Automated Home 2.0 – #15 The Mechanical Ventilation Heat Recovery (MVHR) System

MVHR Ducting - UK

Our mechanical first fix is almost complete so it’s a good time to look at our MVHR system.

Drimaster PIV

When spec’ing our first self-build in the late 1990’s we added this Drimaster PIV unit (Positive Input Ventilation).

This sent a low pressure feed from a vent in our hall ceiling, driving moist air out of the house and doing away with the requirement for trickle vents on all our windows and extractor fans in the wet rooms. Although it worked well, the down side was that as it pushed out our warm heated air, it drew in cold air from outside to replace it.

We knew we wanted a more efficient system in the new house and so we looked around for a company with expertise in low energy heating. We were lucky to find an expert right on our doorstep and back in February of 2017 we had our first meeting with Daly Renewables.

Daly’s describe themselves as “an engineer-led company committed to designing low energy efficient renewable energy systems”. We liked the fact that they are, as they put it, “a Single Point Responsibility”. We weren’t talking to a sales team either, but the engineer that would be designing our system.

An MVHR is effective in homes with an airtightness rating of around a 5 or lower but what exactly is it? Over to Ryan for more of an explanation…

[UPDATEHere are the figures for our first years running cost]

Old School

The minimum form of ventilation currently required to satisfy Building Control is a combination of trickle vents and extract fans. A trickle vent is the most basic form of ventilation and consists of a slot opening in a window which can be manually opened and closed to let fresh air straight in from outside. This is uncontrollable and the problem with these arise during a cold windy night when you get a cold draught from the vent entering the room, which affects the comfort of the occupants. Combined with extract fans in bathrooms, it begs the question – why insulate your home so well and leave what are effectively holes in your walls and windows?

When we tighten a house to reduce energy consumption, we also risk making the building envelope vulnerable to moisture problems, including mould (a major health issue) and rot. Excess indoor humidity can also increase dust mites and other allergens, damage electronic equipment and accelerate the outgassing of formaldehyde from common building materials and furnishings. If the house is in an area prone to ground radon, then radon accumulations can also increase in a tight house that is not properly ventilated (though separate radon mitigation is more effective at reducing this risk).  A tight enclosure with mechanical ventilation will almost always provide better indoor air quality with lower energy bills and more comfort than a leaky house depending on the house to “breathe”.  Houses don’t breathe – people breathe and they do it 24/7 year around. An important aspect of thermal comfort is humidity levels and directly related air quality.

Quite simply put- the better insulated and sealed a house is, the more important a controlled form of ventilation becomes.  

Ryan Daly

A Better Way

Vent-Axia High Flow MVHR Unit

The most efficient and effective type of ventilation is mechanical ventilation with heat recovery. In this system a pre-calculated flow of air is extracted from wet rooms, removing moisture, odours and VOC (found in paints, adhesives etc).

A supply of air is accurately placed into habitable rooms, ie each and every bedroom and living areas. A high efficiency heat exchanger recovers up to 90% of the heat energy in the extracted air into the incoming filtered fresh air.

We have fitted this Vent-Axia Sentinel Kinetic High Flow unit into the new Automated Home. Once it’s setup it requires little or no adjustment with an automatic summer bypass and a built-in humidity sensor that boosts the fan speed when it detects an increase in moisture (for example when taking a shower).

Vent-Axia MVHR in the Automated Home

To it we have connected the Hybalans Ducting System and this routes the supply, as well as the discharge of ventilating air with the highest possible energy saving and maximum convenience.

Early planning is really beneficial here, so ensuring your Architect, Mechanical Expert and Builder all know the site for the MVHR and the routes your ducting will take.

It consists of 2 manifolds, 1 for Supply and 1 for Extract. The ducting is 92mm Semi Rigid Plastic which runs to each individual room. The main advantage of this system is that it is very easy to balance, especially compared to a traditional teed off system which can be very hard to get the air flows correct on. The air quantities per air valve are simply centrally adjusted in the air distribution boxes. Adjustment of the air valves is unnecessary.

MVHR Ducting

Due to low resistance losses, the working point and fan motor rpm of the HRV unit are reduced. This creates an extra reduction of the system noise.

We carefully select the MHRV unit to ensure that the operating capacity of the System is in or around 50%, or less where possible.

For several years we have been installing HRV into an increasing number of homes, with this system having several benefits over others:

  • Negates the need for trickle vents and extractor fans.
  • System sized to provide 0.75 Ach (Air Changes per Hour).
  • Double skinned steel unit with 25mm Insulation surrounding- ultra quiet in operation.
  • Counterflow Heat Exchanger – up to 90% heat recovery.
  • Hybalans Radial ducting system designed to negate crosstalk between adjoining rooms.
  • Automatic Summer Bypass.
  • Energy saving EC fans (electronic commutation technology).
  • Controller should provide real time adjustment to fan speeds, required air temperature and a pre programmable boost facility.
  • Automatic boost on unit with built in humidity sensor.

