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HRV Modifications to heat home

  • 10-03-2021 12:28pm
    #1
    Registered Users Posts: 149 ✭✭ wicklow_hunter


    Hi All,

    Looking for some advise or anyone with experience of this

    I have Hrv System installed and UFH

    uf Heating is starting to grate on me as its a bit on the expensive side and if you want an Extra Degree or 2 to be cosy its going to cost Ya

    Typically we pay €1200 per Anum Esb to drive the UF Heating (3000Sq Ft House) Stat Set to 20 Degrees

    It seems to be acceptable to pay this figure from reading threads

    However i do notice that the HRV seems to be a double edged sword in that it is providing fresh air but at the same time pumping in cold air from outside
    (And Yes i get the principles of HRV IE it is semi heated from Bathrooms Etc)

    Anyway my question is, are there any ways of preheating the air going in or out of the HRV that would reduce the load on the Heat Pump

    Without any Heating i can get Say 18 Degrees with the UFH Heating Off
    With Heating on Heat Pump set to 20 Degrees Heating

    In Summary to heat the house by an extra 2 Degrees to be some what comfortable its costing 1200/6 Months of Year = €200 per Winter Month

    is there anyway of getting that extra 2 Degrees via the HRV System

    using something like a heat Ex changers via Solar Panels or some other renewable that is fed into the hrv to warm up the air

    Any experience or advise is welcome :pac:


Comments

  • Registered Users Posts: 11,199 ✭✭✭✭ KCross


    However i do notice that the HRV seems to be a double edged sword in that it is providing fresh air but at the same time pumping in cold air from outside
    (And Yes i get the principles of HRV IE it is semi heated from Bathrooms Etc)

    If its HRV you actually have its not just pumping in cold air or just taking bathroom air. Its exchanging the heat from all the exhaust air and putting it into the incoming air.

    If you are feeling that the incoming air is very cold then something is up with that and might require a service or filter change etc.

    I know you said you get this principle but you seem to be somewhat blaming the HRV for the house being cold?

    Ultimately you need ventilation so that air needs to continue to be pumped in. If you feel the incoming air is too cold and actually making your house cold then you need to get that looked at but if its operating as it should it is not the reason why your house is cold... HRV systems are reasonably efficient.


    Maybe measure the temp on one of the incoming vents and see what you get. It should not be drastically different from the room temperature..... certainly not the same as the outside temp. Work from there to decide your next step which might be to tweak your heat pump settings.

    using something like a heat Ex changers via Solar Panels or some other renewable that is fed into the hrv to warm up the air

    Thats exactly what the HRV has... a heat exchanger.


    You can, I believe, add additional heaters to the incoming air but that will be worse than using your heat pump as the best you will get there is 1kW of energy used to produce 1kW of heat.... the heat pump will be more efficient than that so you would in effect increase your electricity consumption in that case.

    Solar PV wont do it either since the sun doesnt tend to shine much when you need the heat the most... winter.


  • Registered Users Posts: 7,502 ✭✭✭ Outkast_IRE


    Its a fairly large property you have there. Unfortunately the bigger it is the more it costs to heat , energy efficient or not. There are many homes half that size that have larger bills than you.

    As Kcross has alluded to if you have a full HRV system in your home thats as good as it gets. Most homes get by with wall vents directly to outside.

    I agree with Kcross , get a service on the HRV with filters changed etc.

    I dont think at any stage you mention what you are using to generate heat for the UFH system , is it , ASHP , Geo ? Thats a key piece of information thats needed. The system design can play a factor with that side of things to, if its ASHP is it on/off alot more than youd expect or have you noticed it behaving oddly is it linked to a buffer/accumulator tank? I assume the costs shown are for all you hot water also ?


  • Registered Users Posts: 2,544 ✭✭✭ MicktheMan


    Notwithstanding the other replies above, to answer your question yes you can get various types of preheaters for mvhr systems. That said however, a kWhr of heat is a kWhr of heat regardless of where you get it from so if you need to supply extra kWhrs then your heat pump is still the most efficient way of delivering it.

    You might however be much better off investigating your heat loss (where & how) and addressing main weaknesses found.


  • Registered Users Posts: 252 ✭✭ Biker1


    Was the HRV system commissioned by competent persons. Get a NSAI ventilation validator to check the system for you and they will advise on the issues if any.


