Mechanical Heat Ventilation Recovery MHVR

kav2011

Hello all,

I am in the middle of a new build and am considering putting in a heat recovery system. I am putting in UFH with an air to water heat pump.

The ventilation system will cost 5K and I am wondering is it worth the money as opposed to just putting trickle vents in the windows and letting good old fashioned fresh air vent my home. I understand it should be more efficient and save on heating bills but to be honest I don't believe that it would make enough of a difference that it would justify the upfront cost but im more interested in the comfort levels it is supposed to provide and the other benefits of the system.

Could someone who has one installed provide feedback on the benefits of the system? Any and all opinions appreciated as most of the information online is from companies who are installing the systems.

Thanks

Drift

What air tightness value do you need to hit to meet your DEAP requirements?

In my opinion the value is so low on most new builds that MHRV is essential to make the house comfortable.

I recommend them to all clients with new build houses - there just isn't enough air leakage in new houses to make them un-stuffy without mechanical ventilation.

MightyMunster

Not much point in triple glazing
, insulation etc then having holes in the walls and windows. Found it excellent for drying older houses too. No more mould on ceilings or in wardrobes.

Curious Geroge

kav2011 wrote: »

Hello all,

I am in the middle of a new build and am considering putting in a heat recovery system. I am putting in UFH with an air to water heat pump.

The ventilation system will cost 5K and I am wondering is it worth the money as opposed to just putting trickle vents in the windows and letting good old fashioned fresh air vent my home. I understand it should be more efficient and save on heating bills but to be honest I don't believe that it would make enough of a difference that it would justify the upfront cost but im more interested in the comfort levels it is supposed to provide and the other benefits of the system.

Could someone who has one installed provide feedback on the benefits of the system? Any and all opinions appreciated as most of the information online is from companies who are installing the systems.

Thanks

Whats the makeup of the build re cavity build, floor insulation, are you doing air tightness, what are the windows, south facing ? It all lends itself to the decision as there is no point throwing money at the other items and then cutting short on something that is not a practical retrofit.

MicktheMan

kav2011 wrote: »

Could someone who has one installed provide feedback on the benefits of the system?

Have mine installed 8 years now and quite simply wouldn't be without it.

kav2011

Drift wrote: »

What air tightness value do you need to hit to meet your DEAP requirements?

In my opinion the value is so low on most new builds that MHRV is essential to make the house comfortable.

I recommend them to all clients with new build houses - there just isn't enough air leakage in new houses to make them un-stuffy without mechanical ventilation.

hmmm, not sure. What is air tightness value measured in? I have 0.25 in some of my preliminary BER assessment, does 0.25 sound right?
would window vents not make the house 'unstuffy' the same way?

kav2011

MicktheMan wrote: »

Have mine installed 8 years now and quite simply wouldn't be without it.

Good to hear, thanks

kav2011

Curious Geroge wrote: »

Whats the makeup of the build re cavity build, floor insulation, are you doing air tightness, what are the windows, south facing ? It all lends itself to the decision as there is no point throwing money at the other items and then cutting short on something that is not a practical retrofit.

its a new build. 2 story house with 150mm pumped cavity. All u-values of floor insulation, attic insulation, doors and windows to comply with building regs giving me an A3 rated house.

MicktheMan

kav2011 wrote: »

hmmm, not sure. What is air tightness value measured in? I have 0.25 in some of my preliminary BER assessment, does 0.25 sound right?
would window vents not make the house 'unstuffy' the same way?

At that level of air tightness (0.25 in DEAP equates to 5m3/hr/m2 air permeability), you are on the border of getting any heat recovery benefit from a mvhr system.

On a related note, imo, that level of airtightness is poor on a new build and I would consider it a missed opportunity.

delfagio

MicktheMan wrote:

At that level of air tightness (0.25 in DEAP equates to 5m3/hr/m2 air permeability), you are on the border of getting any heat recovery benefit from a mvhr system.

Agree with Mick the Man on that one. Really you would want to be hitting 1m3/hr/m2 or better. That way you will really benefit from the HRV. You will save a lot on heating bills and your house will be way more comfortable to live in. Have a chat with your BER Assessor or Architect to see where and how you can address this now before you start or go to far.

Drift

kav2011 wrote: »

would window vents not make the house 'unstuffy' the same way?

No. They are unbalanced and will behave completely differently on different sides of the house and in different weather conditions. A properly balanced mechanical system will deliver and remove appropriate amounts of air on a consistent basis.

