To zone UFH or not to zone?

heavydawson

I've been getting quotes from a variety of GSHP installers, and while I've nearly settled on one, I've got a quick question on UFH.

One of the suppliers doesn't zone the house, and the others do.
This supplier suggested that the constant on and off of a zoned set up would reduce the life-span of the system. There's probably some truth in that, but I'm just wondering what peoples opinion on the matter is?

The house is being properly insulated with a minimum on-paper spec of a 0.12u (save for the windows) all-round envelope with proper detailing at all critical points, and will be looking to achieve a very high standard of air-tightness.

I can PM details of the supplier if they'd like to know more about the specific GSHP system I'm talking about. Both the supplier and system have had excellent feedback here on boards

soundskin

If going for a GSHP (depending on it's controls, should be weather compensating) then you will need a certain amount of your UFH to be 'open zoned'(i.e. no stats), usually the living areas. Therefore whenever the GSHP comes on due to a drop in temperature outside then you will always have an open area of UFH that can take heat from the GSHP. If this area isn't large enough then it can lead to cycling of the GSHP and therefore reduce it's lifespan.

If you then have thermostats or zoned control in bedrooms etc then you can keep these rooms at lower (~17 degrees) temperatures to the living (~20 degrees).

Even if you don't have any zoned control on your UFH then you can always regulate the flow rates to your rooms at the UFH manifold, therefore giving control over the room temperature in those individual room. All rooms have varying amounts of heat loss depending on size, external walls, fireplace, orientation etc, the more heat loss you have, the higher the flow rate required to that room, the lower the heat loss, the less flow rate required.

Normally the heat pump controls will be far more intelligent than a simple thermo/chronostat. These stats should really only be used in area that you want cooler that what the GSHP will keep the house, or rooms that have a second heat source (besides UFH) like a stove or fireplace.

Hope that helps.

heavydawson

soundskin wrote: »

If going for a GSHP (depending on it's controls, should be weather compensating) then you will need a certain amount of your UFH to be 'open zoned'(i.e. no stats), usually the living areas. Therefore whenever the GSHP comes on due to a drop in temperature outside then you will always have an open area of UFH that can take heat from the GSHP. If this area isn't large enough then it can lead to cycling of the GSHP and therefore reduce it's lifespan.

If you then have thermostats or zoned control in bedrooms etc then you can keep these rooms at lower (~17 degrees) temperatures to the living (~20 degrees).

Even if you don't have any zoned control on your UFH then you can always regulate the flow rates to your rooms at the UFH manifold, therefore giving control over the room temperature in those individual room. All rooms have varying amounts of heat loss depending on size, external walls, fireplace, orientation etc, the more heat loss you have, the higher the flow rate required to that room, the lower the heat loss, the less flow rate required.

Normally the heat pump controls will be far more intelligent than a simple thermo/chronostat. These stats should really only be used in area that you want cooler that what the GSHP will keep the house, or rooms that have a second heat source (besides UFH) like a stove or fireplace.

Hope that helps.

it does help indeed. thanks soundskin

JD6910

heavydawson wrote: »

I've been getting quotes from a variety of GSHP installers, and while I've nearly settled on one, I've got a quick question on UFH.

One of the suppliers doesn't zone the house, and the others do.
This supplier suggested that the constant on and off of a zoned set up would reduce the life-span of the system. There's probably some truth in that, but I'm just wondering what peoples opinion on the matter is?

The house is being properly insulated with a minimum on-paper spec of a 0.12u (save for the windows) all-round envelope with proper detailing at all critical points, and will be looking to achieve a very high standard of air-tightness.

I can PM details of the supplier if they'd like to know more about the specific GSHP system I'm talking about. Both the supplier and system have had excellent feedback here on boards

please PM me the supplier and system.

heavydawson

JD6910 wrote: »

please PM me the supplier and system.

PM Sent

PeteHeat

soundskin wrote: »

Therefore whenever the GSHP comes on due to a drop in temperature outside then you will always have an open area of UFH that can take heat from the GSHP. If this area isn't large enough then it can lead to cycling of the GSHP and therefore reduce it's lifespan.

Sorry, the above does not make sense to me, why should any heat source be activated by anything other than a call for for heat from within the building?

I can understand the wisdom behind timed step back thermostats in every room especially for underfloor heating, however using expensive fuel when everyone is comfortable seems like a waste.

Is the heat pump not an appliance that should do what it is told instead of dictating to the owner?

.

JD6910

PeteHeat wrote: »

Sorry, the above does not make sense to me, why should any heat source be activated by anything other than a call for for heat from within the building?

I can understand the wisdom behind timed step back thermostats in every room especially for underfloor heating, however using expensive fuel when everyone is comfortable seems like a waste.

Is the heat pump not an appliance that should do what it is told instead of dictating to the owner?

.

peteheat - this is exactly my gripe as well. i cannot understand a system that decides by itself to come on a 3am in the morning (or indeed anytime) and boost the entire house just because the temp drops - we will be all under the duvet at 3am and the Heatpump coming on of its own accord is madness i think.

i think we should be in control and decide when the house/house occupants want heat. if you are busy cooking in the evenings and the kitchen is warm, why would you want a heat pump kicking in!!! if you are away from the house - why would you want the HP kicking in!!!

is it just me - but im not sure i agree with the constant temp theory

PeteHeat

JD6910 wrote: »

peteheat - this is exactly my gripe as well. i cannot understand a system that decides by itself to come on a 3am in the morning (or indeed anytime) and boost the entire house just because the temp drops - we will be all under the duvet at 3am and the Heatpump coming on of its own accord is madness i think.

i think we should be in control and decide when the house/house occupants want heat. if you are busy cooking in the evenings and the kitchen is warm, why would you want a heat pump kicking in!!! if you are away from the house - why would you want the HP kicking in!!!

is it just me - but im not sure i agree with the constant temp theory

I have no problem with weather compensating thermostats in fact they can be a very good source of control for flow temperatures, a bit like automatic control of the temperature setting on a standard boiler.