Read On…

Now read about our Heat Pump and remember to check out our Instagram to follow the project, read the rest of the Automated Home 2.0 blog posts and find the links to all the products we’ve used in our self-build. : Listen to this Podcast on MVHR Design

Bestseller No. 1
FANTRONIX FTX MVHR D105-A Heat Recovery Ventilation Unit Heat Exchanger for Low Energy Consumption Reduced Condensation Mould Control Improved Air Quality
1 Reviews
FANTRONIX FTX MVHR D105-A Heat Recovery Ventilation Unit Heat Exchanger for Low Energy Consumption Reduced Condensation Mould Control Improved Air Quality
  • ✅PLUG and PLAY: Self-contained plug and play MVHR slimline heat recovery ventilation unit with built in frost protection easy to use wall mounted speed controller designed and manufactured by FANTRONIX, available in a complete kit for domestic and commercial installations for 2-10 rooms, or just the unit can be purchased on its own. Install with ease with our kit which includes everything required for a full installation, including vents, grilles and ducting
  • ✅ULTRA COMPACT & EASY TO USE: Specially designed for use in small properties like studio apartments, offices, toilets where there is less airflow and space is limited. Continuously supplies clean, fresh, filtered air, whilst simultaneously extracting pollutants, so your environment is cleaner and free of harmful pollens and dust. Eliminates the presence of condensation which fights the presence of harmful damp, rot and moulds in wet areas.
  • ✅REDUCED NOISE LEVELS: Supply & extract heat recovery airflow rates up to 29 l/s (106 m3/hour). Acoustically insulated, sound absorbing double skinned units reducing overall sound noise levels down to 24 dBA. Protect the environment whilst saving money with our professionally tested and low energy consuming heat exchanger unit that works quietly using ultra-low voltage.
Bestseller No. 2
Fantronix Aerium Mini Smart Eco Heat Recycling Ventilation Unit for Efficient Silent Operation - Energy Recovery Ventilator System Control Air Quality CO2 Humidity Condensation MVHR Extractor – Beige
3 Reviews
Fantronix Aerium Mini Smart Eco Heat Recycling Ventilation Unit for Efficient Silent Operation - Energy Recovery Ventilator System Control Air Quality CO2 Humidity Condensation MVHR Extractor – Beige
  • ECO-FRIENDLY SMART VENTILATION SOLUTION: Fantronix Aerium Mini Heat Recovery Unit is a modern and superior ventilation system that provides greater levels of indoor air quality and makes the most of the warmth in their immediate environment while recycling heat normally wasted with traditional extractor fans. Its economic operating mode with high heat recovery is designed to achieve the lowest power consumption, the lowest noise and the lowest life-cycle costs.
  • EFFICIENT ENERGY CONSUMPTION (ROI): The Aerium economic operating mode makes extremely low running costs with energy consumption down to 1.8w per unit. It recycles up to 81% of the heat & retains it within the room. Not only does this ensure a net energy gain, but the upfront costs can also be reclaimed much sooner than any other energy-efficient investment. Less than 0.03p per hour running cost, per unit (15p kw/h tariff). Overall costs are typically recovered in less than four years.
  • ENHANCED AIR QUALITY: Smart heat recovery has an air quality sensor that connects to an external temperature, humidity, CO2. The HRV mode allows preserving heat in the room and ensuring humidity balance, reducing the load on the heating system during winter. During summer, the HRV mode operates with two cycles, which allows reducing the load on the air conditioning system. Integrated filters, filter fine dust, pollen and nitrogen. Designed to lower the risk of condensation, humidity and mould.
Bestseller No. 3
Brookvent Aircycle 1.3 Digital Control Wall Mount MVHR
  • Up to 90% heat recovery efficiency
  • Down to 0.57w/l/s specific fan power
  • Integral humidistat, summer bypass and automated frost protection
Bestseller No. 4
Brookvent Aircycle 1.2 Heat Recovery MVHR Unit (Wall Mounted- Standard Configuration- Summer Bypass)
  • EFFICIENT OPERATION- The Aircycle 1.2 operates by efficiently recovering heat from the air extracted from wet rooms (bathroom, kitchen, etc.) and transferring it to the fresh air being drawn into the system
  • HEALTHY AIR CONTROL- Once fresh air has been drawn in to the system, it is filtered and then distributed throughout the property to provide a healthier and more comfortable indoor environment
  • AUTO-BOOST INTEGRATION- The programmed boost (high) speed setting can be easily triggered via any 230V switched live signal (e.g. bathroom light, boost switch, PIR motion sensor) offering multiple means of automatic control integration. This ensures pollutants are extracted immediately
Bestseller No. 5
BLAUBERG Heat Recovery (MIDI) Unit Wall Mounted Silent Decentralised Office Bathroom Kitchen Toilet Wet Room d-MVHR Ventilator Smart WiFi Control – White (Terracotta)
  • Silent continual heat recovery operation with manual or automatic control of humidity, time, airflow and ventilation rate.
  • Control from your smartphone, home automation system or tablet, Alexa, Echo etc.
  • Units are connected using WiFi to other units to provide a whole house MVHR solution.

Last update on 2021-10-04 / Affiliate links / Images from Amazon Product Advertising API

3 Comments on "Automated Home 2.0 – #15 The Mechanical Ventilation Heat Recovery (MVHR) System"

  1. Will the kitchen hob have dedicated extraction or a recycling filtration system within the room?

  2. The hob will extract through a carbon recirculation filter, rather than having to create a hole in the airtight envelope to extract to outside.

  3. Beverly Williams | January 21, 2020 at 5:53 pm |

    If only the same system could be used to filter and recirculate cooled air in the summer…

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.