However as the posters above said if you have a leaky draughty house it's a waste of time!

An air tightness of 5m3/m2/h is quite high in modern terms. I haven't seen one that high specified on a new house in quite a while. No point spending a fortune on insulation if all the heat is leaking out around the windows and through the service voids.

kav2011

thanks all, . the reason I am asking the question is all down to budget. I need to achieve an A3 BER (among other things) for building regs and in my opinion that will be good enough for me, I doubt I have ever lived in anything higher than a D. So what I am getting at is if it turns out to be that mvhr isn't compatible with a house just bearly achieving part L of the building regulations, then it probably isn't going to be for me.
Also I am trying to figure out if it is worth investing in air tightness at all if I am not going to use a mhvr.

my house was planned to use open ventilation and not mhvr. Now that I am a bit deeper into it I am considering my options. Block work just finished so not too late to plan a house with much higher air tightness. My architect hasn't given me much of a steer on the subject so far.

from what I see, 5m3/m2/h is the minimum required to meet building regulation (This used to be 7m3/m2/h). Given how the 2014 building regs are so strict, I am surprised to hear that the minimum values allowed are seen as poor. Forgetting about mhvr, for an open ventilation house, what is a typical air permability figure achieved for a new build?

Back to mhvr. 1m3/m2/h seems to be almost passive standard. Is this really required? What value does mvhr begin to become effective?

MicktheMan

kav2011 wrote: »

1.Back to mhvr. 1m3/m2/h seems to be almost passive standard. Is this really required?
2.What value does mvhr begin to become effective?

1. Are you building a house to live comfortably in or to scrape past b.regs and wonder why in your A3 rated house the place cools down as soon as the heating is off or it is costing you a lot more to heat than you thought it would?
2. depends on a number of factors but generally <4m3/hr/m2

Drift

5m3/m2/hr is not in any way difficult to achieve for a half competent builder. A large amount of the "investment" required for a reasonable value is just attention to detail that a proper builder should be doing anyway.

Is it a direct labour project or is a contractor doing it for you?

delfagio

kav2011 wrote:

from what I see, 5m3/m2/h is the minimum required to meet building regulation (This used to be 7m3/m2/h). Given how the 2014 building regs are so strict, I am surprised to hear that the minimum values allowed are seen as poor. Forgetting about mhvr, for an open ventilation house, what is a typical air permability figure achieved for a new build?

yes the regulations call up 5m3/hr/m2 as the minimum airtightness level that should be achieved. But think of it like this, you should always aim for the maximum or best you can get.

For example if a travel agent said that you could have a two week holiday in 5star luxury in Spain for ONLY 599euro per person. You think brilliant, but that's the MINIMUM it's going to cost, you will still need spending money, so you will aim to save maybe 1299euro per person to have spending money. So you aim to get more than 599euro. So the regulations are sort of similar. They say minimum is 5m3/hr/m2 but you would want to be aiming for less than this really.

This applies to all the elemental U Values called up in the regulations, the minimum values stated are literally the bear minimum in order to meet the building regulations, but in reality you would try to aim to beat these in all areas if possible. So say walls are called up as 0.2 u-value, aim for 0.10 - 0.15 U Value.

kav2011 wrote:

Back to mhvr. 1m3/m2/h seems to be almost passive standard. Is this really required? What value does mvhr begin to become effective?

No 1m3/hr/m2 isn't really required but as I said above, it's best to try achieve it. Benefits of achieving low figures like this include;
1.) savings in running costs of heating the house,
2.) more comfortable living,
3.) little to no draughts,
4.) even temperature throughout the house,
5.) no freezing cold rooms like older houses,
6.) Fresh air feel to all rooms, no stuffy rooms with stale air
7.) CONTROLLED air movement and ventilation in the house from the HRV unit

The HRV suppliers would definitely say that for HRV to be of any benefit to the home owners that a result of 3m3/hr/m2 or lower must be achieved.

sydthebeat

kav2011 wrote: »

thanks all, . the reason I am asking the question is all down to budget. I need to achieve an A3 BER (among other things) for building regs and in my opinion that will be good enough for me, I doubt I have ever lived in anything higher than a D. So what I am getting at is if it turns out to be that mvhr isn't compatible with a house just bearly achieving part L of the building regulations, then it probably isn't going to be for me.
Also I am trying to figure out if it is worth investing in air tightness at all if I am not going to use a mhvr.

my house was planned to use open ventilation and not mhvr. Now that I am a bit deeper into it I am considering my options. Block work just finished so not too late to plan a house with much higher air tightness. My architect hasn't given me much of a steer on the subject so far.

from what I see, 5m3/m2/h is the minimum required to meet building regulation (This used to be 7m3/m2/h). Given how the 2014 building regs are so strict, I am surprised to hear that the minimum values allowed are seen as poor. Forgetting about mhvr, for an open ventilation house, what is a typical air permability figure achieved for a new build?

