ERV
What it is
Energy-recovery ventilator (ERV) — a heat-recovery ventilator designed to transfer heat and moisture.
While bringing in this fresh air, the ERV/HRV exhausts an equal amount of stale air from the home, ensuring balanced pressures throughout the home.
Heat recovery ventilators (HRVs) simultaneously bring in outdoor air and exhaust indoor air, with both ducts passing through a heat exchanger for heat recovery. Energy recovery ventilators (ERVs), function like HRVs but move transfer both heat and moisture.
The ERV/HRV should be located so that duct runs can be short and straight, power and control wiring can be connected easily, and the unit can be easily accessed for maintenance. Many ERVs/HRVs produce a fair amount of noise; keep this in mind if units will be located near sensitive areas (e.g., bedrooms).
Most of the HRVs and ERVs discussed here are ducted systems—i.e., two ducts run from the unit to the indoors, and two ducts run from the unit to outdoors. Cost for installing these duct systems is often a large part of total system cost. To help address this challenge, Panasonic has introduced a local ERV called the WhisperComfort.
Its parts
- Exhaust fan
- Exhaust fans are installed in kitchens and bathrooms to expel moisture, odors, and particles.
- Many older homes are equipped with kitchen and bathroom exhaust fans. While these fans provide intermittent ventilation to remove contaminants near the source, whole-house ventilation is intended to operate continuously (or at automated intervals) to provide dilution of potential contaminants across the whole house.
- Air filter
- Most filters are designed to filter either particles or gases.
- Furnace and HVAC filters work to filter the air only when the system is operating.
- Most comfort conditioning systems that circulate air incorporate some form of air filter.
- Air balancing
- Alternatively, manual balancing dampers in supply trunk ducts provide air balance control to different areas or zones of the house (rather than individual rooms). This is a common solution for two-story houses where one trunk serves the first floor and another trunk serves the second floor.
- Ideally, each supply branch duct should already have a manual balancing damper, typically located at the supply trunk take-off, to adjust airflow to each room. If so, incrementally adjust the dampers to reduce airflow to the comfortable rooms and thereby increase airflow to the uncomfortable room(s).
- Two-pipe reverse return: Again, heat emitters are piped in parallel, but return and supply piping are sized so that the overall piping path length for each heat emitter is identical. Consequently, the flow rate and temperature of the water entering each heat emitter are roughly the same, and balancing is much easier than in direct return systems.
Related pages
- Glossary: ERV
Its entry, and the guide's pages that use it.
- Home ventilation
Fresh air, bathroom and kitchen fans, range hoods, and ERVs and HRVs
Sources
- ENERGY STAR. Draft 1 ENERGY STAR Version 1.0 Heat/Energy Recovery Ventilator Specification.
- U.S. Department of Energy. Balanced HRV/ERV Checklist (PNNL Home Improvement Expert).
- U.S. Department of Energy. Whole House Ventilation Strategies for Existing Homes.
- U.S. Department of Energy. DOE Building America Measure Guideline: Selecting Ventilation Systems for Existing Homes.
- U.S. Department of Energy. Health and Wellness with a Zero Energy Ready Home.
- U.S. EPA. Guide to Air Cleaners in the Home.
- ASHRAE. ASHRAE Handbook Chapter 1: Residential Space Conditioning.
- U.S. Department of Energy. Pressure Balancing Supply and Return Ducts in Existing Homes.
- U.S. Department of Energy. Balancing Hydronic Systems in Multifamily Buildings (DOE Building America).