# MVHR - Mechanical Ventilation with Heat Recovery - pros and cons



## eamonn123456

I am looking for a good summary of the pros and cons of MVHR - Mechanical Ventilation with Heat Recovery.

Obviously I would like to find something written from an independent viewpoint, not something written by one of the firms selling these systems.

I would be particularly interested in something written in the context of the irish climate.

Reports from real-life experience of installing and running an MVHR system would be very welcome, so if you have one in your house and would share your thoughts, that would be much appreciated.


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## eamonn123456

PS I know there already is a thread on this here but its a bit out of date, am looking for an up to date perspective if possible please.


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## Buildright

MHRV

pros.
1. controlled ventilation system independent of outside wind and pressure.
2. Air quality and filtration.
3. steady stable heat delivery.
4. Humidity reduction (very important for Ireland with av RH of over 80%
5. Heat recovery.
6. Can deliver heat through the ventilation system for near passive spec. removing the need for radiators, you can just put some underfloor in tiles areas and maybe a couple of towel rails and the MHRV will distribute
7. can run at multiple speeds depending on occupancy c02 meters.
8. Feels fresh inside.
9. Cost neutral over 4 years.
10. New part F ventilation requirement means 4% bigger hole in wall vents.
11. can halve space heating bills.
12. adds future proof value to house, even if you just install the ducts now, as if you sell it in ten years, the market will want MHRV.
13. Improves BER asset rating if combined with airtighness below 3 ach@50pa

cons.
1. Cant use open fire must use room sealed stove( why would you use an open fire)
2. Filters need cleaning twice a year (suppose you cant do that with your lungs0
3. perception of risk of mould growth in ductwork. This is due to early installers using flexi's for main ducts instead of metal ducts. However generally if ducts are insulated where fresh air is brought in, mould cannot happen because of reduced humidity.
4. dosent work with our speculator based construction methods of build it cheap and feck off. Therefore hole in the wall vents seem more economical at build stage when occupancy costs are ignored.
5. Most self builders use substandard designers and builders who dont understand that energy efficiency can be incorporated at zero cost with a little bit of planning. For bolla sake, lettin engineers design houses! madness. Moreover to be a builder in Ireland all you need is a Navarra and a mobile phone, a plumber needs a four year aprenticeship and his papers.
6. Only makes sence to homebuilders as part of an integrated systems approach to building comfort. Dosent work for eejits who throw up a building reg standard house with chimneys and vents. 'oh i've only got €240k to build my one off, that means I can only go with cavity with kingspan, chimney, wall vent, massive oil boiler, 3000 square foot, with corridors everywhere. maybe stick on a ecobling heat pump to an inefficient house.' The problem is our designers and builders havent a clue. The people building efficient passive or near passive houses are self builders who have gone and done the research themselves and realised that spending on insulation and airtightness instead makes sence.


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## eamonn123456

Hi buildright, many thanks for such a long and detailed reply, it's very convincing in favour of MHRV / MVHR.

I have a few questions if that's OK:

1.  What is the basis of your expertise and experience? 

(a) Do you have MHRV in your own home?

(b) Do you install these systems?  or 

(c) have you been in charge of building a house where these systems have been installed?

2.  How do you arrive at the calculation that it is cost neutral over 4 years?  

For a 2500 sq ft 1.5 storey house, airtightness work has been estimated at 3k, and about 6k for installing the system itself (ducting and unit).  
Space heating for a well insulated house of this size should only take a *max* of 1500 litres of oil, which should be less than 1000 euro this year (currently < 900 euro).
If space heating cost is halved, that brings it to 500 euro per annum, or a saving of about 2k over 4 years. 
 Even allowing for a lot of inflation in oil prices over 4 years, I can't see how it is cost neutral over that time frame.

I am not trying to doubt what you say or contradict you, I would just like to be clear on what you are saying.  

Many thanks again.


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## Buildright

Hi Eamon,

My background is in designing and supervising the build of passive and near passive houses. I also do airtest and thermography investigations. Your max space heating is 60kWh per meter square, even for a hypothetical figure, thats far too much, half your heat will go to heat the pavement outside and your roof tiles. You need to eliminate the cold bridges. You should be concentrating on detailing the insulation continuity and airtighness before looking at MHRV. Then again once you decide to go with MHRV you start to go towards passive. Hopefully its early enough to make the sensible decisions on insulation.