Ideal for the older house (Pre 2008) which tends to have much higher heat loss than the new houses many which are being built with insulation levels that make the current building regs look like old news.

Every room can have a timed step back thermostat which can be set at the temperature the customer likes, for example during the day it can drop 1 > 2 degrees in the bedrooms or similar at night in the living areas.

With UFH it is important for the customer to understand the system needs more time to recover any lost temperature than a radiator system with oil or gas flow temperatures in excess of 70c.

Perhaps the idea is to remove the control from the customer who may not understand the recovery times?

A lot of heat pumps were sold on the basis that they use off peak or night rate for electricity, it appears that some have dropped that idea and instead of using buffer tanks have opted to use electricity 24 / 7 even heating rooms that don't need it.

.

JD6910

PeteHeat wrote: »

I have no problem with weather compensating thermostats in fact they can be a very good source of control for flow temperatures, a bit like automatic control of the temperature setting on a standard boiler.

Ideal for the older house (Pre 2008) which tends to have much higher heat loss than the new houses many which are being built with insulation levels that make the current building regs look like old news.

Every room can have a timed step back thermostat which can be set at the temperature the customer likes, for example during the day it can drop 1 > 2 degrees in the bedrooms or similar at night in the living areas.

With UFH it is important for the customer to understand the system needs more time to recover any lost temperature than a radiator system with oil or gas flow temperatures in excess of 70c.

Perhaps the idea is to remove the control from the customer who may not understand the recovery times?

A lot of heat pumps were sold on the basis that they use off peak or night rate for electricity, it appears that some have dropped that idea and instead of using buffer tanks have opted to use electricity 24 / 7 even heating rooms that don't need it.

.

so peteheat would you agree with a RAD system off a big buffer tank which will have multiply fuel sources such as solar, stove with back boiler, and oil or gas??? the theory is that the solar will do the hard work for free, stove will contribute to the buffer tank in the evenings when it is on and finally the gas boiler kicks in as and when it is needed. MHRV is also used to distribute warm air from wet rooms to bedrooms. surely this sytem allows the home owner control over costs and allows you turn the heating on and off when you want!!!!

soundskin

JD6910 wrote: »

peteheat - this is exactly my gripe as well. i cannot understand a system that decides by itself to come on a 3am in the morning (or indeed anytime) and boost the entire house just because the temp drops - we will be all under the duvet at 3am and the Heatpump coming on of its own accord is madness i think.

i think we should be in control and decide when the house/house occupants want heat. if you are busy cooking in the evenings and the kitchen is warm, why would you want a heat pump kicking in!!! if you are away from the house - why would you want the HP kicking in!!!

is it just me - but im not sure i agree with the constant temp theory

The advantage of weather compensation over s-plan heating controls (timeclock & thermostat) is that is a predictive control for house temperature instead of a reactive control that will will get a standard heating controls.

Traditional heating system sequence of events:
1. Outside temperature drops
2. More heat is lost through the walls & windows
3. Rooms get colder - which is detected by the room thermostat
4. Thermostat 'tells' the boiler to fire/work harder (if timeclock allows)
5. Rooms get warmer again

In the above example, it isn’t until stage 4 that the boiler gets any ‘feedback’ and is able to respond to changing conditions.
The chances are that at this stage, the householder will be feeling the cold and will turn the thermostat up even further - wasting even more fuel.
If the outside temperature rises, the boiler will not respond until the rooms have become uncomfortably warm - so in addition to
adjusting thethermostat, there’ll probably be the temptation to open some windows, releasing more heat and wasting more energy

Weather Compensation Control
1. Outside temperature drops - which is detected by outdoor sensor
2. HP/Boiler will come on sending heat into house
3. Radiators get warmer to compensate for heat lost*
4. Room temperature is maintained

Therefore weather compensation is only looking to send in just the right amount of heat into the building, no more nor no less to keep it at a contant temperature. Various forms of heat pumps then will have temperature set backs built in that will allow greater use of night rate electricity.

WCC (weather compensation controls) will always be looking at the outside temperature (main factor in heating demand of a building) and calculate a desired flow temperature into the UFH/rads, this calculated flow temperature will increase in cold weather and decrease in warm.

The WCC will them compare the actual flow temperature in the rads/ufh (which reflects building temp) and compare it with the desired flow temperature (based on outdoor temp and homeowner setting) and run the heat pump if deemed necessary.

WWC is the only cost efficient way to control UFH.

JD6910

And all this wcc is still happening when I am at work or tucked up in bed!!!!!

I have no doubt the wcc works if u want a constant temp but we think we want old school like we were raised!!!! Turn on heat when cold and when you are at home. Turn off heat when leaving the house!!!!

We are of this opinion because we are putting serious effort and money into insulation and airtightness and think we won't need very much heat to have the place comfortable.

I think geo and air to water may be an ideal on all the time system if the tiger was still roaring but the Celtic tiger is dead and heating on 24/7/365 is madness!!!! Speed the money on insulation and reduce the need for constant temp heat!!!!!

BryanF

JD6910 wrote: »

And all this wcc is still happening when I am at work or tucked up in bed!!!!!

I have no doubt the wcc works if u want a constant temp but we think we want old school like we were raised!!!! Turn on heat when cold and when you are at home. Turn off heat when leaving the house!!!!

We are of this opinion because we are putting serious effort and money into insulation and airtightness and think we won't need very much heat to have the place comfortable.

I think geo and air to water may be an ideal on all the time system if the tiger was still roaring but the Celtic tiger is dead and heating on 24/7/365 is madness!!!! Speed the money on insulation and reduce the need for constant temp heat!!!!!

