I was hired a few years ago to consult on a new luxury residence to make the house as green as possible. At about 7,500 square feet, many people would argue that it could never be a green home, but as I was brought in after the design was complete, my job was to do the best I could with what I was given to work with. While the builder, Mike LaBelle, had no prior experience in high-performance homes, luckily for everyone, he was very interested and enthusiastic about learning how to build better.
We had some very good, open discussions on how this new, high-performance home would work differently than the owner’s existing older home, and the builder, the owner, and I worked together to make the best decisions for the project. ICFs were selected for the wall structure early in the process, primarily for aesthetic reasons. My recommendations included a spray-foam insulated roofline to bring the attic furnace and ducts into conditioned space, solar water heating, high-performance HVAC systems, and an ERV.
So far, so good
Construction went smoothly, and the builder ultimately decided to have the house certified as an EarthCraft House, achieving a HERS index of 56 and meeting the then-available federal tax credit threshold. The owners moved in, and all was well in the world of luxury housing.
After a few months, I heard from both the owner and the contractor that the power bills seemed very high. We discussed possible problems, and I offered to come out to the site to help figure out their problem. Ultimately, the owner hired Southface Energy Institute to investigate the problem.
A mechanical engineer from Southface did a thorough review of the energy usage and equipment in the house, and generously provided me with a copy of his report on the house. The heating and cooling loads were appropriately low for a house of this type, but the electrical baseload was through the roof at about 7,000 kWh per month.
Inspections of the existing house systems identified three items that together accounted for over 6,000 kWh of the baseload: a hot water pump, pool pumps, and HVAC supply fans. After the house was occupied, a continuous pump was installed to create a hot water circulation loop to eliminate the wait for hot water in the bathrooms. This pump was installed on the electric backup tank rather than the solar storage tank, causing the electric elements to run continuously as the water was being circulated around the house in an uninsulated line. This accounted for about 4,000 kWh per month.
Two pool pumps — one for filtering, one for vacuuming — were running full time, adding another 1,400 kWh per month. Finally, the owners kept the furnace blowers on full time (not realizing that the ERV provided necessary fresh air throughout the house), adding another 900 kWh to the baseload.
Recently, the continuous hot water pump was changed out with a timed pump, the pool pumps were set on timers to run only when needed, and the furnace fans were set to auto. Results are not yet in, but it is expected that these changes will help bring the baseload down to a reasonable level and allow the owners to benefit from the high-performance home they live in. I will report on the progress as I learn more.
As the consultant, I was not involved in the pool equipment selection, nor do I have the expertise to make appropriate recommendations in this area. I will, however, research pool equipment for any future projects and share my knowledge with new clients.
I always recommend against hot water circulation loops, opting for demand-operated systems. The pump was probably added at the suggestion of the plumber — a typical solution for long hot water runs, with no consideration of the energy penalty involved.
Keeping the furnace fans on full time may have been a habit left over from the owner’s previous house or possibly a suggestion of the HVAC contractor; in either case, it was a poor decision that added to excess electrical use.
What I took away from this project is the need for everyone involved to always keep the big picture in mind throughout the process, to maintain open communication, and to avoid making changes and additions in a vacuum. The entire construction team must stay in communication throughout the project and stick to the plan; no one should make any changes unless they are considered in the context of the whole house and its systems. Finally, commissioning of mechanical systems is important but rarely done in residential construction; this situation should change.
Fortunately, the problems with this project proved to be relatively minor and simple to correct. A less-conscientious builder could have made significant changes and created problems with the building envelope or moisture management that would have been complicated and costly to correct. In this case, all that was needed were some minor adjustments, and the only penalty was some wasted energy.