MVHR - Mechanical Ventilation with Heat Recovery - pros and cons

Discussion in 'Home energy' started by eamonn123456, 28 Feb 2010.

  1. newirishman

    newirishman Frequent Poster

    I have added a Beam MHRV system to my house last year (not a new build, renovation / extension of old terraced house).
    House is only about 110 sqm, so using the at the time smallest Axco C75 unit. Three extracts (bathroom, utility, one in open plan livign/kitchen/diner above kitchen island), 5 inlets (one each bedroom, one living room, one kitchen/dining area). No other ventilation at all. House is reasonably air tight, triple glazed windows.
    Works very well, would never again go without it in Ireland. IMO, money well spent (was about 4500 including planning and installation).

    filter replacement ever 6-12 months, filter is about 25 euro.

    Had some limitations in terms of placement of inlets and extracts, and some of the piping as it wasn't a new build, but all in all very happy.
    Branz likes this.
  2. Mark Mackay

    Mark Mackay Registered User

    Hi David Pritchard

    We also are living in Spain, nr Malaga and looking at MVHR systems for incorporation into the refurbishment of our house, but finding contractors to do the work is hard. Any recommendations? Thanks
  3. Kiflekiff

    Kiflekiff Registered User

    Hi All,

    Very interesting tread indeed. I have spend lot of time reading about the MHRV, pros and cons, with or without air tightness, with heat pump or not heat pump etc... the bottom line is that everyone has an opinion on things and I am still unsure what is the best process to define what should be the most adequate, cost efficient systems for my new build and how do you go about defining it? I have been having debates for about 12 month with my engineers and I had to agree to disagree, but am I right ;)... he is a celtic tiger type of builder without a doubt...

    This is a split dormer and 2 storey house, block build, where the builder is saying he will achieve under 3 if not 2.5 air exchange at 50pa of pressure. With this. Happy to provide further info if anything needed.

    Currently we have a heat pump with underfloor heating downstair (dormer area and bedroom), then underfloor heating upstair (on concrete slab floor), airtightness just around the windows and doors (minimum). I want to put an MHRV for comfort and reduce humidity level, avoid draft etc... and not specifically for heat cost efficiency. That said, it does support cost efficiency as heat goes up and redistribute.

    Question 1: Is it required to have underfloor heating upstairs?
    Question 2: Should I put the MHRV?
    Question 3: Is 5K€ Airtightness needed to get ROI on the MHRV.

    Thank you all for your help..
  4. OC7500

    OC7500 New Member

    Hi All,

    Interesting posts. I hope you are all still keeping an eye on this thread as I was hoping for some updates and experiences to help me decide.

    I am building a 2500ft2 house in N. Ireland. It is conventional cavity block construction but with enhanced 150mm cavity insulation. The design of the house, comprises 2 blocks - the 1st block being a 1.5 storeys and the second block just being an open plan living area with a vaulted ceiling. Both blocks are linked by a short walkway & utility room. I should add that we will also have insulated plasterboard on the inside of the external ceilings.

    We had originally spec'd a MVHR as I assumed the heat recovery would help save on energy costs, but the builder has said he wouldn't recommend them as they are not worth the money and more recently a salesman has told me the same. Specifically they have said they are good for air quality but if you are expecting to reduce energy bills by using one you will be very disappointed. Instead they are suggesting a PIV (1 unit for each block) or PIV linked to a central extract stack.

    The price for the MVHR installed is approx. £4k. Whilst the PIV system is more like £1400.

    I need to decide urgently, so would appreciate your steer given my circumstances and if there are specific things I need to ask to inform my decision, please say.

    Many thanks
  5. OC7500

    OC7500 New Member

    I should also add the builder (and others) have said that when considering potential energy savings from MVHR you must take into account that you are building a new well insulated house, that will have a much less energy demand than an older house - which makes sense. So what I am saying is that from my perspective the payback period should be based on installing a MVHR versus not installing one in the same new well insulated house. Your learned thoughts would really be appreciated, as things stand I don't have an extra £4k+ to spend if it aint gonna save me money in under 10years and/or before it breaks!.
  6. OC7500

    OC7500 New Member

    As a new user I can't paste a link, but there is an article posted on the Telegraph website entitled "How-to-green-your-home-without-wasting-money" It is pretty damning on MVHR.
  7. Leo

    Leo Moderator

    Here's the article.
  8. bleary

    bleary Frequent Poster

    That doesn't seem too expensive. I got a quote for demand controlled ventilation recently for a small house for 3k. I would have had to get electric sockets installed and cores before they would install
  9. Coldwarrior

    Coldwarrior Frequent Poster

    Interesting article, I had planned to get solar hot water heating retrofitted to my house but recently ran the numbers and found it'd take over 20 years to break even on the installation and servicing costs, at which point the solar tubes would be out of warranty and probably need replacing.
  10. mike2017

    mike2017 Registered User

    How air tight in your house going to be and will it be tested at any point? If not then don't bother with MVHR as your builder obviously is old school and doesn't mind you losing heat via draughts and thermal bridges. Just get the PIV system to get some fresh air/extract going and you're done. One thing on PIV - will it have a heater? How much will you have to use it and will you feel the cold near the vents? Ask to see a house the builder has done with a unit and quiz the owner out of the builders earshot!