HRV & Low Temperature Heat Source Alternative

gaelicyoda

Hi All,

Am looking at the purchase of a (new) shell of a house with floors yet to be put in, so am trying to come up with the best way of heating it.

It's about 220m sq. in area, and I would be opting for UFH downstairs and oversized/high output rads upstairs.

In a bit of a conundrum about how to heat the house however - have two sets of advice from two (hopefully) decent sources, and would like to get people's views on them to see what the consensus is.

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(1) Geothermal ground source heat pump:
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Would be looking at an approximate quote for this @ around the 30k mark - 35k at the outside (all in - with UFH, rads, etc.). This was my original plan (final cost dependent of course, and I think it would have to be quite a bit lower than that to qualify) - but have heard nasty stories about €600 bi monthly ESB bills in a house in which not much expense was spared in the insulation (this is a year and a half after the house was built, so it should be reasonably dried out by then). Basically, it's a VERY expensive thing to get wrong and that makes me (understandibly, I think) nervous as hell. I don't want to get shafted on the double - i.e. installation AND running costs.

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(2) Mechanical Heat Recovery & Ventilation (MHRV):
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This is where I start to get patchy and would really appreciate people's input - the builder who suggested this system to me came with a very good reputation, and was well versed in u-values, etc. and sounded like he knew his stuff with regard to energy efficiency. These systems are apparently part of the building regs. in Scandanavia now. About 7 - 8k for this, but left me wondering where the initial input of heat would come from. He said that the energy given off by people living in the house (washing, cooking & body heat) would generally be enough to keep it at the 20 - 21 degree mark most of the time. The system would also come with a built in element that could be used to provide a boost when necessary.

Obviously, the danger here is that if the system is crap, and I have to have this boost on most of the time just to keep warm - in which case I might as well leave a bunch of hair dryers on - it's an unacceptable waste of cash. :mad: Thinking rationally, I just don't see how a couple of people could generate that kind of heat without something else to augment it, which makes me wonder if he just doesn't know what he's on about. He's offered to take me to a house where he says it's in place, so I guess I should at least give him a chance to prove me wrong.

So, I wanted then to try and find some kind of hybrid - a MHRV system, with some other low temperature heat source that could feed the UFH and rads initially. Looking at some of the other posts, I came across a storage wood burning stove, Tonwerk (google it and see). This would be nice I think, if it were possible to attach this somehow to my UFH and rad system, to give a gradual and long lasting release of heat - but I don't know if that's possible or not.

I should have mentioned as well, the utmost priority would be given to good insulation for the house, regardless of the heating system being chosen. In the case of MHRV, air tightness would be prioritised as well.

Has anyone out there got an MHRV system installed?, and if so some questions:

(1) What is your primary heat source in the house?
(2) Does it work well with MHRV
(3) Do you have Underfloor heating (UFH)?
(4) How much did you end up paying for the full setup?
(5) What do your annual heating bills look like?
(6) What volume of fuel would you say you use annually?
(7) Any "if I was to do it all again..." tips?

On the geothermal front - I guess I'm looking for some real life use cases to see if it's a job worth doing, or just a big headache.

Hope someone out there has some first hand experience that can help me out!

Cheers!

CJhaughey

(1) What is your primary heat source in the house?
I have Elec. underfloor and a small woodburning stove, 5kw Morso 1430
Primarily woodstove though

(2) Does it work well with MHRV
Yes the HRV shifts the heat around quite well but would benefit from an extract vent near the stove to take the hot air at source

(3) Do you have Underfloor heating (UFH)?
Yes Electric 2 zones and waterpipes laid for wet UFH but not used yet.

(4) How much did you end up paying for the full setup?
Stove was 2200 with flue UFH < 400

(5) What do your annual heating bills look like?
Average ESB bill is 150

(6) What volume of fuel would you say you use annually?
1 cord of mixed wood

(7) Any "if I was to do it all again..." tips?
I would put another extract point near the stove with a shutoff valve, also integrate the DHW with a backboiler on the woodstove.
apart from that nothing else really.
House is low energy build with 3-glazed windows and attention paid to passive solar gain.

