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Community and Q&A

Semi-detached vs Detached home

user-1044545 | Posted in Energy Efficiency and Durability on


Can someone educate me on typical heating costs for a semi-detached vs completely detached home? I’m considering two homes and both are about 2000 sq feet. I’ve heard the average in this area in NYC during cold months is about $500/month for detached homes but can’t get a number for the semi-detached. The broker told me it will be 1/2 or 1/3rd of a completely detached home but that seems hard to believe

Does anybody know if having a shared wall saves you that much in electricity costs?


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  1. user-869687 | | #1


    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 | | #2

    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 | | #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.

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