Proposed Change 1835

Drain-water heat-recovery (DWHR) units capture lost heat from hot water as it drains. The energy performance path in Section 9.36. of Division B of the NBC permits Code users to account for the contribution of DWHR units to overall energy performance. However, the Code does not currently assign energy conservation points to DWHR units for compliance with the prescriptive trade-off path.

DWHR units are popular due to their ability to save energy and are mandatory in some jurisdictions.

Failure to assign energy conservation points to DWHR units would prevent the Code users who choose to install them from accumulating the associated energy savings when complying with the prescriptive trade-off path. In order to accumulate energy conservation points for higher performance tiers, more options in terms of energy conservation measures are required than are currently provided in the Code.

This proposed change assigns energy conservation to DWHR units. Code users would benefit from additional options for achieving the minimum energy conservation points for compliance with the energy performance tiers if DWHR units were added to the list of eligible energy conservation measures in Subsection 9.36.8.

Additionally, this proposed change adds granularity for energy conservation points provided in tabulated form for DWHR units by allowing interpolation. If this proposed change did not permit interpolation, Code users would only be able to claim the lower of two point values when the minimum performance of the chosen DWHR unit falls between two values listed in proposed Table 9.6.8.10.-B.

Failure to add additional energy conservation measures to the Code could prevent Code users from accumulating sufficient points to comply with higher tiers, as required by their respective jurisdictions.

This proposed change would improve the affordability of complying with the energy performance tiers through the prescriptive trade-off path. By assigning energy conservation points to drain-water heat-recovery (DWHR) units, Code users can get credit for the energy savings associated with these units. DWHR may be less costly than other energy conservation measures. In some jurisdictions, DWHR is mandatory.

In Table 1., the DWHR units with a heat-recovery efficiency of 70% and 75% have a 4 in. drain compared to a 3 in. drain for other efficiencies, resulting in a higher cost. The costs listed in Table 1. were valid on May 11, 2023.

Code users who choose to install a DWHR unit would be credited with between 1.5 and 5.4 energy conservation points, which represents the percentage energy savings, and would incur a cost of between $402 and $1,674.

Table 1. Comparison of Costs and Energy Savings of Various DWHR Units by Region

Source: homedepot.ca and renewability.com; prices include retail markup and Canada-wide free shipping.

Notes to Table 1.:

* Powerpipe DWHR unit, 3 in. drain (for unit with 30% efficiency).

** ThermoDrain DWHR unit, 3 in. drain with PEX (for units with 40% to 60% efficiency).

*** Powerpipe DWHR unit, 4 in. drain (for units with 70% and 75% efficiency).

This proposed change could be easily enforced by the existing Code enforcement infrastructure because the percentage efficiency of the DWHR unit appears on the product sticker.

Designers, engineers, architects, builders and building officials.