May I ask are you building? What air-tightness, thermal envolpe spec and KWHR/m2 are you expecting?

JD6910

All living spaces south facing with glazing.narrow plan design - passive principles. 200mm pumped cavity, 200mm in floor. No thermal bridges etc.... Trying to make it as low energy as possible. Aiming for full airtightness from a reputable company.

PeteHeat

soundskin wrote: »

The advantage of weather compensation over s-plan heating controls (timeclock & thermostat) is that is a predictive control for house temperature instead of a reactive control that will will get a standard heating controls.

Traditional heating system sequence of events:
1. Outside temperature drops
2. More heat is lost through the walls & windows
3. Rooms get colder - which is detected by the room thermostat
4. Thermostat 'tells' the boiler to fire/work harder (if timeclock allows)
5. Rooms get warmer again

In the above example, it isn’t until stage 4 that the boiler gets any ‘feedback’ and is able to respond to changing conditions.
The chances are that at this stage, the householder will be feeling the cold and will turn the thermostat up even further - wasting even more fuel.
If the outside temperature rises, the boiler will not respond until the rooms have become uncomfortably warm - so in addition to
adjusting thethermostat, there’ll probably be the temptation to open some windows, releasing more heat and wasting more energy

Weather Compensation Control
1. Outside temperature drops - which is detected by outdoor sensor
2. HP/Boiler will come on sending heat into house
3. Radiators get warmer to compensate for heat lost*
4. Room temperature is maintained

Therefore weather compensation is only looking to send in just the right amount of heat into the building, no more nor no less to keep it at a contant temperature. Various forms of heat pumps then will have temperature set backs built in that will allow greater use of night rate electricity.

WCC (weather compensation controls) will always be looking at the outside temperature (main factor in heating demand of a building) and calculate a desired flow temperature into the UFH/rads, this calculated flow temperature will increase in cold weather and decrease in warm.

The WCC will them compare the actual flow temperature in the rads/ufh (which reflects building temp) and compare it with the desired flow temperature (based on outdoor temp and homeowner setting) and run the heat pump if deemed necessary.

WWC is the only cost efficient way to control UFH.

All of the above makes sense I have WCC on my own boiler but it's wood pellet with flow temperatures ranging from 70 > 85c not a low temperature system as I don't have UFH.

That said I would still like to be control room temperatures, as you know each system must suit the occupants, for example there are four rooms in my house that need a constant 23 > 25c, the main living area is fine at 21 > 22c and bedrooms at 19c with step back to 16c during the day, so I need more control than most.
.

soundskin

JD6910 wrote: »

And all this wcc is still happening when I am at work or tucked up in bed!!!!!

I have no doubt the wcc works if u want a constant temp but we think we want old school like we were raised!!!! Turn on heat when cold and when you are at home. Turn off heat when leaving the house!!!!

We are of this opinion because we are putting serious effort and money into insulation and airtightness and think we won't need very much heat to have the place comfortable.

I think geo and air to water may be an ideal on all the time system if the tiger was still roaring but the Celtic tiger is dead and heating on 24/7/365 is madness!!!! Speed the money on insulation and reduce the need for constant temp heat!!!!!

My point is weather comp is best suited for UFH. If you wish to be turning the heat on and off when best suits you the rads is what you want, heated by whatever means suits.

I agree that money spent on insulation is never wasted, it's saving you money in the long run.

Condenser

PeteHeat wrote: »

Sorry, the above does not make sense to me, why should any heat source be activated by anything other than a call for for heat from within the building?

I can understand the wisdom behind timed step back thermostats in every room especially for underfloor heating, however using expensive fuel when everyone is comfortable seems like a waste.

Is the heat pump not an appliance that should do what it is told instead of dictating to the owner?

.

It is only operated by the heat within the building but the heat required is always dependant on the heatlosses of the house. The higher the heat loss the more energy required in order to remain in stasis. This is what weather compensation does and does very well. You set the temp and the heatpump decides how much energy the house needs depending on outside temp (or in other words how fast you're losing it)

Saying heating rooms that don't require heat is a waste of money is a basic misunderstanding of thermal dynamics. You do not decide how energy moves within a building structure, temperature differentials do. You may not want to heat them but they cost you energy anyway by drawing heat from warmer rooms.

PeteHeat

Condenser wrote: »

It is only operated by the heat within the building but the heat required is always dependant on the heatlosses of the house. The higher the heat loss the more energy required in order to remain in stasis. This is what weather compensation does and does very well. You set the temp and the heatpump decides how much energy the house needs depending on outside temp (or in other words how fast you're losing it)

Saying heating rooms that don't require heat is a waste of money is a basic misunderstanding of thermal dynamics. You do not decide how energy moves within a building structure, temperature differentials do. You may not want to heat them but they cost you energy anyway by drawing heat from warmer rooms.

I have a good understanding of thermodynamics, I also understand that every person is different, using my own home as an example I have one person who needs room temperature at no less 23c preferably as high as 25c.

I feel my own bedroom is too warm at 19c and as far as heat loss goes I always have a window open regardless of the outside temperature and that goes back a very long time well before the person who needs 25c arrived in my home.

When dealing with a persons home we are usually dealing with a number of individuals, each has their own idea as to what the ideal temperature of their environment is, so we do our best to give them what they are comfortable with.

There is a transfer of heat from the warmer rooms to the cooler rooms, by having temperature controls in each room no heat is required in the rooms with the lower temperature setting, the room with the person who needs the high temperatures will require the heat lost to the cooler rooms to be replaced, the thermostat in that room will call for heat to replace the heat lost to the cooler rooms (simple thermodynamics).

We are not just dealing with the building we are trying to make peoples homes comfortable for every person who lives there.

