Heat Recovery Ventilation Units are products designed to replace utilised air with outdoor air that provides an option to recover (or salvage) waste heat from the exhaust air stream from a building ventilation system and use it to heat the incoming air stream to the same building ventilation system.
Heat Recovery Ventilation Units use heat exchanger technologies to recover heat from the exhaust air of building ventilation systems that would otherwise be lost to atmosphere. Some products may also be used to reduce the energy used by air conditioning systems by removing heat from the incoming air.
A wide range of heat recovery ventilation units is available. The Energy Technology List (ETL) Scheme aims to encourage the purchase of products with higher levels of effectiveness in heat recovery.
The ETL Scheme covers two categories of product:
- Ventilation Units with plate heat exchangers.
- Ventilation Units with rotating heat exchangers (including thermal and desiccant heat wheels).
To be eligible for inclusion on the ETL, products shall meet the requirements as set out below.
1.3.1 Eligibility requirements
To be eligible, in addition to a heat exchanger, products shall be equipped with:
- Fans for supplied and extracted air,
- Filters for supplied and extracted air,
- Sensors with an embedded control system or an interface to an external control unit,
- Housing encompassing the above.
1.3.2 Performance requirements
Products shall have:
- A dry heat recovery efficiency at the product’s 100% nominal air flow balanced flow condition that is greater than or equal to the values set out in Table 1.1 below.
- A pressure drop across each side of the heat exchanger(s) within the product at the product’s 100% nominal air flow that is less than or equal to the values set out in Table 1.1 below.
Table 1.1 Performance requirements for Heat Recovery Ventilation Units.
Dry heat recovery efficiency (%)
Pressure drop (in pascals)
Units with plate heat exchangers
>= 78 %
<= 250 Pa across each side.
Units with rotating heat exchangers
>= 78 %
<= 200 Pa across each side.
">=" means "greater than or equal to"
"<=" means "less than or equal to"
- The 100% nominal air flow is the flow rate specified by the manufacturer according to the product’s design. If no nominal air flow is specified, air flow resulting from the full fan speed (at standard air conditions 20 °C and 101 325 Pa) may be used.
1.4 Measurement and calculations
1.4.1 Measurement standards
All products shall be tested in accordance with the relevant procedures and test conditions in one of the following standards:
- BS EN 308:1997 “Heat Exchanger: Test procedures for establishing performance of air to air and flue gases heat recovery devices”.
- ANSI / AHRI 1060 / 1061:2018 “Performance rating of air-to-air heat exchangers for energy recovery ventilation”, Air-conditioning, Heating & Refrigeration Institute. ANSI / AHRI 1060 /1061:2014 and 2005 will be accepted until further notice.
- JIS B 8628: 2017, “Air to air heat exchanger”. JIS B 8628:2003 will be accepted until further notice.
- Other equivalent test standards where the resulting performance data can be scientifically proven, using the methodologies in ANSI/ASHRAE Standard 84-2008 “Method of Testing Air-to- Air Heat/Energy Exchangers”, to be equivalent to that obtained under BS EN 308:1997.
- In particular, submitting results of tests performed to obtain Heat Recovery System’s thermal efficiency for a Non-Residential Ventilation Unit as defined by Commission Regulation (EU) No 1253/2014, is encouraged.
1.4.2 Test requirements
The dry heat recovery efficiency shall be calculated using the formula for thermal efficiency in Annex IX of Commission Regulation (EU) No 1253/2014 and test data collected when rating the product’s performance in heating mode at the test conditions specified in the selected standard for the type of product.
Where products are too large to be tested at their 100% nominal air flow under the standard test conditions specified in AHRI 1060 / 1061: 2018, BS EN 308: 1997 or JIS B 8628: 2017, then performance data obtained at other test conditions may be extrapolated using validated models.
For the avoidance of doubt test data should be presented to zero decimal places. As an example, a plate heat exchanger with a minimum dry heat recovery efficiency of 77.4%, or a pressure drop of 250.5 pascals, would be deemed to be a fail.
1.5 Verification for ETL Listing
Any of the following testing routes may be used to demonstrate the conformity of products against the requirements:
- In-house testing – Self-certified
- In-house testing – Self-tested and verified or cross-checked by an independent body
- Witnessed testing
- Independent testing
- Representative testing (see clause 1.5.1)
Further information regarding the first four routes can be found in Guidance Note 5 on the ETL product testing framework1.
1.5.1 Representative testing
Where applications are being made for two or more products that are variants of the same basic design, test data may be submitted for a representative selection of models, provided that all variants:
- Use the same heat transfer mechanisms as the representative models.
- Are constructed from materials with same heat transfer characteristics.
- The 100% nominal rated output of the products being applied for is not more than five times, or less than one-fifth, the 100% nominal rated output of the product tested
It should be noted that:
- If a manufacturer voluntarily removes the representative model from the ETL then other products linked with that representative model may or may not be permitted to remain on the ETL.
- If any product submitted under these representative model rules is later found not to meet the performance criteria when independently tested, then all products based on the same representative model will be removed from the ETL.
1.6 Conformity testing
Products listed on the ETL may be subject to the scheme’s conformity testing programme in order to ensure listed models continue to meet the ETL requirements.
1.7.1 Indicative review date
The next technical review is scheduled for 2023-24.
1.7.2 Illustrative future direction of the requirements
Future changes to the Specification may include:
Further uplift of thresholds