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Green Building Bible, Fourth Edition
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    • CommentAuthormarsaday
    • CommentTimeSep 22nd 2021
     
    I know nothing about air source heat pumps, but thought i would ask here as my first port of call.

    I am starting to renovate a top floor flat which is only small (55 sqm). Normally i would put in a combi, but i was having a chat with a neighbour and he mentioned about the ASHP. So i need to get researching.

    With this flat I am fully renovating it. Walls will come down, the ceiling taken down so i can go right into the apex. there is no insulation in the dormas (quite big one) and only 100mm soft insulation in the current flat ceiling.

    So i intend on insulating with kingspan between the roof joists and on the underside all to Bld regs.

    The flat will need to run a small rad in the bathroom and 2 medium ones in the 2 bedrooms. In the lounge / kitchen area I could probably get away with a bigger rad, but will probably fit 2 medium sized ones.

    Would the air source heat pump work for this set up ? Can it be secured to the rear wall of the flat. It could not be located on the ground or at the front of the building.

    Any idea on the cost to buy one and get it fitted ?

    Do they use a wet normal rad system ?

    The rear wall outside the bedroom is the best place to fit as this area has a large flat roof to work off (flat 2's kitchen below my flat). So install is not a problem even though we are higher up. There is also a good fire escape at the rear to provide easy access.
    • CommentAuthorTomasz_P
    • CommentTimeSep 23rd 2021
     
    Hi,
    I am by no means an expert but the first two things I would be considering are the noise generated by the heat pump and whether it will be a nuisance to the flat below or the occupant in the bedroom.
    They can run with radiators but because they run at a lower temperature you would need larger rads. Would you have space for that? Could you consider underfloor heating? It might be worth getting a company to come and quote for you (even if you plan to fit much of it yourself).
    • CommentAuthorphiledge
    • CommentTimeSep 23rd 2021
     
    As mentioned have a good think about the noise directly above your neighbours flat. If the roof belongs to the neighbours, you dont want to upset them and risk being denied maintenance access! If you use their roof, board it out so it doesnt get damaged during install.

    Depending on your hot water usage you may need a small DHW cylinder but that could be avoided if youve got an electric shower and happy with instantaneous heaters over sinks/basins etc.. Cylinder may be able to go where the combi would go?

    If you want to use a variable electric tariff it will likely be expensive to run the heat pump at peak times so you may need a thermal store so you can run the HP off peak?

    If you insulate to a high level and get the flat air tight you may need very little in the way of heating. Being in an upper floor flat you might get enough from the flat below if theres not much insulation between you??
  1.  
    +1

    Also consider an air-to-air heatpump? Ideal for smaller spaces and heat loads, more efficient and much cheaper than a wet system. Looks like an aircon system and can also be used for cooling in Summer.
  2.  
    +1 to air-to-air HP. Kit can be much cheaper but it can be tricky to find installers in some areas, despite the use of air-con ('cause that's what it is, in heating rather than cooling mode) in a large percentage of commercial buildings. When I tried a few years ago it's like I was to be charged a 'faff tax' (additional cost of a fiddly-piddly little install).
    • CommentAuthorrevor
    • CommentTimeSep 23rd 2021
     
    I am a bit confused if you are taking the ceilings down to open up to the "apex" then how will you avoid the sound from one room travelling over the dividing walls to another? If you are going to open up to the roof then underfloor heating is best any radiator heating will not be effective where you want it. You could do electric UFH and run at night on cheap tariff. A heat pump may not be cost effective for such a small area whatever the size the installation cost is a sizeable chunk and as previously mentioned they can be noisy.
    • CommentAuthorowlman
    • CommentTimeSep 23rd 2021
     
    Hi Tim,
    Just to clarify the layout, is the accommodation all on one level with a "soon to be opened up " pitched roof space above. If that's the case would/could, you have a trapdoor opening with access ladder into that roof space, once done?
    • CommentAuthormarsaday
    • CommentTimeSep 23rd 2021
     
    The whole flat will have most walls taken down as currently stud, and rebuilt to go much higher as i am extending ceiling height. The new ceiling will be clad in birch ply hopefully and the extra height will improve the sense of space.

    If the air source pumps are noisy then this has to be an issue. Affecting my flat and the one below. I have a feeling this will rule it out.

