Green Building Forum - Heating and cooling

Air-to-air heat pumps

djh — Tue, 18 Nov 2025 17:34:03 +0000

So, the government has included air-air heat pumps in the BUS (see https://www.gov.uk/government/news/discounts-for-families-to-keep-warm-in-winter-and-cool-in-summer ), which has set me thinking about them again. Does anybody have any ideas about whether this will decrease or increase prices, and when. Or how to find a competent and trustworthy installer? (in Suffolk if it matters) And about any specific products?

PS They've also included subsidies for 'heat batteries', but since heat batteries are now more expensive than electrical batteries for the same capacity, it seems like another poorly thought-out scheme!

ASHP choices - cylinder size and zoning opinions needed

stonecold — Mon, 16 Jun 2025 23:49:03 +0100

Opinions wanted on the following ASHP decisions (specs at the bottom). Currently we have EWI and MVHR too recently to get accurate bill data so working from estimates. Planning to get it in within 3 months to avoid refilling oil tank (price has gone up 50% since 2021). Also getting new heating pipes since they are end of life and small microbore
(leaks keep happening). DHW uses immersion heater which will go.

1. Heat pump hot water cylinder of under 130L recommended by eco energy retrofit report but quotes all suggest 200-240L. We have 1 mixer shower and second shower may be mixer or electric. Which cylinder size is best - small or large? Is the large cylinder worth trying to use to store extra hot water as an alternative to a second battery for the solar PV we have planned? ASHP shift will move us 100% to electric and main heating need is daytime (I am housebound so always home, get cold fast and very little solar gain).

2. Cylinder location: no garage, can't use space boiler or current hot water cylinder currently use. Is it really really bad to use a bedroom alcove? Possibility covered by acoustic access panel and nicer boxing in. Another option is far end of kitchen but this crosses a doorway and it can't go under solid uninsulated flow - pipes would need to go in ceiling void above doorway then around corner and down - a long pipe run on coldest side of house.

3. See photo - could space 850mm x 450mm be used for cylinder? The 450mm wide is the frpnt, basically next to MVHR. Is there enough elbow room and plumbing room? If not would solar PV 2 inverters and 2 batteries fit here? Second inverter should apparently allow solar PV use during our very very frequent power cuts (30+ gets you a cheque from energy network company).

4. We would be looking at around 8kw solar PV and ASHP between 7.5 - 15 kwh plys obviously some stored hot water. We already use electric for hob and oven, if we have ASHP connected to solar PV with batteries are we going to have enough power to actually run the ASHP (colder temp ok)? This is for daytime since I am home all day, housebound and easily get cold.

5. Upstairs and downstairs zones for heating - any thoughts? Atypical use means lounge and downstairs office are used all day (I am housebound and get cold easily) and very very little solar gain. It seems daft to heat bedroom when it is empty. MVHR helps kitchen and bathroom temp a lot.

6. The Gulf Stream looks set to collapse or become dramatically unstable within the next 20 years.. causing Artic temperatures in the UK. We already have -10C several nights a year here. Is it worth getting the larger size of heat pjmp suggested (15kw) rather than 8-11 kw and will the larger size be environmentally much worse? Local experienced plumber always overspecs and suggested 15kw but is not familiar with our degree of insulation or MVHR and Internorm triple glazing. Aira also said the same. Others are in the 8-11kwh range. We have accurate plans (dwg) and accurate U values but energy needs are estimates (only 6 months since EWI and MVHR). Do small or large?

Basic details are
1830s stone house, 3 bed 2 bath, 150 sq m
Full repiping needed, microbore is at the end of its life and like spaghetti
loft 0.11-0.13 U, walls 0.60 U (EWI), MVHR in use
no floor insulation and too little head height for underfloor heating
Oil use should be approx 16,000 to 18,000kwh/year maybe less (from eco report) - because MVHR and triple glazing to near EnerPhit standards
Water heating 1,800 kwh/year - scrapping immersion heater

Ladomatt 21 60 Changing the thermostatic element

jwd — Sat, 23 Aug 2025 21:30:16 +0100

Hi All
I'm changing the thermostatic element on my ladomatt 21-60 and could do with some advice.
The old element was really jammed into the brass collar but the new one doesn't sit all the way. It looks like it needs to be pressed into place. Does anyone have any suggestions as to a) do I need to push it home, and b) how can I do that without damaging the element ?
Also should I replace the o ring on the brass collar at the same time?

