Home Heating Help

Squeaksoutloud

Hi Folks,

We are currently preparing our tender specification and drawings for a new build 2,900 sq. foot two story house. The house has been well designed for solar gain and we will be aiming for high levels of insulation and airtightness.

But we still need to get a heating system installed and this is where the confusion hits! Our preference is for underfloor heating so we are leaning towards an air to water heat pump.

Our architect got a reputable renewable engineering company to carry out some calcs and they are proposing the following system:

• Solar Panels combined with the Heat Recovery Ventilation to provide ventilation and a heating source during mildish weather. (Solar panels will also be used to heat water and possibly even for space heating).
• Air to Water heat pump as the main heating source for the house.

I am quite happy with the above system although we also intend installing a log burning stove in our sitting room and would love to integrate this into our heating system as a back up system. Basically in really cold weather I am reading that the heat pump efficiency goes down and costs go up so the stove might be a useful boost to have in the colder weather! Also if there was a power cut at least the log stove can be used as a back up to the heat pump.

Someone has told me that heat pumps don’t like unregulated heat sources and that you’re getting into a complicated plumbing system, and that the benefit won’t be worth it. Anyone have any advice to offer on the matter? Is a thermal store suitable in this case? Anyway basically wondering if I am barking up the wrong tree or if it is a suitable system? Also I wonder would a back boiler stove really be compatible with an underfloor heating system?

Someone else is telling me not to bother with the air-water heat pump as we are less than a mile from the sea and this will corrode the equipment. Is this common?

Any help appreciated!

feckincrazy

Sorry chief i know very little about renewable forms of energy. But if the resourse is there i dont see why i would not use either solar panels or heat pumps. Just look into the heat pumps there are different methods.
1 methods is deep borehole where they go down a depth in a straight line. The other method is where topsoil is excavated to a level and a pipe is layed in a patern at a depth below the soil. Looking at under flooring heating it wudnt be my first choice. I know trad rads are big amd square looking. I think they produce a more instant heat than under floor heating. With under floor heating is a very exspensive process laying pipe and tracks different floor screeds as well. Im a QS by trade so trad rads be a lot cheaper in the long run i feel as well. Anyway buddy enough of drunken talk!

muffler

Moved to RE forum

BryanF

Squeaksoutloud wrote: »

Hi Folks,

We are currently preparing our tender specification and drawings for a new build 2,900 sq. foot two story house. The house has been well designed for solar gain and we will be aiming for high levels of insulation and airtightness.

But we still need to get a heating system installed and this is where the confusion hits! Our preference is for underfloor heating so we are leaning towards an air to water heat pump.

Our architect got a reputable renewable engineering company to carry out some calcs and they are proposing the following system:

• Solar Panels combined with the Heat Recovery Ventilation to provide ventilation and a heating source during mildish weather. (Solar panels will also be used to heat water and possibly even for space heating).
• Air to Water heat pump as the main heating source for the house.

I am quite happy with the above system although we also intend installing a log burning stove in our sitting room and would love to integrate this into our heating system as a back up system. Basically in really cold weather I am reading that the heat pump efficiency goes down and costs go up so the stove might be a useful boost to have in the colder weather! Also if there was a power cut at least the log stove can be used as a back up to the heat pump.
Someone has told me that heat pumps don’t like unregulated heat sources and that you’re getting into a complicated plumbing system, and that the benefit won’t be worth it.

1. Anyone have any advice to offer on the matter?
2. Is a thermal store suitable in this case?
3. Anyway basically wondering if I am barking up the wrong tree or if it is a suitable system?
4. Also I wonder would a back boiler stove really be compatible with an underfloor heating system?
5. Someone else is telling me not to bother with the air-water heat pump as we are less than a mile from the sea and this will corrode the equipment. Is this common?

Any help appreciated!

you cant answer this without more questions:) for a start whats your expected kwh/m2 / expected heat load

1. well does seem like you should be asking this guy that you've paid:)
2. thermal stores are a really interesting concept but you want to employ the best of passive levels of building fabric and the best of heating eng's to ensure it will work...
3. i guess your main worry is the AtW heat pump, as the solar and MVHR are a good investment assuming you get near passive levels of thermal bridging,insulation and air-tightness
4. once you have a heat dump i cant ever see a problem with a back boiler stove.. as you said its the back up if your heat system fails.. I do often wonder why people dont go that step further with building fabric, layout and orientation and just have the stove with the MVHR and nothing else.. save on the UFH and spend on air-tightness, windows and insulation...
5. that's a good question about the unit corrosion, maybe ask the supplier for a written parts guarantee that outlines your particular location issues and you could insist on performance energy monitoring of the unit...:Dsome chance.. I'm against heat pumps as I dont belive there COP is good enough and as they are a relatively straight forward bit of kit they could be installed in say 20 years when there is more renewable electrical energy available. I presume you are rural so I would investigate a log gasification boiler...