We are also supposed to do that in the most energy efficient way possible, I believe the people should be able to have control over the environment they live in and to that they need temperature controls to prevent their environment being either too warm or too cold.
.

JD6910

peteheat - do you reckon the high efficency rads will work with the low temperature buffer system???
or will the system be high temperature?? i would imagine the solar will be low temp, stove high temp and the gas ????

air

The constant temp requirement is simply down to the response time of UFH.

It's fine saying you don't need heat at 3am when you're in bed or when you're out, but UFH has a large thermal mass of screed to heat up before this can start heating the air in the house.
This means that if you want your room to be up to temp at 8am you very well may need to start heating the screed at 3am (exact time dependent on numerous factors).

Weather based predictive controls make a lot of sense in conjunction with UFH for this reason, it helps to ensure that the house is up to temp when you want it - despite the slow response of UFH.

There will be increased looses with UFH during these long ramp up times, however I feel these are far outweighed by the positive benefits of UFH - especially in a well insulated house.

JD6910

air wrote: »

The constant temp requirement is simply down to the response time of UFH.

It's fine saying you don't need heat at 3am when you're in bed or when you're out, but UFH has a large thermal mass of screed to heat up before this can start heating the air in the house.
This means that if you want your room to be up to temp at 8am you very well may need to start heating the screed at 3am (exact time dependent on numerous factors).

Weather based predictive controls make a lot of sense in conjunction with UFH for this reason, it helps to ensure that the house is up to temp when you want it - despite the slow response of UFH.

There will be increased looses with UFH during these long ramp up times, however I feel these are far outweighed by the positive benefits of UFH - especially in a well insulated house.

air - i am planning on high efficiency rads throughout - NOT UFH. any thoughts on the solar, stove, gas boiler with a buffer tank system???

air

UFH is much better suited to a buffer tank system as it can make use of much lower temperature water.

Rads and UFH are both primarily convective heating systems, their power output is dictated by their surface area and the temp difference between their surface and the air.
The UFH has much greater surface area so can output far more power given the same circulation water temp.

If for example on an Autumn day, your solar manages to raise your buffer tank to 35 degrees during the day. You come home and want heat.
The rads would take forever to heat the house as the temperature difference is too low between the rads and the air in the house.
The UFH on the other hand has much greater surface area so can use this low temp water.

The same thing will happen every time you do a burn on the stove and heat the store fully.
The rads will perform well until the water in the store gets down to 45 degrees perhaps.
However the UFH will continue outputting useful heating power from the store water until it drops far lower - perhaps as low as 25 degrees.
So you'll get more useful heating for the house out of each stove burn with the UFH.

Regardless of what you use keep the buffer tank within the envelope of the house if you can so you get the benefit of any standing losses from it.

Finally "high efficiency" rads is a BS term IMO, every RAD ever manufactured is 100% efficient. Maybe they mean low volume for quick response (which will improve overall efficiency a negligible amount) but generally it's just marketing speak.

JD6910

air wrote: »

UFH is much better suited to a buffer tank system as it can make use of much lower temperature water.

Rads and UFH are both primarily convective heating systems, their power output is dictated by their surface area and the temp difference between their surface and the air.
The UFH has much greater surface area so can output far more power given the same circulation water temp.

If for example on an Autumn day, your solar manages to raise your buffer tank to 35 degrees during the day. You come home and want heat.
The rads would take forever to heat the house as the temperature difference is too low between the rads and the air in the house.
The UFH on the other hand has much greater surface area so can use this low temp water.

The same thing will happen every time you do a burn on the stove and heat the store fully.
The rads will perform well until the water in the store gets down to 45 degrees perhaps.
However the UFH will continue outputting useful heating power from the store water until it drops far lower - perhaps as low as 25 degrees.
So you'll get more useful heating for the house out of each stove burn with the UFH.

Regardless of what you use keep the buffer tank within the envelope of the house if you can so you get the benefit of any standing losses from it.

Finally "high efficiency" rads is a BS term IMO, every RAD ever manufactured is 100% efficient. Maybe they mean low volume for quick response (which will improve overall efficiency a negligible amount) but generally it's just marketing speak.

i think the plan is for the gas to kick in and heat the buffer tank water the last few degrees needed before sending it out to the rads?????

if we go with UFH we are going back to the constant temp theory and we will have a slow responding UFH system. the rads can be turned on and get a pretty much immediate response. during the summer months our heating will be OFF and the solar gain into the living areas, solar panels for hot water and MHRV system distribute hot air from wet rooms to bedrooms will do the requirments. IF needed, the stove could always be lit and get hot water from that too and/or the gas boiler on rads could also be turned on to give the place a boost!!! what you reckon guys????:rolleyes:

we are working on the theory that we only need heat from September to April max. the rest of the year the solar panels and solar gain and stove the odd evening will do the business. the gas boiler is always available to give us a boost if needed.

air

Yeah, that's fine using the gas to kick in, but it wouldn't need to kick in with UFH as there would already be usable heat in the store.

The whole rads vs UFH setup is as much down to lifestyle and personal preference as anything else and you need to weigh up the pros and cons for yourself and make a decision, which it sounds like you have. There's no right or wrong system.
Personally I like the idea of contant temp and UFH from a comfort point of view. I think a lot of the desire for fast response is based on people's experience of old houses that would be freezing upon coming home after a day out, not really relevant to life in a modern structure.

I would recommend though if you want the quick response approach, then don't bother linking the stove to the store and just link the stove's boiler directly to the heating system.
You won't be able to make use of low temp water in the store without UFH so not much point in having it at all tbh.

JD6910

air wrote: »

Yeah, that's fine using the gas to kick in, but it wouldn't need to kick in with UFH as there would already be usable heat in the store.

