Thursday, August 4, 2011

Retrovent in the future

3 August 2011: While I was at Ecobuild 2011 in March, I took an interest in MVHR, or Mechanical Ventilation with Heat Recovery.
   The house is well insulated, but it is a prime maxim of the Passivhaus concept to use MVHR because the insulation levels are so good that only the ventilation heat loss remains to be dealt with.
    In our case, even with quite pessimistic assumptions, our ventilation heat loss is probably 50% more than the loss through roof, walls and windows. Some of this is lost through coming and going through doors, the rest is leakage, or windows left on trickle vent or left open. One only counts heat loss during the heating season, the windows are open all the time at this time of year.
   I have spent months thinking about Whole House MVHR like the diagram below - because it is more efficient, and is the way it should be done in a new building.

  After much thought and diagram drawing, I decided that the whole house solution will not work because we have underfloor heating and it is too risky to have vertical ducts passing through the first floor. I had to do this to get my Sunbox pipes down to the Heat Pump and that was a nightmare of plumbing, to avoid the floor heating pipes. It would be possible to do a Box-in-the-Loft solution for the bedrooms only, but that seems to be a project for the year after.
    I shall have to compromise and go for a Room-at-a-time solution, and the only room worth doing on this basis would be the Kitchen-Dining combo.  This is our 'Winter Snug', and the one we most want to retain heat in whilst having good ventilation.
Illustration from Homeventilation website

At EcoBuild 2011, the Retrovent from Envirovent seemed to be the most advanced product for single room heat recovery and ventilation, so I decided that I must research this and get a quotation for installation.
   It seems to be very low energy (3 watts in normal ventilation mode) and hopefully, it will reduce the workload of the heat pump by maintaining good air temperature.

13 Sept 2011 Postscript: I have now paid for the Retrovent and hope it will be installed by the end of September.

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