Thanks in advance

Jw

Ground Source/Air Source for an older house

lookseehear — Wed, 14 Oct 2020 16:07:16 +0100

Hello everyone,

First post here - hoping to get some feedback on our thoughts about replacing a >30 year old oil boiler with an ASHP/GSHP in the house we're prospectively buying (a couple of weeks from exchanging).

Firstly, a little about us - we're a young family (my wife and I and two children, 3 and 1) and although being cost efficient is important, the most important thing for us is going to be a balance of comfort and convenience. I want to try and avoid the inevitable arguments in the years to come about where to set the thermostat, which has led us to AS/GSHP because we love the idea of keeping the house at a steady temperature year round with constant heat. I've been doing a lot of research on the subject but I'm still struggling a little with viability.

We are buying an old house which we believe the oldest part is likely to be 18th century, with 0.5m thick stone wall construction. I understand that stone walls aren't good insulators but are good heat sinks, so the last thing we want to be doing is trying to heat the house up in a hurry. It's a 5 bed detatched, approx. 180 m2. It needs more loft insulation which will be the first job when we move in (sheeps wool looking most likely) up to 300mm. The house is double glazed and although not a hugely drafty house, it's not that airtight either and we're likely to improve the ventilation.

Doing some calculations on the heat loss calculator (https://www.resurgence.org/resources/heac.html) seems to indicate that the total heat lost during a typical year might be in the region of 35,000 kWh, and that the peak power output required of a heating system would be c12-14kW. Using the 'rule of thumb' on this resource https://synergyboreholes.co.uk/information/calculations/ seems to indicate that more like 22kW of power output would be required in the coldest periods to maintain 20 degrees in the house. There's a massive discrepancy here and the last thing we want to do is under-spec a system. 12kW looks to be achievable for ground source or for air source.

For a ground source system, we'd have to look at either one very deep (~200m) or two shallower (~100m) boreholes (using 35w/m of collector) which would probably be feasible, but more than two boreholes would be difficult from a logistical and cost perspective. We would prefer ground source for potentially higher COP and higher RHI payments to offset the higher cost of installation.

For air source, there seems to be a decent amount of choice at the 12kW-14kW including Ecodan which appear to be highly rated and we wouldn't have the same space concerns.

The property has solid floors and is slightly split level, but I've assumed we could probably fit wet underfloor heating next year to take advantage of low-temperature heat, but currently the house has decent size (but not 'oversized') radiators in all rooms.

All this to say does anyone have experience with ground source or air source for a similar property? Can anyone offer insight on whether 12-14kW is likely to be sufficient, paired initially with radiators then subsequently with underfloor heating?

Thanks in advance for reading this.

HELP NEEDED - Backboiler to Thermal store

Jacket84 — Tue, 20 May 2025 12:32:09 +0100

Hi All,

My first post so please bear with me . I joined the forum as looks like a lot of knowledge here with regard to these types of systems. Therefore hoping someone might be able to assist with the problem described below that I’m experiencing with my biomass heating system. To say I’m beyond desperate to get this fixed is probably an understatement.

In summary, I had the system installed 2 years ago and it’s never worked properly. I have a 2200 litre Akvaterm thermal store which has the following circuits i.e. flow and return:

1. For the biomass cooker in my kitchen which has a 22kW back boiler (at about 80% efficiency so say 17kW) the towel radiators in our ensuite bathroom, main family bathroom and spare bedroom ensuite are also on this circuit.
2. Central heating i.e. all other radiators in the house
3. Domestic hot water
4. For the oil boiler which I kept for redundancy / convenience

The problem I'm experiencing in the winter months (i.e when I want to use it!) is that as the temperature of the store itself gets hotter, the water in the boiler of the biomass cooker itself (32 litre volume) seems more and more prone to overheating and as a result the safety valve built in to the cooker (PRV?) is coming on and dumping the water out. The end result is that we can’t use the cooker to heat the store or we can but the fire is so small it can’t produce any meaningful heat to raise the overall temp in the store. I’m probably not describing this very well but it is like the water in the boiler of the cooker isn’t getting moved quick enough and sort of sits in the cooker.