The whole rads vs UFH setup is as much down to lifestyle and personal preference as anything else and you need to weigh up the pros and cons for yourself and make a decision, which it sounds like you have. There's no right or wrong system.
Personally I like the idea of contant temp and UFH from a comfort point of view. I think a lot of the desire for fast response is based on people's experience of old houses that would be freezing upon coming home after a day out, not really relevant to life in a modern structure.

I would recommend though if you want the quick response approach, then don't bother linking the stove to the store and just link the stove's boiler directly to the heating system.
You won't be able to make use of low temp water in the store without UFH so not much point in having it at all tbh.

air - we are trying to avoid the constant temperature model therefore aiming for RADS - so therefore the gas will need to kick in when we want heat to deliver high temp to the RADS???

you are dead right - no new house will be freezing especially with the insualtion and airtightness levels!!!

if we dont link the stove to the buffer then the rads will be heated by the stove whether we want it or not.. i think???? the buffer allows us store the energy until we want it and we can decide if we want it for heat or hot water or perhaps a bath!!!! the super insualted buffer will keep the water for a day or two im being told??

the low temp water in the buffer will be raised by the stove and/or the gas via the triple coil... is this theory correct?

air

JD6910 wrote: »

air - we are trying to avoid the constant temperature model therefore aiming for RADS - so therefore the gas will need to kick in when we want heat to deliver high temp to the RADS???

That's your own decision ultimately, and will work

JD6910 wrote: »

if we dont link the stove to the buffer then the rads will be heated by the stove whether we want it or not.. i think????

Yes, but it will also heat the room that the stove is in.
I would have though you would want heat in the rads most of the time you want heat from the stove.

JD6910 wrote: »

the buffer allows us store the energy until we want it and we can decide if we want it for heat or hot water or perhaps a bath!!!! the super insulated buffer will keep the water for a day or two im being told??

Yes but a batch boiler would make a lot more sense if you want to burn and store energy. The buffer will certainly stay warm a while but will still have a reasonably large standing loss. A stove is going to take forever to heat a large buffer tank (typically 1000L +)

JD6910 wrote: »

the low temp water in the buffer will be raised by the stove and/or the gas via the triple coil... is this theory correct?

Yes, but there would possibly be useable energy in the buffer if you were using UFH.

You're getting a bit carried away with the technicalities, you need to question what you want a buffer for?

A buffer is normally used where you have a source of heat such as a gasification boiler that is used in a batch system and has a higher output than your ongoing heat load. It makes sense to burn, store the energy in the buffer and then release it from the buffer as needed.
UFH is suited to this model as it allows you to extract a large percentage of the energy from the buffer (eg when the water in the buffer is between 30 and 50 degrees).
You:
1. Do not intend to install underfloor heating
2. Will not have a heating system suited to the buffer, the stove will have a small output.

In my opinion you should install a buffer big enough for your hot water demands only - probably 300L max for an average home.
Anything larger and you are wasting your time, space in your house and your money.

To make it clear, IMHO:
Buffer + RADS makes no sense
Big Buffer + room stove makes no sense

My suggestion for you:
Triple coil heating cylinder sized for DHW needs - stove coil, solar coil, gas coil.
Gas / Oil (or whatever) boiler and stove joined using a manifold to CH system.
QED.
Forget about the buffer, it's doing nothing for you!!!

JD6910

air - because we plan to install circa 90 tubes of solar - we need the big buffer tank i think???
the large amount of solar is so that we try achieve and capture as much "free" solar energy as possible (thats the hard work done getting the water from cold to luke warm). the stove will be then only topping up this semi-warm solar water so we are not trying to heat 1000L of cold water with the stove.

i think the buffer is to act a thermal store or battery. the battery is then available for a day or two to do all the showers, baths, hot water needs and heating. we cant gaurantee the solar from day to day so by using a big buffer we capture as much as we can - while we can - make hay while the sun shines!!!

dont get me wrong - i would love to eleminate the buffer as it is a pricey item and i would love to install the minimum amount of solar - but i am going on what i am being told????? we obviously want to install the bare minimum system that will do the job!!! really appreciate your thoughts - keep em coming!!!!!!!!!

air

In my opinion you are wasting your time and money installing the additional solar tubes and buffer tank.

Install a domestic hot water tank / thermal store big enough for your domestic hot water needs and enough tubes to match (probably 40 max).

This "free" energy that you're looking to capture energy is not there 9 out of 10 days that you will want it. Buying the equipment to capture it that one day out of ten will cost you an arm and a leg - a complete and total waste of money.

JD6910

air wrote: »

In my opinion you are wasting your time and money installing the additional solar tubes and buffer tank.

Install a domestic hot water tank / thermal store big enough for your domestic hot water needs and enough tubes to match (probably 40 max).

This "free" energy that you're looking to capture energy is not there 9 out of 10 days that you will want it. Buying the equipment to capture it that one day out of ten will cost you an arm and a leg - a complete and total waste of money.

so you reckon - put in a "standard" gas central heating system with the normal amount of solar doing the hot water requirements and also connect the stove DIRECTLY to the heating system??????

lot to be said for this - simple, cheap and tried and tested!!!!!!!

PeteHeat

If you install a high temperature radiator system you need a flow temperature of minimum 70c, the return temperature of a correctly balanced system will be 50 > 55c.

If your proposed solar works to manufacturers best figures your buffer will reach about 60c on a good day, but there are few very good solar days especially between autumn and spring.

If we take the large buffer combine solar and your stove you may achieve a stored heat of 45 > 50c.

So even on the best day your gas boiler has to fire to satisfy one zone because your proposed rads do not suit the low temperature you have stored.

If you use a low temperature system which must not have a timer fitted the solar, stove and buffer will provide some value.