  • Registered Users Posts: 149 ✭✭ wicklow_hunter


    Some goods points raised here.
    Unlikely if there is a commissioning issue but worth taking a look

    It’s probably a stove that I will end up going with to give the house a bit of heat when it’s needed

    some errors were made with the ufh design didn’t put enough loops into the kitchen living area. The kitchen living room is open plan with Vaulted ceilings 1000sq ft approx

    Heat pump supplier advised to minimise the amount of stats as it makes the system cut in and out more frequently driving up the inefficiency of the system

    Other design issues was having the heat pump at the opposite end of house ie the furthest point from kitchen living roomIn order to get proper heat into the kitchen Hall and utility room were like a furnace.

    In the end I disconnected the hall and utility from the system by closing the valves

    The supply lines going to the kitchen living room were sufficient to heat the hall and kitchen and helped balance the temps across the rooms

    Very frustrating to learn this after two years of trial and error


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  • Registered Users Posts: 2,173 ✭✭✭ 1874


    I didnt see anything about insulation and airtightness, from what Ive read and been told they would be major elements to ensuring a heat pump and MVHR work effectively/efficiently.


    A HVR or MVHR system is a heat exchanger and you are not just getting heat from the bathrooms, the supplied air and the extracted air should be the same, so fresh (pre heated air) is fed to living spaces and the same volume of air is extracted through wet spaces, ie bathrooms/toilets/kitchen to extract warm moist air and remove odours. Modern heat exchangers transfer sensible and latent heat so heat built up in the building (people/powered items/anything) and heat released when warmed moist air is condensed within the heat exchanger it gives off energy (thats my basic understanding of it), in reality, if your insulation was substantial and your airtightness was very effective you might not need a heat pump or underfloor heating.
    Maybe you have inefficiencies, losses or weaknesses in your insulation or imo as importantly in your airtightness.
    Putting a stove in is just going to throw the balance of things out as it unless it is airtight and has its own air supply/extract, plus you might be losing heat not recovered from its exhaust.


  • Registered Users Posts: 149 ✭✭ wicklow_hunter


    1874 wrote: »
    I didnt see anything about insulation and airtightness, from what Ive read and been told they would be major elements to ensuring a heat pump and MVHR work effectively/efficiently.


    A HVR or MVHR system is a heat exchanger and you are not just getting heat from the bathrooms, the supplied air and the extracted air should be the same, so fresh (pre heated air) is fed to living spaces and the same volume of air is extracted through wet spaces, ie bathrooms/toilets/kitchen to extract warm moist air and remove odours. Modern heat exchangers transfer sensible and latent heat so heat built up in the building (people/powered items/anything) and heat released when warmed moist air is condensed within the heat exchanger it gives off energy (thats my basic understanding of it), in reality, if your insulation was substantial and your airtightness was very effective you might not need a heat pump or underfloor heating.
    Maybe you have inefficiencies, losses or weaknesses in your insulation or imo as importantly in your airtightness.
    Putting a stove in is just going to throw the balance of things out as it unless it is airtight and has its own air supply/extract, plus you might be losing heat not recovered from its exhaust.

    The house was tested for air tightness and passed the spec. Spray foam insulation in ceilings. 50mm cosy board on external walls. Air tightness tape around all windows and doors and floors

    Auto valve on the cooker vent and chimney is blocked out😉

    100 mm floor insulation and 25 mm upstands around the base of the rising walls to stop cold bridging.

    I do notice some minor leakage around door and window seals. But they are what I would deem minor



    Thermal camera or a retest of air tightness could be worth a punt.


  • Registered Users Posts: 2,173 ✭✭✭ 1874


    The house was tested for air tightness and passed the spec. Spray foam insulation in ceilings. 50mm cosy board on external walls. Air tightness tape around all windows and doors and floors

    Auto valve on the cooker vent and chimney is blocked out��

    100 mm floor insulation and 25 mm upstands around the base of the rising walls to stop cold bridging.

    I do notice some minor leakage around door and window seals. But they are what I would deem minor

    Thermal camera or a retest of air tightness could be worth a punt.


    I,m not an expert, but Ive looked into energy loss in a bit of detail for myself.
    Do you have any figures to work off, U/lambda values, what material is the EWI insulation of? 50mm doesnt sound like much, did anyone do any modelling/assessment of the design? Did you get a value for how many air changes per hour? Do you have window or wall vents or other openings that were sealed for a test?