Taking a price of 5k for the unit, and not including airtightness, (building a house over 3 ach @50pa is just shoddy building work). I immediately reduced the boiler size and eliminated a full 1990's type central heating system and instead put in a system with 1000l tank feeding heat exchanger feeding underfloor to the tiles areas. To meet part L of the building regs, i assumed solar is required and the tank is part of the solar budget. The savings in plumbing are about 3 grand, leaving 3 grand to cover. While modeling looks at supplying energy to keep the house temp over 20 degrees for the 2,200 degree day hours, in practice because of the lowered humidity of the MHRV, 18 degrees is fine as a comfort level, In our monitoring of completed buildings, we find that houses of that size would rarely use more than 400l for space and hot water when solar is installed. So its a saving of about €600 per year, so that's about 5 year payback. 

Payback is a bit of a nuisance term, what payback have your other purchases like your car or the kitchen, you'll notice that most kitchens get replaced after 15 years anyway.


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## olddog

Buildright said:


> ..................... Most self builders use substandard designers and builders who dont understand that energy efficiency can be incorporated at zero cost with a little bit of planning. For bolla sake, lettin engineers design houses! madness. Moreover to be a builder in Ireland all you need is a Navarra and a mobile phone.........................



Thats a great bit of a rant you went off on there. 

Couldnt agree with you more !


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## Vincenzo

Bit misleading to claim there'll be a five year payback.
In order to have mvhr you need to start looking at having airtightness membrane around the house so there are no leakages affecting the system . Before all of this you should be considering insulation. 

How could you possibly

1 insulate 
2 install membrane 
3 plaster surfaces
4 not to mention ducting and heat recovery unit for 3 grand.


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## John1957

A lot of the comments above are valid re air tightness, buyil quality etc. Assuming you have a great build quality then not sure you should be looking at the payback scenaio of a MVHR unit.

Their main aspect is controlling the interior air quality of a house. If you use either trickle vents or hole in wall vent then you have an uncontrolled method of venting your rooms.

If you install a MVHR unit that is set up with proper baffles, booster for wet areas, etc then you can control the ventilation requirements of all the rooms, moisture levels, condensation, etc.  

I have seen so many cheap installations that are poorly designed that therefore do not offer value for money and in some instances purely don't work. Be carefull you get what you want. The cheapest option may not be the best.  Performance is what should be the first bottom line.


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## Buildright

Vincenzo said:


> Bit misleading to claim there'll be a five year payback.
> In order to have mvhr you need to start looking at having airtightness membrane around the house so there are no leakages affecting the system . Before all of this you should be considering insulation.
> 
> How could you possibly
> 
> 1 insulate
> 2 install membrane
> 3 plaster surfaces
> 4 not to mention ducting and heat recovery unit for 3 grand.



Vincenzo,
Look at the big picture for a minute, Even if you just use hole in the wall vents 10 air changes at 50 pascals is equivalent leakage area to leaving a door open. You dont need membrane. Hardwall plaster and OSB do the job better. The membrane is not technically an airtight barrier, its a vapour control layer. It is essential to have vapour control no matter what build up you select. This generally means lining the dormer in OSB and taping as a vapour control. This creates a services cavity with battens between osb and plasterboard. I usually put softboard on the rafters, as wind acting on the insulation reduces its performance. 

In Germany and Austria they design houses to last 60 years, in Ireland every weekend I'm testing houses often no older than 2 years old, which are impossible to heat, have condensation problems and are drafty. The way we build houses is 'shocking bad'.

Solar is now mandatory to meet regulations. The new ventilation regulations say you need to increase the size of the hole in the wall vents by 40% if under 7 air changes, and boilers have to have efficiencies of over 86%. This is the extra cost in building, its coming from regulation, so that extra cost is just for good practice. In this type of house having to heat the air twice an hour is an expensive task. The MHRV retains about 90% of the heat. The extra over good practice building for adding MHRV is about €3k. Ya sure if you compare a bog standard one off and leave out the mandatory renewables and stick kingspan in the cavity and drill big holes for services and cables it will cost about €15k to add MHRV.