A low temperature system will cost more, the proper controls will cost more, my biggest concern reading your posts is no timer might cause you health problems.

Your home can be warm and comfortable to walk into anytime if and only if you allow the system (any system) to work properly, there is no point fitting all the bells and whistles designed for a low temperature system into a heating system that is designed for high temperatures.

What you have described to Air is not a buffer but an accumulator, a different beast, looks like a buffer but it's not a buffer and a really good one costs around €5,000.00, a middle of the road unit costs around €3,000
.

air

JD6910 wrote: »

so you reckon - put in a "standard" gas central heating system with the normal amount of solar doing the hot water requirements and also connect the stove DIRECTLY to the heating system??????

lot to be said for this - simple, cheap and tried and tested!!!!!!!

Exactly. There was never anything much wrong with traditional heating systems apart from the fact that the houses they were installed in lost heat from all angles.
Your stove is unlikely to have enough power to heat all the radiators so I would link it to one zone only. Get somebody to calculate the size of this zone based on your stoves rated output.

heavydawson

JD6910 wrote: »

All living spaces south facing with glazing.narrow plan design - passive principles. 200mm pumped cavity, 200mm in floor. No thermal bridges etc.... Trying to make it as low energy as possible. Aiming for full airtightness from a reputable company.

Will you PM me the name of the airtightness company?

sheff the ref

A great topic to be honest.

I had half made up my mind to go for a Ground Source Heatpump with Underfloor heating, primarily to avoid spending money on oil but a lot of points raised here have put me thinking.

Obviously regardless of the heat source, the concept of underfloor heating is basically maintaining the temperature in a slab of concrete which radiates upwards and heats the house as demanded by the thermostats. That is fair enough and will maintain a constant even level of heat throughout the house.

However a valid point raised is that modern houses with top spec insulation and air tightness will no longer be iceboxes like some of the older houses. Therefore is there really a need to provide a constant even level of heat 24/7. Will a shot of heat through rads at certain intervals do the same job? A matter of personal choice I guess, but rads will not really work effectively with a heatpump so its back to Oil or perhaps pellets which are also going up in price.

Decisions Decisions Decisions

PeteHeat

sheff the ref wrote: »

A great topic to be honest.

I had half made up my mind to go for a Ground Source Heatpump with Underfloor heating, primarily to avoid spending money on oil but a lot of points raised here have put me thinking.

Obviously regardless of the heat source, the concept of underfloor heating is basically maintaining the temperature in a slab of concrete which radiates upwards and heats the house as demanded by the thermostats. That is fair enough and will maintain a constant even level of heat throughout the house.

However a valid point raised is that modern houses with top spec insulation and air tightness will no longer be iceboxes like some of the older houses. Therefore is there really a need to provide a constant even level of heat 24/7. Will a shot of heat through rads at certain intervals do the same job? A matter of personal choice I guess, but rads will not really work effectively with a heatpump so its back to Oil or perhaps pellets which are also going up in price.

Decisions Decisions Decisions

Hi,

You may have read the posts that touch on thermodynamics?

The heat in a very well insulated house will eventually find its way out and the temperature will match the colder temperature outside so it is important to maintain the temperature of the concrete radiator (UFH).

Our electricity prices track the prices of fossil fuels due to the mix of fuel used in our generators similar to the way pellet appears to track oil it doesn't really the problem there is the delivery trucks use diesel.

As you have seen some prefer to allow weather compensating controls to manage the system whereas I prefer step back thermostats inside the house, what we all appear to agree on is no timers on boilers or heat pumps where UFH is concerned.
.

Condenser

PeteHeat wrote: »

As you have seen some prefer to allow weather compensating controls to manage the system whereas I prefer step back thermostats inside the house, what we all appear to agree on is no timers on boilers or heat pumps where UFH is concerned.
.

Weather compensated controllers also have set backs, set ups and every other control your top end stat could possibly do, plus it monitors the in house temp. In a good system its miles ahead of any stat on the market for comfort and control.

sheff the ref

PeteHeat wrote: »

Hi,

You may have read the posts that touch on thermodynamics?

The heat in a very well insulated house will eventually find its way out and the temperature will match the colder temperature outside so it is important to maintain the temperature of the concrete radiator (UFH).

Our electricity prices track the prices of fossil fuels due to the mix of fuel used in our generators similar to the way pellet appears to track oil it doesn't really the problem there is the delivery trucks use diesel.

As you have seen some prefer to allow weather compensating controls to manage the system whereas I prefer step back thermostats inside the house, what we all appear to agree on is no timers on boilers or heat pumps where UFH is concerned.
.

There are a lot of permutations for heating and all forms have their advantages and disadvantages. I am still unsure as to what is the cheapest form of heat though. One thing I am sure of is that there is no such thing as free heat.

JD6910

ya no such thing as free heat and therefore surely a system that you can turn off and on and you want is the bests our new super insulated houses.

i think the geo systems are celtic tiger systems when we all had money to meet the bills and tell the buddies about it down the pub!!!!!

sheff the ref

You could be right. A super insulated house will keep the heat in longer, therefore an injection of heat every so often will remain in the house for longer. Dare I say that oil and rads or wood chip and rads could potentially be the cheapest form of heat for a bungalow less than 2000 square feet.

JD6910 wrote: »

ya no such thing as free heat and therefore surely a system that you can turn off and on and you want is the bests our new super insulated houses.

i think the geo systems are celtic tiger systems when we all had money to meet the bills and tell the buddies about it down the pub!!!!!

PeteHeat

JD6910 wrote: »

ya no such thing as free heat and therefore surely a system that you can turn off and on and you want is the bests our new super insulated houses.

i think the geo systems are celtic tiger systems when we all had money to meet the bills and tell the buddies about it down the pub!!!!!

