Common Questions About Energy/Heat Recovery Ventilators

1.What is a heat recovery ventilator? 

Heat recovery ventilation(HRV), also known as mechanical ventilation heat recovery (MVHR), is designed to enhance the amount of heat energy exchanged between the two airflows(fresh air and exhaust air). In winter, the warm exhaust air preheats the supply air as it enters the building. In summer, the warm supply air will be cooled by the exhaust air.

Put simply, heat recovery ventilation allows you to bring fresh air into a home without letting the heat escape.

2.What is an energy recovery ventilator?

Energy Recovery Ventilator(ERV)is used to provide energy savings in mechanical ventilation systems. They recycle energy from the building’s exhaust air to pretreat the outside air/ventilation air. Except for recovering heat, it also allows for moisture exchange between the supply and exhaust airflows. This allows for the regulation of humidity which can prevent or mitigate excessive dryness, particularly over the winter months. So Energy recovery is the combination of Heat recovery and Moisture recovery.

3.What's the difference between HRV and ERV(which one to choose)?

Not all HRVs or ERVs work in exactly the same way. 

Normally HRV transfer only heat in the air, which reflect on the unit itself is that it should be equipped with condensation drain.

While, energy recovery ventilation (ERV) works in a similar way but transfers some of the moisture from the outgoing airstream into the incoming air, so it keeps the humidity in your home at a constant level. This is important if you don't want your home too dry. 

As a general rule, ERV is a better option if you have air conditioning and live in a humid climate, because it will help to keep moisture outside, reducing the load on your air conditioner and saving on the air-con bills. HRV is often better if you don't have air conditioning, or live in a less humid climate since it will help keep the humidity down by transferring excess indoor moisture outside.

4.How does an energy recovery ventilator works?

Fresh air is continuously brought into the home by the system and a like amount of stale indoor air is exhausted at the same time; in other words, the air is being exchanged. However, the hot or cold energy (depending on the season) is extracted from the indoor air before it’s exhausted and transferred to the incoming air so that there is little energy lost.

5.Why you need to recover heat?

Modern homes are usually built to far higher technical standards than buildings constructed a few decades ago and are much more energy-efficient, largely thanks to better heat insulation.

One key area of improvement has been to make buildings more airtight so they hold onto the heat we put into them for longer. But there's a drawback: our homes need regular changes of air to keep them healthy. Baths and showers, doing the dishes, clothes washing machines, drying clothes indoors, and even simple breathing produce astonishing amounts of water inside our homes: according to leading ventilation manufacturer Vaillant, a typical family will produce 10–15 liters (3–4 gallons) of moisture each day!

Let that problem go unchecked and you'll get problems like mold and mildew, dust mites, and a greater risk of asthma. Opening doors and windows are the obvious way to get rid of moisture and bring in the fresh air, but if you do that in winter you might just as well flush your money down the toilet: all the heat you've expensively introduced into your home will blow away in the breeze.

An old drafty house solves this problem by being automatically well ventilated, but it's probably also freezing cold because it's useless at holding onto heat; a modern energy-efficient home solves the draft problem but may be stuffy and underventilated. 

6.How many types of heat/energy recovery ventilators on the market?

Generally, heat recovery ventilation systems can come in a variety of forms, but all involve some form of the heat exchanger, for example, rotary thermal wheels, enthalpy or plate heat exchangers, heat pipes, and Run-around coil systems (RAC), etc.

7. Will an ERV remove humidity?

An ERV doesn't dehumidify. If you want to dehumidify and ventilate, you will need supplemental dehumidification. An ERV+dehumidifier is one option, or you can choose that ERV built-in dehumidifier, but the price is extremely high.

8. How long have energy recovery ventilators been on the market?

Accordingly to an article issued by Ph.D., Manager of Swegon Air Academy, the history of mechanical supply and extract air ventilation becomes common in European buildings in the 1950s.

“After the Second World War, there was a great demand for new housing and non-residential buildings. In order to reduce building costs, ceiling heights were lowered and, subsequently, the need for well-functioning ventilation systems increased.

American ventilation technology, with mechanical supply and extract air solutions, was introduced in a number of countries in Europe. To save heating energy, the return air principle was used, whereby a proportion of the extract air was mixed with the fresh supply air. In wintertime, more than half of the extract air was often reused in this way. This was a cheap and very efficient solution and was used almost exclusively in non-residential buildings.

However, in the early 1980s, in Sweden as well as in other countries, critical voices were raised challenging the suitability of having to breathe extract air, even if diluted with fresh air. In the USA and countries with humid climates, the return air principle is still used and is the completely dominant solution.”