Thankfully I got the installer to do a drawing of the system for me. See image below.

I’ve tried to rack my brains as to what is causing this. The system is pressurised so I wondered if it was possibly the issue with the pump on the cooker return (above garage Black one as described on drawing above) either not being near enough to the cooker which is in the kitchen. Or an additional pump on the cookers flow near to the cooker itself is needed to more effectively pump the now heated water in the cooker’s boiler away quicker? My other thought was is there an issue with flow rate but the circuit from cooker to store/accumulator was put in at the same time as the store and pipe work all looks to be same size however the cooker circuit also has our towel radiators in the rooms as per point 1 above so I wondered if the smaller dimension pipework on these could be causing the problem?

Any help would be really, really appreciated.

P.S. The store was actually sized with the idea of a second 40kW batch boiler being added, hence why it is so big.

Slab with ASHP and overnight rate

neelpeel — Tue, 25 Feb 2025 10:55:47 +0000

I've always thought a large 'interseasonal store' type slab and PV was the ideal way to go for a new build / extension. But...
- We now have tariffs with very low overnight rates (or low periods for ASHP tariffs). These rates are much lower than you can get for PV export so if you have a battery you are actually better off exporting all of your solar.
- Heat pumps can give you a CoP of 4+.

So I think the killer combo is now probably a smaller slab with UFH that is getting charged up during the Autumn overnight with an ASHP (and then topped up as required through Winter/Spring)

In the warmer months the CoP will be highest so you could be looking at 4.5X efficiency at least. At £0.07/kWh (IOG overnight rate for example) this would equate to only 1.5p per kWh to charge the slab. IOG tariff gives 6hrs cheap rate each night so in theory you could be putting in 6x7kW = 42kWh each night.

Is anyone doing this yet??

The Pros and Cons of Direct Air for a Wood Stove (when there’s no mandatory requirement)

greenfinger — Wed, 12 Feb 2025 22:38:33 +0000

Hi all

Direct air / External air…

Additional air requirements are mandatory for stoves above 5kW in older houses, and for any stoves in newer houses (post-2008) or houses with an air permeability of 5 m3/hm2 or less. I can understand the logic in having DA when the alternative would be an air vent (hole in the wall); although even then there are arguments on both sides. But putting that aside a moment, when no additional air requirements are needed for a stove, is DA still a worthwhile option? I’ve spent the day reading up on this and thought I’d post what I’ve found, as much to share my research as to get feedback and thoughts from people if anyone is interested in discussing it.

******In Favour of DA*****
- Draughts. There are quite a few people on the internet who can’t say enough good things about DA and highly recommend using it whenever possible to reduce draughts and cold air in the room. It’s an enticing idea! However, I did notice that this is usually as opposed to having to have an air vent. When the alternative to DA is no air vent (for a 5kW or less stove), I’m not so sure how many of these people would still recommend it.
- Draughts – Anecdotes. That being said, I found instances where people were saying they used to have a stove which took air from the room, they weren’t happy with the draughts being created, and so retrofitted a DA feed and it made a world of difference.
- Wasting Heated Air. Some say that without DA, you are wasting air in the room that has already been heated and replacing it with cold air. This quote sums it up: “…I would definitely fit a direct air supply not only [for] the prevention of draughts but for the conservation of heat. Using room air you would be using air already heated and a wood burner will use a considerable amount of combustion air out of the room you have heated.” REBUTTAL: However, stoves actually use quite a small amount of air when compared to the average standard air changes required in a room. The air changes will have to happen one way or another, so unless MVHR is used, won’t hot air still have to be replaced with a fresh cold supply regardless?
- Colder Air Burns Better. Quote: “The colder the air – the denser it is and more oxygen per unit volume it contains, so it must be good to assist combustion.” REBUTTAL: However, I’m sure I’ve also heard the opposite, that colder denser air is detrimental to combustion. Not sure which is right.
- Cold Air Expands When Heated. The claim therefore is that this can assist chimney draw as it is taken away up the flue.
- Control. Although DA means less air changes compared to air from the room, it means you have more control over when you ventilate the house. IE – opening windows in the morning, or before going out. You can control the ventilation, and separate the times to ventilate from the times to heat. Also, you can introduce more ventilation when required due to the weather (damp days) and less when not (dry crisp days). As one person puts it, “Using the stove air to ventilate, means you wouldn't ventilate the right amount at the right time.”

