Heat Recovery System - worth the money?

Linto

Hi,
We're just starting extensive renovation in our recently purchased home. Its a 2 story detatched house ~ 1970. When looking into heating systems and insulation we're not sure if we should consider heat recovery system?
Any idea on cost? are they worth it? Any drawbacks?

JohnnieK

I done a new build last year and there was one of these systems installed. It works very well but the house has high levels of air tightness.

Unless the house is sealed well the system wont work efficiently. An air tightness test will need to be done to make sure of this.

Regards cost I think he said he paid €4900 for his system.

amandaparker

Heat Recovery Ventilation (HRV) System employs a counter-flow heat exchanger (countercurrent heat exchange) between the inbound and outbound air flow. HRV provides fresh air and improved climate control, while also saving energy by reducing heating (and cooling) requirements. Here is an article which explains the working process of HRV Systems; this will give you good idea about heat recovery ventilators. Also I found a link which has a list of HRV providers where you can make your choice; also you can clarify your doubts if any.

BobMcBob

Linto wrote: »

Hi,
We're just starting extensive renovation in our recently purchased home. Its a 2 story detatched house ~ 1970. When looking into heating systems and insulation we're not sure if we should consider heat recovery system?
Any idea on cost? are they worth it? Any drawbacks?

I'm no expert, but if you go through some of the previous posts on this topic it appears HRV is not ideal in a retrofit. HRV needs a high level of air tightness which is difficult to achieve in a retrofit.

BmcB

larchill

Was talking to someone over the last few days who had this done recently. This was a retrofit to a 70's house. He's pleased with the result. Cost €3,000ish.

afinador

larchill wrote: »

Was talking to someone over the last few days who had this done recently. This was a retrofit to a 70's house. He's pleased with the result. Cost €3,000ish.

We're doing much the same, and the cost quoted for HRV and all ducting is about €5000!...any idea what sort of system your friend used?

AMG86

Look at insulation, air tightness and ventilation. You should do all three if possible to give you a low energy, healthy and comfortable house. Doing the ground floor could be more difficult than the first floor. This will be depend of course on how deep the refurb will be. Further you should try to locate the unit in the house itself as opposed to the loft. The unit will work better.

QBE

if installed correctly with proper construction methods . it can pay for itself in less than 5 years. it will reduce your space heating cost by around 50%. you wont be able to use an open fire. but you can use room sealed stoves and it will defo increase ber rating and air quality.

id recommend only if been fitted or been advised by a pro in that field.

jose66lorenzo

Hi ,

I am in the process of finishing a house that was started on 2003. The walls were built with 9" cavity blocks. I intend to insulate using spray foam. Is a heat recovery system a waste of time for me as i will probably get some cold bridging?

Outkast_IRE

jose66lorenzo wrote: »

Hi ,

I am in the process of finishing a house that was started on 2003. The walls were built with 9" cavity blocks. I intend to insulate using spray foam. Is a heat recovery system a waste of time for me as i will probably get some cold bridging?

I wouldn't use the spray foam on these, whoever told you this or is recommending it is a chancer and I wouldn't leave someone do that in a million years. Theres too many coldbridges its a waste of your time and money in my opinion

External insulation would be my favoured form of insulation in your situation consider it cause your only wasting money with the spray foam solution.

jose66lorenzo

Thanks for that outkast. I already have the external walls plastered and had a look at external insulation. Getting quotes over 20k. Bit too rich for my blood. I was hoping to put a geothermal heating system and heat recovery into this dormer. I will be making it air tight and will get the attic insulated with the foam. Should I just go for insulated slab on the cavity block walls?

Outkast_IRE

I had a big huge reply wrote out but I pressed backspace and lost it all :mad:

Now basically I am happy to chime in with advice here, no problem with that. But we need a good discussion on priorities.

We can all accept the fact that the better insulated a home is(assuming its relatively airtight) that there will be a corresponding reduction in installation and running costs of the heating system.

It can therefore be said that anyone with any sanity will see that you should be putting as much money as you can into insulation and should see a drop in the heating systems costs.

In terms of the order I would advise spending your money it would be.
1. Insulation (Walls, Floors, Ceilings, Window Upgrade if necessary)
2. Airtightness (this doesn't mean an airtight home but ensuring steps are taken to reduce draughts etc as much as possible.
3. Heating system, MHRV.

You mention wanting to put in geothermal , Have you Costed this idea? Geothermal has very large installation costs, and if your home isn't well insulated its going to be running a hell of a lot because it works at a low temperature generally around 40 degrees or so.

My point being if you insulate your house well enough you wont need to install geothermal, air to water or a traditional boiler would be fine for you because you would be running it such little time.

I would ask you to seriously consider engaging an architect so you can set some goals in terms of U-values, and put together a plan, also I always recommend a Quantity surveyor, they will ensure you are buying the correct amounts, are paying the correct amount to any builder or contractor and are staying in budget. They do almost pay for themselves.

Paying for professional advice at this stage will save you thousands and thousands over the life of the home.

Honestly to me you don't sound like you have the Knowledge to oversee this job correctly. Feel free to ask any questions I am more than happy to answer any I can.

jose66lorenzo

Thanks a mil for this advice. I got a quote for geo thermal pump, boreholes, tank and UHF upstairs and down for around 20k. What insulation would you recommend for the walls if I don't go with external? Should I still get the airtight membrane if I will have some cold bridging? Is heat recovery a waste of money in this case?

Outkast_IRE

jose66lorenzo wrote: »

Thanks a mil for this advice. I got a quote for geo thermal pump, boreholes, tank and UHF upstairs and down for around 20k. What insulation would you recommend for the walls if I don't go with external? Should I still get the airtight membrane if I will have some cold bridging? Is heat recovery a waste of money in this case?

