4 Storey Wood Frame Apartment Building

20-40 years old

image of a 4 storey wood frame apartment building

Building Overview

  •  Four storey wood frame multi-unit residential building (common in the BC Lower Mainland)
  • Copper piping for domestic hot water. There is a re-circulation pump on the hot water system, which is controlled by an aquastat, so that the supply and return temperatures remain relatively constant (leaving water temp = 60ºC, entering water temp = 50ºC).
  • The heat flux from the domestic water piping contributes to space heating during winter months
  • Heat source: direct fired gas water heaters with a nameplate efficiency of 80%
  • Indoor design temperature: 20ºC
  • Heating season: September 15 to May 15 (8 months)
  • Gas cost: $9.486/GJ • Service life: 20 years
  • Building conditioned floor space: approx. 45,000 square feet (4,200 square metres)

Modeled Scenarios:

1. No insulation on hot water pipes

2. 25mm thick insulation on hot water pipes


Over the course of one year the following savings would result from the use of insulation.

The following table summarizes the impact on overall building energy consumption.


The estimated payback for the investment in insulation during construction would be less than 4.0 years based solely on the energy costs.

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