I thought this article was particularly useful in highlighting benefits, although note the “conditions” on page 2.
https://mtbest.net/wp-content/uploads/sites/12/2023/02/cold-air-intake-1.pdf

*****Against DA*****
- Simply Not Needed. Many people claim DA is not necessary, for various reasons. Also, all of the installers and stove shops I have spoken to (which is quite a few!) have unanimously said not to bother and that we would not gain anything. The “Outdoor Air Myth Exposed” article – link below – claims that it has been studied and DA (or even just air vents) are most often of no benefit.
- Stoves Don’t Create Draughts. Some say it is not true that you feel draughts. They say to try putting your hand by the stove’s air inlet, where the air is being sucked through a small aperture and should therefore be the aggregate of all air being pulled. If there were draughts you would feel it there, but you don’t.
- Cold Air Cools the Stove. Pulling cold air directly into the stove will be worse for combustion and will cool the internal temperature of the firebox.
- Cold Air When Not in Use. The duct will be cold and will emit cold air, especially when the stove is not in use (or even when the stove is in use, to be fair, as it’s still sucking in cold air). Thermal bridge to outdoors.
- DA is Worse for Ventilation and Humidity. If the stove takes air from the room, it encourages more air changes in the house. This in turn can increase ventilation and help with humidity too. Outside air is almost always drier/lower RH, so frequent air changes help.
- MVHR. Of those people who think DA is a good idea, they sometimes add that MVHR is needed too for air changes. Without MVHR, some say it’s best to vent the stove from the room air. I don’t and won’t have MVHR, so that’s an “against” for me.
- Wind and External Air Pressure (Backdraught) Problems. If the wind is at a particular strength and direction it can cause smoke to blow back into the room, as well as CO. It can also make it difficult to start the stove. Unpredictable and variable. There can also be a potential fire risk if the reversal of the flue system flow results in the hot gases being expelled from the DA intake. Also, if mechanical extraction in the house de-pressurises more than the chimney draw, smoke and gases can be drawn out of the stove and into the room. REBUTTAL: See “cold-air-intake” pdf (link above). He says to have the external vent positioned in a place where there will be no wind (consistent known pressure), which would deal with this problem. If that’s not possible, I wonder is something like the DR21 could help with this?
- Air from Below Stove (and Entry Into Ash Pan Area). See “cold-air-intake” pdf (link above). He states that the DA needs to be supplied from below the fire as a requirement for it to be effective. This is not possible for many wood only stoves as they have no ash pan.
- More Money! Kits are often £100+. Fitting will add to the bill as well (unless DIYing).
- Historic Precedent. It’s not how they used to do it in the old days! Older houses need older methods?

The strongest article I found arguing against DA – and air vents in general – and claiming that studies have proved it:
https://www.woodheat.org/the-outdoor-air-myth-exposed.html

I appreciate the post is long, and probably quite boring! So feel free to ignore it; although if you've got this far then I guess it's a bit late to say that! But if it interests anyone, I’d love to hear your thoughts, arguments and agreements. Personal experiences always great to hear as well.

Cheers

Air-to-air with DHW

GreenPaddy — Fri, 10 Feb 2023 12:21:15 +0000

I'm re-posting this comment by "bogal2", as it was sort of bypassed in the middle of another thread.