The HRV unit is a Temovex and is very good IMO, PM if you want the supplier.

gaelicyoda

Cheers CJ, really appreciate your input.

This house unfortunately has the windows already in (Munster Joinery), so passive gains will not be as effective for me, so will probably mean a bit more strain on my heating system.

Couple of Q's on your responses:
(5) That figure is per month, yes? (so total would be 12 x €150 = €1800?)
(6) What's a cord? (excuse my ignorance here). Can you put that in the context of kg or [FONT=&quot]m3[/FONT]? And what would the cost of this be (on top of your ESB bill)?

Electric UFH was not actually something I considered - I just assumed that would be really expensive, but judging by your bills, it's not too bad. Can you tell me a bit more about it - energy consumption and how often it's on, that type of thing?

CJhaughey

gaelicyoda wrote: »

Cheers CJ, really appreciate your input.

This house unfortunately has the windows already in (Munster Joinery), so passive gains will not be as effective for me, so will probably mean a bit more strain on my heating system.

Electric UFH was not actually something I considered - I just assumed that would be really expensive, but judging by your bills, it's not too bad. Can you tell me a bit more about it - energy consumption and how often it's on, that type of thing?

5) That figure is per month, yes? (so total would be 12 x €150 = €1800?)
In the summer The bills are a lot lower Probably because of the Solar panels heating the DHW more(sorry forgot to mention this)
I think some were around €75 for the 2 months and the last one was 150 or so.

Elec UFH is very convenient, we have 2 zones dividing the house in half lengthways.
Ours is DEVI and I just flick a switch and it runs on night storage rate for 8hrs.
It is not too expensive and there are controllers available that control the input depending on external temps, I didn't bother with that and just turn it off and on as required.


(6) What's a cord? (excuse my ignorance here). Can you put that in the context of kg or [FONT=&quot]m3[/FONT]? And what would the cost of this be (on top of your ESB bill)? A cord is a pile of tightly stacked wood 4x4x8ft or 128cu ft
Weight is not much of a help when dealing with wood because of the variations between different species, Oak vs Cypress.
I paid a guy 120 for a heaped trailer of split seasoned Alder that measured 8x5x4ft
This was thrown not stacked so probably just over a cord.

gaelicyoda

Hi CJ, thanks again for your input.

In terms of your zoning, I take it your setup would roughly equate to:
Z1 = living (day) rooms
Z2 = sleeping (night) rooms
and I'm guessing it's a bungalow, would that be fair to say?

Are there any special considerations that need to be made for electric UFH?

What floor insulation and screed depth do you have for example?

CJhaughey

Yes, thats how it is arranged Z1 is the S side and Z2 is the N side (sleeping area)
It is a dormer bungalow 1.5 story.
The UFH Both water and Elec was installed as the Slab was poured with 150mm Polystyrene insulation.

gooner99

gaelicyoda wrote: »

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(2) Mechanical Heat Recovery & Ventilation (MHRV):
=======================================
This is where I start to get patchy and would really appreciate people's input - the builder who suggested this system to me came with a very good reputation, and was well versed in u-values, etc. and sounded like he knew his stuff with regard to energy efficiency. These systems are apparently part of the building regs. in Scandanavia now. About 7 - 8k for this, but left me wondering where the initial input of heat would come from. He said that the energy given off by people living in the house (washing, cooking & body heat) would generally be enough to keep it at the 20 - 21 degree mark most of the time. The system would also come with a built in element that could be used to provide a boost when necessary.

Obviously, the danger here is that if the system is crap, and I have to have this boost on most of the time just to keep warm - in which case I might as well leave a bunch of hair dryers on - it's an unacceptable waste of cash. :mad: Thinking rationally, I just don't see how a couple of people could generate that kind of heat without something else to augment it, which makes me wonder if he just doesn't know what he's on about. He's offered to take me to a house where he says it's in place, so I guess I should at least give him a chance to prove me wrong.

