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  1.  
    Every FreshR HRV has a WiFi connection so a log of the air quality, ventilation rate and occupancy of close to 50+ Passive Houses has been collected over the last 12 months. One 4 house Passive House scheme in Holland shows an average ventilation rate of 35m3/hr for families of 4 (2 adults and 2 kids) while maintaining excellent air quality, so I did some number crunching. The recommended ventilation rate for 4 people living in a Passive House is 25m3/person/hr. I entered this reduced ventilation rate into the PHPP for a 200m2 Passive House we're presently building and it reduced the heating demand from 15kWh/m2/annum to 5kWh/m2/annum.

    Most clients building Passive Houses who come to us have the idea to use a heat pump with ducted HRV but the reduction in heating demand when FreshR is used instead of ducted HRV allows for some interesting Heating/Ventilation options.

    Option One
    Heating/Ventilating a 200m2 Passive House with a €6k ducted HRV unit, a €5k Heat Pump (4kW) plus €2k for Under floor Heating, Total installation cost = €13k.

    Heating 15kWh/m2.annum = 3,000kWh, Heat Pump COP 3 so 1,000kWh x €0.17c/kWh = €170.
    Hot Water 15kWh/m2.annum = 3,000kWh, Heat Pump COP 3 so 1,000kWh x €0.17c/kWh = €170.

    Electricity 15kWh/m2.annum = 3,000kWh/annum @ €0.17c/kWh = €510/annum.
    Filter Changes €50/annum.
    15 year replacement cost of €5k Heat Pump = €350/annum.
    Total annual costs = €1,250.

    Option Two
    Heating/Ventilating a 200m2 Passive House with two FreshR HRV units @ €5.5k plus €5k for 10m2 of Drain-Back Solar Hot Water/ Space Heating. A 65% reduction in the heating demand of a house ventilated with FreshR allows 10m2 of Solar Thermal to supply hot water and heating from mid February to mid November, 2kW low temperature radiator = €500. Total Installation cost = €11,000

    The heating and hot water deficit not supplied by solar is supplied by electricity, this comes to 850kWh/annum x €0.17c/kWh = €145.

    Electricity 10kWh/m2.annum = 2,000kWh/annum @ €0.17c/kWh = €340/annum.
    35% of the electricity used in a Passive House goes to keep the always on ducted HRV running, FreshR reduces the electricity usage by 35%.

    Total annual running costs = €485.

    When option 2 is employed only half the amount of roof PV is required to reach the Passive House Plus standard.
    • CommentAuthorgravelld
    • CommentTimeAug 24th 2017 edited
     
    On what basis did you choose the number of units? My house is 50% larger, yet apparently requires 150% more units.

    Can't people just run their MVHR slower? How do the units reduce the ventilation rate while maintaining air quality any better than a traditional MVHR unit?
    • CommentAuthortony
    • CommentTimeAug 24th 2017
     
    I have 240m2 house ventilation day 20m3/h over person and night 10, exelent air quality, continuous slow air changes seem to give good results for me.
  2.  
    Posted By: gravelldOn what basis did you choose the number of units? My house is 50% larger, yet apparently requires 150% more units.
    300m2 house with 2.5m ceilings = 750m3 Volume x 0.3Air Changes per Hour = 225m3/hr, so 2 FreshR units have sufficient capacity to ventilate a 300m2 house. You just have to figure out where to place them properly, in the hall beside bedrooms and bathrooms so the side ducts can suck air from the nearby toilet.

    Posted By: gravelldCan't people just run their MVHR slower? How do the units reduce the ventilation rate while maintaining air quality any better than a traditional MVHR unit?
    FreshR is currently in discussions with the PassivHaus Institute about reducing the average ventilation of Passive Houses with FreshR units fitted by 55% but the latest test results of 50+ Passive Houses show an actual automatic 65% reduction in the ventilation rate while maintaining excellent air quality.
    When building a Passive House, you fill in the PHPP tweaking the insulation levels so the heating demand is 15kWh/m2/annum, then you fit FreshR instead of a ducted system that self regulates and delivers 0.1ACH so your Passive House now has a heating demand of 6kWh and not 15kWh.
    Fitting FreshR instead of a ducted system has a similar effect on the heating demand of a Passive House to fitting an extra 150mm of insulation in the walls/floor and roof.

