We install geothermal heat pumps for a living. We believe in them and also feel there is no better solution to provide heating and cooling for a home or business in New England. But geo is only part of the answer. Let’s look at a home that incorporates a lot of efficiency features. None of them are over done, and the end result is a very cost efficient and very handsome home. This home demonstrates that high efficiency and classic good looks can go together very well.
This is a six year old home in Columbia Connecticut. Lee and Diane have been interested in energy efficient designs for a long time, having built their own passive solar home back in 1983. For this home, they chose a classic New England design know as a Cape Cod. Cape Cod and Salt Box designs go way back, to when mechanical heating systems were either rare, primitive or unheard of. They are efficient in that they minimize one exposure and maximize another. This one is further enhanced by a south facing full shed dormer (other side). Not only does the expansive south face collect the sun, but the low and angular north face does a great job deflecting those wicked north winter winds. Since the old timers didn’t have the luxury of cranking up the thermostat, they had to plan to live in concert with Mother Nature’s cold side. Although this home has a number of state of the art energy efficiency features, I think it would be hard to tell if this house was 2 or 200 years old by just looking at it. It looks like a classic to me.
Compactness is an element to be incorporated into a design. Squares are better than long rectangles. Stacking floors on top of each other also helps. A design should try to get the most floor area you can build into the space for the least area of surfaces facing the outside. Geometrically, the shape with the least surface area for its volume is a sphere. A Cape Cod is a good example of a shape that comes somewhat close to a sphere. It’s compact. An example of an inefficient layout is a long one story bonus area over an unheated garage. You end up with heat loss in five directions. A two story design is better than a ranch for the same reasons.
Passive solar and orientation
The above picture is the north exposure of this home. As previously mentioned, there is a full shed dormer on the back (south) side. This is the south side.
The southern exposure is heavily glazed. Generally, south glass is a net heat generator from the sun streaming in the windows. This effect is called passive solar, and orienting the home to the south with the biggest windows makes the most of it. Passive solar is well known and often utilized. You don’t need anything unsightly to take advantage of it. Just turn the house so that the biggest windows face the south. Since non-south facing glass is a net heat loss, window sizes on the non-southern exposures were kept to a minimum, with the exception of meeting egress codes for bedrooms. Since windows have a dramatically higher heat loss than insulated walls, reducing the number and size of non-south windows is a simple strategy to enhance the energy efficiency of any home. Often, the most important elements of an energy efficient design are not in the equipment, insulation or technology, but in the simple decisions like solar orientation and shape. Diane is the resident gardener, and as you can see, the results are beautiful. I’ve been there live, and the picture doesn’t do it justice.
The insulated shell (envelope)
The shell of the home was built to EnergyStar standards. The R-values are 19 in basement ceiling, 24 in the walls and 38 in the ceiling and finished slopes. The wall and ceiling insulation is moist spray cellulose. The windows are Low -E glass. None of these numbers are inordinately high, but they are good numbers. The shell passed a blower door test for air leakage and a duct blaster test for the tightness of the duct system. There are two heat loss components that account for the lions share of a homes heating requirements. Heat loss through the windows and air infiltration. The moist spray system did a fine job of sealing up air leakage. Considerable attention to sealing up all penetrations contributes to overall tightness (lots of caulk). By minimizing the non-south facing glass, the owner was able to reduce the loss through the windows.
Geothermal heat pump
The heat/cool system is a four ton two speed geothermal heat pump. The system runs at an efficiency of roughly 400%. It is connected to a 400′ deep closed loop vertical well and provides 100% of the heating and cooling requirements. There is a back-up electric heater, but it has never been used.
Hybrid domestic water heater
Lee recently installed a hybrid electric water heater. This appliance produces domestic hot water at an efficiency of at least 220%, and often higher. The unit has the side benefit of dehumidifying the space (basement) it is in.
Solar photo voltaic system
The final piece of the energy puzzle is an 8.5 kw solar photo voltaic array on the roof. You got a partial look at the collectors in the south facing picture. They are on the back of the house, and even people who find them unattractive can’t really think they are a detriment here. The system can over produce in the summer and the excess is ‘banked’ by the power company to offset lesser production in the winter months.
The electrical bills for this home from 4-23-2013 to 3-21-2014 was $1,434.40. This cost includes a $16.00/month meter charge, which is a fixed monthly fee. When the meter charge is pulled out, the cost of the electricity used is $1,242.40, or $103.53/month. The thermostat stays at 68 all winter, and the owners maintain a comfortable summer temperature. This is a great number. Remember, except for the solar and the geothermal system, very little additional costs were incurred. Thoughtful layout and orientation, quality insulation and attentive air sealing are not big ticket items, but they contribute dramatically to potential savings. Of course, the geothermal and solar play a big part, but when incorporated into a complete energy plan, the benefits seem to exceed the sum of the parts.