micro heat pumps and heat recovery units

babybuilder

Hi

Having originally decided to invest in a heat recovery ventilation system from MTD-Solutions I recently came across an Austrian company called Ochsner who manufacture micro heat pumps. The exhaust air which is normally used to heat incoming cold fresh is instead utilised to heat water for domestic uses by passing it through this micro heat pump. It purportedly gives a COP of around 4 - 6.
The exhaust air is taken from bathrooms, kitchens, wet rooms etc. The bid difference between this system and the HRV one is that the Ochsner system draws in the cold fresh air into living spaces through vents in living room walls.

Has anyone out there installed a unit like this or indeed a normal HRV system? I would be grateful for any feedback.

Thanks
Babybuilder

CJhaughey

I have a HRV from Scanhome.ie it is the Temovex unit.
We have found it excellent, the house stays very dry and warm, any heat from cooking etc is recovered and heats the house.
If we are roasting something or baking we have to turn the UFH off the night before or the house gets too hot!
I know that Scandinavian homes are now selling the Panasonic Air to air heat pumps and that they have very good COP ratings from 3.8 to 5.2 depending on model.
I have not got one of these Air to Air heatpumps but am seriously considering buying one as they can cool as well as heat which is nice in the summer!
I would not like to have cold draughts coming ion through vents in the wall, I prefer to use ducts to supply the air to the rooms as and when we need to.
For instance our upstairs is not finished yet and until it is useable there is no real need for the system to be running upstairs, with the ducting I have I can turn off the valves in the rooms upstairs and just keep the airflow to a minimum.

ben04

I hear the HRV works the best in a draft proof house which is usually a new build. Has anyone used one in an old house and if so how effective is it?

babybuilder

Thanks for the reply CJhaughey. Ben04, indeed the system will fail if the house isn't sealed completely airtight. I've heard of two houses in Donegal and one in Galway which have had to switch off their (they switched over to micro heat pumps). I don't know about the level of air tightness or insulation in these houses. I would reckon that the level of heat loss through air infiltration and draughts must be greater along the western sea board due to the prevailing blustery conditions.

gonk

babybuilder wrote:

Thanks for the reply CJhaughey. Ben04, indeed the system will fail if the house isn't sealed completely airtight.

That's what I thought, and so was astonished to see a HRV system being fitted to a rather ramshackle looking old country cottage in the BBC TV series It's Not Easy Being Green a couple of months ago. Does anyone know if it is feasible to retrofit such systems to houses which weren't designed from the outset to include them?

ollie30

hi folks,i,m interested in this as i,m about to build and was trying to get as air tight as i could,i have doubts if trickle vents in the windows would do and was thinking about some sort of venting system.i could do with some help 1.how do you get air tight,is it by taping and sealing around windows,doors,light fittings ,plug sockets ,skirting boards etc.i know this is contradicting but the wife wont hear tell of not having at least 1 fireplace,2.is it possible to get airtight glass fireplace doors and use an under grate air duct taking air from outside?if its possible and i follow the air sealing measures i mentioned would they warrant getting an air venting or hrv system.the fireplace wont be comprimised so i would love to know if there's a way around it(glass doors,chimney damper?)fire probably will hardly ever lit anyway!!hrv's are probably great but if it wont suit our house its an expensive bad buy

CJhaughey

We have a solid fuel stove yet to be installed, A HRV system should work with a stove as it can be closed unlike an open fire which cannot be regulated at all.
You should be fine with one fireplace, you won't need a balanced flue as you can usually control the amount of air entering the house with the HRV system.
Sealing is done by lining the house inside with a Moisture barrier ie, heavy gauge polyethylene

Do-more

You can get a damper to close off a chimney when it is not in use, so you could have a HRV system and still have an open fire (for occasional use) although you are better off with sealed stove.

I was having a look at a HRV system from The Energy Depot info@energydepot.ie in Cork a few weeks back and it looks like a good system, being an active system with a small air to air heatpump built in, rather than a passive HRV system like most on the market. They also supply a low profile insulated ducting system which is 4" in diameter in total inc. the insulation, so it would be a lot easier to retrofit into an existing house.