Sorry I can't agree, if ever heat pumps had a chance of working properly and achieving everything the manufacturer, supplier, installer and home owner hoped for its today not five > ten years ago.

While I don't advertise it heat pumps are part of my business, so why not advertise them?

In the past the biggest problem I had with heat pumps were the customers who appeared to listen but only heard what suited them, I gave up counting the number of sales I let go from 2004 to 2009 because the houses were insulated to 1990's standards.

The final nail in the coffin as far as I was concerned was delivering a system to a customer who had left out a large part of the insulation essentially making the heat pump he had ordered and paid for nothing more than a potential nightmare for both of us.

When I asked why the insulation was left out his reply was he saved €6,500.00 by leaving it out, as I was leaving (with the heat pump) I had to pass by the lads fitting his new really beautiful automated gates that he had spent over €10,000 on, so where were the Celtic Tiger priorities of many?

Today the message about insulation and heating controls appears to have reached most consumers, sadly it took heating oil touching one Euro per litre to deliver that message, a lot of Irish suppliers and installers gave up and moved on some to different technologies others to different countries.

Consumers are looking for the best / most cost efficient way to heat their new super insulated homes, there are obvious suppliers / installers on this this thread we all appear to agree on one thing, the best way to heat those new homes is using low temperature heating systems.

Why? because the houses are now being built to a standard that does not need high temperature systems.

You still have the options of every heating technology, fossil fuels, wood (in its many forms) solar assisted, heat pumps (geo & air) the big difference between today and the Celtic Tiger (pub talking) is you can choose any or a combination of all and the system will work if you get the basics right.
.

JD6910

ya we all agree insulation is the key, however it is not cheap therefore we have to ask the question - if i go insane with insulation and future proof the house surely we don't need the constant temp all day everyday. we all live busy lives and even when we are in the house we are running around - therefore surly a stove and standard heating system in our super insulated airtight house is adequate.

i have no doubt the heat pump will work as it should in the super insulated house but do we need the constant temp in the same houses!!!!! also because of the capital cost of insulation surely that combined with high heat pump capital costs - something has to give!!!!

also i understand that the life expectancy of a heat pump is circa 15 years - what happens then??? new heat pump?? i suppose at that stage the technology will have changed and the reality is the homeowner will upgrade to the newer model to maximise efficiency etc...?? a heat pump is circa 10,000 and after 15 years you typically have to replace it therefore it "depreciates" by circa 650 a year - 650 would buy close to a fill of oil or gas!!!!!!!!!!! thats a nice start in keeping your super insulated home warm during the heating season cos you wont need heat over the summer months in the airtight super insulated house.

PeteHeat

JD6910 wrote: »

ya we all agree insulation is the key, however it is not cheap therefore we have to ask the question - if i go insane with insulation and future proof the house surely we don't need the constant temp all day everyday. we all live busy lives and even when we are in the house we are running around - therefore surly a stove and standard heating system in our super insulated airtight house is adequate.

i have no doubt the heat pump will work as it should in the super insulated house but do we need the constant temp in the same houses!!!!! also because of the capital cost of insulation surely that combined with high heat pump capital costs - something has to give!!!!

also i understand that the life expectancy of a heat pump is circa 15 years - what happens then??? new heat pump?? i suppose at that stage the technology will have changed and the reality is the homeowner will upgrade to the newer model to maximise efficiency etc...?? a heat pump is circa 10,000 and after 15 years you typically have to replace it therefore it "depreciates" by circa 650 a year - 650 would buy close to a fill of oil or gas!!!!!!!!!!! thats a nice start in keeping your super insulated home warm during the heating season cos you wont need heat over the summer months in the airtight super insulated house.

Insulation is a one off expense, think of it as the foundation you build from, also probably the one item in every house that has the fastest pay back over any other component.

There are heat pumps in use for over 20 years without any major maintenance, very few if any gas / oil boilers can claim to have that working life.

Maybe it's an age thing but I fail to see the point in working hard all day (sometimes well into the night) and coming home to a cold house.

Leaving the personal preference aside it is easier, quicker and cheaper to bring the temperature back up 2 > 3 c than 5c or more.

You appear to have missed this;

"You still have the options of every heating technology, fossil fuels, wood (in its many forms) solar assisted, heat pumps (geo & air) the big difference between today and the Celtic Tiger (pub talking) is you can choose any or a combination of all and the system will work if you get the basics right."

Nothing stops you using oil, gas, wood gasifier, wood pellet, wood chip, solar efficiently all into a buffer if you can use all of the stored energy, the way to do that is use a low temperature heating system.
.

JD6910

can the new high efficiency rads be used for a low temp system???

Ok so the heat pump will last 20 years -that 500 a year!!! What happens after it's life span - refurb it or replace it???? The big differ is an oil or gas boiler is 2K!!!!! That's an easy item to replace every 15 years.

My point is because we are building such insulated houses are the heat pump heating systems required within those homes?

I wonder will the rads be ok with a low temp system??????????

PeteHeat

The radiators should be designed for low temperatures, that way you can a buffer at 80c and by using the proper controls you can reduce the flow to 40c.

A few examples:

Here


Here

Here
.

air

Those look really cool Pete, surely quite expensive though?

Condenser

JD6910 wrote: »

can the new high efficiency rads be used for a low temp system???

Ok so the heat pump will last 20 years -that 500 a year!!! What happens after it's life span - refurb it or replace it???? The big differ is an oil or gas boiler is 2K!!!!! That's an easy item to replace every 15 years.

My point is because we are building such insulated houses are the heat pump heating systems required within those homes?

I wonder will the rads be ok with a low temp system??????????