The fact is to build celtic tiger type houses now is a stupid idea. Bolting heat pumps or renewables onto a minimum standards build is ridiculous unless your a speculator who can sell it fast and leave the homeowner with an underperforming asset. The way we build now has changed dramatically but many builders are left behind because of the low levels of knowledge and skills in the industry. Anyone still building bog standard will probably see me visiting their house in a couple of years to show them the uninsulated knee walls, or the wind blowing through downlighters and dormer crawl spaces, uninsulated boiler pipes, blocked wall vents and closed trickle vents, the underfloor leaking heat through the rising walls, the open fireplaces which get used just twice a year, quilt insulation on the slope, I could go on. 

All I'm saying is, think about where your wasting energy in a home and think about what comfort is. You'll soon arive at the inevitable conclusion that you need to pay attention to maintaining the integrity of the insulation using thermally storing insulats like cellulose and softboard in the roof. You'll need to remove the rising wall, eaves and windoe cill/head/reveal cold bridge and you'll need to prioritise minimising heat loss over buying a huge boiler. In the end of the day you'll have a future proofed home that will be comfortable and healthy and pretty close to passive. So good luck with that


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## eamonn123456

Hi buildright, thanks for the response, great to get help from someone who knows what they are talking about.

A couple of things:  

1.  the house is planned to have a standard central heating system so no saving in plumbing there (you may argue that there is no need for standard central heating, but would that be true in a non-passive house?);

2.  assuming solar is included then we are not comparing like-with-like to a traditional heating system, so the installation, running and maintenance costs of solar would have to be factored in for comparison;

3. I really do think payback is absolutely relevant for these energy saving measures. You might say that air quality is the main reason for MHRV, but I don't think so - surely air quality is adequate in most houses in Ireland?  Assuming the main reason for MHRV is energy efficiency, which most people would agree, then installation, maintenance and running has to be seen as an additional cost.  That cost needs to at some point be recouped by means of savings in energy bills compared with the same house without the system.   Otherwise, why bother?

(I don't agree with the comparison with a car or a kitchen - the function of a car or a kitchen is not to save energy, so payback is not an issue, but that is the point of an energy saving system, so you expect to break even on costs at some point and then start saving).

Open to correction on any of the above, thanks again for the advice.


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## Buildright

1. Look at the design of most standard central heating systems the porpose of which is to compensate for the massive heat loss through fabric and windows. Its very ineeficient, the heat rises and draws in cold air at your feet. You'll always have cold feet . The hot air rising, blows out through the top of the house drawing cold air in at low level. You shouldn't need to heat upstairs, the natural stratification of air should mean that the warmest air is at the top of the house. Underfloor downstairs is all thats required just to the tiles areas, the combination of rising air and HRV distribution will elliminate the need for central heating. The central heating is an analogy to a massive engine over- compensating for the fact that you designed your car with square wheels. Evan a half passive house with 30kWh per m2 heat demand benifits from such a strategy.

2. Solar is a seperate decision to MHRV. Its mandatory and is a regulatory burden.

3. Air quality is bad in most houses. Air quality is related to humidity, particulate matter, organic matter, microorganisms, odours, carbon dioxide and monoxide. The heat recovery is a free added benefit. You are designing your house to achieve comfort for human habitation. The house should be designed as a system, you cant look at each element in isolation. I've worked with clients who are building to passive standard at very close to conventional cost, but it does take a little more work to find cost effective solutions. Just get out of the mindset of the celtic tiger era. Thats over and it'll be ten years before we have growth above inflation. You're building for future energy shocks and long term asset value. Most the property we've built in the last ten yyears i svirtually worthless beyond its land value. Protect your investment by building a house that will still be relevent in ten years time.

We all have regrets after completing a build, I don't want to say I told you so, measure twice, cut once.


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## eamonn123456

Good points well made buildright.  Thanks for taking the time.

Lots to think about.

(Haven't heard too many dissenting voices either which is interesting in itself.)