They have all the stuff running in their showroom in Cork.

Details of the Airexe HRV system they supply can be found on www.lowenergy.ie

Hope this helps.

ollie30

thanks for your help,for a concrete block built house that wont be drylined (cavity insulation upgraded)would good plastering be enough or are there other measures to ensure airtightness

s2_ireland

Hi Haven't posted here before but can give you some good pointers on airtightness.
IMHO
1. wrap the ends of the (1st floor) floor joists penetrating the inner block of your cavity wall. This can be done using a commonly available breathable membrane, but will involve co-operation between carpenter & block layer.
2. 1st floor ceiling gets the same breathable membrane installed completely accross the ceiling & returned about 100mm down each of the walls on the inside.
3. Ideally counter batton the roof trusses after the membrane to create a service void & route all services through this. With a membrane upstairs be careful if you install downlighters.
4. The only services to penetrate the membrane will be HRV ducting & piping to cold water tank.
5. If you have a habitable attic space let me know I'll send you a detail, otherwise seal & insulate your attic hatch. There are manufactured attic access doors available well worth the money.
6. regarding the plaster detail on the ground floor the -plasterer needs to go completely to the floor.

S2

davidoco

gonk wrote:

That's what I thought, and so was astonished to see a HRV system being fitted to a rather ramshackle looking old country cottage in the BBC TV series It's Not Easy Being Green a couple of months ago. Does anyone know if it is feasible to retrofit such systems to houses which weren't designed from the outset to include them?

In a later episode of INEBG they mentioned that the house was freezing and that they had to turn off the HRV.

ollie30

thanks s2 ireland,house will be a 2 story with concrete 1st floor slabs do i wrap the ends of them also and would running the membrane down the wall 100mm not entale drylining?i will be getting attic trusses made up and more likely will be with a habital space but no real notion of using it for living just thinking now's the time to do it not in 10yrs time and have the space there.as you can tell i have no knowlege of airtight construction and i dont know if anyone involved with the design or build have,is there anywhere i can go for a full run down on airtight building
thanks

s2_ireland

Hi Ollie,
IMHO
1. Wrapping the ends of the hollowcore slabs is possibly the best investment you'll make in the house. If you imagine that the open ends of the hollowcoce are exposed to the ventilated cavity then you will have air movement from one side of the house to the other. The other place for leakage will be directly above & below the slab with air trickling around behind the skirting board upstairs & around through the light fittings etc on the ceiling of the ground floor. The membrane solves both of these problems.
On the ground floor you need to drop the membrane to a level slightly below (say 50mm)the level of the (most likely) suspended ceiling. The membrane is taped or glued to the wall & plastered over.
2. There is another area around the installation of the hollowcore slabs. This is on the other 2 walls where the slabs will not penetrate the inner block. In this area just install the membrane vertically along the inside of the wall (between the wall & the slab) & seal it to the wall above & below the slab.
3. The membrane should be a breathable material. Strictly speaking a plastic material will do the job for airtightness but it is possible (even if unlikely) that the building will sweat in that area with plastic.
4. The membrane is only about 2mm thick & you will not need to dry line the walls. it is easily covered by the plasterer.
S2

ollie30

thank you s2 ,appreciate your advice

dubkarl

Hi,
Having fresh cold air been drawing in via a vent hole in the wall goes completly against the reason of having hrv. Hrv brings fresh air into the living rooms from a heat exchanger unit which transfers the heat energy from the warm stale air which is being expelled. this negates a need for vent holes to draw in fresh air from outside.
It doesn't matter whether your house is air tight or not but obviously your house (and system) will be more energy efficent if it has good air tightness and heat energy is not been lost.
Retro-fitting an existent house is more trouble than its worth generally as you need to run a ducting system throughout the building in various cavities which are more than likely inaccesable after building is built. However some can be retrofitted such as a bungalows.