Back to mhvr. 1m3/m2/h seems to be almost passive standard. Is this really required? What value does mvhr begin to become effective?

1m3/m2 is not near passive standards as the lower aim the harder it is to achieve
Ie its much easier to go from 5 to 1 than from 1 to 0.6

You might also find that if you achieve a lower air tightness result, your building may not comply with regs anymore.

In my opinion your assessor was quite wrong to specify a mhrv system AND an air tightness result of 5m3/m2

ht9zni1gs28crp

sydthebeat wrote: »

1m3/m2 is not near passive standards as the lower aim the harder it is to achieve
Ie its much easier to go from 5 to 1 than from 1 to 0.6

You might also find that if you achieve a lower air tightness result, your building may not comply with regs anymore.

In my opinion your assessor was quite wrong to specify a mhrv system AND an air tightness result of 5m3/m2

This is it in a nutshell. I'm really struggling to believe that anyone who is building today isn't trying to future proof their investment as much as possible. Aim for the best figure you can NOT the bare minimum....

THE DON FANUCCI

Going starting a new build soon. I,m the type of guy who has d windows open during the winter and does not get cold very easily. I am also planning an open fireplace in one of my sittingrooms. Does mhrv sound ridiculous for my situation? I will have to put it in for to meet part L regs i presume. Bit of a joke really. Will there be unsightly vents in my rooms?

Metric Tensor

You have to have wall vents if you don't have MHRV so there will be air vents in every room regardless of which way you go.

Also you almost certainly won't be able to put in an open fire. The ways of meeting Part L compliance with an open fire are VERY limiting.

You really need to get your BER done soon so you know what your options are.


Edit: I see you say "one of my sitting rooms" - you might just get away with the fire with some clever BERing if you have a lot of reception rooms.

Calahonda52

sydthebeat wrote: »

1m3/m2 is not near passive standards as the lower aim the harder it is to achieve
Ie its much easier to go from 5 to 1 than from 1 to 0.6

You might also find that if you achieve a lower air tightness result, your building may not comply with regs anymore.

In my opinion your assessor was quite wrong to specify a mhrv system AND an air tightness result of 5m3/m2

SJB, while I think I know whats at play here, but not 100% sure, so it might help the discussion with a few pointers as to what the considerations are.
Thanks

THE DON FANUCCI

Metric Tensor wrote: »

You have to have wall vents if you don't have MHRV so there will be air vents in every room regardless of which way you go.

Also you almost certainly won't be able to put in an open fire. The ways of meeting Part L compliance with an open fire are VERY limiting.

You really need to get your BER done soon so you know what your options are.


Edit: I see you say "one of my sitting rooms" - you might just get away with the fire with some clever BERing if you have a lot of reception rooms.

Well i have one small sittingroom and one larger sittingroom. I want to put an open fireplace in the larger room. Stanley black stove in the smaller one. And do i need to use air tightness tape if i'm getting in Hrv ?

Calahonda52

THE DON FANUCCI wrote: »

.... do i need to use air tightness tape if i'm getting in Hrv ?...

As opposed to what?
A/T tape is not just like band-aid:D

A?T considerations start at the design stage

The following might help
See
Acceptable Construction Details
in this link, about half way down
http://www.environ.ie/en/TGD/
alos
https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx
its 12 mb

893bet

Hi Don,

You appear to be trying to go it alone on the build.

You need an engineer as per your posts for the concrete first floor and an architect or similar with expertise relating to Airtightness and part L etc.

THE DON FANUCCI

Metric Tensor wrote: »

You have to have wall vents if you don't have MHRV so there will be air vents in every room regardless of which way you go.

Also you almost certainly won't be able to put in an open fire. The ways of meeting Part L compliance with an open fire are VERY limiting.

You really need to get your BER done soon so you know what your options are.


Edit: I see you say "one of my sitting rooms" - you might just get away with the fire with some clever BERing if you have a lot of reception rooms.