-------------------------------
Hereâ€™s a new air to air heat pump with a HW cylinder. Not got a lot of info about itâ€™s efficiency. Sounds good in theory!

https://www.daikin.eu/en_us/product-group/air-to-air-heat-pumps/multiplus.html

---------------------

It seems to me to be an excellent solution for certain situations, and develops on the experience of "owlman", and others, whereby not a lot of space heating is required, but direct electric immersion is used for DHW generation.

I've seen a number of questions about simple air-to-air for space heating, but if only there were a way to get DHW too.

Not sure about the price, as like bogal2, there doesn't seem to be that much info on it on Google, but perhaps worth discussing, following up on?

Single Wall vs Twin Wall flue for section inside house? Pros and Cons...

greenfinger — Wed, 05 Feb 2025 11:26:47 +0000

Hi

Back again with a second wood stove query, if anyone would be kind enough to share their thoughts please...

We're planning to have a stove fitted into a single storey room. The stove has a 5" flue. The installers who have quoted said they think the flue will need to be a total height of 4.5m. It will be a straight run, no bends. If there were to be a single wall flue in the room up until where it has to change to twin to pass through the ceiling, the single wall section would be around 1.6 to 1.7m. The rest would be twin wall, although most of it would be outdoors.

We only burn well seasoned hardwoods.

From what I've learnt, the advantage of single wall would be more heat to the room. One installer said he thinks for each 1m of single wall flue you get 1kW of heat, which would be a great bonus. I'll also admit a bias - I think the stove looks so much nicer with the single wall 5" flue. I've only found a couple of photos online where the same stove has been installed with twin wall and to be honest I think it looks f-ugly. Also, more space on the stove top for a kettle etc would be an extra bonus.

However, I've also learnt that the advantage of twin wall is the flue maintains a higher internal heat, creating a better draw, which results in a stove that is easier to start, runs better, and a flue that doesn't block with creosote so much. (Although I should add that some say they have none of these problems with single wall).

It seems to be a very divided topic, with strong opinions on both sides. While I want the aesthetics and extra heat to sway me to single wall, I also don't want a stove that is tough to light and doesn't run well.

So over to you guys for some thoughts and insights...

Many thanks

Dik Geurts Ivar 5 Wood Stove - anyone have one or have opinion on it?

greenfinger — Wed, 29 Jan 2025 12:16:47 +0000

Hi

We're looking to have a new wood stove installed and have narrowed it down to a Dik Geurts Ivar 5. It's a good size and shape for where we'll be putting it, we like the aesthetic, and it seems to get great reviews on the whole.

I wondered if anyone here has one and could share their experiences if so? Or if anyone is familiar with it and has an opinion, good or bad, regarding that particular stove.

More wood stove questions may follow over the next few days!

Many thanks

Clay core storage heaters?

Carol hunter — Wed, 04 Dec 2024 12:36:06 +0000

Dear illustrious Virtual Community.
many years since posting, living well in our straw bale/timber home heated by wood only. several other small "out" buildings all heated by wood too, new wood burning Rayburn and Finnish soapstone masonry heater.
It's just that we're getting stiffer and older and there are a devil of a lot of fires to light; not to mention the likes of Monbiot breathing his new Righteous Fervour down our necks. So...

Thinking Mass/storage heater type of electric back up just for background warmth when/if we're away or when we can't light fires any more. I only know of very expensive German ones controlled "smartly". Is there still an old school version like the ones that used to be full of bricks, does anyone know? Surely these could be reasonably efficient?

Much appreciate any pointers and my apologies if I've missed an already existing thread,

Carol

Radiators on a central manifold?

Victorianeco — Sat, 30 Nov 2024 11:18:38 +0000

Our renovation which includes an ASHP is now ready for radiator positioning so we can work out the supply pipework location's.

Are Trunk and feed layouts now outdated? Should I be best running everything back to a central manifold? It would mean more pipework but potentially less joints.

Does this then make it easier for balancing etc?

If we do that, can all of the radiators be fed from 10mm potentially? Where can I get some kind of calculation or diagram made? The traditional S plan would be easy to do in 22mm and 15 to the radiators. Probably a separate circuit for upstairs and one for downstairs

Any thoughts please?

