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Thread: Evohome and MVHR

  1. #1
    Automated Home Jr Member
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    Oct 2004
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    20

    Default Evohome and MVHR

    I have Honeywell Evohome controlling my central heating. 11 zones and 16 TRVs. Been in close to four years now and happy with it regarding controlling temperatures. However, we do get a bit of condensation on insides of our double glazing. Adding a couple of other things to that I've started to look at what options I have to improve air flow (and quality?). Has anybody looked at using an MVHR with an Evohome system and do you have any guidance or suggestions?

    I've found reference on one site to MVHR being 'homogeneous temperature' across house, which if true would negate the benefits we're getting from Evohome.

    Any thought/comments appreciated.

  2. #2
    Automated Home Jr Member
    Join Date
    Jan 2019
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    Default

    Id get a humidity sensor, they are fairly cheap and will give you an indication of where you are at in your house.

    MVHRs are expensive although from general awareness would definitely improve airflow.

    The condensation could be caused by several factors.
    -True poor airflow causing high humidity, air bricks covered, poorly installed cavity wall insulation etc.
    -over introduction of water into the house, poorly ventilated kitchens/bathrooms, drying washing in the house, small leaks on pipes etc.
    -old/faulty double glazing causing overly cold surfaces inside the house allowing water to condense.

    There could be a plethora of other reasons.

    My advice would be to try to identify what the root cause of the humidity is before necessarily fixing the symptom.

  3. #3
    Automated Home Guru
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    Sep 2018
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    Scotland
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    I have a Zehnder ComfoAir/Cool Q600 and Evohome. They work independently.

    It keeps CO2 levels down and boosts automatically if higher humidity is detected for instance when showering.

    Extracted air is used to heat incoming so of course there is typically a couple of degrees drop in supply temperature.

    I agree though, you need to track down the cause of condensation. How old is your house?

  4. #4
    Automated Home Sr Member
    Join Date
    Feb 2019
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    Default

    We live in a 1926 semi detached house and not long after we moved in we started having major problems with condensation on not only our windows,but on some of the internal walls but only upstairs. I contacted someone regarding this and their answer was to fit new double glazed units that were energy efficient such as pilkington K glass,unfortunately we were given the wrong information which I didnt find out until it was too late,this in fact made the problem worse.It turns out that our property when constructed has a cavity on the lower half which has been insulated but the upper half of the house is solid brick,hence no cavity.We were at our wits end because unless we left our windows open,the walls were streaming with water,not good having windows open in the middle of winter.By chance after a lot of searching I came upon a product made by a company called Nuair,they have a unit called a drimaster which is a piv or positive input ventilation which is basically a big fan unit with two filters which is installed in your loft which draws fresh air in via your loft space providing its not completely air tight in there,you have to cut a hole in your ceiling for the vent to fit which has a grill on the underside,what this basically does is creates air movement which then doesnt allow condensation to form,this works on a one to five bedroom house.I was very sceptical but was assured that this was the answer to our problems,Im very happy to say it was,weve had this unit for about twenty years and the only thing you have to do is change the filters every five years.The new ones are much better in that you can have an on board heater to warm the air as it comes in the property,handy in the winter,can alter the fan speed and some have a humidity sensor and a sensor to tell you when the filters need replacing.These are absolutely fantastic and our neighbours were having the same problems so I told them about this,they were very grateful.With ours installed after three days there were no condensation problems and never have been,problem solved.

  5. #5
    Automated Home Guru
    Join Date
    Dec 2012
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    174

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    Ive had an MVHR system in our house since it was built in the early 90s and in 2012 I added Evohome. Whilst I have run tests and can say that with the MVHR on there is a noticeable “balancing out” of temperatures with no heating on. Once heating is applied then rooms behave relatively in isolation and respond to the individual temp setting of the TRV. The MVHR does have a loss on recovery and the % theoretical vs actual can sometimes being interesting to note (I ran tests using temp sensors in the extracts and inlets and measured the outside air and final exhaust). That being said, my main rational for installing an MVHR in my new build was a) to reduce condensation b) to provide a fresh environment whilst recovering as much heat as possible.

    I can say that with the Evohome system I find no issues or conflicts with the MVHR and that every so often I check balance of inlets to outlet. I also have had to replace the cross flow core once due to age as it “collapsed” but otherwise other than the filter cleaning and replacement I just let the system “tick over”. I did initially have humidity sensors in the bathrooms but these had to be adjusted based on relative humidity as when damp outside they would switch on despite no one using the bathroom and not turn off. I would have to adjust the relative humidity on them and then they would respond to the humidity change. When the second sensor failed (20 years going so not bad) I decided to simply revert to a timed boost function as that worked just as well I felt.
    In summary, I am very pleased with having a full MVHR system and alongside Evohome which I am also very pleased with, I find they work well together ��

  6. #6
    Automated Home Jr Member
    Join Date
    Oct 2004
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    Default

    Thank you all for the responses, my apologies for not replying sooner, unfortunately Christmas and New Year got in the way (along with meshed wifi install) and only just got time to reply.

    I will get a humidity sensor, will be useful as I'm changing the house (actually it's a bungalow).
    Bungalow is a 1980s build (early 1980s), cavity walls which are filled. Most of the windows are double glazed and installed 14 years ago. The rest were done by us within the last two years and meet building regs (which do not seem to have changed since our last renovation in 2011).
    We've added 200 mm of insulation into the loft on top of the 100 or so that was there. Plus we've added some insulation to the walls of some rooms.
    I've definitely reduced airflow as there were a couple of holes in the floor which were 2" in diameter to bring 2half inch pipes up from under the floor, which is a traditional timber build not solid concrete block.
    We've not blocked any air bricks, which are all under the floor into the void under it.

    I actually think the bungalow is reasonable well sealed as it can get 'stuffy' in the bedroom overnight, so getting some additional movement will help and drive down a potential CO2 'problem'.

    We did notice a difference in the roof space when we'd added the insulation, with condensation forming on the roofing felt under the tiles, but I resolved that last year by adding in more vents in the soffits (good) and some felt lap vents (not so good).

    Thanks again for the comments.

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