When you say get a BER done is that the same as a DEAP assessment? Will a deap assessment basically design my heating system to meet L-Regs ?

BryanF

THE DON FANUCCI wrote: »

When you say get a BER done is that the same as a DEAP assessment? Will a deap assessment basically design my heating system to meet L-Regs ?

A heating engineer designs a heating system
Look at BER info on:
Seai.ie

THE DON FANUCCI

Haha tis a gas forum lads. In the last few weeks on this thing i've been advised to get
i) quantity surveyor
Ii) engineer
Iii) architect
Iv) energy assessor
V) structural engineer no less
Vi) and a heating engineer haha

....and a partridge in a pear tree

Calahonda52

THE DON FANUCCI wrote: »

Haha tis a gas forum lads. In the last few weeks on this thing i've been advised to get
i) quantity surveyor
Ii) engineer
Iii) architect
Iv) energy assessor
V) structural engineer no less
Vi) and a heating engineer haha

....and a partridge in a pear tree

Thats me all done here

893bet

THE DON FANUCCI wrote: »

Haha tis a gas forum lads. In the last few weeks on this thing i've been advised to get
i) quantity surveyor
Ii) engineer
Iii) architect
Iv) energy assessor
V) structural engineer no less
Vi) and a heating engineer haha

....and a partridge in a pear tree

The QS is optional but should save you money in the long run.
The engineer and structural engineer are the same person and you have to have one.
The architect, energy assessor and heating engineer as all likely to be the same person. Pick one an architect that has the skill sets you need.

galwaytt

5m3/hr is poor imho. People should be aiming for 1m3/hr or better, but a little higher isn't the end of the world as it might help you to meet Part L more easily.

As for MHRV or no, well my experience is that the house is quieter, dryer, no mould anywhere ever, and more comfortable. Does it 'save' money on heating ? No idea. Does it matter ? Not really - imho I consider it efficient, managed, ventilation. If there's any heat 'gain' then I'd just take that as the icing on top.

Metric Tensor

galwaytt wrote: »

As for MHRV or no, well my experience is that the house is quieter, dryer, no mould anywhere ever, and more comfortable. Does it 'save' money on heating ? No idea. Does it matter ? Not really - imho I consider it efficient, managed, ventilation. If there's any heat 'gain' then I'd just take that as the icing on top.

Spot on! Don't view it in terms of heating systems. View it in terms of proper ventilation and all the benefits that brings.

THE DON FANUCCI

Metric Tensor wrote: »

Spot on! Don't view it in terms of heating systems. View it in terms of proper ventilation and all the benefits that brings.

how much is mhrv? and is there big unsightly vents or are they small ? and is the Open fireplace a thing of the past?

Metric Tensor

THE DON FANUCCI wrote: »

how much is mhrv? and is there big unsightly vents or are they small ? and is the Open fireplace a thing of the past?

Depends on the size of your house! The vents are usually around 100mm diameter. Open fires are a thing of the past to me but there may be ways of getting one if you really want one and have a certain set of circumstances. As with any other trade off it will cost you elsewhere.

I was about to write a smart arse reply to your previous know-it-all response but seeing as it's Christmas I'm going to give you the benefit of the doubt.

You're about to spend a quarter of a million euro or more of your own money building a home that you plan to live in for many years if not the rest of your life. It is sheer madness not to get the best advice you can to get the best house you can. You will have to pay for this advice but it will pay for itself many times over. You are NEVER going to know as much about building houses as people who have many years experience and studied and qualified as experts in their fields. It boggles the mind that people think building a house is something anyone can do. Would anyone be able to walk in off the street and do your job as well as you?

To a greater or lesser degree you need all the services listed above. In many cases there a professionals who can provide a combination of these services to the level that you will require.

All the questions you are asking here are dependent on your house type, size, location and your budget. The professionals you hire to help you spend your money wisely will answer them for you.

Finally - you are getting very good FREE advice here. Insulting the advice is a great way to stop getting any more!

THE DON FANUCCI

I suppose 5k for mhrv isn't much considering the scale of the project. deffo goin for that so. 150mm kingspan in floor, 150mm pumped bead in walls, 300 in attic, mhrv, airtightness, back boiler, solar tubes, .. should get me over the line as regards L-Regs.

sydthebeat

That spec would be very borderline on posing or not. If it's a large house (2200+) I'd predict it wouldn't without having to get ridiculous with the solar input.

fclauson

THE DON FANUCCI wrote: »

I suppose 5k for mhrv isn't much considering the scale of the project. deffo goin for that so. 150mm kingspan in floor, 150mm pumped bead in walls, 300 in attic, mhrv, airtightness, back boiler, solar tubes, .. should get me over the line as regards L-Regs.

