How Does a Heat Recovery Unit Work?

How Does a Heat Recovery Unit Work?

How Does a Heat Recovery Unit Work?

With household energy bills increasing by over 50% in 2022, people are now assessing options to invest in appliances that limit the need for excessive heating. This is followed by the UK aiming for 95% of its electricity usage to be low carbon by 2030.

I-Sells is here to show you the appliance you can invest in, that will help you reduce your energy bills and keep you warm too. This is done through a heat recovery unit.

In this article, we will address the question ‘How does a heat recovery unit work? Whilst also share with you the benefits and some appliances that could solve your problems today.

What is a heat recovery unit?

A Heat recovery unit facilitates the process of heat recovery ventilation (HRV). This is the process of extracting indoor stale or moist air and replacing it with filtered fresh air from outside, recycling the warmth from the air it was replacing.

As of 2022 England and Wales scored a D in the latest stats for energy efficiency. (With A being the best and E being the least energy efficient).

From this, it is clear to see we still need some help with recycling heat and making the most of our energy. With a heat recovery unit, you not only your home more energy efficient, but also free from mould and condensation.

So how does a heat recovery unit work?

Heat Recovery Recuperation System Installation by Professional

A heat recovery unit facilitates the removal of indoor humid or stale air and replaces it with fresh outdoor air which is also heated by recycling the heat from the indoor extracted air. Along with this, they have the ability to reduce the buildup of condensation, making your home or business less susceptible to mould.

The recycling of heat makes them more energy efficient and a good long-term investment to help you save on your energy bills.

Here are some benefits of having a heat recovery unit:

  • Less of a need to use your central heating frequently as the heat generated through your house is recycled through the heat recovery unit.
  • The recycling of indoor air without removal keeps the air fresh without having to lose any heat which is vital, especially in winter.
  • Helps to create an environment not fit for mould and condensation
  • The reduced use of heating as a result of the heat conservation granted by a heat recovery unit can help you save on energy bills.

Types of heat recovery units

ceiling mounted air conditioning unit

There are various types of heat recovery units we offer at I-Sells, what works for you is entirely dependent on the size of your home and your needs. Let us share some examples.

This heat recovery unit is useable for medium-sized houses and apartments:


The Nuaire MRXBOX95AB-WM1 has the ability to commission the supply and extract fans independently at both minimum and maximum speeds. This allows the unit to provide the perfect ventilation for the environment in which it is placed.

This is a medium-duty unit, ideal for small to medium-sized houses and apartments. It is compact, low profile and simple to install, providing the perfect solution for a wide range of properties.

The MRXBOX95 range of products can recover up to 95% of heat which would normally be wasted, meaning this is a highly efficient product which will attract a high score on SAP Appendix Q and help meet building regulations.  This particular version is fitted with an automatic summer bypass as standard, which provides cooling during the warmer months.

The range is designed to provide an optimised, balanced supply and extract mechanical ventilation with heat recovery, and the MRXBOX95AB-WM1 is ideal for small to medium-sized houses and apartments as it can be mounted in either a wall or cupboard.

 It incorporates the most efficient low-voltage DC fans, a counter-flow heat exchanger and easily accessible controls. Added to extremely low noise levels and minimal maintenance requirements, this is an ideal way to provide effective MVHR new-build properties.


  • Compact, lightweight and easy to install
  • Fan controls designed for quick and easy commissioning
  • Easily accessible filters from the front cover – no tools required
  • Integrated, automatic summer bypass
  • Code 3 or above through SAP Q-eligible products
  • Part F & L building regulation compliant
  • Constant quiet running fans to ensure occupant acceptability
  • Integral frost protection
  • With a 5-year warranty: 1-year parts and labour, remaining years parts only (UK and Ireland only).

We also have the option to have single-room heat recovery units, from a bedroom to a bathroom, it just depends on your needs. This can be especially helpful in rooms that suffer from damp or mould. Here is a product for a single room.

Kair Heat Recovery Extractor Fan – 12VAC SELV – Humidistat

The Kair KHRV150/12RH Single Room Heat Recovery Ventilator is perfect for you if you are looking to solve a damp problem in one of your rooms. Such as your kitchen, bathroom, utility room, living room, lavatory, washroom, conservatories, office and bedroom.

This unit is perfectly suited to your needs as it automatically controls the humidity of your room for you, so you can relax knowing that it will take care of everything for you. The unit also offers you continuous trickle ventilation, so it will constantly clean and purify the air you breathe. Continuous ventilation is the key to keeping your home mould free.

The unit is highly energy efficient so it will help you save money on your heating bill. Up to 86% heat recovered from extracted air, means even in cold winter weather the incoming clean air will remain at almost the same room temperature.

The unit is 100% completely safe for you to put in your bedroom or your child’s bedroom since it has a very low voltage. By providing adequate ventilation the unit maintains the recommended humidity levels, preventing harmful bacteria from being breathed in.

We understand that appliances can be investments that can put you out of pocket, but we at I-Sells have every base covered. Here is an example of one of our affordable units that will help you save money on your bills and on your bank account.

Vent Axia Lo-Carbon Tempra P Heat Recovery Unit (443312)

The Vent Axia Lo-Carbon Tempra P Heat Recovery Unit (443312) is available with pullcord control, timer control or humidistat, timer and pullcord. All models are also available in SELV (Safety Extra Low Voltage).

Low energy consumption means the Tempra exceeds the energy-saving requirements in Part L, Conservation of Fuel and Power. With several optimisation options available to adjust the fan speed.

The units are fitted with a 24V ECDC motor with a state-of-the-art built-in power supply. This has the ability to operate at only 2 Watts power consumption on normal setting, offering a 90% energy saving over conventional AC equivalents

Apart from removing odours, providing fresh air and recovering heat, this appliance extracts airborne impurities such as dust, dirt and grease. These gradually build up and detract from the efficiency and appearance of the appliance. To ensure peak performance, the heat exchanger should be cleaned as required in accordance with the instructions supplied.

Is it worth the investment?

We feel like we have answered the question ‘how does a heat recovery unit work’ so now let us briefly summarise why they are worth the investment.

As energy bills increase along with the growing sentiment from the government to be energy efficient, a heat recovery unit is definitely worth investing in to make the most out of your heat rather than unintentionally wasting it and potentially adding more to your energy bills.

Not only are you making a conscious decision to help the environment, but you are also keeping your home and its inhabitants warm and refreshed.

The extra benefit of helping to create a mould and condensation-free environment in your home is also invaluable, especially for those with mould allergies or existing health conditions.

The versatility and amount of options available when it comes to heat recovery units means that regardless of what room it gets put in, you instantly get to reap the benefits.

Here for your Heat recovery unit needs

ventilation technician

We at I-Sells endeavour to make sure our customers have all the information they need before making the choice to invest in our products. Be sure to visit our blog page to gain knowledge on the wide array of factors and issues surrounding ventilation, mould, condensation, and much more.

We hope to have helped you by answering the question ‘how does a heat recovery unit work?’

We understand you may have more questions, Please do not hesitate to contact us for more information with regards to heat recovery ventilation. If you’d like to send us an email, click here. For other contact options, see below:

Call us on 020 8463 9696

Visit us at our showroom:


Monday – Friday: 8:00am to 17:30pm

Saturday: 9:00am to 12:00pm

Sunday: Closed

15 St John’s Parade



DA14 6ES

United Kingdom

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