HRV as a heating system?

Old Jim

Can a Mechanical HRV be used as the primary heating system in a Timber Frame House with good levels of insulation and air-tightness? Is there any HRV system that will take heat input from a boiler or other source and distribute this throughout the house?
I am trying to investigate if it is feasible to heat the house without rads or UFH.

CJhaughey

My HRV unit has an internal electric element to provide a boost if needed.
I wouldn't want to have it as the primary heating source as it would be expensive to space heat an entire house with this method.
If you had a woodburning/solid fuel stove that had a convection style of heating such as the Morso 3440 and sited an intake for the HRV near the stove then I would imagine the potential for such heating would be high.
I have a Morso 1430 and it doesn't use convection it is the radiant model.
However with the double doors open from the living room it makes a big difference to the heat of the house via the HRV moving the heat around.
Bear in mind that the HRV outlets are usually near the ceiling and that any heat distributed via this method will tend to stay near the ceiling, as opposed to UFH which distributes heat over a wider area.

Juantorena

CJ, you don't think a specifically radiant stove combined with your HRV unit would sufficiently heat the house?

I'm strongly thinking of going down this route for heating. I'm getting an off-plan heating requirement analysis done which, combined with good u-values, I'm hoping will determine that MHRV (with mini heat pump) and a wood stove will be sufficient.

My understanding was that the HRV outlets in the rooms were sited in ceilings as the heated air's method of transportation around the house was under doors...hence the air travels from ceiling down to floor level (eventually). Although, maybe siting outlets diametrically opposite the door and low down might allow the air to rise and fall through the room on it's way towards the door? Draughty?

Interesting thread for me, Old Jim.

CJhaughey

Juantorena wrote: »

CJ, you don't think a specifically radiant stove combined with your HRV unit would sufficiently heat the house?

No, I think the convection type would be better, after all it is air you are talking about heating, so using a stove as an air heater then using the extract to take the air straight to the HRV unit would be the most efficient way, IMO.

Juantorena wrote: »

I'm strongly thinking of going down this route for heating. I'm getting an off-plan heating requirement analysis done which, combined with good u-values, I'm hoping will determine that MHRV (with mini heat pump) and a wood stove will be sufficient.

My house is pretty warm if the stove has been burning for any length of time, if it was a convection type with a back boiler, I don't think I would need much else.
I regret not fitting a back boiler when I got the stove, with solar in summer and the wood heater in the winter my year-round water heating could be accomplished virtually off-grid.
As opposed to the immersion being used at present.

Juantorena wrote: »

My understanding was that the HRV outlets in the rooms were sited in ceilings as the heated air's method of transportation around the house was under doors...hence the air travels from ceiling down to floor level (eventually). Although, maybe siting outlets diametrically opposite the door and low down might allow the air to rise and fall through the room on it's way towards the door? Draughty?

I can only speak from my setup, but I have 4 extract vents and 6 inlets
extracted from bathroom1+2, kitchen, utility,and inlet into bedrooms and living rooms 1+2.
All vents in ceiling.

jasperok

Does this mean its wise to have an extract close to your main heat source to improve on the heat exchange occuring?
At the moment i just have a inlet in the stove room....

CJhaughey

jasperok wrote: »

Does this mean its wise to have an extract close to your main heat source to improve on the heat exchange occuring?
At the moment i just have a inlet in the stove room....

Same here.
I think an inlet with a closable valve would be no bad thing.
Too bad my floors are down upstairs and I cannot retrofit.

jasperok

dont you mean an extract with a closeable valve?
so you could be drawing air up when you want the heat to go to the exhanger and leave it off when you don't.
I presume the inlet always has to be on in order to aid in supply of O2 to the fire?

Old Jim

CJH, Thanks for your very helpful input.

Juantorena wrote: »

I'm strongly thinking of going down this route for heating. I'm getting an off-plan heating requirement analysis done which, combined with good u-values, I'm hoping will determine that MHRV (with mini heat pump) and a wood stove will be sufficient.

Juantorena, when you say a MHRV with a mini-heat-pump, what type of HP had you in mind? Any specific make?

Do-more

Old Jim wrote: »

when you say a MHRV with a mini-heat-pump, what type of HP had you in mind? Any specific make?

From my understanding, HRV units fall into two categories those being active and passive types. Passive HRV units recover heat by means of a simple heat exchanger, whilst active HRV units incorporate what is effectively an air to air heat pump which improves the efficiency of the system.

It's important to note when companies claim that there unit is XX% efficient for passive units this relates only to sensible heat, where as for an active HRV unit the efficiency relates to sensible and latent heat, i.e. passive units do not recover latent heat.

I'm not an expert in the field but this is my understanding from researching for my next build, I'm sure if I'm incorrect people will put me straight.;)


I'm looking at a passive or low energy house build myself and it seems that HRV with a supplemental heat source is a popular choice for Passive houses.

Many use a system where a heat exchanger (similar to a car radiator) is placed in the duct after the HRV unit which can be fed from a variety of sources such as a small gas boiler or a wood pellet stove with back boiler. The key element is that the system can be fully automated so that if room temperatures fall below a set temperature then the stove or boiler will be started automatically to boost the heat and then will be shut off automatically when the target temperature has been reached.

Juantorena

Old Jim wrote: »

Juantorena, when you say a MHRV with a mini-heat-pump, what type of HP had you in mind? Any specific make?

Old Jim, pm sent.

slicedpanman

Hi all, Interesting thread...

I'm in the initial stages of a rennovation/extension project and am looking for an oil/gas/coal free solution to all of our space + water heating. I'm thinking of something similar to what has been suggested in this thread namely...

1) Solar Panels/solid fuel Stove (with back boiler) combo to heat our water
2) MHRV with a water-to-air heat pump i.e. use hot water from the DHW system to top-up the warm air (after air exchanger and before air is sent to output vents)
3) an Air Source heat pump as a back up to both the Panels/Stove

I'm hoping that between the 3 (Solar Panels/Stove/Air Source Pump) we can supply all our hot water needs and use some of this hot water to beef up the MHRV to provide all out space heating needs [needless to say we are putting lots of effort into insulation and air tightness]

Does this sound like a possible/sensible solution?

0lddog

Many of the air to air heat pump manufacturers also make ( and indeed hold primary patents on ) MHRV units.

Why not look at an inverter heat pump with an internal duct unit coupled with MHRV ?

I would be thinking Daiken or Mitsubish Electric but I'm sure others offer these by now.....

I'd also get a wood burning stove - would be good for deep winter as a backup

It seems that this is now a common config in New Zealand ( climate similar to Cork - Northern Scotland ? ). To such an extent that, over there, some of the heat pump manufacturers advertise on TV !