Stove and MHRV

Lyixd

Hi, I am building a bungalow with UFH and plan to fit a stove in our large open plan kitchen/living area. The basis of my question is, I was planning to use a back boiler system in the stove and link this to a maxipod so I can let it contribute to the UFH. I was speaking to a person today who said as I am intending to fit a MHRV sysytem that I would have another option. I fit a room only stove and let the MHRV system transfer the heat between rooms, this means I would only need a stainless stell tank for my UFH which is half the cost of a maxipod, the room only stove would be cheaper and hence no plumbing required between the stove and pod. Any suggestions as which set up would be best? Thanks

1100010110

I've something similar going into my own new build, and went for the back boiler, reason being that as much energy as possible goes to a central storage location in the tank which can then be used by the heating system and DHW as required.
Also with air tightness and using an external air supply for the stove, it keeps it sealed from the internal circulation of air as governed by the MHRV and the balancing of same would not be adversley affected by the firing of the stove drawing internal air up the flue.
But that's just my opinion, I guess that the efficiency of the MHRV in redistributing the heat energy from the air which has been heated in the room with the stove through the heat exchanger of the MHRV unit to the incoming fresh air would have to be considered against the contribution a backboiler makes to UFH & DHW and it's associated costs would have to be weighed up, against the costs of each option.

OOD

Hello.
I am supplying and installing MHRV systems for more than 7 years and can give you some information to think about.
Part L continuous mechanical ventilation with heat recovery:
Kitchen - 13l/s
Other wet rooms(utility, bathroom, en suite) - 8l/s
Sanitary Rooms(toilet) - 6l/s
Example:
Your kitchen HRV extract valve is nearest to the stove will extract only 1/7 of all the extracted air and the rest 6/7 will be extracted from other wet rooms, which not as warm.
So by mixing one part(30C`) air with six part of (22C`) would not make mach of the difference in overall house temperature.
And system design to have one air exchange in 2-3 hours. It is considerably slow for the type of heat distribution you want it to be used for.
So it might be more expensive to fit maxipod, but in that case, you can use exes of the heat in the right way.
Just another opinion.

manufan16

I have a similar set up to the OP , having UFH , stove with back boiler , MHRV etc

With the benefit of hindsight I probably would have gone for a smaller room only stove , the reason being is to get the stove up and running to provide enough hot water to the buffer tank for the UFH it has to be a big hot fire which is basically means the room (even though large open plan lounge kitchen dining sunroom) gets too hot with the level of insulation and air tightness in builds today. This is probably a result of my stove being oversized but still something to consider.

joeirish

manufan16 wrote: »

I have a similar set up to the OP , having UFH , stove with back boiler , MHRV etc

With the benefit of hindsight I probably would have gone for a smaller room only stove , the reason being is to get the stove up and running to provide enough hot water to the buffer tank for the UFH it has to be a big hot fire which is basically means the room (even though large open plan lounge kitchen dining sunroom) gets too hot with the level of insulation and air tightness in builds today. This is probably a result of my stove being oversized but still something to consider.

What is the rating of your stove, heat to room and heat to water? We have been thinking of similar set up but we were aware of this type of overheating problem. The stove we are looking at has a rated output of 2.1 kw to room and 6.3 kw water. Any opinions?

manufan16

Mine is 18kw with 60% to boiler and 40% to room so you can see why it overheats, mind you it is still great to have and if it gets too hot we just open doors to let it to heat the remainder of the house.

I would imagine the 2.1kw to room and 6.3kw your thinking of would be more suitable for an insulated airtight house built to the latest regs but there are calculations and formulaes available now that your energy assessor can use to help size the stove appropriately.

BarneyMc

Interested in this as I'm building at the moment and will have to decide on whether to go with a room only stove or connect it up to contribute to the UFH system. Very interested to see if anyone else than ManUFan has had good/bad experiences with this setup.