9.What is the main benefit of an energy recovery ventilator?

There are some important benefits an ERV can offer you and your home:

Better energy efficiency – the pre-treating of the incoming air takes some of the workloads off your HVAC system. When your system works less, it uses less energy, making it more energy-efficient.

Improved indoor air quality – with an ERV, you have a continuous stream of fresh air entering your home, improving the ventilation and quality of the air inside.

Less stress on your system – when your system doesn’t have to work as hard to achieve the temperature set on your thermostat, it results in less stress for the system.

10.Can an energy recovery ventilator be installed in an existing building, as well as a new building?

Yes, sure. For the new building, if ducting is acceptable, then a suspended energy recovery ventilator is recommended as the cost is relatively competitive.

While for an existing building or the ducting not workable, then the ductless energy recovery ventilator is better.

11.How to choose a suitable ERV for the project?

1). Choose the proper installation types based on the building structure

2). Determine the fresh air flow required according to the use, size, and number of persons

3). Select the right specifications and quantity according to the determined fresh airflow

Airflow rate requirement varies from different countries.

For example, based on the standard of China:

Like, the area of a computer room is 60 sq. meters (S=60), the net height is 3 meters (H=3), and there are 10 persons (N=10) in it.

If it is calculated according to “Personal fresh air consumption”, and assume that: Q=70, the result is Q1 =N*Q=10*70=700(m3/h)

If it is calculated according to “Air changes per hour”, and assume that: P=5, the result is Q2 =P*S*H=5*60*3=900(m3/h)

Since Q2 > Q1, Q2 is better for selecting the unit.

As to special industries such as hospitals (surgery and the special nursing rooms), labs, workshops, the airflow required should be determined in conformity with the regulations concerned.

12.Where is the unit installed?

Usually adjacent to or near the heating or cooling system on the basement ceiling or wall, or if in parts of the country where basements are not common, in an area like a laundry room or garage. Some types of energy recovery ventilators must be installed suspended, certain types are positioned on the wall or near the heating or cooling system equipment.

13.How to maintain the energy recovery ventilator?

Step 1: First, turn off your ERV and unplug it.

Step 2: Clean or replace air filters: Dirty or clogged filters can lower ventilation efficiency. Try to clean your filters at least every three months. Filters in most new ERVs can be easily removed, cleaned with a vacuum cleaner, and then washed with mild soap and water. Older units have replaceable filters. If your ERV is easily accessible, this is a five-minute job.

Step 3: Check outdoor intake and exhaust hoods: Remove leaves, waste paper, or other obstructions that may be blocking the outside vents of your ERV. Without this vital airflow, your ERV won’t function properly. During winter, clear any snow or frost build-up blocking outside vents.

Step 4: Clean the heat-exchange core: Check your ERV manual for instructions on cleaning the heat-exchange core. Vacuuming the core to reduce dust that can build up inside the core.

Step 5: Clean grilles and inspect the ductwork: Once a year, check the ductwork leading to and from your ERV. Remove and inspect the grilles covering the duct ends, then vacuum inside the ducts. If a more thorough cleaning is required, call your service technician.

Step 6: Service the fans: Remove the dirt that has accumulated on the blades by gently brushing them. Most new ERVs are designed to run continuously without lubrication, but older models require a few drops of proper motor lubricating oil in a designated oil intake.

14. How to choose a qualified ERV manufacturer?

You probably have looked into your local market and noticed that the ERV is starting to take up an increasingly larger space on the market.

ERV is an investment for your business, so you want to be sure you are choosing the correct one to fulfill your market and budget.

And We all know that a good supplier is one of the most important key factors to success, but choosing a good ERV Manufacturer is not easy, especially for those who have no experience in HVAC experiences. There are several things you need to consider before placing an order:

• How long does the company have been in the ERV field?
• What is the company’s production capacity?
• What is the company’s machining quality control?
• Do overseas sales have a mechanical engineering background or engineer support?
• Is their quotation competitive?
• How is their after-sale service?

16. How to install the ERV?

If you bought an ERV no matter from China or any other country, you'd better contact your local engineering company to complete the installation.

Because the installation should be carried out by a qualified person.

To know how the engineers usually install the ERV unit, this video we took in the domestic market for your reference:

More FAQs will be listed soon, please stay tuned.

＊Source:

https://www.explainthatstuff.com/heat-recovery-ventilation.html

https://www.buildwithrise.com/products/mechanical-energy-and-water/ventilation/energy-saving-ventilation-system/energy-recovery-ventilator-erv

https://www.idealservicesonline.com/blog/what-is-an-energy-recovery-ventilator-and-why-do-i-need-one/