Heat Recovery Ventilation

What is Heat Recovery Ventilation (MVHR)?

Mechanical Heat Recovery Ventilation (MVHR) systems are systems that provide better indoor air quality in homes and commercial buildings by extracting stale air and supplying fresh air.

A Mechanical Ventilation Heat Recovery (MVHR) system is an energy recovery ventilation system that uses an air-to-air heat exchanger that recovers heat that is usually wasted. It works by supply and extracting airflows in and out of homes and buildings to ensure a better indoor air quality. Heat recovery ventilation can recover up to 90% of normally lost heat depending on the unit and the application. A MVHR system works independently from a heating system and due to the heat recovery feature, it can have great savings on your energy bills.

A MVHR system works to eliminate condensation and mould within a building by constantly ventilating a property. By eliminating condensation, it also eliminates the risk of damage to the structure of a building and stops the build up of mould and damp. MVHR systems are suitable for small residential products to large commercial projects.

What can Warmth do to help?

At Warmth we can greatly simplify your buying process. Our technical team will advise you on the best system for your property. Whatever your requirement, budget or setting, Warmth can provide the solution you need.

How Does Heat Recovery Ventilation Work?

A heat recovery system works (also called HRV or MVHR) via a heat recovery ventilation unit which is usually located in the attic, roof space or plant room of a building. Rather than just extracting air and replacing it with the air from outside, a heat recovery system draws the heat from the extracted air and passes it to the air which is being filtered in from outside. The extract and supply air do not flow within the same pipes and there would be no cross contamination of the different air flows. The heat recovery unit is connected to room air valves via a network of ducting throughout the building.

With a heat recovery system, you make use of what already exists as well as reduce our collective impact on the environment, and that includes the amount of heat we lose to the environment daily. Heat recovery systems work by using the valuable warm air or water in a property and use it in a positive way.

A heat recovery system works independently of your normal heating system, in each room there are ventilation valves with filters that supply air in and out of each room which all leads to the heat recovery unit. The unit works by moving the stale air through the pipes whilst drawing in cold air from the outside via other ducts.

The two airflows pass one another within the heat recovery unit without mixing physically, the heat from the extracted air is then transferred to the new fresh air brought from outside and supplied through the pipework and into each room. Once the stale air’s heat has been extracted and it is then extracted out and into the atmosphere.

How is a heat recovery system beneficial?

How is a heat recovery system beneficial?

A heat recovery system is beneficial as everyone wants their house to be as airtight as possible to get the most out of their heating, however, this can cause poor air quality due there being no sources of natural ventilation. Having an airtight building with no ventilation leading to poor indoor air quality can significantly increase the effects of asthma and other respiratory problems. Other issues that can be caused as a result of poor indoor air quality are condensation, mould, dust mites, unpleasant smells and the build-up of toxic gases.

If you install a heat recovery system it will extract the moist, stale air from all the wet rooms in your house and replace it with clean, filtered, fresh, warm air to all your habitable rooms and bedrooms without letting the heat escape. Your home will be fully ventilated throughout the year with as much as 95% of the normally wasted heat being recovered providing you with substantial energy savings. Having a heat recovery system installed allows your property to stay air tight with no window vents or bathroom extractor fans required, this creates a healthier, cleaner and quieter environment.

With technology moving forward into greener energy, heat recovery systems are a perfect example of how we are trying to improve our own quality of living as well as being energy efficient. A heat recovery system helps the air circulate within a building by replacing it with colder air that is warmed by the ventilation system. Over the years the technology for heat recovery systems has vastly improved and there are now systems available that extract up to 95% of the heat from stale air and return it to the fresh air that is circulating back into the system.

Key benefits of a Heat Recovery System

Some of the key benefits of a MVHR is that they reduce dust and pollen throughout the house and are collected via a filter within your system. They greatly reduce moisture, condensations and smells cause by cooking as well as greatly reduce energy usage with your home. Reducing moisture and condensation will in turn reduce risks of damp and mould throughout the home. A heat recovery system can certainly save on energy bills and keep you warmer in the winter. New build houses can boast up to 30% savings on heating bills.