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## Capt. Beaky

eamonn123456 said:


> PS I know there already is a thread on this here but its a bit out of date, am looking for an up to date perspective if possible please.


If 18 months is out of date for info/technology, think of what your unit will be at the end of projected payback time.


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## tick tock

yesterday morning outside temp was 4c. inside house was 18 to 20c. the air temp coming out from the supply vent was 19c.
is MVHR thesame  as HRV ?


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## eamonn123456

Capt. Beaky said:


> If 18 months is out of date for info/technology, think of what your unit will be at the end of projected payback time.



Fair point Capt Beaky but as I don't have either a crystal ball or a time machine, all I can do is find out the latest up to date info and opinions and make the best judgement based on those.

What's your own opinion / experience on MVHR / MHRV ?


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## kfh

Hi all,

interesting thread,


buildright you quoted 
2. Solar is a seperate decision to MHRV. Its mandatory and is a regulatory burden.

what exactly does the building regs say re solar - would HRV not be a from of renewable energy which would suffice for building regs??


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## Leo

kfh said:


> what exactly does the building regs say re solar - would HRV not be a from of renewable energy which would suffice for building regs??


 
No, HRV is not a renewable energy source!


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## onq

kfh said:


> Hi all,
> 
> interesting thread,
> 
> 
> buildright you quoted
> 2. Solar is a seperate decision to MHRV. Its mandatory and is a regulatory burden.
> 
> what exactly does the building regs say re solar - would HRV not be a from of renewable energy which would suffice for building regs??



Nearly all renewable is Solar at source.


Geo thermal is a more limited endless supply, taking heat from the earth.

Its arguable that this is solar/ambient in nature withing say 10-100M of the surface, but if you go deeper you're tapping the heat of the core.


Solar is an virtually endless supply [2 billion years to go - sure we won't find it at all].

Wood is just solar energy trapped in complex hydrocarbon chains by biological systems called trees.

Wind, wave and hydro [rivers] power are solar power that's motivated the atmosphere and the seas to do things with convection, conduction, radiation and evaporation.

Passive heating and ventilation also comes from solar power acting directly on heat stores.

The more advanced houses in America use ducts with the slab to heat air and disperse it around the house.

Moving air around requires special measures to prevent fire spread.

I'll stop rambling now.

FWIW

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.


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## Buildright

2 otions for Parl L compliance
10 Kwh/m2/annum has to be delivered from renewables. Thats either group heating, pellet boiler, solar or the heat delived from a Heat pump above a coefficient of performance of 2.5 (60% of electric energy is lost between power station primary fuel and delivery to your house, so the heat pump is only efficient above and beyond producing 2.5 times more heat energy than its supplied electric energy.
or a combination.

see page 15
http://www.environ.ie/en/Publicatio...g/BuildingStandards/FileDownLoad,16557,en.pdf
or
4kWh/m2/annum of elecric power


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## creedp

Hi Buildright, I am very interested in your views on this topic and at the expense of being labelled clueless I would like your opinion on whether it is worthwhile installing MVHR in a 2,800 sq ft 1 1/2 storey new block build with  high levels of insulation, i.e. in excess of manadatory min. I'm not up with the technical issues associated with air tighteness etc but I have been told that it is possible to achieve high levels of air tightness with a block build - obviously if the builder does his job!  I suppose the real issue  here is if not going with an airtight timber frame of SIP system is MVHR still worthwhile? 

A secondary issue here relates to the Building Regs and the installation of solar panels. I was of the view that if you installed a renewable heat  source like a geothermal heat pump this obviated the need to go with solar panels, at least that is what I have been advised. Thanks in advance


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## galwaytt

creedp said:


> ...I'm not up with the technical issues associated with air tighteness etc but I have been told that it is possible to achieve high levels of air tightness with a block build - obviously if the builder does his job! I suppose the real issue here is if not going with an airtight timber frame of SIP system is MVHR still worthwhile?
> 
> A secondary issue here relates to the Building Regs and the installation of solar panels. I was of the view that if you installed a renewable heat source like a geothermal heat pump this obviated the need to go with solar panels, at least that is what I have been advised. Thanks in advance


 
You've caught my eye with mention of SIP (it's what I do), so a few things there: 
1. Even built well, unless you undertake a specific airtightness 'programme' in a block build, it will not be airtight. This is simply a reflection of the properties of blocks/etc. You can of course make it airtight, but that is a distinct separate task, and trade. And it brings a cost with it.
Another limitation is that you're only talking about walls - the roof is another huge issue, as is the connection of it, to the walls. Again, you're talking about time and materials. And , again, money.   As you probably know what a SIP is, you'll know this is a non-issue in a SIP system.

