Heating System for new build query

Sorry my typing is not the best !!! I am not trying to argue but There would be at lease five other house around the Same size as Mine in the immediat area and mine would be running 45--55% the cost to run of the Ones on oil,I am anything but expert,Just thought my info would be handy as it is head wrecking to know What system to put in as I was in that position.
 
Even up to 2006 it was always €1800-€2300 only 1800sq ft approx and not very well insulated But I was totally depending on oil
 

I had considered such a system for my house but read that the hot dry air does not create the best living environment.
Any views on this?
 
The HRV system takes the stale air and removes the heat from it, pumps it outside and then takes in fresh air from outside. It then puts the heat back into the fresh air and pumps it back into the house through the ducting. The more efficient the HRV is the less supplementary heat you need.

If you have a passive house your system could be up to 90% efficient meaning over 24hrs the temp would drop from 20c to 18c. (figures just for example) This is why a small electric element in the HRV would be sufficient for a passive house as it loses such little heat. A small stove could also be suitable as the supplemental heat source
 
HeadTheWall said:
If you have a passive house your system could be up to 90% efficient meaning over 24hrs the temp would drop from 20c to 18c. (figures just for example)
Click to expand...

I find it hard to believe these figures. I am in favour of HRV but I believe achieving such figures are next to impossible WITHOUT use of significant energy - ie a heat pump - which most HRV systems incorporate.

I know you are not making up these figures, the HRV sales people spout them all the time. The only problem is that they are practically impossible to achieve - WITHOUT supplying significant energy to the system. Would love for someone to come along and prove me wrong.
 
MacTheKnife1,

Are you saying you doubt the whole passive house principle?

Incidently, most HRV system do no not incorporate a heat pump from my enquiries.
 

[broken link removed]
This is the SAP report from a HRV I was considering using done by the BRE.
This does not have a heat pump.
This confirms heat recovery of around 90% with very little energy usage.
 
sas said:
Are you saying you doubt the whole passive house principle?
Click to expand...

NO!!!! - On the contrary I think the passive house concept is terrific. But I do doubt the 90% efficent claims for HRV - in fact I believe it is more like 40-50% - which is still excellent. I just wish salesmen would tell it like it is. I would advise anyone building today to massively insulate, glazing to south, sheltered site etc etc ... AND use HRV but do not expect miracles from HRV. Use it as a simple ventilation system with some of your expelled air-heat recovered. And when I say some I mean a lot less than 90%.


sas said:
Incidently, most HRV system do no not incorporate a heat pump from my enquiries.
Click to expand...

Maybe I am not informed enough. But I see brochures that state things like....they use 20 watts - BUT they have a boost button which then consumes 250-350 watts - that, I guess, is the heat pump - what else can it be??? Maybe some form of electrical heating??

Is there a HRV expert here who can clarify? Where is the 300-350 watts going? It is not moving a fan - it must be either working a heat element or a heat pump.
 
sparky78 said:
[broken link removed]
This is the SAP report from a HRV I was considering using done by the BRE.
This does not have a heat pump.
This confirms heat recovery of around 90% with very little energy usage.
Click to expand...

You are going to have to forgive my ignorance here. What does "90% heat recovery" mean? For example:

If the internal air temp is 20 deg C and the outside is 0 deg C - what will the incoming air temp be after it has passed thru the heat exchange system?? Will it be 18 degrees? My bet is that it will be at the very best 10 degrees. But most likely 7-8 degrees.

Now please note that I am not knocking HRV - I think they are useful - just not as good as they are made out to be in terms of efficiency. But it seems impossible to me that you can recover 90% of the difference between the incoming and the outgoing air temperatures. Maybe my interpretation of 90% efficency is incorrect - but then I have met a lot of HRV salesmen.
 

Again, from what I've been told it is a moving fan. The boost button is to increase the level of extraction during showers, cooking etc. It has nothing to do with boosting the heat recovery capacity. It's simply to get moisture and cooking smells out quickly.

The passive house institute does accept that efficiencies (for some models) are above 70%. Apparently the performance of a HRV system has alot more to do with the actual design of the ducting than the HRV unit themselves. Something which seems to have completely escaped the local suppliers...