Installing a heat recovery system could save on energy bills and help keep the house warm during the winter months. It costs money to heat our homes but if we open a window or a door that warm air simply goes out into the atmosphere. With a ventilation system you have a constant supply of warm, fresh air circulating throughout your home. For businesses and industry on the other hand, heat recovery helps make the work place a far more efficient place.

Nowadays most heat recovery systems behave smartly, reducing the amount of heat that is extracted during the summer months so that comfort levels are maintained or instead can be used for drawing more heat from areas such as a kitchen or wet room where the temperature is likely to be higher.

Investment Returns

Because there is a constant supply of recovered warm air, your energy costs are reduced, and your initial investment could be paid back within 5 years. Ventilation systems cost pennies to run coming in at around 10p per day.

Without doubt a heat recovery system will save you money on your energy bills. A system in a domestic property can recover up to 95% of normally lost heat, therefore, saving you up 25% on your heating bills compared to using window trickle vents and bathroom fans.

One thing to keep in mind when thinking about purchasing a heat recovery system, is that in the next few years energy prices are certain to increase so a system which reduces your costs is sure to be a benefit.

Although purchasing and installing a whole house heat recovery system may seem costly, it is well worth it. It is a worthwhile investment not only in costs but also in health, cleanliness and makes your home a better place to live.


By maintaining your ventilation system you are maintaining your indoor air quality

Installing a Mechanical Ventilation with Heat Recovery (MVHR) ventilation system is a lifetime investment which will provide you with improved indoor air quality by extracting mould, damp and stale air while supplying fresh, filters air into living areas in your home.

The Purpose of Heat Recovery Maintenance

By regularly maintaining your ventilation system you will increase its lifespan and improve the effectiveness of your ventilation system and by checking your system regularly you will avoid bigger complications further down the line.

Most maintenance jobs can also easily be done by an owner, (electric work must be carried out by a trained electrician)

Maintaining your Heat Recovery System

If you have noticed more than normal condensation, a stuffy environment of at worst dust around the air valves it is now time to service your system.

It is not complicated, and most regular maintenance tasks are suitable for any competent DIY person to do.

Your systems should be commissioned and set up so that a user will have little to no alteration to their MVHR system but we would recommend that if you adjust or replace the room air valves that you have the system recommissioned.

As maintaining your system will ensure that no problems can arise from having poor ventilation, problems will be noticed earlier if there is anything needing fixed and check regularly is preventing problems from greatly worsening.

To help with future maintenance it is recommended that when installing the system that the following areas are easily accessed:

  • The MVHR unit can be easily worked on, removed, or replaced
  • The controller is in a convenient location to check performance
  • Access to filters are unrestricted
  • Condensate drain is easy to check
  • If installed in attic that the area is floored with good lighting
  • If accessed through a loft ladder that the opening is large enough

Maintenance Checklist

We recommend thorough checks are done at the time of installation but also to be done frequently to ensure that your system is working to full capacity.

  • Check and clean filters every 6 months*.
  • Change filters every 12 months*.
  • Ensure all connections are well sealed and that there are no air leaks, repair any seals that may seem loose.
  • If your unit has a condensation drain, check this to ensure it is not blocked as this can cause a build-up of bacteria.
  • Check that controls are working properly.
  • Clean air valves and grilles (both inside and out) as dust and dirt can begin to settle on these surfaces.
  • After 5 years some units will require the heat exchanger to be cleaned, please refer to owner’s manual or contact our team to find out more on how to do this as units may differ.
  • Any electric work must be taken out by a trained electrician.

*We recommend that you change/clean your filters at least once a year, and more in often in areas with high pollution.

Please remember that if you are replacing or adjusting the air valves that your system may need rebalanced so that your airflows are correct.

Everything You Need to Know MVHR Filters

A good way to think of your MVHR filters is like a vacuum bag, when they get full of whatever they may be collecting, it is time to change! You would not vacuum your home will a full vacuum bag, why ventilate you air with unclean filters?

Filters ensure that air is cleaned before entering your home, but over time these filters will become dirty with the dust and particles that they are filtering. Filters will ensure that dust, dirt, and pollen will not enter your home from the outside air being brought in. They are amazingly simple to check and change, most units will have service doors to the MVHR filters. Filters will start off perfectly white, turn grey with build-up and can eventually go black if not changed.

Not changing filters frequently enough can make your system noisier as the system then has to work harder to push air through dirty and blocked up filters.