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.

Gas heating costs, winter 2008

Here's a tabulation of our gas bills for last winter, which totaled about $830 for heating, excluding the average $32/month we use for hot water.

• Domestic Hot Water usage is estimated based on our summer bills
• Total cost excludes National Grid's $13 connection fee

Roof insulation performance, warm weather

The cathedral ceiling in the third-floor/attic, an unvented roof insulated with icynene foam and a double radiant barrier, seems to perform well in warm weather. We didn't install central air conditioning (too expensive both upfront and operating cost), and we both have office space in the third floor, so we depend on that roof insulation system for comfort both winter and summer. So far, in hot weather the attic temperature is always lower than the outside temperature, which I think is pretty good.

Boston's had our first heat wave the past few days, and I took some measurements today. We keep most windows closed during the day, opening them at night to pull cooler air through with a small "whole-house" attic fan.

Location	11 am	3 pm
Outside air	89 F	93 F	air temp
Exterior siding (south wall)	95	114	surface temp
Exterior shingles (roof)	132	152	surface temp
Attic ceiling	86	92	surface temp
Attic air	83	89	air temp
Second floor air	81	84	air temp
First floor air	80	82	air temp

The cathedral ceiling is only 6" thick (made of 2x6 rafters), so all that separates the interior drywall from the 150-degree shingles is 6" of icynene foam and the 1" radiant-barrier airspace.

Happy New Year

It's our first new year in our new home. The house is wonderful, both in our everyday life with the complications of work and school days, and for the entertaining we've started to do. It has performed well in the winter and there are no real problems in any of the structures or systems.

I haven't posted here for a very long time, but have a backlog of material I'd like to get online, including interior painting progress (about 2/3 done now) and heating system performance (good).