building performance

A Healthy Tension

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Post contributed by Aaron Fairchild:

Doing good for society and the planet and being profitable at it isn’t easy, nor does it come about without a healthy dose of daily tension. At G2B Ventures, the tension we deal with comes with our mission, which is to drive energy efficiency in existing buildings to the greatest extent possible while continuing to make solid, for-profit, self-sustaining decisions. Last week a segment on G2B and our program of buying distressed homes and driving energy efficiency was aired on our local NPR affiliate, KPLU. The day after the segment I received some emails that challenged us on our efficiency work. They didn’t doubt our approach; they challenged the need to replace the windows and tightened up the home in West Seattle to prevent leaks.

Whenever you put yourself out there in the way we have done so far, you have to be open to feedback and criticism. G2B is not only open to it, we encourage and welcome it. So I thought I would put the email discussion out there and available for everyone to understand what goes into these sorts of decisions. So without divulging the source, the concern with windows relates to the imbedded carbon associated with simple replacement verses refurbishment as witnessed through a life cycle assessment. In many cases the embedded carbon associated with replacing windows can be much higher than the efficiency gained through new windows. The second concern is the indoor air quality issues that come from and older house that has been tightened up and is not well ventilated, potentially causing mold/rot problems. The G2B response to these concerns can be read below:

“Restoring the original windows in the West Seattle home was not an option. We had five different types of windows from different vintages, with many of those cracked or not sealing due to the house settling over time and through multiple earth quakes over its 100+ year life. Once the house was lifted and leveled-out, at least one window broke in the process and many others became dysfunctional and couldn't open preventing egress. We are happy to point out that in our next house we will receive Built Green Certification and dramatically improved energy performance, while NOT replacing the windows.

"As you know, “sealing up air gaps” is a common phrase used in building performance, but obviously it’s not as cut & dried as running around the outside of the house with caulk guns and 2part foam.  Using the West Seattle house as an example: exterior rigid foam acts as an additional drainage plane and reduces thermal bridging between framing members, but horizontal seems are loose, ‘Z’ flashed with building paper for moisture vapor escape.  We had ship lap for exterior wall sheathing to deal with, so the wall needing to breathe is one of multiple problems to address.  Attics are vented of course, and special care was taken to fir out the vaulted ceilings to create additional space for ventilation.  Insulation is largely blown cellulose.  And finally, airtight barrier is at the drywall with air sealing at light switch and outlet boxes, penetration & physical air sealing in joist bays, below the knee walls if blocking is missing.  You are correct that mold/moisture is an issue in old homes, and frequently this occurs due to condensation at the cold/hot junctures inside the wall cavity due to a lack of insulation.

"G2B Homes does NOT approach each project with a cookie cutter and pre-planned approach. This is the challenge with existing building rehabilitation. We try to be thoughtful and deliberate and in addition to the G2B institutional knowledge we work with some of the best residential building science folks in town to help inform each project.

"I hope this helps address/alleviate concerns. We are very dedicated to this discussion and have it on-going with every project. Our intention is to be mindful of these issues and to transparently create thoughtful solutions. We want to set the bar as high as we can, but we may not always get it right. We are human, makes mistakes, and as you know the market will only allow for so much efficiency to be profitably pushed into projects.”