I would suspect that this setup is working well in a passive house,not in a strandard (even well insulated) house.As you say you have a shell of a house,that is probably not built to take into account passive solar gains.Also you may be limted to the insulation you put in the wall,floor and roof.Your windows have already been installed,so no improvements can be made there.

I would say that the energy demand of the house is very important in the running costs of the house.If you put a heatpump into a house that has poor insultaion or detailing and poor airtightness,then it will cost quite a lot to run.The other thing is poor installation of the heatpump and heating system.The installer will give you the cop for the pump,but I would nearly bet everything on not one supplier giving you a cop for the full system.

I think the best route is to get good sound advice on insulation and airtightness.No point in running underfloor heating and finding that half the heat is going into the ground.Likewise finding that you house is leaking the heat.

I am not an expert on this (I'm sure you will get more posts on this subject),but I think that you need to get a heating demand calculation done once you have decided on the level insulation and airtighness measures.Then and only then will you know what system will suit best and be in a position to size it correctly.

gaelicyoda

Thanks for the input guys.

Yes the windows are already in, which is a bummer.

Another, and possible the largest, constraint as well is the fact that there is only another 6" of floor to be put in (unless I want to raise that, and also start raising all the door lintels, which absoutely I don't). This might be in fact one of my biggest constraints - it means 75mm insulation and 75mm screed. CJ, it looks like you had 150mm of insulation alone!

I should mention as well the only insulation currently in place is 60mm Kingspan in the wall cavity. I have been advised to leave this alone and add drylining to the extenal walls inside the house.

holdfast

I agree with gooner get a professional not your builder because either he explained badly to you HRV or he does not understand HRV. In most cases builders are not up to speed on u-values etc. Moreover you are stuck with what you have bought and if no existing insulation in floor prior to you won’t be able to comply with building regs for underfloor. Last point geothermal and rads are a no no. please get yourself a architect/at/engineer with a good background in such technologies for the money it will cost versus the money you’re going to spend its nothing. I have HRV, geothermal and a stove, heating bills is around 600 euro a year, about 450 for elec and 150 for stove. House is an A3. Best of luck

gooner99

gaelicyoda wrote: »

Thanks for the input guys.

Yes the windows are already in, which is a bummer.

Another, and possible the largest, constraint as well is the fact that there is only another 6" of floor to be put in (unless I want to raise that, and also start raising all the door lintels, which absoutely I don't). This might be in fact one of my biggest constraints - it means 75mm insulation and 75mm screed. CJ, it looks like you had 150mm of insulation alone!

I should mention as well the only insulation currently in place is 60mm Kingspan in the wall cavity. I have been advised to leave this alone and add drylining to the extenal walls inside the house.

If you do a search on here,you will find lots of threads on drylining.The experts recommend a condensation risk analyis to ensure that you do not end up with mould growth.If I remember rightly they recommend that the thickness of the insulation material used to dryline is half or less than the insulation thickness in the cavity.I'm sure someone will clarify this.One the heatpump front holdfast is correct in saying that underfloor and rads are not a great combination due to the different temperatures needed.A good installer will tell you this,the others are only interested in your money.Also holdfast has an A3 house and this is ideal,as the heat demand is lower and therefore lower running costs.However their installation must also be pretty good,as heatpump systems that are poorly installed are also known to cost big bucks in good rated houses.If I was going the heatpump route,I would like to see a few houses that are similar in terms of size, construction and insulation levels and then talk to the owners about the running costs.Again if the heatpump installer can not arrange this for you,then run a mile.If it were me I would insulate and see to airtightness over fancy heating systems.Get the heat demand down first and then you have lots of options.Remember with insulation and airtightness,the devil is in the detail!

gaelicyoda

Thanks guys, some good advice on here.

On the heatpump/rads combo. aspect - I should have expanded a bit more on that - I was told that using low temperature rads that are suitably oversized (25-30%) would mean that both delivery systems could use the same low temp water, and would also mean that the rads weren't scalding to the touch, which is more kid friendly as well.