A HP would not cost the same price to replace. Firstly you may get away with only replacing the compressor and drier and doing an oil acidity test. About €1000-1500 would cover this.
In the case of replacing the entire heat pump, you would not be replacing the collector, pipework, divertor valves, expansion vessels, labour involved in initial installation etc. All of this makes up a significant cost in the installation of a heat pump in a new build. So you're depreciation figures are way off.
Jaga rads are the best out there for running at low temp but I would not use rads with a heat pump in a new build. Heat pumps are designed for long periods of running and long periods of downtime. The intermittent requirement for heat from rads do not lend themselves to that fact and only a huge buffer tank would overcome this fact. Use UFH while you have the option. You can use setbacks for when you're not there to let the house cool away slightly and it will take very little time to heat back up just before you arrive back.

Do-more

I'm following a similar discussion on another board about zoning etc. Someone in that discussion says that Honeywell produced research which suggests a 15% saving in running the heating "always on" rather than "on, off" but they haven't provided a link to the study, but you could have a search for it.

I live in Sweden which has a long history of well insulated, well heated houses. Regardless of the heat source used, be it oil (very few left) wood or heat pump or whether they have rads or ufh everyone runs their heating "always on". Swedes are not known for wasting money.

The "on, off" method is purely a way to heat badly insulated houses where the heat losses mean that much of what is spent on heating them ia wasted anyway.

Condenser

Do-more wrote: »

I'm following a similar discussion on another board about zoning etc. Someone in that discussion says that Honeywell produced research which suggests a 15% saving in running the heating "always on" rather than "on, off" but they haven't provided a link to the study, but you could have a search for it.

I live in Sweden which has a long history of well insulated, well heated houses. Regardless of the heat source used, be it oil (very few left) wood or heat pump or whether they have rads or ufh everyone runs their heating "always on". Swedes are not known for wasting money.

The "on, off" method is purely a way to heat badly insulated houses where the heat losses mean that much of what is spent on heating them ia wasted anyway.

Exactly, it takes alot of energy to repeatedly heat the building fabric. Consistent heat, with setback periods if desired and all areas treated equally is by far the most efficient.

JD6910

efficient ...... but at what cost(capitial cost, on-going cost per month and ultimately replace or upgrade cost after the life expectancy of 15 years) and . the point still remains why would you want the house heating kicking in while you are at work.... and yes i know because the house will be warm when u get home - you could still set the heating for 4.30pm for an hour before you return home!!!!!!

air

JD, you've asked questions in this and several other threads over the past few days and you've gotten a lot of very good advice. However you either seem to have not understood any of it or don't want to listen to it so I don't really know why you asked in the first place.
The reason it's no good turning on the heating an hour before you come home is that fast response systems don't make much sense in modern low energy homes.
Half the benefit of a low energy home is that the internal thermal mass never cools down much which makes for a lovely environment. Walls and floors aren't cold to the touch and radiate heat back to you.

Sure, you could install an over sized boiler and high output rads and then blast the house for an hour before coming home. However the internal walls and floors will still be cold (they will take almost as long to heat up as a "normal home" as the thermal mass is going to be similar). On top of that, when you are home for longer periods of time, your over sized boiler is going to be constantly cutting in and out for short periods, making it inefficient and reducing the lifespan of itself and all associated components.

With the greatest of respect, I don't think you have a great grasp of the whole area and I would advise you to take some qualified independent advice. Go with whatever they advise as it is highly likely to perform better than any scheme you are likely to devise yourself.

PeteHeat

air wrote: »

Those look really cool Pete, surely quite expensive though?

Sorry for the delay replying, I don't know the prices today they were expensive a few years ago when I priced them.

Personally I would go with UFH if building new, in fact I will be building new in the next 24 months and I will be using UFH.
.

fclauson

soundskin wrote: »

The advantage of weather compensation over s-plan heating controls (timeclock & thermostat) is that is a predictive control for house temperature instead of a reactive control that will will get a standard heating controls.

Traditional heating system sequence of events:
1. Outside temperature drops
2. More heat is lost through the walls & windows
3. Rooms get colder - which is detected by the room thermostat
4. Thermostat 'tells' the boiler to fire/work harder (if timeclock allows)
5. Rooms get warmer again

In the above example, it isn’t until stage 4 that the boiler gets any ‘feedback’ and is able to respond to changing conditions.
The chances are that at this stage, the householder will be feeling the cold and will turn the thermostat up even further - wasting even more fuel.
If the outside temperature rises, the boiler will not respond until the rooms have become uncomfortably warm - so in addition to
adjusting thethermostat, there’ll probably be the temptation to open some windows, releasing more heat and wasting more energy

Weather Compensation Control
1. Outside temperature drops - which is detected by outdoor sensor
2. HP/Boiler will come on sending heat into house
3. Radiators get warmer to compensate for heat lost*
4. Room temperature is maintained

Therefore weather compensation is only looking to send in just the right amount of heat into the building, no more nor no less to keep it at a contant temperature. Various forms of heat pumps then will have temperature set backs built in that will allow greater use of night rate electricity.

WCC (weather compensation controls) will always be looking at the outside temperature (main factor in heating demand of a building) and calculate a desired flow temperature into the UFH/rads, this calculated flow temperature will increase in cold weather and decrease in warm.

The WCC will them compare the actual flow temperature in the rads/ufh (which reflects building temp) and compare it with the desired flow temperature (based on outdoor temp and homeowner setting) and run the heat pump if deemed necessary.

WWC is the only cost efficient way to control UFH.

One of the clearest descriptions I have ever seen

You will see other posts of mine where I thought Oil or gas plus solar thermal would be the best - but if you do the maths/return on investment etc then a HP wins every time.

JD6910

fclauson wrote: »

One of the clearest descriptions I have ever seen

You will see other posts of mine where I thought Oil or gas plus solar thermal would be the best - but if you do the maths/return on investment etc then a HP wins every time.

is this based on both systems being ON all the time and maintaining a constant temp??