    If i really insulate well, what do folk think about these small electric wall heaters you find in many flats ? Would they be ok to heat the space? I am thinking it will not need that much heating because it is going to be well insulated. I am doing new D/G. The roof should get 120mm overall kingspan insulation (or what ever the minimum is now), plus i will reline the walls with 50mm insulation as well.

    The floor will be insulated with 170mm approx loft type insulation. This is really for sound deadening as there is no sound barriers between these flats as they were done in 1965 (old victorian house split into 3 flats).
    • CommentAuthorrevor
    • CommentTimeSep 23rd 2021
     
    I would insulate in between the rafters with rock wool as much as you can get allowing forair gap above it then overboard with the Kingspan. You will find it difficult to get a good fit of Kingspan between joist as they will not be parallel and you will get gaps. Sanding to fit will create a health hazard. I know I tried and that was in a new roof I had built. I used 170 rockwool and 100 mm PIR but jointed secured with screws and retaining clips used for holding insulation in a cavity wall. Over tape the joints and clips with aluminium tape to get a good air seal. Check on the building regs for noise insulation between floors otherwise you may fall foul of BCO. There was a discussion on this topic here recently about this. Google "robust detail" for ideas.
    •  
      CommentAuthordjh
    • CommentTimeSep 23rd 2021
     
    Posted By: marsadayIf i really insulate well, what do folk think about these small electric wall heaters you find in many flats ? Would they be ok to heat the space?

    If by 'really insulate well' you mean to passivhaus level and assuming you include an MVHR system then yes, electric wall heaters will be fine.

    The floor will be insulated with 170mm approx loft type insulation. This is really for sound deadening as there is no sound barriers between these flats

    Doesn't do much for impact noise though. That needs specific treatment.
    • CommentAuthormarsaday
    • CommentTimeSep 23rd 2021
     
    Do i have to meet BR regarding the floor ? I thought this was not relevant as it's an old converted flat done in 1965.

    On a new conversion, yes i would have to meet these requirements, but not in this instance. All i am doing is trying to improve the acoustic levels. Can you clarify as I dont want to get into these red tape issues.

    I will need to baton out the rafters anyway to accommodate the new insulation. Currently only a 75mm deep rafter and i will need to leave 50mm gap.

    I'm used to cutting rigid insulation. Its a messy job, but not that difficult.
    • CommentAuthorrevor
    • CommentTimeSep 24th 2021
     
    Think at end of day what is it you want? an OK job or a quality job. We are all different in our expectations. I agree with DJH floors need specific treatment to prevent noise, guess you do not want you neighbours complaining maybe they will be ok with it but they could change and new ones might complain so might as well do a proper job whilst at it.
    What I should have mentioned was that insulation boards shrink a lot when exposed to heat which they will between rafters have seen evidence of it big gaps. The rockwool above it cushions the effect.
    •  
      CommentAuthordjh
    • CommentTimeSep 24th 2021
     
    Posted By: marsadayI dont want to get into these red tape issues

    To my mind it has nothing to do with 'red tape'. Sound insulation has to do with consideration of human comfort both for yourself/your tenants and for your neighbours, who are also human beings and deserving of respect.
    • CommentAuthorowlman
    • CommentTimeSep 24th 2021
     
    As WillinAberdeen suggested, consider Air to Air.

    If after conversion you still have loft space available, then the indoor distribution could all be housed up there, with supply registers in each room. Return registers are easily built into new stud walls, or also in the ceiling, if pushed; and no radiators required, freeing up all that wall space in a smallish area.

    Installing the outdoor unit on cantilever arms on a wall is no problem, and rubber dampers cushion against vibration, IMO noise isn't really an issue with quality modern equipment.

    Although you'll need F gas final connection, filling, and commissioning much of the other tedious legwork you can do yourself with your gas engineers approval.

    As for DHW cylinder with a couple of immersions is the simplest route. For the bathroom an electric towel rad would be useful.
    • CommentAuthormarsaday
    • CommentTimeSep 24th 2021
     
    Air to air will need a lot of ducting i imagine. There will be no space in the loft as it is disappearing to be replaced with a full height roof clad in plywood.

    I will read about it though.
    • CommentAuthorowlman
    • CommentTimeSep 24th 2021
     
    If ducted Air to Air is impractical also look at wall hung units, or low level units.
    • CommentAuthormarsaday
    • CommentTimeSep 25th 2021
     
    I have seen infrared heating and this sytem may well be what i need.

    Having a full pitched roof clad in ply I can mount all the heaters away from the walls higher up. They will look quite good and per form well from up there.

