil prices, we’ve all heard increasing talk of weatherization. This is good, important work that needs to happen. But there is another model that needs to gain momentum, and that is the Deep Energy Retrofit (DER). Unlike weatherization (weather stripping, some insulation in the easy to reach places etc.), which is often relatively affordable, DER’s can be expensive. This tends to make people hesitant. But, isn’t the money already on the table? It doesn’t take too many years for the thousands of dollars we spend every single winter to heat our homes to approach the cost of a DER.

The City of Montpelier has 3,115 single family homes (source: U.S. Census Bureau, 2000) which represents over half of the built structures within the city. Of these houses, just under half were built before 1940. As a builder/remodeler, I have worked on a lot of these houses, and it is clear to me just how much the builders of that era were not thinking about energy issues (my house was built in the 30’s and had absolutely no insulation in it at all when I bought it in 2008!) Heating these houses consumes a tremendous amount of fuel, and they cost small fortunes to operate.

A blower door test done on one home showed that cold air was entering the house through the equivalent of a two-foot-square hole.

We are fortunate in Montpelier to have three recent examples (that I know of) of deep energy retrofits, interestingly all done or contracted by homeowners who make their livings within the field of Building Performance. Each household that I will review used a unique approach to achieve the same goals: to use less resources to operate the house, and to be more comfortable within that house.

John and Liz Snell have lived in their house on First Ave for thirty years. Their utility costs had always been reasonable, but only as a result of keeping the thermostat set low. They can see their retirement years ahead of them, when they will be spending more time in their house than they currently do, and they would not want to have their thermostats set at 55 degrees all day. The Snells adopted a DER approach and worked with Clar Construction to detail the project. John and Liz were also interested in remodeling their house, to create the opportunity for a bedroom on the first floor. This presented the obvious option to add the performance details on the inside of the building envelope (within the wall sheathing of the building).

John and Liz built 10” thick walls that were air sealed, and filled with cellulose, yielding an R-value 38. (R value is a unit of measure that determines the resistance of heat flow).  They sprayed urethane foam on the basement walls, and in the attic they air sealed the floor, and blew 20 in. of loose fill cellulose (R-76).

In order to measure the quality and success of this type of work, a blower door test is often set up. This unit measures the air tightness of a building and helps to determine where the problem areas are. Although there is not enough room within this article to go into detail about this, let it suffice to say that the results of the blower door test on this house started at 4700cfm50 (this is approximately equivalent to a 2 square foot hole in the house, that is leaking hot air all the time), and have thus far been reduced to1800 cfm50, and we expect drop below 1000 (about a 10” x 10” hole) when the project is completed later this summer. Those of us involved in the project are anxious to see the projected savings realized in the next heating season.

Roofers shouldn’t just be roofing. Siders shouldn’t just be siding. We need to demand more from our contractors.

Another example of a deep energy retrofit is on George St. Elliott Curtin and his family bought a house in 2005 that had been severely neglected. Here is a case where the interior of the house required major remodeling to make the house livable and comfortable, and a few hours after closing on the house, Elliot began the demolition. They gutted the entire house and established a building envelope that has performed extremely well. The Curtins live in a 2000 sq. ft home and burn approximately 250 gallons of oil/year. That includes six showers a day (they have four kids), plus heat. Elliott used a combination of foam and cellulose to create the air and thermal boundaries of the house. His blower door test yielded an impressive 300cfm50 (about 3” x 10” hole, and is considered an extremely high performing house).

On Hebert Rd, another example of a retrofit can be found. This one employed the principles of treating the exterior. Brian Abbott, a remodeling contractor here in Montpelier, was ready to sever his ties to the oil company when he began stripping the siding off his house. Unlike the aforementioned projects, the interior of Brian’s house was in excellent condition, but the siding was 25 year-old vinyl that had faded and was ready to be replaced. Once the siding was stripped, Brian embarked to diligently wrap his entire house (except the roof) in foam insulation. In conjunction with the exterior treatment, Brian air-sealed his attic, and blew in 16” of cellulose insulation, yielding an R60. According to the blower door test, Brian has cut the air leakage of his existing house by more than half, and he continues to identify and address the sources of the remaining infiltration.

Here we have three local examples of significant improvements. These three homeowners are going to realize considerable savings in their heating bills, achieve a level of comfort in their homes that they had not known before, and live in houses that are healthy for themselves and their families (with the use of ventilation not discussed in this article) while minimizing the impact that our built environment has on the rest of the world.

I’m a builder and remodeler. I love to build things. But we need to stop building and renovating our houses as if fuel doesn’t matter. Roofers shouldn’t just be roofing. Siders shouldn’t just be siding. We know how to build better, and even if every homeowner who is doing work on his house doesn’t have the money right now to put into the performance of the house (although the incentives in 2009 are pretty tempting), we need to demand more from our building contractors. We need to make the deep energy retrofits illustrated above the norm, so that the enormous stock we have of leaky, old existing housing can continue to house us in an affordable and comfortable way.