Mechanical Ventilation with Heat Recovery (MVHR) works by recovering heat from extract air that would normally be expelled to the atmosphere and transfers this heat to fresh air being drawn into the property via a heat exchanger. The Heat Recovery Ventilation (HRV) system then distributes this throughout your property via a network of ducting.
The ducting is brought to each habitable room and each wet room within your property. Each wet room is fitted with an extract valve and each habitable room with a supply valve.
The HRV system continually extracts from the wet rooms, boosting if necessary, removing the pollutant air quickly and effectively at its source. This air then passes up through the network of ducting and travels through a heat exchanger where its heat passes to the fresh filtered air which is being brought into the property at the same time.
The HRV system runs on trickle speed continuously and is boosted when an increased rate of ventilation is needed, for example bathing or cooking.
When the weather is warmer a summer by-pass function helps to ensure comfort levels in the home. When this function is activated the property continues to be ventilated with fresh filtered air but the heat recovery process is switched off intermittently and therefore ‘by-passed’.
Brookvent design and manufacture extremely efficient aircycle HRV systems, which are capable of recovering upwards of 93% of the heat from the outgoing air.
Some of the main benefits of a Heat Recovery Ventilation (HRV) system are:
• Whole house ventilation – continuous balanced ventilation with improved indoor air quality, providing a healthy living environment and preventing condensation by keeping moisture levels low
• Energy saving – recovering the heat from your extract air instead of simply sending it to atmosphere can lead to significant energy savings by reducing the cost of your heating bill
• No additional kit – with the growing trend towards property air tightness, HRV systems cancel out the need for background ventilators
• Gain SAP points – Brookvent’s aircycle HRV systems are SAP approved and succeed in reducing CO2 Dwelling Emission Rate (DER). Specifiers, Low Carbon Consultants and Architects can gain SAP points for your property by using our product’s specific performance information instead of standard default information provided in the SAP register
Design: it is absolutely vital to have your Heat Recovery Ventilation (HRV) system installed properly. This begins with a good design. Brookvent is very experienced in system design and provides professional guidance on ducting routes across a wide variety of residential properties.
Installation: HRV systems are generally installed in two stages – 1st and 2nd fix. At 1st fix stage the majority of the ducting is installed, as per the system design, and any wiring requirements are provided for, including the tracking of remote sensors such as humidistats. At 2nd fix stage the system is installed, all ducting and wiring is connected, ceiling valves are fixed to the ducting point in each room, and the condensation drain from the system is installed. Finally the system is commissioned as per the appropriate Building Regulations.
Performance: the size and location of the HRV unit is extremely important. The unit must be fit for purpose, taking into consideration the size of the property and associated airflow rates. Brookvent is a BPEC Centre of Excellence and installs to the highest standards to achieve best performance.
Commissioning: Brookvent issue commissioning certificates detailing the measured installed airflow performance of each system against design requirements. Finally, each unit’s operational and maintenance requirements are clearly defined and demonstrated to ensure competent user operation and optimum system performance. At Brookvent we have adapted our products based on customer feedback so they can be installed easily, often in compact spaces, and accurately commissioned.
Mechanical systems require electrical power to operate, including power to the fans, any compressor(s) and transformer(s) and control and safety devices. The term ‘specific fan power’ is used to compare the electrical energy use for different ventilation systems as installed (i.e. allowing for system resistance).
Specific Fan Power (SFP) is defined by the Energy Savings Trust as: ‘The power consumption, in Watts, of the fan (plus any other electrical system components) divided by the air flow through the system, in Watts per litre per second (W/l/s)’.
Specific Fan Power Calculation: Heat Recovery Ventilation (HRV)
For a small house with a Kitchen + 1 Wet Room the minimum extraction airflow rate is 21 l/s (Part F: Eng & Wales 2010). If the unit consumes 15 watts to achieve this rate of air flow then: SFP: 15 / 21 = 0.71 W/l/s
The Energy Savings Trust Best Practice recommendation for SFP is 1 W/l/s or lower. Brookvent’s aircycle 3.1 Heat Recovery Ventilation unit currently achieves a SFP down to 0.37 W/l/s, which makes it the market leader in terms of efficiency.
Most Heat Recovery Ventilation (HRV) systems including the Brookvent aircycle range, are air-to-air types. These recover heat from the exhaust air stream and use it to pre-condition the incoming air from outside. The effectiveness of these units is given by its heat recovery efficiency i.e. the proportion of waste heat that is usefully recovered by the process (this figure is typically expressed as a percentage).
A heat recovery unit will reduce the amount of energy needed to heat up the incoming air to room temperature. This benefit must always be balanced against the electrical power requirements needed to drive the process. HRV systems are most efficient in more airtight homes, where almost all ventilation takes place via the heat exchange core. The concept is simple, the less heat that is lost through the leaks in the building envelope then the more heat there is to recover.
The Energy Savings Trust Best Practice recommendation for heat recovery efficiency is 85% or higher. Brookvent’s aircycle 3.1 Heat Recovery Ventilation unit currently achieves up to 93% heat recovery efficiency which makes it one of the market leaders in the industry.
All Brookvent aircycle Heat Recovery Ventilation (HRV) systems are SAP approved and use EC fan technology which helps to ensure a low Specific Fan Power (SFP) which means our systems run as efficiently as possible.
Heat Recovery Ventilation systems will generally save significantly more money through heat recovery versus what it costs to run the system, therefore covering its own cost of running and also contributing towards savings on the space heating bill of the property, in some cases up to 20%.
The Energy Savings Trust state that in an energy efficient house with high insulation values, the energy loss due to purpose provided ventilation accounts for approximately one third of the space-heating energy demand (i.e. the energy lost by extracting warm pollutant air from bathrooms, opening windows, and opening window vents).
(Energy Savings Trust (2006), GPG268: Energy Efficient Ventilation in Dwellings ‘A Guide for Specifiers’ pg.3)
This means in a average property where the space heating bill can typically cost around £750 per year, £225 of this total is lost due to purpose provided ventilation. Brookvent Heat Recovery Ventilation (HRV) systems typically operate at up to 93% efficiency depending on the ventilation demand of the property.
Larger homes with larger ventilation requirements result in the air moving though the heat exchange core at a faster rate, therefore reducing the amount of heat transfer time. If at the very minimum, the system recovers 80% of this £255 loss, this results in an estimated energy saving of £180 per year.