Replies

1. 
   user-869687 | Oct 25, 2011 05:23am | #1

   Sam,

   There's no way to answer this question in such general terms. Energy usage depends on many variables including when and how a structure was built, design of the thermal enclosure, details of mechanical equipment installed, type of occupancy and occupant behavior. Sharing walls is one way to reduce heat loss in a cold climate, so an attached house will generally consume less energy than a detached house of the same size with similar build quality, similar mechanical equipment and similar occupant behavior. You would have to quantify that on a case by case basis, and it will depend partly on geometry--the percentage of shared surface area for the heated volume of the house. For example a middle rowhouse unit may have a narrow front elevation and a lot of shared wall surface along the sides, which will save a lot of exterior surface relative to heated volume. An end unit will have less shared surface, and a wider plan would also reduce shared wall surface.

2. GBA Editor
   Martin Holladay | Oct 25, 2011 05:37am | #2

   Sam,
   Ditto to what T.J. Elder said.

   Also: you asked about your monthly electric bill. Clearly, your heating costs are only related to your electric bill if you heat with electricity.

3. 
   jklingel | Oct 26, 2011 11:28pm | #3

   Sam: To elaborate on what was indicated above, heat loss is a simple and linear math equation. Assume that two buildings are similarly insulated and one has twice the surface area exposed to the cold as the other: the larger one will lose twice as much heat as the smaller one. If one has 50% more exposed area, it will lose 50% more heat. Assume there are two houses of the same size, same place, and one has twice the insulation (same kind) as the other: the better insulated one will lose half the heat of the other. There are important details in the mix that I ignored for simplicity, but that is a good generality.