Squeaksoutloud

Thanks for the responses lads. Been busy and have only managed browsing boards on the mobile for the last week so first chance to get a response in.

1. As for advice on the stove thing and the overall heating system we have got 2 quotes from Renewable energy designers/suppliers so obviously they are giving me advice on their system. Which is pretty much the system I envisaged myself which is Air source heat pump, HRV and solar panels for DHW. I am guessing the heat pump will be used for DHW but a bit unsure about how efficient that is. I haven't paid anyone anything yet..our architect knows his stuff but the 2 suppliers are the ones who have done rough calcs and suggested solar panel sizes and 14kw heat pumps to meet our needs.

2. I am beginning to think the thermal store and using a backboiler as a backup is just too difficult and incompatible with the heatpump etc. and probably not worth it. Apparently a back boiler stove needs a lot more fuel than a normal stove so unless I intend using it a lot there is no point. Also the heat pump is a pressurised system whereas the stove would be an open vented system. Therefore I am notgoing to even try going down this route now...it seemed like a logical idea!

3. I suppose I am wondering is the heat pump, solar panels and HRV are overkill as we do intend specifying high levels of insulation, airtightness to reach almost passive levels.

4. As I said above the stove thing incorporated into the heating system along with the heat pump seems like a difficult proposition so I am thinking it might not be worth it. As you are suggesting Bryan it might be an idea to just scrap the ufh altogether however with both of us working full time jobs and sometimes home late in the evening I intend only using a stove as a once in a while type heatingsource.

5. The 3rd supplier we spoke to is also recommending a boiler with making future provision for a heat pump if required. Basically he feels the same about the heat pump and also the saltwater issue. We are rural so no gas supply and from research the gas tank route seems too expensive. I'll look into the possibility of a log gasification boiler(no idea yet what it is tho see a thread just now!) or an oil condensing boiler.

I was under the impression that the heat pump was ideal with underfloor heating although prob not as effective for DHW which I think we intend doing! How would a boiler fit in with underfloor and DHW? Do people generally get a specialist in the area to do some calcs andsuggest a suitable system for our needs? It is definitely the mostconfusing aspect of the build design as I can't find anyone to give me an impartial view on what to do...anyone have any suggestions?

One of the suppliers has given me some rough calculations based on areas of wall, floor, glass etc. with an assumed U value (we haven't specified exact values yet) and worked out area by u value and taken into account thermal bridging loss, heat loss due to air infiltration and thermal capacity of floors/internal walls. We get a total heat loss of 302.72W/K. I guess that is how they worked out their requirements?! Any further advice appreciated.

I have 2 quotes for the heatpump/HRV/solar panels system. Need to nail down a quote for the alternative boiler/HRV/solar panel system. Will still be confused onwhat to go with though. We would prefer underfloor heating so seems a good fit with the heat pump but still concerned about DHW!



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Squeaksoutloud

Excuse the messy post above.had to copy from an email and post on my phone!

muffler

Squeaksoutloud wrote: »

Excuse the messy post above.had to copy from an email and post on my phone!

I'll tidy that up a wee bit for you.

krissovo

I have a 2500 sqft home with a similar spec to yours with an emphasis on insulation and solar gain. We moved in last year and ended up with the following:

8.4 sqm Solar panels for water only
Room sealed Stove with back boiler and thermal store
Oil fired boiler
Radiators
MHRV

We were going to use a Air to Water heat pump and quite happy that we didnt as friends who have this with underfloor heating could not get their home warm enough last winter for the week of -15 weather we had in Cork, they managed 15deg at best and it cost them a fortune in electricity. We filled our oil tank last year with a total of 900ltrs and still have approx 500ltrs left in the tank. Our water and heating is on 24hrs and the thermostat is set for 19 deg and has not been switched off all year. Oil to install was cheap and will fit a better system once there is a clear leader of renewable heat sources.

The solar gain has been the beat heat source, even at its coldest last year the house was around 19/20 deg during the day and the heating did not kick in. Most nights we lit the stove for comfort more than anything and the stored heat from this would be enough to heat the home in the morning until the solar gain had an effect. We burnt under a half cord of wood during Dec, Jan and February.