Some of the PHI certified systems are available with electric heating elements and small heat pumps. The heat pump equiped models are for houses that are falling short of satisfying the requirements for a passive house. The other is for houses that clearly meet passive standard.
This is what I was told by http://www.drexel-weiss.at/?setlng=1

As regards the efficiencies, my understanding is that it relates to the percentage of heat recovered from the stale air leaving the house i.e. 70% efficiency for 10 degree extract air means that the air actually vented to the outside will be 3 degrees, with 7 degrees having been recovered. That 7 degrees is transfered to the incoming air and has an effect on it but obviously that depends on the temperature of the incoming air. My physics isn't good enough to understand it fully but this is how I understand it in simple terms.
 
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The best advice is keep it simple, all these new H.E systems are great until you need to find a service engineer. They are ten a penny when you dont need them but when you do they are like hens teeth.
You can have a simple system that is also efficient and not as expensive as some of the elaborate systems out there. Talk to a few Plumber/heating Engineer and ask them what he would have in their own homes and draw from that to form you own conclusion
 

My rule No 1 is salesmen lie(The Majority). Start with that and do your own real research.

Remember that a HRV system works in tandem with the envelope of the building, the better sealed the envelope is the less heat that will escape in the first place. There would be no need for HRV's in an airtight house if we wern't concerned about getting fresh air in and condensation out of the building. The house should basically keep most of the heat in, thats where you start from.

The heat exchanger will have been tested and has to conform to what it says it's efficiency is, but that is in a lab environment. If you are hearing about them losing up to 50% heat it's probably not the HRV that is at fault. The heat is probably escaping elsewhere through the envelope

Head
 

This is the key piece that bothers me. The salesmen tell me that they simply take the extract air and it passes through a mesh of tubes and the incoming air passes thru a mesh of tubes. Now both sets of tubes are in contact and so of course some off the heat from the outgoing is passed to the incoming. Very clever idea.

Now if interior temp is 20 C and outside is 0 C I maintain that they will NEVER get the new incoming air to a temp higher than 10 C - and even to get that far is some bloody achievement.

I am very much in favour of HRV - just want to understand the efficiency claims thats all.

And I totally agree with another poster - keep it simple. Insulation is great - it has no moving parts and will remain perfectly functional for 50 years or more. HRV is simply a fan and a simple heat exchange - even at 30 % efficiency I will take it.
 
I agree with Daveyjones,
better to keep it simple while being efficient, after service should be a major issue you need to address.
Great having the most effective system out there, but a total pain when it sits down and you cant get it repaired let alone serviced.
 
I have found this thread really interesting and wonder is anyone interested in doing something like this http://www.boards.ie/vbulletin/showt...p?t=2055263818 here. Syd put me on to it earlier in this thread.

I think if we could get together installation c and running cost of systems it would give people a better idea of the system to pick for their own home.

Anyone up for it?
 

I don't dispute the idea but I would wonder how many people on here actually have HRV?

That heatpump thread is different because everyone in the country that was building one offs fell for that craze over the last 5 years. Now the biggest Irish manufacturer of them has gone to the wall and no one will service the systems they put in. How long before lots of the little guys importing various heat pumps also disappear and leave people high and dry.

Of course this leads back to the question already raised about servicing and repair on HRV but I don't think it's quite the same issue as I've raised about heat pumps. The cost of a HRV system isn't massive (compared to say a heatpump) and they are not terribly complicated either I gather. Plus when kingspan start flogging something it certainly suggests that they are going mainstream, i.e. every plumber will know how to service them soon enough.

I also agree with the concept of keeping it simple but the issues are interlinked. Adding lots of insulation will only add benefit when a structure is airtight. If the structure is airtight all practicality suggests that HRV is the best way to ventilate.
 
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True, but it is about comparing heating systems, size of property, insulation etc. you don't have to have HRV, heat pump etc. IF would even help people with existing system, different controls and the like.
 

Keep ot simple and efficent,
Simple simple. Simple stupid.
Sometimes the best is the easiest and simplest,
The tolerances are very fine with these type of systems and yes they are great on paper.
But god help you, because no one else will, when, as the guys have said "you cant get parts or service"
You will have a very expensive white elephant and a very cold house and no hot water
Sad to say Ireland is only a large city in the grand scale of things and the market here is very limited.
So best to stay with the main stream for service and reliability.
See if you can get feed back on systems 5-10 years old operating either here or the UK, say, Wales or Scotland.
Any system or controls should be sourced from an established manufacturer who has a strong share of the Irish market.
 
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