BarneyMc

manufan16 wrote: »

I have a similar set up to the OP , having UFH , stove with back boiler , MHRV etc

With the benefit of hindsight I probably would have gone for a smaller room only stove , the reason being is to get the stove up and running to provide enough hot water to the buffer tank for the UFH it has to be a big hot fire which is basically means the room (even though large open plan lounge kitchen dining sunroom) gets too hot with the level of insulation and air tightness in builds today. This is probably a result of my stove being oversized but still something to consider.

What's your primary heat source? Surely if you light a modest fire, the back boiler will contribute to heating the water and reduce the demand on your primary source?

blast06

I am 5 months in my new build and a simple observation... If you are part L compliant with Ufh and air tightness and Hrv then you won't need a stove. I have 1 fitted and havent even lit it yet. Yes in theory it could reduce your heating bills (although you would be a long time paying off the additional capital investment) but do you really want to be messing putting down a fire every evening to save damn all plus probably making the area where the stove is uncomfortably warm?
Yes, fit the stove cos its still in the irish psyche to have a place to light a fire but dont waste money hooking it up to UFH cos ultimately you will rarely end up lighting the stove

BarneyMc

blast06 wrote: »

I am 5 months in my new build and a simple observation... If you are part L compliant with Ufh and air tightness and Hrv then you won't need a stove. I have 1 fitted and havent even lit it yet. Yes in theory it could reduce your heating bills (although you would be a long time paying off the additional capital investment) but do you really want to be messing putting down a fire every evening to save damn all plus probably making the area where the stove is uncomfortably warm?
Yes, fit the stove cos its still in the irish psyche to have a place to light a fire but dont waste money hooking it up to UFH cos ultimately you will rarely end up lighting the stove

So lf committed to putting in a stove then you would recommend a stand alone one?

BarneyMc

manufan16 wrote: »

I have a similar set up to the OP , having UFH , stove with back boiler , MHRV etc

With the benefit of hindsight I probably would have gone for a smaller room only stove , the reason being is to get the stove up and running to provide enough hot water to the buffer tank for the UFH it has to be a big hot fire which is basically means the room (even though large open plan lounge kitchen dining sunroom) gets too hot with the level of insulation and air tightness in builds today. This is probably a result of my stove being oversized but still something to consider.

I'm just off the phone with a supplier of the Maxipod and he strongly suggested not using it for UFH & heat pump systems. He said it really needs a radiator system. I'm therefore going to ditch the idea of hooking my stove up to the central heating system and just use it as stand alone.
I suppose this has the advantage of being able to heat the house in the event of electricity downtime. It might also be handy in autumn/early spring to be able to heat the house without the need of the heat pump.

Sandman777

Hi
I'm 7 mths into a self build, Installing Heat Pump with UF heating along with airtightness and MHRV!

I plan on installing 2 stand alone insert stoves, one in on open plan living /kitchen/dining room and one in sitting room(instead of open fire)! I intend to have both sealed with external air supply but i am considering venting some of the warm air to other rooms in the house to take some of the demand away from the HP especally in winter!

My question is..is this worth it and will it effect the air flow of the MHRV system in any way?

Also there is a massive range of stoves out there and can anyone offer any advice or recommend any particular types?

Thanks
S

galwaytt

blast06 wrote: »

I am 5 months in my new build and a simple observation... If you are part L compliant with Ufh and air tightness and Hrv then you won't need a stove. I have 1 fitted and havent even lit it yet. Yes in theory it could reduce your heating bills (although you would be a long time paying off the additional capital investment) but do you really want to be messing putting down a fire every evening to save damn all plus probably making the area where the stove is uncomfortably warm?
Yes, fit the stove cos its still in the irish psyche to have a place to light a fire but dont waste money hooking it up to UFH cos ultimately you will rarely end up lighting the stove

or, as in a house I visited this week, put in a stove and HRV and you may not need UFH.... Nor all the capital costs associated with it... There's more than one way to skin a cat...

touchdown77

Sandman777 wrote: »

Hi
I'm 7 mths into a self build, Installing Heat Pump with UF heating along with airtightness and MHRV!

