We had already walked and jogged on our journey to green, but we began to worry that we would miss out on our chance to run. We had a pretty good reputation as one of the few builders in town familiar with green building, but the real estate market was headed down, so we weren’t building any more spec homes. We introduced all of our new customers to a range of green building programs, but none of them were very interested.
Back to the classroom
In an effort to expand our knowledge and create a new revenue source for our company, I got certified as a Building Analyst by the Building Performance Institute. This was probably the best class I had taken to date. That was when the whole “house as a system” idea really clicked in my head.
After that class, everything I read made much more sense. When I needed to make decisions, I was able to ask much better questions of our subs and suppliers. I would recommend this class to any new home builder — even if you have no intention of building green or getting into energy audits or weatherization. (I would also recommend doing some remodeling and home repair – nothing teaches how to build better than seeing houses that were not done properly).
This was also about the time that GreenBuildingAdvisor came online, so I spent hours every night reading all the new articles.
Clients with a vision
While working as an exhibitor at one of the local green building events, we met a fascinating couple who wanted to build a LEED Platinum home. Finally – our chance to run. What made it better: this couple had a mission to build their green house for an average cost. We were very excited to work with this couple and really liked the fact they had an alternate purpose to building a green home.
So we got a project team together and started working on the specifications. This project got under way right after the National Green Building Standard had come out. We recommended doing that certification as well as LEED for Homes — in order to compare the two rating programs — and they were up for it.
While working through the checklists for the two certifications, we learned about the DOE Builder’s Challenge. We all liked the fact that the house must score below 70 on the HERS Index — other green building programs don’t really insist on a target HERS number — so we thought this would be a good thing to shoot for as well. We were really running now!
Reconsidering advanced framing
After conducting a few energy audits, I had a new appreciation for advanced framing. As we looked at what we thought were well-built homes, we were shocked at how cold the studs were during the winter months in some of the houses we visited. We immediately knew that we needed to improve our thermal envelope and reduce thermal bridging.
We spent a lot of time looking at cost-versus-value on the thermal envelope. We finally decided on 2×6 wall construction, 24 inches on center, with blown-in insulation, rigid foam sheathing, and radiant barrier roof sheathing.
I was still a little reluctant on the 24-in. spacing so I called the Sheetrock manufacturer to ask if ½-in. Sheetrock would be okay. The manufacturer said that in a vertical application, the ½-in. thickness would be plenty. On a horizontal application, however, we should use Type X or go to 5/8 in. Since we were on a tight budget, we kept with the ½ in. If I were doing this on a more expensive house, I would probably consider upgrading to 5/8 in. everywhere.
Will the walls be able to dry?
One of the first things we did was to contact the manufacturers to get spec sheets on all the new products we were planning to use, to be sure we understood how to install them properly. In addition, we needed this documentation for the certifications as well.
While looking at Dow Structural Insulated Sheathing (SIS), I saw that the perm rating was under 0.3. This worried me – it appeared that everyone in the green world recommended exterior foam as a thermal break, but this meant installing a vapor retarder on the outside of your wall. We had always learned from Fine Homebuilding and BuildingScience.com that in our climate you don’t want to have a vapor barrier in your wall; you want to allow the wall to dry in both directions. This is opposite of everything we had learned over the years.
Well – I went to my favorite website, GBA, and asked them what they think. The site proved to be a great resource, and I had some great discussions and received good advice. I also asked several other questions on the site as well — we had moved to a high-performance felt as well, but that too was putting a vapor barrier on our roof which concerned us. But after speaking with the experts at GBA, we felt much more comfortable about where we were headed.
Careful planning yields rewards
We learned our lesson — don’t move forward without having a firm plan — so we had many meetings with our verifier and all of our subs. We went through every detail and every point of the home before we started. Some of the other features we included in the home: passive solar design, a solar water heater, a rainwater harvesting system, an ERV, and a very high-performance HVAC system. Of course we used Energy Star appliances and lighting fixtures, Water Sense plumbing fixtures, low VOC paints, locally produced and non-formaldehyde cabinets and countertops, etc.
We had a great verifier and the construction process went very smoothly. It was nice to have the homeowners so involved in the process – we felt like it was more of a team approach rather than us working for them. All inspections went well and when we ran our blower-door test, we got the lowest reading our verifier had ever done. We ended up with a HERS Index of 52, and the house was built for $126 per square foot. We felt like we had accomplished all of our goals.
The house was one of only three LEED Platinum homes in the state of North Carolina, and the first Gold-certified house in the National Green Building Standard program. You can learn more about this house here.
Danny Kelly is a co-owner of Kelly McArdle Construction in Charlotte, North Carolina.