2. As to the value of going with MHRV etc, well the fact is, that airtightness is now a measured requirement, so if you have a particularly good reading, you're probably going to need it anyway. Simply put, the choice of your building method shouldn't be influencing your decision on the MHRV, as your requirement for airtightness is the same, irrespective of the build type you choose.

3. In any modern house, built to a high standard, and working well, it's requirement for heating will be (relatively) low. This being the case, heating system choices, and their costs, need to be considered even more carefully than before. I like solar, because, in a new build, it is not a big cost as part of a new system, and imho, it does make a measurable contribution. As usual, YMMV and all that 

4. I'm still not personally convinced about heating systems that are heavily reliant on electricity. Again, this is not a reflection on the systems themselves, but more the cost of electricity itself.


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## rugbyguy

Hi I recently installed a heat recovery system into my home. Initially I intended to do a diy job on it myself as posts here say it's diy friendly but decided to get a crowd home heat recovery to do it for me as i was busy working. Glad i did in the end as they had two ductors that spent 4 days doing the work so i greatly under estimated the amount of work on rigid ducting and the expertise required to do the job right. You pay for what you get and if i done the job i would have done a cheap job far less professional to what the guys done.


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## buyingabroad

I have spent a fair bit of time researching MHRV and concluded it's not the way to go for me. Will be going with a Mechanical Extract Fan system that's humidity and presence sensitive with ducts extracting moisture from wet rooms. In habitable rooms, I plan to install either hole in the wall / trickle vents in windows, both of which would be humidity sensitive.


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## house

Hi,

Can anyone shed some light on the running costs ?


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## Patrick2008

Hi All, 

Very good thread and some very valid comments. Can I ask a question which is related to what we are discussing? Is timber frame the way to go in lieu of blockwork? e.g timberframe with 50mm cavity and external blockwork with render. I know of some people who are using cavity wall with 80mm cavity insulation and sand cement, urethane board mushroom fixed to interna face of external walls.

I would have imagined timber frame is the way to go but this all depends on the quality of the timber frame contractor etc.


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## Buildright

You can't ask a qustion comparing timber frame versus masonery. Its can't be done. Quality control is a big problem on our domestic building sites and generally results in a low quality product. 

I have 2 specifications, both deliver near passive performance levels at slightly over conventional build rates. Performance levels are walls 0.14 u-value. I have other standards at 0.16 and 0.18. Airtighness is 1 air change @50pa underpressure. MHRV is used to run at 0.75 air changes per hour wit polyetheelenr ducts. Heating oil boiler with underfloor to tiled areas and 2 towel rails on a seperate circuit. 5m2 solar evc tube. 1000l buffer. room sealed stove.

One is masonery, 250 mm wide cavity masonry, precast first floor, cellulose filled double rafter roof with cellulose fill and softboard racking. Foamglass and Quinlite inner leaf starter blocks on standard rising wall.

Two is timber frame, vapour diffuse to outside: aquapanel renderboard rainscreen, panel vent racking board, 220 stud with 75 rail, cellulose filled, osb inner board, insulated services cavity, osb substrate, plasterboard. On an insulated formwork EPS raft.

Heres where the fun starts..... Firstly, I need to build a thermal bridge free rising wall/edge beam and get the Radon barrier right. I need to get the building windtight from outside, softboard on the roof does this. Then when the windows are in, I get the inside airtight using OSB rather than intello. Then the trades come in and poke holes everywhere... thats why I use OSB.  