The insulation was key, we have ICF and I am happy with that and there is very good air tightness, not perfect due to the stove and cooker extractor but not far off. Our windows are from Norway and we have triple glazed on all non south facing windows and double glazed for the south facing to maximize solar gain. At one stage during the cold snap we ran out of oil and didnt even notice it for two days, it took a further 2 days to get oil due to the demand.

We originally wanted underfloor heating but found that the success rate of people we contacted during our build process is around 85%. 15% of them are still having a nightmare with excessive costs due to burning too much oil or using vast amounts of electricity to warm the house and water.

Another interesting point is that we have is a concrete first floor. We find that this is regulating the temperature of the home quite nicely. It absorbs heat when solar gain is very high and releases it back slowly when there is none.

BryanF

1. "14kw heat pump" but you siad near passive levels?
2. so your ruling out the backup heat source to suit the heat pump- something which in cold weather can give trouble.. I wouldn't be concerned about the extra fuel used in a stove wit backboiler, If you are lighting a fire, you turn of your central heating..
3. "heat pump, solar panels and HRV are overkill, as we do intend specifying high levels of insulation, airtightness to reach almost passive levels." you have me worried here.. you need to quanitify this.. and it will help you to work out you actual heat demand
4. "scrap the ufh altogether" imho yes.. for convenience i appreciate your needs, but i still think the wood G boiler can work..
5. "recommending a boiler with making future provision for a HP" yes now look into the log boiler, try to stay clear of oil/gas as apart fro your rural location, the price of it will always be on the up

I think your at a very important stage and as krissovo discussed, orientation, insulation and air-tightness can really reduce your fuel bill and keep your home comfortable ( ICF is just one option to do this:))

yes a specailist would be helpful BUT first why not get your arhc to do a PHPP calc or empliy someone to do one to work out the kwh/m2, this then allows for a more accurate heating sizing.

ask yourself why you want UFH, a modern home isn't a cold place to walk in! save on UFH forget and the Atw, spend your money on getting the building fabric & solar gain right and try to have the minimum fuel requirements which ideally come from a local renewable source

good luck with d build

beyondpassive

Core Components for a particular project as an example
(trade names redacted)
Boiler. The max Load is no more than 8kW for Space heat and hot water on the coldest day allowing for colder winters than predicted this decade. A modulating condensing gas boiler such as a the V____a M____e 12 or SEDBUK A rated appliance with LPG kit if required. Balanced rear flue option available. Gas Boiler will keep the top third of the tank heated above 60 degrees, a lower coil in the stratified tank can also be used to heat a larger volume to meet high demand. Balanced flue to external walls or flue. Plumb to allow for future replacement with wood pellet stove.
Tank. 1000L A___m Solar plus Accumulation tank from C___Energy or Ti__n p___n from R_R. This combines a solar buffer tank and hot water heat exchanger with inputs from both renewable and conventional boilers and stoves. Top of tank is always at 60 degrees, stratified middle will hover around underfloor temp.
Solar Panels. Evacuated tube Solar Panel s 6sq.m aperture area 48mm 60 tube array. annual energy yield of approx 3600KwH. Angle of inclination ideally 33 degrees. (roof is 20 degrees). Coupler, Pumping station, controller and expansion vessel included.
Domestic Hot Water- heat exchange is via a baffle plate in tank, Tank water is grey water,in that it is not used for consumption and runs constantly through the underfloor and any stove back boilers. Hot water is heated indirectly as the boiler heats the top of the tank above 60 degrees as the DHW draws off heat, when solar cannot be relied apon to meet the Hot water demand.
Underfloor. Distribution for the ground floor will be fed through 4 zones of underfloor. Evened out through MHRV.
Tank can feed underfloor from middle of tank or from top, at as low as 23 degrees if the thermostat and weather compensator allow.
Towel Rails. Upstairs rooms can be heated from one or 2 towel rail circuits with thermostatic control and timed boost. (including one in hot press and any bedroom that might need extra heat than set temperatures.
MHRV. 3 speed counterflow Mechanical heat recovery ventilation system with snap fit polyethelene ducts. Heat recovery efficiency <90%, Fan power efficiency less than 0.36W/m3. A___s or P__l N__s 300DC or S__s.
Room fire. Room sealed independant Gas fire insert with twinwall flue to roof.
Controllers, LCD display, Local area network adapter and Weather compensator

Options:
A: Change room gas fire to Wood burning room sealed stove such as the J__l or C____w with a pressurised back boiler, gravity fed coil to tank. With blow off valve and solenoid mains supply for cold water cool down. Pumice chimney kit over flue gatherer, no bends, air supply with valve. Chimney in-line damper.
B: Underfloor to upstairs, option of providing underfloor circuit to 50% of the upstairs rooms with Doubling up of loops under the wet rooms which are also on a boost circuit.
END

Do-more

@Squeaksoutloud, having gone through a similar period of confusion as to what heating system to specify, my advise to you would be to get a PHPP done.