Never use the word"should" - do the maths or employ someone - my build on initial calcs FAILED part L and its A1 & Passive certified !!!!

JonathonS

THE DON FANUCCI wrote: »

Haha tis a gas forum lads. In the last few weeks on this thing i've been advised to get
i) quantity surveyor
Ii) engineer
Iii) architect
Iv) energy assessor
V) structural engineer no less
Vi) and a heating engineer haha

....and a partridge in a pear tree

WHATEVER you do don't ask any questions on the Health Forum - they recommend all sorts of expensive help on there......doctors, dentists, physiotherapists. Crazy stuff.

galwaytt

THE DON FANUCCI wrote: »

I suppose 5k for mhrv isn't much considering the scale of the project. deffo goin for that so. 150mm kingspan in floor, 150mm pumped bead in walls, 300 in attic, mhrv, airtightness, back boiler, solar tubes, .. should get me over the line as regards L-Regs.

...sorry, but as if to illustrate an earlier post, just randomly picking 'specs' as you have done doesn't give any idea about Part L compliance or not. You need to get a proper, full BER/PHPP calculation done. Then you'll know, not before.

It would be more-than-remiss to build a house to the 'spec' you have above and only then find out you don't meet the required standards.........and it'll cost you to you fix as well....

THE DON FANUCCI

galwaytt wrote: »

...sorry, but as if to illustrate an earlier post, just randomly picking 'specs' as you have done doesn't give any idea about Part L compliance or not. You need to get a proper, full BER/PHPP calculation done. Then you'll know, not before.

It would be more-than-remiss to build a house to the 'spec' you have above and only then find out you don't meet the required standards.........and it'll cost you to you fix as well....

ah ya I must get a Full Deap Ber assessment done. the only way to fully know. is there a list of qualified Nsai standard ber/deap energy assessors that I have to use?

BryanF

THE DON FANUCCI wrote: »

ah ya I must get a Full Deap Ber assessment done. the only way to fully know. is there a list of qualified Nsai standard ber/deap energy assessors that I have to use?

Go on to seai.ie

THE DON FANUCCI

sydthebeat wrote: »

That spec would be very borderline on posing or not. If it's a large house (2200+) I'd predict it wouldn't without having to get ridiculous with the solar input.

Add your reply here.


Without having done a preliminary Ber DEAP assessment I would hope Mvhr, Air-To-water heat pump, 150mm walls and 150 floor insulation, 300mm attic,&also Airtightness. Should fulfil L-regs. I am going to my ber assessor with this plan

fclauson

will be interested in the BER - I am guessing that you will fall short on renewables

sydthebeat

THE DON FANUCCI wrote: »

sydthebeat wrote: »

That spec would be very borderline on posing or not. If it's a large house (2200+) I'd predict it wouldn't without having to get ridiculous with the solar input.

Add your reply here.


Without having done a preliminary Ber DEAP assessment I would hope Mvhr, Air-To-water heat pump, 150mm walls and 150 floor insulation, 300mm attic,&also Airtightness. Should fulfil L-regs. I am going to my ber assessor with this plan

Even the highest efficiency a2whp will struggle to meet renewable requirements

THE DON FANUCCI

Air to water will meet it on its own alright. That spec will do it. - must get my ber done this week

sydthebeat

Eh, it most likely will not. Especially at that minimum spec.

I'm an assessor!

THE DON FANUCCI

If this spec is borderline what small thing would bring it over d edge into compliance

gctest50

sydthebeat wrote: »

Eh, it most likely will not. Especially at that minimum spec.

I'm an assessor!

:eek: omg you are teh very man to do that assesment - you could put it all right here on boards,ie

fclauson

Its not that easy - the DEAP model used to calc the BER is not something you can guess at - you need dimensions, window types, openings, fires, porches ......... the list goes on before you can actually calc BER

we have been advising the OP that the building will not meet requirements but this is more of a gut feel than a final calc

Do the maths with the facts is the rule for BER

sydthebeat

Thats a question for your assessor, there's probably 50 different things that impact compliance

893bet

sydthebeat wrote: »

Even the highest efficiency a2whp will struggle to meet renewable requirements

Better chance with wood stove and large solar with that insulation spec.