To me its utter madness to be willing to pay 20k for geothermal and not be willing to pay for external insulation. You should be spending the 20k on external insulation and putting in a cheaper heating system as you wouldn't be running it too much in a very well insulated home anyway.

I cant recommend an internal insulation for your situation I would need to see it as to fair you need to look at the whole picture. You need to engage an architect or similar who has an interest in this area, a small amount of money spent on advice now is going to be paid back with interest in the longrun.

You need to do heat loss calculations for the entire building and an architect can look for existing cold bridges and how to tackle them . Seriously professional advice now will be paid back many times over.

The heat recovery will only be a waste of time if your cant get your airtightness to a certain level. As far as im concerned doing the airtightness with all internal insulation would be far more difficult than external insulation.

afinador

Have to agree with Outkast on this, Jose...
we're on a rebuild of a 70's house, and all the advice and research available pointed at insulation and air-tightness. It's a no brainer really. 20k on external insulation will be recovered much faster than the equivalent spent on an expensive geo rig in a house with thermal bridging issues and drafts. It's up to you how far you go with the insulation, but ideally pump the cavity as well and have someone (architect/ thermal engineer etc) draw specs for dealing with the thermal bridges...particularly around windows and external doors, and where walls meet roof
Otherwise it's like trying to fill a bucket when it's full of holes

Outkast_IRE

afinador wrote: »

but ideally pump the cavity as well

That's the main problem no Cavity, there are cavity blocks which I never recommend pumping as its a waste of time, better to keep all the insulation in one layer if possible I think.

jose66lorenzo

I was just onto my architect and he was suggesting to plaster the cavities inside the house with a sand cement mix to make air tight, then air tight membrane then insulated slabs. Use tape around windows and doors. For the attic use rafter insulation not spray foam as he reckons this is a fire hazard. Any thoughts on this. For me I don't see how more concrete would be a solution but im no expert.

JohnnieK

JohnnieK wrote: »

I done a new build last year and there was one of these systems installed. It works very well but the house has high levels of air tightness.

Unless the house is sealed well the system wont work efficiently. An air tightness test will need to be done to make sure of this.

Regards cost I think he said he paid €4900 for his system.

Just to add to this topic, I was recently back in the house and I was amazed at how fresh the air was in the house. IT didn't feel stuffy.

He said the winter was fine with the heating too. His heating is bulk LPG because he wanted to cook with it also.

He seems to like the whole set up. I have no idea how well it would work on a retro fit but you can get a level of good air tightness with an older building at a cost.

Outkast_IRE

jose66lorenzo wrote: »

I was just onto my architect and he was suggesting to plaster the cavities inside the house with a sand cement mix to make air tight, then air tight membrane then insulated slabs. Use tape around windows and doors. For the attic use rafter insulation not spray foam as he reckons this is a fire hazard. Any thoughts on this. For me I don't see how more concrete would be a solution but im no expert.

Architect advice will differ depending on solutions they have worked with before, some are reluctant to go outside their comfort zone, others are willing to research and try new methods.

Yes Sand cement plaster on the Interior of walls is done, and I have heard of this being done in other projects after that we are back to the insulated slab vs exterior insulation.

Insulated Slab Pros - Possibly cheaper but you need to account for all costs, such as possible electrics and plumbing being moved.
Your house will generally have a quick warm up time, but with little thermal mass so how long it stays warm would be very dependant on air tightness.

Insulated Slab Cons - You lose a massive amount of interior space when you add it all up.
You have very little thermal mass.
If you go looking to hang tvs or cupboards etc the insulated slabs can be a pain.
Far more cold bridges than exterior insulation.
As previously said, account for any additional works which need to be done such as electrics or plumbing moved.

Personally I would get the costs worked out for both methods and make the decision myself. I know I would choose external, and choosing external makes additional sense if you want to choose a heatpump to heat the house, as the additional thermal mass of the walls will work well with a heatpump to create a stable temperature in the home.

Markcheese

jose66lorenzo wrote: »

Hi ,

I am in the process of finishing a house that was started on 2003. The walls were built with 9" cavity blocks. I intend to insulate using spray foam. Is a heat recovery system a waste of time for me as i will probably get some cold bridging?

9" cavity wall or 9" cavity block ??
(would the spray foam be any good in a cavity wall)

Outkast_IRE

Markcheese wrote: »

9" cavity wall of 9" cavity block ??
(would the spray foam be any good in a cavity wall)

Its cavity Block. And as far as I know there is not approved spray foam on the market for Cavity Walls. When I say approved I mean agrement Certified.
And on that basis alone I wouldn't put it near cavity walls.

jose66lorenzo

Class advice. Really getting me thinking. The house hasn't been first fixed in anything yet so no probs moving pipes etc. the front of the house has fancy stone work around the doors and windows aswell as on some of the wall. Would external insulation on 3 of the walls and then insulated slab on the front wall be a benefit in relation to the extra cost?

Outkast_IRE

jose66lorenzo wrote: »

Class advice. Really getting me thinking. The house hasn't been first fixed in anything yet so no probs moving pipes etc. the front of the house has fancy stone work around the doors and windows aswell as on some of the wall. Would external insulation on 3 of the walls and then insulated slab on the front wall be a benefit in relation to the extra cost?

I believe what your asking could be done, you might need an architect to check how to help prevent cold bridges etc.

It is possible to keep stone cladding finishes with external insulation.
If you google External insulation Stone Cladding, one of the first companies which come up is "retrocladding" they seem to have experience with this.
Im not saying to use this company but it certainly makes it look like its possible to keep some of the features.