    I'm not a particular fan of spray insulation, it may be that it's effective but Im not convinced its any better than other methods.

    Are your windows certified in anyway for airtightness or insulation, what kind of airtightness layer do you have?

    Not an expert, who did the work for you? I think its possible to do the work and detail by a competent person who has an insight into heat loss and factors that affect it


  • Registered Users Posts: 2,544 ✭✭✭ MicktheMan


    The house was tested for air tightness and passed the spec.

    The air tightness pass criteria is the poor relation in the b.regs for heat loss so passing the spec is no guarantee of quality I'm afraid.

    Do you remember what the actual test result was? The units would have been m3/hr/[email protected]


  • Registered Users Posts: 149 ✭✭ wicklow_hunter


    MicktheMan wrote: »
    The air tightness pass criteria is the poor relation in the b.regs for heat loss so passing the spec is no guarantee of quality I'm afraid.

    Do you remember what the actual test result was? The units would have been m3/hr/[email protected]

    No I did request it but can’t put my hand to it. What would be the best way of tracking down the heat loss

    They are selling thermal cameras on eBay for €150
    Would this provide an indication of where the heat loss is coming from over an air tightness test?

    Was present on the air tighness test and the guy hooked up fans etc to a laptop. He blocked all hrv vents and walked around the building placing the back of his hand around windows and doors and said I passed. I then requested the report but it didn’t really mean anything to me at the time🀔


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  • Registered Users Posts: 2,173 ✭✭✭ 1874


    Id say its likely the best way to determine what the heat loss should be is by calculation, based on what insulation was installed and to what value.
    I dont know what value placing the back of the hand to windows/doors, never did a complete course for airtightness testing but I carried out airtightness with someone where I did it as an intro, I was working under the assumption that the windows were airtight so never tested for or saw a back of the hand method! for a test at 50 Pascals, Id imagine it would be imperceptible. It has been a while but I thought the test measured differences in pressure using a sensor in the equipment.


  • Registered Users Posts: 2,544 ✭✭✭ MicktheMan


    No I did request it but can’t put my hand to it. What would be the best way of tracking down the heat loss

    They are selling thermal cameras on eBay for €150
    Would this provide an indication of where the heat loss is coming from over an air tightness test?

    Was present on the air tighness test and the guy hooked up fans etc to a laptop. He blocked all hrv vents and walked around the building placing the back of his hand around windows and doors and said I passed. I then requested the report but it didn’t really mean anything to me at the time��

    It would be useful if you could find the report.

    My thermal imaging camera set me back €15k so I wouldn't be expecting too much from a €150 one. Besides, even the best camera in the hands of an untrained and inexperienced operator would more than likely lead to inaccurate and misleading conclusions.

    Using thermal imaging in conjunction with the blower door is optimum for finding weaknesses.


  • Registered Users Posts: 2,544 ✭✭✭ MicktheMan


    1874 wrote: »
    Id say its likely the best way to determine what the heat loss should be is by calculation, based on what insulation was installed and to what value.
    I dont know what value placing the back of the hand to windows/doors, never did a complete course for airtightness testing but I carried out airtightness with someone where I did it as an intro, I was working under the assumption that the windows were airtight so never tested for or saw a back of the hand method! for a test at 50 Pascals, Id imagine it would be imperceptible. It has been a while but I thought the test measured differences in pressure using a sensor in the equipment.

    The issue is that while a certain insulation type may have been installed, you are depending on it being installed properly and uniformly everywhere.

    The back of hand technique is a quick way of determining if there is air leakage at certain junctions during the depressurisation cycle of the test. Even the slightest leakage will be noticed and would be somewhat quantifiable as important or not by the experienced tester.


  • Registered Users Posts: 68 ✭✭ Mr Gumby


    If you fit a stove to an air tight house it needs to also be airtight and have it's own supply of air taken from outside. From first hand experience few people keep their house air tight regularly opening windows for 'fresh air' etc. A stove is your best alternative, at it's best if you have large air volumes to heat and very quick to react, it would allow you to run the underfloor a few degrees lower.


  • Registered Users Posts: 688 ✭✭✭ keno-daytrader


    What flow temperatures is your UFH running at? Im assuming you have a heat pump?

    Also do you have proof of MVHR commissioning? If your system is out of balance it you will most likely be losing heat.

