Energy efficiency measures

At the outset of the project, a key objective of ours was to increase the energy efficiency of the new house. We looked at fancy stuff like geothermal heat pumps and photovoltaic solar, but all those technologies are evolving rapidly, and now doesn't seem like the best time to invest. So, we planned for what I'd call conventional "best practice" energy efficiency. Here's a summary of those measures, and how they've worked out so far:

• No central air conditioning

There are usually about 10-20 days in Boston with temperatures near or above 90. So far, on those days we can keep the indoor temperature down just by closing windows during the heat of the day, then opening the house and using the whole house fan in the evening.


• No fireplace or internal chimney

This was a big aesthetic compromise, but I think it really helps keep the house tight.


• Exterior 6" walls, insulated to R20


• Efficient double-pane low-E windows

We have a lot of large windows, and clearly lose a lot of heat through them in the winter. We did try to minimize glass on the North side, however.


• Attic roof insulated with icynene foam and double radiant barrier

The semi-finished attic has a small crawlspace on top, which is vented in the summer with a Broan attic fan (1200 CFM), acting as a simple and quiet whole-house fan.


• Hydronic (hot water) baseboard heating, one zone per floor



• High-efficiency, modulated-flame, condensing gas boiler

A Weil-Mclain Ultra 80 boiler, properly sized, theoretically runs at about 92% efficiency. "Modulated" means that it reduces its flame when it's not too cold outside, analagous to shutting off cylinders in
a car engine that doesn't need full power. It doesn't run at full capacity until it's -10 degrees F outside.


• Indirect water heater

A Weil-Mclain Ultra 60 gallon tank is heated by a dedicated "zone" of the main boiler. Water temp is turned down to about 120 deg F, since the dishwasher and clothes washer (both Bosch)
have their own internal heating for sanitization.


• Compact fluorescent and LED lighting where appropriate



• Non-metallic ducting for all exhaust fan penetrations

Sometimes the ducts for bathroom fans or dryer vents are made of aluminum and create an efficient "thermal bridge" from the inside to out. We used plastic components. For the kitchen exhaust fan, by Nutone, we found a rubberized canvas sleeve by Excelon to connect to the outer vent.


• Bathroom fans are still a problem...

I think we lose a fair amount of heat through the bathroom fans in the winter. There are energy-recovery systems for these that we should look at sometime.