I plan on installing 2 stand alone insert stoves, one in on open plan living /kitchen/dining room and one in sitting room(instead of open fire)! I intend to have both sealed with external air supply but i am considering venting some of the warm air to other rooms in the house to take some of the demand away from the HP especally in winter!

My question is..is this worth it and will it effect the air flow of the MHRV system in any way?

Also there is a massive range of stoves out there and can anyone offer any advice or recommend any particular types?

Thanks
S

I'm in similar situation, airtight house with HRV & stove and will be installing underfloor pipes but not buying the heat-pump until I'm sure its necessary.

I'm considering installing a stove that doesn't have external air supply and put up with the imbalanced HRV air flow for the times when stove is lit...

galwaytt

touchdown77 wrote: »

I'm in similar situation, airtight house with HRV & stove and will be installing underfloor pipes but not buying the heat-pump until I'm sure its necessary.

I'm considering installing a stove that doesn't have external air supply and put up with the imbalanced HRV air flow for the times when stove is lit...

The former is a good idea, I know a house where he ran the pipes, but didn't buy manifolds or anything. Didn't need to in the end.

The latter I would NOT do. It's not just about imbalancing the HRV, it's about sufficient draft for the stove to burn correctly. For a whole bunch of reasons, draughts being the least of them, I think proper operation, combustion and safety (CO) reasons put the pipe in.

dfader

Not an expert on HRV but just an observation. Does it not need to be designed to prevent risk of creating negative pressure in room with stove. if extracting from that room would that not increase risk of flue gasses being drawin in from a poorly airtight stove? Any mhrv installers abke to advise

Sandman777

touchdown77 wrote: »

I'm in similar situation, airtight house with HRV & stove and will be installing underfloor pipes but not buying the heat-pump until I'm sure its necessary.

I'm considering installing a stove that doesn't have external air supply and put up with the imbalanced HRV air flow for the times when stove is lit...

From what i have researched and from talking to others the external air supply to stove seems to be a must if using HRV!

touchdown77

galwaytt wrote: »

For a whole bunch of reasons, draughts being the least of them, I think proper operation, combustion and safety (CO) reasons put the pipe in.

Good point, having never lived in an airtight house, I'm probably underestimating its significance in relation to the stove....

Sandman777

dfader wrote: »

Not an expert on HRV but just an observation. Does it not need to be designed to prevent risk of creating negative pressure in room with stove. if extracting from that room would that not increase risk of flue gasses being drawin in from a poorly airtight stove? Any mhrv installers abke to advise

Generally (and i'm not an expert) the HRV extracts are only located in wet rooms, utilities and kitchen area, the living areas where stoves most likely located have the supplys!! However in an open plan situation prehaps this could raise question marks if say a living room had the supply but the connecting kitchen had an extract!!

galwaytt

Sandman777 wrote: »

From what i have researched and from talking to others the external air supply to stove seems to be a must if using HRV!

touchdown77 wrote: »

Good point, having never lived in an airtight house, I'm probably underestimating its significance in relation to the stove....

It's not the HRV that are making it 'necessary' - it's the airtightness of the building fabric (because HRV is optional, not mandatory).....any air or ventilation currently calculated, by means of passive or mechanical, is purely for habitation purposes.

There is no allowance within that for providing air for a combustion process (stove etc). Hence the need for a pipe/air supply calculated purely for the burning appliance.

BryanF

touchdown77 wrote: »

I'm in similar situation, airtight house with HRV & stove and will be installing underfloor pipes but not buying the heat-pump until I'm sure its necessary.

I'm considering installing a stove that doesn't have external air supply and put up with the imbalanced HRV air flow for the times when stove is lit...

what does your BER require?

Sandman777

BryanF wrote: »

what does your BER require?

BryanF
I am considering diffusing some of the stove heat to different rooms with a ducting system to supplement my heat pump! Is this worth the extra cost and will it have any effect on the HRV system?

Thanks

BryanF

Sandman777 wrote: »

BryanF
I am considering diffusing some of the stove heat to different rooms with a ducting system to supplement my heat pump! Is this worth the extra cost and will it have any effect on the HRV system?