There is no difference in performance if you detail the build well and have good quality control on site. The build spec I have selected, is the optimum level which balances enhanced performance against cost. It is an affordable spec which delivers a thermally stable, good quality indoor climate and healthy air, with a spec designed for longevity and very low running costs. The spec, its devised using a systems approach. What is saved on heat pumps is simply put into insulation. Its common sense, heat pumps with a payback of 20 years vs insulation and airtightness with a payback of 3. 

Running costs can be calculated from your PHPP (passive house planning package) MHRV will half your space heating bill.  The house to the above spec, is a celtic tiger design, two storey with gables and dormers and stuck on stone. Perched on a hill. ' hey look at me' you know the type. At about 250 square metres it will cost about €700 a year for space heating and hot water, pumps etc.

MHRV uses a pair of Santos units with solid ducts (no flexis or flatpacks). two 25w fans in each running continuously.


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## galwaytt

Patrick2008 said:


> Hi All,
> 
> ... Can I ask a question which is related to what we are discussing? Is timber frame the way to go in lieu of blockwork? e.g timberframe with 50mm cavity and external blockwork with render. I know of some people who are using cavity wall with 80mm cavity insulation and sand cement, urethane board mushroom fixed to interna face of external walls.
> 
> I would have imagined timber frame is the way to go but this all depends on the quality of the timber frame contractor etc.


 


Buildright said:


> You can't ask a qustion comparing timber frame versus masonery. Its can't be done. Quality control is a big problem on our domestic building sites and generally results in a low quality product.


 
And buildright has nailed it on the head, in one. Naturally, I have an interest, as I build homes in a timber based system, but the single biggest issue is, and will continue to be, quality. Good materials, poorly assembled, still gives a poorly built house.

The current downward ratcheting of prices, is only going to end in tears, as you always, always, get what you pay for. Get a quote for X, and then get the job done for x/2 - then, you don't need to be scientist to figure out that that saving is coming from somewhere..........and it isn't your future energy bills !

When we did our accrediation with the BRE, a major thing for them is 'How do you manage quality on-site' ? And every second visit that they make to us is to a site, to check. For us, the simple way to control quality, is use factory-employed staff directly - we don't use subbie's - for too long, they've been paid on a per sq ft basis (and bring your own fixings !  ), and that only gets you one result.........


Back on-topic, btw - quick question - if people are considering NOT using MHRV, I'd love to know what they ARE planning to use, in lieu.......


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## Patrick2008

Hi Galwaytt. Can I ask the name of your company. By all means PM me.


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## feileacan

*Mhrv*

re topic: has anyone any experience with or comment on finewire HRV? am considering this on grounds of cost and simplicity


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## buyingabroad

A thought struck me recently. Why do MHRV systems need filters (and need regular replacing of those filters) while the old hole in the wall and demand/humidity driven ventilation systems don't. Is it to keep debris/insects out of the fans to prevent damage or is it an air quality issue?


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## L Driver

feileacan said:


> re topic: has anyone any experience with or comment on finewire HRV? am considering this on grounds of cost and simplicity



Hi,
Looks very impressive and simple. Will be looking more into it. I think it will be the way to go


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## sunnyside

Really interesting posts. I was hoping to reignite the discussion as we are now in 2013. Have any of the original contributors any updates? Or does anyone else have a view ?

Are heat recovery systems more advanced now?

I am in the midst of choosing a builder for a 2300 sq foot house and today the builder who are leaning toward told me he thought they weren't worth the money. It goes against my research to date.... I'd love to hear any opinions
Cheers


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## lowCO2design

sunnyside said:


> I am in the midst of choosing a builder for a 2300 sq foot house and today the builder who are leaning toward told me he thought they weren't worth the money. It goes against my research to date.... I'd love to hear any opinions
> Cheers


there not worth the money when a builder cant achieve a decent standard of air-tightness!

if you dont have a performance spec for your builder forget about it.

btw do you have a provisional BER done?


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## sunnyside

Thanks very much for the reply. 

The site we have bought has just the foundation poured and services in so, no Ber yet.

What do you mean by a builders Performance spec?

Any other tips when choosing a builder ?

Am I to take it that your a fan of hRv systems?  
Any and all advice appreciated. 