I preemptively took you advice holdfast & gooner - I've had a consultation with an energy efficiency expert who calculates U values for constructions and that type of thing - and most of this advice came from him. However, I didn't discuss MHRV with him because I thought the cost of air tightening the house would be prohibitive. Seems a bit ridiculous now when the cost of geothermal is so bloody high! Now I wish I had discussed this with him!!! Arrrgh! Having that chat with the builder who suggested MHRV has put the cat amongst the pigeons in my head now.

Agree with you 100% gooner - am definitely going to insist on seeing multiple installations of whatever technology I choose to go with, or no sale.

Would the MHRV system reduce the risk of condensation with respect to the drylining? I understand this also controls humidity levels within the house - or would this be condensation actually within the cavity and therefore not affected by the MHRV system?

The house has been built to 2002/3 building regs., so I don't think that the underfloor insulation standards apply in this case, meaning not much incentive for the builder to add them during the development.

I've noticed as well that nobody has commented on the quote figures I was given, which says to me they sound reasonably accurate? Any comments on this front?

holdfast

Talk to energy expert, he/she know if they weren`t someone that jumped on the band wagon. They shoud be able to do the calcs for condensation aswell as advising you on the air tightness needed for hrv, and setup for geothermal and sizing the HP correctly. I would expect there to be insulation there in the floor, but then again this is ireland.

you have no given the heat demand and if you are going for horizontal of vertical for the geothermal. For us to look at the price. Did the guys giving the quote know your heat demand ?

gaelicyoda

Hi holdfast, thanks for your comments.

Yes, the energy guy did roughly calculate the energy requirement for the house in kWHr/year, and it was sized at a 10 - 12 kW HP requirement. But no, the quotes I was getting did not ask me this.

sharh

CJhaughey wrote: »

(1) What is your primary heat source in the house?
I have Elec. underfloor and a small woodburning stove, 5kw Morso 1430
Primarily woodstove though


(2) Does it work well with MHRV
Yes the HRV shifts the heat around quite well but would benefit from an extract vent near the stove to take the hot air at source

(3) Do you have Underfloor heating (UFH)?
Yes Electric 2 zones and waterpipes laid for wet UFH but not used yet.

(4) How much did you end up paying for the full setup?
Stove was 2200 with flue UFH < 400

(5) What do your annual heating bills look like?
Average ESB bill is 150

(6) What volume of fuel would you say you use annually?
1 cord of mixed wood

(7) Any "if I was to do it all again..." tips?
I would put another extract point near the stove with a shutoff valve, also integrate the DHW with a backboiler on the woodstove.
apart from that nothing else really.
House is low energy build with 3-glazed windows and attention paid to passive solar gain.

The HRV unit is a Temovex and is very good IMO, PM if you want the supplier.

Can anyone tell me where I can get a Temovex HRV from? We're building at the moment and as the house is going to be airtight we want to install a HRV, heard the Temovex is a good model, any other suggestions of HRV systems that work and costs of installation etc. Thanks.

Wally Runs

We have recently refurbished a 1970 four bed and put in the pro-air unit. They are an Irish product and supply and fit came in under €5,000. Appendix Q, solid ducts and all that. It has been in six months now. It did develop a fan imbalance and whine. It was replaced straight away, no quibbles.

Otherwise working fine. It is not a bells and jingles model with high end sensors etc but I think that is an advantage? A number of the systems we looked at had features that were irrelevant for our situation etc. but they were in the price.

The unit is in an annex to our bedroom (behind the built-in wardrobe) and under normal operations we cannot hear it. This was a big worry for us when deciding were to put it. When it is on boost you can hear it.

In the rebuild the house was made air-tight(er) and we have yet to feel the need open the windows for fresh air etc. How it will perform in the summer we have yet to find out.

Very happy with the service. We did find being an Irish product to be an advantage as the others were just re-selling a units built for slightly different markets.

As said above it does not heat the house but controls the heat within the house while keeping the air fresh etc.