    I just need to work out if it will be cost effective.

    For a place which is going to be a holiday home and so used mostly in the summer time i think this could be a good solution. I need to speak to a supplier to get the full low down though.

    It will mean no gas feed into the flat, so saving on standing charges etc. I will just need a storage heater for the hot water.
    • CommentAuthorrevor
    • CommentTimeSep 25th 2021
     
    For hot water you could consider point of use supply. I once met someone who had installed these wherever he needed hot water. Logic was he never wasted electricity in keeping water hot in a tank. Would be ideal I think in a small dwelling as less conflict possible from multiple outlets calling for power at same time. He had no baths just showers.
    • CommentAuthorowlman
    • CommentTimeSep 25th 2021
     
    +1, for point of use water heating.
    Plumbing is easy with just cold feeds, so pipework money saving. Spend the money instead on upgrading the power supply if necessary and ensuring good quality decent capacity, point of use water heaters.
    • CommentAuthormarsaday
    • CommentTimeSep 26th 2021
     
    I am doing everything on this flat so new electrics, new plumbing. So the install cost is not an issues.

    Reading more about the topic, it does seem gas is the best option. I will have hot water on demand and so not wasted hot water being stored for x weeks with no use. The unit will take up less space than HW storage and say heaters.

    Gas will be moving to full hydrogen in the next 15 yrs as well. So i think a move to all electric is not needed.

    Still plenty to weight up though.
  3.  
    Gas sadly will not be moving to full hydrogen within the lifetime of your new boiler, or even your next boiler after that, whatever the gas boiler manufacturers would like you to believe. The UK government Hydrogen Strategy is estimating that only small amounts of hydrogen will be delivered for home heating from around 2035, significant amounts of hydrogen might be in use around 2050.

    https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1011499/Hydrogen_Analytical_Annex.pdf
      Screenshot_20210926-103057.png
  4.  
    How about calculating and costing the options?

    I don't think anyone on here will be able to give you a conclusive answer without you identifying the variables and calculating the heat loss.

    First thing I would pick up on is your statement that it ''is going to be a holiday home and so used mostly in the summer time''.

    What will the season be - 6 months? Look at some historical weather data for lowest temps and you can probably work out the likely input required. I would imagine you could use Degree Days but my head refuses to get itself around them.

    Who pays the bills? Is it your (and your family's) holiday home, or is it let out?

    ''If i really insulate well, what do folk think about these small electric wall heaters you find in many flats ? Would they be ok to heat the space? I am thinking it will not need that much heating because it is going to be well insulated. I am doing new D/G. The roof should get 120mm overall kingspan insulation (or what ever the minimum is now), plus i will reline the walls with 50mm insulation as well.''

    djh said: ''If by 'really insulate well' you mean to passivhaus level and assuming you include an MVHR system then yes, electric wall heaters will be fine.''

    He's right, but you may do the calcs to work out the heat requirement and the likely annual bill and feel that, even with your proposed levels of insulation elec heating would be 'affordable'. At least you would be heating with a fuel whose carbon intensity is falling, rather than with gas, where this is not the case.

    Just a final point on your roof plans. You said:

    ''I will need to baton out the rafters anyway to accommodate the new insulation. Currently only a 75mm deep rafter and i will need to leave 50mm gap.''

    If you batten out the rafters to the full insulation depth you add a further 'timber fraction' (bits where there's timber where there should be insulation). If you have 25mm between rafters after the 50 air gap then just go across the whole lot with 75mm PIR, tape at all joints and perimeters as VCL, fix 25 x 50 battens horizontally to match your plasterboard sizes and then friction-fit a final 25mm between the battens. It is reasonable to have the VCL 25mm back in a 125mm 'sandwich', or if you want to be 100% then use a sheet VCL over (under!) the whole lot, taped at all joints and perimeters. I would advise air-tightness tape, not foil tape, particularly at the perimeters - foil tape rips over time.