Thanks

depends on several factors. type of house fabric/heat loos/air-tightness kwhr/m2/yr we're taking about to run it. i see great advantages in diffusing heat in a low energy home where for example 3kw to a room will quickly overheat it. so instead of running around opening doors (or expecting the HRV system to do) you diffuse heat to other areas, but keep the pipes lengths to min(the better stove manufacturers will often have literature on this)

Sandman777

BryanF wrote: »

depends on several factors. type of house fabric/heat loos/air-tightness kwhr/m2/yr we're taking about to run it. i see great advantages in diffusing heat in a low energy home where for example 3kw to a room will quickly overheat it. so instead of running around opening doors (or expecting the HRV system to do) you diffuse heat to other areas, but keep the pipes lengths to min(the better stove manufacturers will often have literature on this)

No tests done yet but good detailing and insulation etc to A3 standard with Airtightness! The area where stove will be in is an open plan living/dining/kitchen area 54m2! Thinking something like a 7kw insert stove and possibly diffusing some of this esp if gonna be overheating this space too easily!

Another reason also is....as HP is providing same temp throughout house, by keeping overall temp down a deg or 2 (keeping HP cost down) i can boost living area and 1 or 2 other areas when stove is lighting in cold weather!

MicktheMan

Sandman777 wrote: »

Thinking something like a 7kw insert stove

Be very careful. 7kw stove in a well insulated and airtight house may very easily be overkill and make the room that it is in too warm for comfort.

galwaytt

MicktheMan wrote: »

Be very careful. 7kw stove in a well insulated and airtight house may very easily be overkill and make the room that it is in too warm for comfort.

You're right: it will.

In the rush to have 'ample' backup, people are over spec'ing mechanicals all the time.

Superdaddy

I was all set to put a stove in my house until i spoke to a few people in the know. An A3 rated house owner and a passive house builder.
I have good access to timber, but it takes a lot of time, cutting, extracting and storing every year. I have been using it as my primary heat source for years. When you consider the dust and dirt a fire creates and all the hassle it brings I am happy to eliminate that work load from my life and spend more time fishing.

From what I was told by those I spoke to, stoves are rarely ever lit because they over heat the living space and make it uncomfortable. You would be better off spending the money on photovoltaic panels instead of a stove with all the associated plumbing and chimney that will be rarely if ever used. It is also going to pull heat from your house when it not lit unless you somehow insulate the chimney and install a mechanical flue cut off device.
But an Irish home needs a fireplace as a focal point so I am still going to have a fireplace/cassette stove-like center piece in the room with a fake fire and electric fan heater built in. They look like the real thing but a fraction of the cost and if you need to warm your toes then switch it on for a few minutes.
In the event of the power going I will have a generator in the shed on a change over switch which will power the house.

galwaytt

Superdaddy wrote: »

I was all set to put a stove in my house until i spoke to a few people in the know. An A3 rated house owner and a passive house builder.
I have good access to timber, but it takes a lot of time, cutting, extracting and storing every year. I have been using it as my primary heat source for years. When you consider the dust and dirt a fire creates and all the hassle it brings I am happy to eliminate that work load from my life and spend more time fishing.

From what I was told by those I spoke to, stoves are rarely ever lit because they over heat the living space and make it uncomfortable. You would be better off spending the money on photovoltaic panels instead of a stove with all the associated plumbing and chimney that will be rarely if ever used. It is also going to pull heat from your house when it not lit unless you somehow insulate the chimney and install a mechanical flue cut off device.
But an Irish home needs a fireplace as a focal point so I am still going to have a fireplace/cassette stove-like center piece in the room with a fake fire and electric fan heater built in. They look like the real thing but a fraction of the cost and if you need to warm your toes then switch it on for a few minutes.
In the event of the power going I will have a generator in the shed on a change over switch which will power the house.

hallelujah !!

Mind you, putting in one an electric fire makes a hoop out of your BER.

In the real world though, it's a great idea. There is more to life than BER certs.