Thank you


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## Lanni

*Mvhr*

It is important to clarify exactly what you want from the building. I am not sure what details are included in your drawings, but sometimes you need a list of specifications.It is better to have everything agreed before engaging with the builder.
A MVHR system is great if you have suitable insulation and air tightness levels in place. Current regulations require an air tightness minimum level of 7m3/hr/m2, but you really need to be under 3m3/hr/m2 for the system to operate more efficiently. Otherwise you are looking at trickle vents, extractor/intermittent vents and permanently open vents for rooms with combustion appliances.
The preliminary BER or DEAP calculations is a condition for certain County Councils which must be issued with the commencement notice. It serves a vital purpose in that from the outset you are confident that the design is compliant with the current building regulations.


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## lowCO2design

sunnyside said:


> Thanks very much for the reply.
> 
> The site we have bought has just the foundation poured and services in so, no Ber yet.
> 
> 
> 
> What do you mean by a builders Performance spec?
> Any other tips when choosing a builder ?
> Am I to take it that your a fan of hRv systems?
> Any and all advice appreciated.
> 
> Thank you


1.


> am in the midst of choosing a builder for a 2300 sq foot house and  today the builder who are leaning toward told me he thought they weren't  worth the money.


your choosing a builder and you have mentioned detail tender/constriction drawings and you dont know what a performance specification is.



2. you need an architect to specify and detail the drawings so there is no squirming in an builders price. you need an engineer because you dont know what foundations/floor you bought,  and you need to do a BER assessment at a minimum, so you can comply with building regulations 

3. HRV is the least of your worries as others have said - the road your heading down seems more like [broken link removed]


i wish you all the best


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## vicar1

*HRV in old house*

Hello!
Looking for some advice please.
Can you install HRV in an old house, or are there any 'stand alone' type units that could be installed in the damp / hot rooms such as bathrooms / kitchen?
Any advice much appreciated - and are they worth the money in terms of heating bills and comfort?
Thanks!


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## Leo

vicar1 said:


> Can you install HRV in an old house, or are there any 'stand alone' type units that could be installed in the damp / hot rooms such as bathrooms / kitchen?



How air-tight is the house? This will play a significant role in the efficiency of MHRV.


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## David Pritchard

I know this is an old thread, but I thought I'd add my experience of HRVs since it might help somebody.

I have a HRV unit in a dry climate (Spain) and I'm an absolute convert to it. I think the benefits of these systems are actually undersold - I get the impression that the idea is so new, that even the businesses selling it don't realise all the implications of living with these systems. Most articles focus on the energy-saving aspect, and conclude that it may not be worthwhile in some climates (for Ireland I imagine you'd get your money's worth in a few years). But even in a moderate climate such as Spain, I reckon that if you add up all the benefits, it's a no-brainer.

Apart from the obvious point that an HRV/ERV squares the circle of insulation and good ventilation, which are otherwise contradictory objectives, here are the plus points I've noted:


- Indoor pollution and smells are expelled. Waking up in the morning with fresh air, but without draughts and cold from open windows, is just great.

- Outdoor pollution is filtered. This is a big deal in cities. My filters were filthy black when I took them out after 2-3 months. I have photos of the filters but I'm not sure how to upload them.

- No bugs! Living next to some gardens, I usually get mosquitos for about 11 months of the year, believe it or not. The filters trap them all.

- Less noise. If you don't have to open windows to ventilate, you keep the noise out. There are some annoying tropical birds in the gardens next to the apartment that really make a lot of noise.

- Less humidity indoors. Obviously this depends on the outdoor climate. Ireland is more humid in general so you'd need to check this.


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## npgallag

Any recent reviews on MVHR systems installed in Ireland. I am currently looking at a Beam system for new build.


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## newirishman

npgallag said:


> Any recent reviews on MVHR systems installed in Ireland. I am currently looking at a Beam system for new build.



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.


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## Mark Mackay

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


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## Kiflekiff

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..


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## OC7500

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


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## OC7500

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!.


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## OC7500

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.


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## Leo

OC7500 said:


> 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.



Here's the article.


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## bleary

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


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## Coldwarrior

Leo said:


> Here's the article.



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.


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## mike2017

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!


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