    I hope this helps.
    • CommentAuthorphiledge
    • CommentTimeSep 26th 2021
     
    Posted By: WillInAberdeenGas sadly will not be moving to full hydrogen within the lifetime of your new boiler, or even your next boiler after that, whatever the gas boiler manufacturers would like you to believe. The UK government Hydrogen Strategy is estimating that only small amounts of hydrogen will be delivered for home heating from around 2035, significant amounts of hydrogen might be in use around 2050.

    https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1011499/Hydrogen_Analytical_Annex.pdf" rel="nofollow" >https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1011499/Hydrogen_Analytical_Annex.pdf
      http:///newforum/extensions/InlineImages/image.php?AttachmentID=8047" alt="Screenshot_20210926-103057.png" >


    The report above suggests that hydrogen infrastructure roll out will commence from 2030 onwards yet Northern Gas Networks have just raised finance through Abundance to upgrade much of the north of englands gas network for completion by 2026. This should make that part of the network hydrogen ready around a decade ahead of the reports forecast??
    Hynet have equally ambitious plans claiming to be producing and distributing hydrogen by 2025 but I think that will be to local industrial users, if it comes to fruition. Apparently Pilkington glass are running part or all of their glass production at St Helens on hydrogen.
    I only know about these projects through a personal interest and have no idea what, if anything, is happening elsewhere in the country.
    Seems a bit of a mess with the gov saying one thing and commerce seemingly doing something different??
    •  
      CommentAuthordjh
    • CommentTimeSep 26th 2021
     
    Posted By: philedgeThe report above suggests that hydrogen infrastructure roll out will commence from 2030 onwards yet Northern Gas Networks have just raised finance through Abundance to upgrade much of the north of englands gas network for completion by 2026.

    Do you have a link? My quick search indicated that Northern Gas were inviting the public to subscribe funds to replace metal gas mains with polyethylene, with the funding organized by Abundance. Which would be a completely different scenario if that's the one you're referring to.

    Replacing mains is a regular maintenance task that the gas supplier would have to fund in any case, so why the public should be asked to stump up for it is questionable, rather than normal commercial funding. Perhaps commercial funding sources are aware that investing in a new gas main when the long-term prospects are somewhat doubtful might not be the best investment they make this year, whilst the great unwashed can be relied upon to buy Blackpool Tower again and again?

    If Hynet ever produces any 'green' hydrogen at scale instead of 'blue' hydrogen, I shall be overcome with emotion.

    Commerce is as usual trying to make a dollar in whatever circumstances it finds itself, and exploiting public and government confusion and ignorance remains an excellent source of an edge, as ever.
  5.  
    Absolutely Phil! I got interested in this 20 years ago, at which point Government thought the Hydrogen Economy was going to be 20 years away. Still do!

    IIUC it takes the time to build all the suppliers of the hydrogen, rather than laying the pipes. Got to build all the CCS and wind farms that go with that, the first pilot projects Hynet/Acorn/Drax are competing for funding now.

    Once a hydrogen supply exists, the first customers need to be glass/cement/steel etc for which no low carbon alternative exists - housing would come later.

    Interesting paper here where BEIS estimated the underlying cost of making hydrogen from nat gas or electricity - is not very certain but their central estimates for 2040 are roughly

    Hydrogen from nat gas with CCS £60-70/MWh
    Hydrogen from grid electricity £120-150/MWh
    Hydrogen from surplus wind electricity £40/MWh (only available on favourable days when nobody else can store it)

    For comparison:
    Nat gas, no CCS £20/MWh
    Electricity £60/MWh
    Fuel oils £55/MWh
    (from ref 23 of the paper, I converted units)

    All prices wholesale, excluding transmission, storage, taxes, retail markups etc

    So switching the grid from gas over to hydrogen will put underlying energy costs up by 3-6x, plus the cost of whatever appliance/meter/pipe modifications.

    I guess this will have to be subsidised to be politically acceptable, same as heat pumps, but I can't see gov paying more than a certain amount of the whole country's gas bill in subsidy. So I suspect they will want to phase that change over many years, not do the whole grid at one time.

    Interestingly, hydrogen could be competitive with oil based fuel for HGVs shipping etc, even if uncompetitive with gas for home heating. Industrial users pay carbon pricing, so the higher hydrogen prices could be less a barrier for them.

    https://www.gov.uk/government/publications/hydrogen-production-costs-2021

    Edit: the gas distribution companies are spending 100s of £m replacing old iron gas mains, wherever they are risky. The £1m they raised with abundance won't pay much of that bill.
    • CommentAuthorphiledge
    • CommentTimeSep 27th 2021
     
    The cash raised through Abundance was only part of what NGN wanted. Ive no idea how much they wanted but likely significantly more than the £1m Abundance investors stumped up. Heres a public summary https://www.abundanceinvestment.com/our-impact/investments/northern-gas-networks

    I appreciate that national infrastructure is significantly more than the 2 projects Ive stumbled across but it seems that hydrogen infrastructure is starting well ahead of the dates stated in the gov doc. Domestic roll out may well be a long way down the road but the gov forecasting a start in early 2030s and NGN seemingly starting in early 2020s is a worringly big difference. Maybe NGN are out on their own getting started and the gov are only looking at whats happening in the south??
  6.  
    Hi Phil, AFAICS the gas networks were mandated years ago to replace the old iron pipes, because of their risk of fracture releasing methane, and long before the present talk about hydrogen cracking.

