Ventilation System

I have had an article published in the AltEnergy on-line magazine here that describes this project.


Our current ventilation system had served us well, but significant technological improvements have taken place in the past 20 years with new models having more efficient heat recovery and having optional air sourced heat pumps that can provide heating in winter and cooling in summer meant it was time for an upgrade. Newer models also have better efficiency, air filtering, control facilities and monitoring.

After reviewing the market for suitable systems, we selected the Genvex GE Premium 1L unit that provides up to 150 cubic metres/hour and which is controlled by the Optima 300 microprocessor controller.


The installation was carried out by Genvex's UK distributors Total Home Environment Limited (THE) and was completed in five days using three people for the first day to remove the old system and one person for four days; we had a particularly competent engineer who installed the system. THE returned after a few weeks to commission the system and fine tune the inlet and exhaust airflows in each of the rooms for optimum operation. The pictures show the completed installation.

Please click on the images to see a larger image in a new window.

Ventilation System
In the photo on the left, the large white box is the ventilation and heat recovery unit. The box also contains the air sourced heat pump. The small white box in front of the large box contains the microprocessor and electronics. The silvery rectangular box at the front is the optional electrostatic filter. The large 'drums' in line with the pipes are the silencers which eliminate noise transmission into the bungalow.
Electrostatic Filter
Here we have a better view of the electrostatic filter which filters out pollen and potentially harmful viruses. Note the kettle lead powering it with the light being on. All ducting in our installation is with rigid galvanised steel tubing with a double wrap of insulation on all pipes that is equivalent to 100mm of fibreglass. The lower pipe is the supply air to living rooms and bedrooms. The upper pipe is for the extracted air taken from the kitchen, utility room and bathrooms. The electrostatic filter removes pollen and so helps asthma and hay fever sufferers.
Inlet and Exhaust
At the other end of the unit is the inlet air pipe at the top that is ducted from outside. The stale moist exhaust air is blown out through the lower pipe. Both of these pipes are 160mm in diameter and are insulated. In winter, when the air sourced heat pump is running the air blown outside can be -12C when the outside air temperature is 5C. Conversely, in summer when the heat pump is operating in reverse, the exhaust air can be up to 45C when the outside air temperature is 25C.
Rigid pipes
Rigid ducting has been used throughout the installation. This has a considerable advantage over flexible ducting as it results in: superior air flow as there is less air resistance; the ability to carry a greater volume of air for a specific pipe diameter; significantly lower noise; and no susceptibility to flattening of the pipes. Note how very carefully the engineer installed the ducting and all the units. The high level of pipe insulation minimises heat loss when heating and heat gain when cooling.
This shows the Optima 300 controller operating in the winter with the air sourced heat pump operating. Note here that "Fresh Air" is brought in from outside at 9.2C, goes through the cross flow heat exchanger and heat pump and is blown to the rooms at 43C. Next stale moist air is extracted at 17.3C and again goes through the heat exchanger and heat pump to be blown outside at 1.6C. Using the heat pump in winter allows us to turn our storage heaters off early. The heat pump uses around 250W, yet it provides the equivalent of 1KW of heat energy. The controller is fully programmable and I will create a separate web page on the controller.
Genvex Cooling
In summer, the heat pump works in reverse and cools the incoming air while reducing the humidity to making the the environment more comfortable. With the recent hot weather, here are details of the heat pump providing cooling. Note here that "Fresh Air" is brought in from outside at 23.9C, goes through the cross flow heat exchanger and heat pump and is blown to the rooms at 11.4C. Next stale moist air is extracted at 27.3C and again goes through the heat exchanger and heat pump to be blown outside at 44.4C. This is not air conditioning, but there is a welcome drop in temperature, and unlike air conditioning, there is no recirculated air.
Data Logging
While the installation can be used just as it was left by the installation team very satisfactorily, it does provide the enthusiast the opportunity to play with it. Sophisticated settings can be optimised very easily using the buttons on the controller above. But, the unit has a USB interface that can be used to easily set up the controller. Additionally it has an D card and the operational data can be viewed using the data logger program. Let us just explore what has been happening to the unit.

These graphs are of the heat pump operating in heating mode. The red line is the supply air being blown into the rooms; notice that when the heat pump is running, the supply air is around 40C; with the heat pump not running, it is 13C.

For a comprehensive review of the Genvex Optima 300 Controller, click here.

For a comprehensive review of the Genvex data logging software, click here.


The features of our system are:

  • Rigid galvanised steel plated insulated ducting, not flexible aluminium foil (see photos).
  • Four different fans speeds, one at 100% and three programmable.
  • Provides cheap heating in winter and cooling in the summer.
  • Almost silent operation, inaudible operation in the house.
  • Controller senses temperatures at seven locations (option of two more).
  • Thermostat operation from one of three places.
  • 100% replacement of air, none recirculated.
  • Electrostatic filter removes dust particles down to 0.01 microns and many viruses giving pure air.
  • 10 programmable combinations of time, temperature and fan speed can be set for each day of a seven day week.


  • Avoids need for heat-wasteful trickle ventilators and bathroom/kitchen extractor fans.
  • Very energy efficient heat recovery and cheap heating with the heat pump.
  • Enables all windows to be kept closed from autumn through to summer.
  • Clean filtered air helps asthma and hayfever sufferers.
  • Eliminates condensation while keeping property airtight.
  • Eliminates smells and odours, house smells fresh.
  • Improved security as opened windows not necessary.
  • Reduction in humidity
  • Reduced energy bills.

Want to know more?

If you would like to know more about the benefits of installing a ventilation system with a heat pump, please email me on I am willing to offer home visits to see our installation live for a small fee if that would be helpful since I really believe they offer significant benefits.

These web pages are written by myself, and the content should not be construed as having the approval of Genvex or Total Home Environment Limited.

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