    But Id be more concerned at how your heat pump is running. The lower you can get the flow temp the better your bills will be.

    Id also try and find your airtightness test result as the results will tell you a lot about your heatloss.


  • Registered Users Posts: 149 ✭✭ wicklow_hunter


    What flow temperatures is your UFH running at? Im assuming you have a heat pump?

    Also do you have proof of MVHR commissioning? If your system is out of balance it you will most likely be losing heat.

    But Id be more concerned at how your heat pump is running. The lower you can get the flow temp the better your bills will be.

    Id also try and find your airtightness test result as the results will tell you a lot about your heatloss.

    Heat pump is set at 20 Degrees

    The hrv system was done by a plumber I didn’t know that it needed commissioning or balancing. What are the implications of a hrv that is out of balance?

    We struggled balancing the uf heating. As mentioned above we had to close some of circuits as some were overheating certain rooms

    Utility and Hall were like a sauna

    Anyone on here finding it more difficult to heat vaulted 6m ceilings to the apex as opposed to std 2.7 m ceilings?


  • Registered Users Posts: 21,783 ✭✭✭✭ mickdw


    Heat pump is set at 20 Degrees

    The hrv system was done by a plumber I didn’t know that it needed commissioning or balancing. What are the implications of a hrv that is out of balance?

    We struggled balancing the uf heating. As mentioned above we had to close some of circuits as some were overheating certain rooms

    Utility and Hall were like a sauna

    Anyone on here finding it more difficult to heat vaulted 6m ceilings to the apex as opposed to std 2.7 m ceilings?

    By the sounds of things, neither your heating or heat recovery systems were designed or commissioned professionally.
    Its pretty much standard now to have the floor loop layout etc designed.
    High ceiling should also have been considered.
    The under floor is what it is now bar adjustment.
    Id certainly have a professional out to balance the Heat recovery system and go from there.


  • Registered Users Posts: 149 ✭✭ wicklow_hunter


    mickdw wrote: »
    By the sounds of things, neither your heating or heat recovery systems were designed or commissioned professionally.
    Its pretty much standard now to have the floor loop layout etc designed.
    High ceiling should also have been considered.
    The under floor is what it is now bar adjustment.
    Id certainly have a professional out to balance the Heat recovery system and go from there.

    There was a design done on the ufh , plumber did deviate from the plan but changes were minor . 1 or 2 loops were omitted.

    We had the plumber back 3-4 times on ufh but like most tradesmen couldn’t give a f#*k and kept telling us to turn up the temp

    Is there any merit in turning off the hrv system temporarily to evaluate if there is an imbalance ?
    Perhaps the house would stay warmer in the offending vaulted room


  • Registered Users Posts: 21,783 ✭✭✭✭ mickdw


    There was a design done on the ufh , plumber did deviate from the plan but changes were minor . 1 or 2 loops were omitted.

    We had the plumber back 3-4 times on ufh but like most tradesmen couldn’t give a f#*k and kept telling us to turn up the temp

    Is there any merit in turning off the hrv system temporarily to evaluate if there is an imbalance ?
    Perhaps the house would stay warmer in the offending vaulted room

    It should stay warmer with it off but you must have ventilation and hrv is the most efficient way of doing that as it exchanging heat from the outgoing air so should be much much better than an open wall vent.
    Any issues around airtightness and insulation in the vaulted room?


  • Registered Users Posts: 688 ✭✭✭ keno-daytrader


    Heat pump is set at 20 Degrees

    The hrv system was done by a plumber I didn’t know that it needed commissioning or balancing. What are the implications of a hrv that is out of balance?

    We struggled balancing the uf heating. As mentioned above we had to close some of circuits as some were overheating certain rooms

    Utility and Hall were like a sauna

    Anyone on here finding it more difficult to heat vaulted 6m ceilings to the apex as opposed to std 2.7 m ceilings?

    Your flow and return temps are different to what you have your thermostat set to. This refers to the temperature of the water entering your underfloor pipes and the temp of the returning water. The lower you can get your flow temp, the less energy you will use.

    When our heat pump was run just using the auto setting it ate electricity! Now have our flow temp set to 28 and this is enough to keep our house at 21.5 even at -2c outside. Before on auto settings the flow temp would sometimes be 40+, very inefficient and hard on the electricity.

    We have vaulted ceilings too, but dont have a problem heating that area. I did notice that one part of our open plan room wasnt heating good enough, I increased the flow rate of that loop and that sorted the problem.