    I'm not going to comment on any particular network selling that spending to the public as 'hydrogen readiness' - as abundance say, potential investors need to do their own critical due diligence on all these claims, which I haven't done.

    The networks are heavily regulated in terms of what they spend when, because of their monopoly status paid for by consumers. They have to propose and justify all their spending plans to the government regulator who are well aware what they are up to.

    Edit: NGN's business plan mentions the H&SE enforced a replacement programme of iron mains in 2002 to improve safety, they plan to complete this in 2032, the tranche in their current 5yr business plan will cost £313million.

    In a separate part of the business plan, they describe a possible change to transport approx 50% hydrogen and biomethane in 2040, rising to 100% in 2050. In their present 5y plan, they include for experimental work to support future policy decisions on this, to be taken later this decade.

    https://together.northerngasnetworks.co.uk/our-business-plan-2021-2026/

    https://www.northerngasnetworks.co.uk/wp-content/uploads/2019/12/NGN-RIIO-GD2-Business-Plan-2021-2026.pdf
    • CommentAuthormarsaday
    • CommentTimeSep 28th 2021
     
    <blockquote><cite>Posted By: Nick Parsons</cite>How about calculating and costing the options?

    I don't think anyone on here will be able to give you a conclusive answer without you identifying the variables and calculating the heat loss.

    First thing I would pick up on is your statement that it ''is going to be a holiday home and so used mostly in the summer time''.

    What will the season be - 6 months? Look at some historical weather data for lowest temps and you can probably work out the likely input required. I would imagine you could use Degree Days but my head refuses to get itself around them.

    Who pays the bills? Is it your (and your family's) holiday home, or is it let out?

    ''If i really insulate well, what do folk think about these small electric wall heaters you find in many flats ? Would they be ok to heat the space? I am thinking it will not need that much heating because it is going to be well insulated. I am doing new D/G. The roof should get 120mm overall kingspan insulation (or what ever the minimum is now), plus i will reline the walls with 50mm insulation as well.''

    djh said: ''If by 'really insulate well' you mean to passivhaus level and assuming you include an MVHR system then yes, electric wall heaters will be fine.''

    He's right, but you may do the calcs to work out the heat requirement and the likely annual bill and feel that, even with your proposed levels of insulation elec heating would be 'affordable'. At least you would be heating with a fuel whose carbon intensity is falling, rather than with gas, where this is not the case.

    Just a final point on your roof plans. You said:

    ''I will need to baton out the rafters anyway to accommodate the new insulation. Currently only a 75mm deep rafter and i will need to leave 50mm gap.''

    If you batten out the rafters to the full insulation depth you add a further 'timber fraction' (bits where there's timber where there should be insulation). If you have 25mm between rafters after the 50 air gap then just go across the whole lot with 75mm PIR, tape at all joints and perimeters as VCL, fix 25 x 50 battens horizontally to match your plasterboard sizes and then friction-fit a final 25mm between the battens. It is reasonable to have the VCL 25mm back in a 125mm 'sandwich', or if you want to be 100% then use a sheet VCL over (under!) the whole lot, taped at all joints and perimeters. I would advise air-tightness tape, not foil tape, particularly at the perimeters - foil tape rips over time.

    I hope this helps.</blockquote>

    I will think about the way i insulate the roof. It sounds a potential better idea. The jointing sounds a good idea.

    I will work out the requirements, but super busy with the renovation.

    I will be paying the fuel bill and i do think all electric will be ok going forwards.

    I am going for basic electric wall heaters with WiFi control, electric shower and two small under the counter HW heaters for the 2 x sink HW demand.

    I will save on the gas meter standing charge, plus the annual check and the meter would need moving anyway as currently sat where the shower room will be. So the install cost will be more compared to going for a combi and normal shower, but overall the price difference is going to be an extra £500.
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