# Building heat recovery: Engineering and integration

Small kit, low risk, but timing and space matter

Source page: https://www.materialinsights.org/energy/e_building_recovery/rc-eng/

What this tab covers Engineering and operating integration: how tightly it is coupled to the host process, how steady the waste stream is, and how hard it is to retrofit.

These are small, mostly plug-in technologies with low coupling risk; the main engineering issues are installation quality and matching supply to demand in time.

#### Process interdependence (coupling risk)
Favourable

Failure rarely stops the host. A drain-water unit simply stops preheating; a heat-pump water heater usually has a resistance element as backup; chiller heat recovery is a side loop that can be bypassed. The exception is ventilation: if an HRV or ERV fails in an airtight building, fresh-air supply is lost, so maintenance of fans and filters matters for health as well as energy.^[6](https://bsesc.energy.gov/energy-basics/hvac-energy-recovery-ventilation)

#### Load factor and intermittency
Mixed

Simple drain-water units only work when hot water is used and drained at the same time, as in a shower; a test house in Ontario recovered about 790 kWh a year. Chiller heat recovery works when cooling and hot-water demand coincide, which they do all day in hotels; the Mumbai hotel case saved about 80 litres of diesel a day. Ventilation recovery runs continuously but gains most in extreme seasons.^[2](https://sustainabletechnologies.ca/?p=5720)^[8](https://iifiir.org/en/fridoc/benefits-of-superheat-recovery-on-chillers-case-study-for-a-hotel-21304)
 Test-house drain-water recovery about 790 kWh/yr^[2](https://sustainabletechnologies.ca/?p=5720) Hotel diesel saved about 80 L/day^[8](https://iifiir.org/en/fridoc/benefits-of-superheat-recovery-on-chillers-case-study-for-a-hotel-21304)

#### Footprint and retrofit complexity
Mixed

Drain-water units need a vertical drain run below the shower, so they are easiest in new build. Heat-pump water heaters need about 700 cubic feet (about 20 m3) of surrounding air and lose efficiency in cupboards. HRV/ERV retrofit needs ducts, which is disruptive in existing homes. Kitchen demand control is a retrofit of sensors and fan drives: a 5,000 cfm hood cost about USD 43,000 installed.^[4](https://energystar.gov/products/ask-the-experts/heat-pump-water-heater-right-your-home)^[7](https://www.wbdg.org/FFC/ARMYCOE/COEECB/ARCHIVES/ecb_2015_3.pdf)
 HPWH air space needed about 700 cubic feet^[4](https://energystar.gov/products/ask-the-experts/heat-pump-water-heater-right-your-home) Kitchen demand control, 5,000 cfm hood about USD 43,000 installed^[7](https://www.wbdg.org/FFC/ARMYCOE/COEECB/ARCHIVES/ecb_2015_3.pdf)

#### Sources

1. [Evaluation of Residential Drain Water Heat Recovery Unit (study begun 2010)](https://sustainabletechnologies.ca/?p=5720) Sustainable Technologies Evaluation Program (Toronto and Region Conservation Authority), 2017
2. [Is a Heat Pump Water Heater Right for Your Home?](https://energystar.gov/products/ask-the-experts/heat-pump-water-heater-right-your-home) ENERGY STAR (US EPA), 2023
3. [HVAC energy recovery ventilation (Energy Basics)](https://bsesc.energy.gov/energy-basics/hvac-energy-recovery-ventilation) US DOE Building Science Education
4. [Engineering and Construction Bulletin 2015-3: Demand control kitchen ventilation](https://www.wbdg.org/FFC/ARMYCOE/COEECB/ARCHIVES/ecb_2015_3.pdf) US Army Corps of Engineers (via WBDG), 2015
5. [Benefits of superheat recovery on chillers: case study for a hotel installation (Rane and Tandale), 21st IIR International Congress of Refrigeration](https://iifiir.org/en/fridoc/benefits-of-superheat-recovery-on-chillers-case-study-for-a-hotel-21304) International Institute of Refrigeration, 2003

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_building_recovery/index.md)
- [Overview](https://www.materialinsights.org/energy/e_building_recovery/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_building_recovery/correlation/index.md)
- [Science and thermodynamics](https://www.materialinsights.org/energy/e_building_recovery/rc-sci/index.md)
- [Economics and contracts](https://www.materialinsights.org/energy/e_building_recovery/rc-econ/index.md)
- [Impact and additionality](https://www.materialinsights.org/energy/e_building_recovery/rc-impact/index.md)
- [What to track](https://www.materialinsights.org/energy/e_building_recovery/tracking/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_building_recovery/links/index.md)