    For this winter (oct-feb)we are averaging 31 euros a month for heating and 13 euros for hot water. House is 215sqm.


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  • Registered Users Posts: 10,926 ✭✭✭✭ Calahonda52


    ..
    Without any Heating i can get Say 18 Degrees with the UFH Heating Off
    With Heating on Heat Pump set to 20 Degrees Heating

    In Summary to heat the house by an extra 2 Degrees to be some what comfortable its costing 1200/6 Months of Year = €200 per Winter Month

    ...:

    This makes no sense
    from
    https://www.met.ie/climate/available-data/monthly-data
    Mean temperature in degrees Celsius for DUBLIN AIRPORT

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
    2021 3.9 6.2 4.8 5.0
    2020 6.3 5.8 5.8 8.5 10.9 13.4 14.4 14.7 12.8 9.5 8.2 4.9 9.6
    2019 5.1 7.0 7.3 8.0 10.2 12.5 15.9 15.4 13.0 9.1 6.0 5.9 9.6
    2018 5.3 3.4 4.3 8.1 11.4 14.5 16.1 15.3 12.2 9.3 8.2 7.7 9.7
    mean 5.3 5.3 6.7 8.1 10.7 13.4 15.4 15.1 13.1 10.3 7.3 5.6 9.7


  • Registered Users Posts: 149 ✭✭ wicklow_hunter


    This makes no sense
    from
    https://www.met.ie/climate/available-data/monthly-data
    Mean temperature in degrees Celsius for DUBLIN AIRPORT

    Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
    2021 3.9 6.2 4.8 5.0
    2020 6.3 5.8 5.8 8.5 10.9 13.4 14.4 14.7 12.8 9.5 8.2 4.9 9.6
    2019 5.1 7.0 7.3 8.0 10.2 12.5 15.9 15.4 13.0 9.1 6.0 5.9 9.6
    2018 5.3 3.4 4.3 8.1 11.4 14.5 16.1 15.3 12.2 9.3 8.2 7.7 9.7
    mean 5.3 5.3 6.7 8.1 10.7 13.4 15.4 15.1 13.1 10.3 7.3 5.6 9.7

    Hi, I can get 18 degrees internally with ufh off. This is from solar gain etc...

    When uf is switched I get an average of 20

    Some investigation work today lead me to switching off the Mhrv

    Low and behold I was getting 22 degrees and the vaulted room was holding it

    I was noticing that there was no longer drafts in the vaulted room most noticeable around the door area leading into the hall way. I normally can feel it by putting my hand around the frame / gaps but not the case tonight

    I have two supply feed in and 1 extract in the vaulted room

    And from reading on the web :

    If the supply rate is higher than the extract rate, there will be a positive pressure, resulting in warm air being forced out through leaks in the building envelope.

    This explains why the room is cooling quickly🀔 for the past two years there was a noticeable flow of air exiting the room via the door frame.


    Time to get the system balanced me thinks ðŸ‘


    Thanks for all the opinions and possible root causes

    Attached is an image of the space for those who may be interested


  • Registered Users Posts: 21,783 ✭✭✭✭ mickdw


    Hi, I can get 18 degrees internally with ufh off. This is from solar gain etc...

    When uf is switched I get an average of 20

    Some investigation work today lead me to switching off the Mhrv

    Low and behold I was getting 22 degrees and the vaulted room was holding it

    I was noticing that there was no longer drafts in the vaulted room most noticeable around the door area leading into the hall way. I normally can feel it by putting my hand around the frame / gaps but not the case tonight

    I have two supply feed in and 1 extract in the vaulted room

    And from reading on the web :

    If the supply rate is higher than the extract rate, there will be a positive pressure, resulting in warm air being forced out through leaks in the building envelope.

    This explains why the room is cooling quickly�� for the past two years there was a noticeable flow of air exiting the room via the door frame.


    Time to get the system balanced me thinks ðŸ‘


    Thanks for all the opinions and possible root causes

    Attached is an image of the space for those who may be interested

    Ya it very much sounds like you are pumping far too much fresh air into the vaulted kitchen. Even though the incoming air gains heat in heat exchanger, it is still cooler air.
    Im not expert in heat recovery system design but balancing should be a huge help here. The fact that you have noticealbe forced air movement from the room suggests the set up is very very wrong.

    Great room though!


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