It's irrelevant whether you are going for passive spec. or not, the process of doing the PHPP will help identify for you which elements of the building design are contributing most to your heat losses so you will be able to see where you can adjust your design to get the best performance.

It should also pretty accurately quantify what your actual heating demands will be so that you can size your heating system appropriately.

Speaking from my own experience it is the best investment I have made so far and I am confident that it will repay itself many times over as I should have a system which will run efficiently as it has not been over spec'd.

kboc

BryanF wrote: »

you cant answer this without more questions:) for a start whats your expected kwh/m2 / expected heat load

1. well does seem like you should be asking this guy that you've paid:)
2. thermal stores are a really interesting concept but you want to employ the best of passive levels of building fabric and the best of heating eng's to ensure it will work...
3. i guess your main worry is the AtW heat pump, as the solar and MVHR are a good investment assuming you get near passive levels of thermal bridging,insulation and air-tightness
4. once you have a heat dump i cant ever see a problem with a back boiler stove.. as you said its the back up if your heat system fails.. I do often wonder why people dont go that step further with building fabric, layout and orientation and just have the stove with the MVHR and nothing else.. save on the UFH and spend on air-tightness, windows and insulation...
5. that's a good question about the unit corrosion, maybe ask the supplier for a written parts guarantee that outlines your particular location issues and you could insist on performance energy monitoring of the unit...:Dsome chance.. I'm against heat pumps as I dont belive there COP is good enough and as they are a relatively straight forward bit of kit they could be installed in say 20 years when there is more renewable electrical energy available. I presume you are rural so I would investigate a log gasification boiler...

I have often wondered this myself, can this happen in our climate and does anybody know of anybody who actually has done this? Would a passive house not allow this situation to occur or is this another level on top of passive?

Regards
K

Do-more

kboc wrote: »

I have often wondered this myself, can this happen in our climate and does anybody know of anybody who actually has done this? Would a passive house not allow this situation to occur or is this another level on top of passive?

Regards
K

This is achievable with a passive house, indeed my spec won't reach passive standard it'll be 12w/m2 rather than 10w/m2 but it will still be perfectly possible to satisfy DHW and space heating requirements with a stove and solar panels.

I'm currently pricing systems from a number of suppliers which will consist of approx. 8m2 of solar panels, a 500 - 750 litre hot water store and either a small wood pellet boiler or a water jacket wood pellet stove which has a 80/20 split between hot water heating and radiant space heating. In either setup I would have a heat exchanger in the HRV duct so that I can add the required heat to the house from the hot water store via the ventilation system and have no other heating system in the house.

about2build

Do-more wrote:

This is achievable with a passive house, indeed my spec won't reach passive standard it'll be 12w/m2 rather than 10w/m2 but it will still be perfectly possible to satisfy DHW and space heating requirements with a stove and solar panels.

I'm currently pricing systems from a number of suppliers which will consist of approx. 8m2 of solar panels, a 500 - 750 litre hot water store and either a small wood pellet boiler or a water jacket wood pellet stove which has a 80/20 split between hot water heating and radiant space heating. In either setup I would have a heat exchanger in the HRV duct so that I can add the required heat to the house from the hot water store via the ventilation system and have no other heating system in the house.

Do more that sounds like an excellent system, putting more money into the fabric and thus getting away with the system precifyed above. Wondering how the ventilation system can extract heat from the hot water store? Also would the system run equally well with a wood burning stove with back boiler?

Do-more

about2build wrote: »

Wondering how the ventilation system can extract heat from the hot water store?

You plumb in a hot water duct heater in the ventilation system duct and have the hot water flow to it controlled by a room stat. It's very similar to a car radiator just a copper coil with fins.

about2build wrote: »

Also would the system run equally well with a wood burning stove with back boiler?

Yes, except that a pellet boiler or pellet stove can be controlled to turn on and off automatically according to hot water demand whereas the wood burning stove cannot.

Squeaksoutloud

Do-More yours sounds like an excellent system if it is possible to get away with it. About to have a read through your thread and looking into getting PHPP done...if anyone knows anyone can do it PM me as I would be interested..