    Ducted HRV producers don't recommended reducing the ventilation rate or switching off their units because they're worried about condensation in the ducts leading to dust build up leading to fungus and mould growth.
    Other de-centralised HRV systems don't have the same heat exchanger capacity to provide sufficient return air temperatures when more than one person is in the room.
    FreshR is on its own in this regard, a real game changer! A Passive House with ducted HRV and a heat pump will have the same annual heating cost as an electrically heated Passive House with just FreshR installed.
      FreshR Everywhere ITW.jpeg
    • CommentAuthorgravelld
    • CommentTimeAug 24th 2017
     
    Posted By: Viking House
    Posted By: gravelldOn what basis did you choose the number of units? My house is 50% larger, yet apparently requires 150% more units.
    300m2 house with 2.5m ceilings = 750m3 Volume x 0.3Air Changes per Hour = 225m3/hr, so 2 FreshR units have sufficient capacity to ventilate a 300m2 house. You just have to figure out where to place them properly, in the hall beside bedrooms and bathrooms so the side ducts can suck air from the nearby toilet.
    A house of any shape? With wet rooms anywhere? While also meeting UK building regulations by ducting?

    Posted By: Viking House
    Posted By: gravelldCan't people just run their MVHR slower? How do the units reduce the ventilation rate while maintaining air quality any better than a traditional MVHR unit?
    FreshR is currently in discussions with the PassivHaus Institute about reducing the average ventilation of Passive Houses with FreshR units fitted by 55% but the latest test results of 50+ Passive Houses show an actual automatic 65% reduction in the ventilation rate while maintaining excellent air quality.

    Right, but why and how? (read on)

    Posted By: Viking HouseDucted HRV producers don't recommended reducing the ventilation rate or switching off their units because they're worried about condensation in the ducts leading to dust build up leading to fungus and mould growth.
    Ok, think that might explain it, not that I know anything about MVHR...
  3.  
    I think this thread is what they call an infomercial !!
  4.  
    Posted By: Peter_in_HungaryI think this thread is what they call an infomercial !!
    Hi Peter, I don't have a commercial interest in FreshR and don't earn any sales commission but I am a fan of the product and recommend it to clients because of its obvious benefits.
  5.  
    Yes, mechanical ventilation needs fans!
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 25th 2017
     
    Are Options 1 and 2 typical or worst and best examples.
    Any chance of posting up a link to the raw data so more analysis can be done?
    •  
      CommentAuthordjh
    • CommentTimeAug 25th 2017
     
    Posted By: Viking HouseWhen building a Passive House, you fill in the PHPP tweaking the insulation levels so the heating demand is 15kWh/m2/annum, then you fit FreshR instead of a ducted system that self regulates and delivers 0.1ACH so your Passive House now has a heating demand of 6kWh and not 15kWh.

    I just changed the ventilation rate in my PHPP from the standard 111 m³/hr to 36 m³/hr (0.1 ach) and my specific heat demand changed from 14 kWh/m² to 13 kWh/m³. If I make it 0.01 ach it only goes to 12 kWh/m².

    It's worth saying that I frequently run my MVHR at 50 m³/hr with no apparent problems resulting and that my certifiers noted: "The standard ventilation flow rate is very high. Use of the ventilation system at the standard flow rate may result in overly-dry air and higher-than-necessary electricity bills." The speed I run the MVHR at doesn't seem to make much difference to the humidity, though I haven't done proper tests.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 26th 2017
     
    Posted By: djhI just changed the ventilation rate in my PHPP from the standard 111 m³/hr to 36 m³/hr (0.1 ach) and my specific heat demand changed from 14 kWh/m² to 13 kWh/m³. If I make it 0.01 ach it only goes to 12 kWh/m².
    But as you said elsewhere, numbers are irrelevant. :wink:
    Just varying the ACH in PHPP says very little as it has to be put into context with all the other elements of the building.
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