MVHR - Inputs and Outputs

Victorianeco — Tue, 08 Oct 2024 07:41:38 +0100

Is it a must to have outputs into every bedroom?

Vikinghouse's Freshair system is one location and relies via diffusion

The ducting for a 4/5 bedroom house seems intensive and getting through solid timber joists may be a problem without having ducting surface mounted and so forth

Plan of house here:
https://drive.google.com/file/d/1K0VZYNhSGukNRW9YarhwgCyhkTz3Qxpz/view?usp=drive_link

I'd also need extracts in kitchen (must it be above hob?), utility (to dry clothes), bathroom and shower room?

I've also read clothes dry faster when you have the dry air being pumped into the room as opposed to extracting? Due to moisture carrying capacity. Thoughts?

BPC have given a quote of ~£2500 for materials but I assume there will be more ducting/cost than what they've indicated

My journey with ASHP under the BUS scheme

Victorianeco — Sat, 12 Oct 2024 22:01:00 +0100

As I ask a lot of questions I thought I'd give back a bit for others and use this thread to document my ASHP installation under the BUS Scheme (£7500 grant): https://www.gov.uk/apply-boiler-upgrade-scheme/what-you-can-get

In my last 4 bed Victorian terraced house I installed my own Mitusbish Ecodan 8.5KW Heatpump and Kingspan cylinder back in around 2014 having minimal knowledge. I ran a mix of rads and UFH mostly run at about 35c 24/7 for the heating season. In the 9 years the only fault I had was one sensor and a zone valve. Other than that it worked brilliantly.

Moving in to our 4/5 bedroom detached house (1960s cavity construction ~200m2 floor area) earlier this year my first thought is to replace the 24 year old system boiler and rads as part of the renovation which will include an extension, cavity insulation, EWI system and upgraded windows.

I calculated my heatloss as approximately 7kw assuming 0.17 U-Value for walls and 1.4 U-Value for windows/doors. U-Values were claculated using:
https://www.changeplan.co.uk/u_value_calculator.php

Heat loss calculation was done using MCS spreadsheet available here:
https://mcscertified.com/wp-content/uploads/2021/04/MCS-Heat-Pump-Calculator-Version-1.10-locked.xlsm

I then contacted 2 local companies to me who offer the BUS scheme using the MCS link here:
https://mcscertified.com/find-an-installer/

The first company came out and said I need a 8.5kw system and quoted £4000 (after the £7500 discount) to supply and commision a Samsung 8.5kw and 210l cylinder which I thought was excessive.

The second installer looked at my calcs and did their own and we agreed we need ~10.5kw to cater for DHW and the proposed extension and potential loft conversion. Their recommendation is a Vaillant 12.5kw, 300l matching cylinder and a buffer tank. Cost to me after the grant is ~£2000. He can supply cheaper units but recommended the Vaillant as better weather protection in our environment.

On site he had advised no buffer tank needed but this was on the quote so their may be some savings to be had and I may ask for a smaller cylinder (only 4 people live here). So will chase this up this week. He also kindly provided radiator sizes which again more or less matched my calcs give or take aprt from 2 rooms which I actually think my figures are right.

All of these prices are for myself to rip out the old cylinder, system etc. get power supply to the 2 new locations and get the cylinder signed off. Also upgrade all the rads and plumbing.

So the rads and pipework are being installed/laid out this week so will update as we go.

Questions
1. Preference on heat pump manufacturer?
2. Thoughts on buffer tanks? Radiators will be oversized anyway and UFH in 50-60m2 area
3. Size of cylinder for 4 people in a 4/5 bedroom house?
4. With all pumps now being inverter type is a 12.5kw going to be an issue if my heat loss ends up being less? (with better insulation etc)
5. Controls? Just use one stat and TRV's on all upstairs rads?

Redundant copper overflow?

john.connett — Thu, 24 Oct 2024 11:12:18 +0100

My old boiler had a separate copper pipe from the safety valve to outside the building. It is now redundant and has been cut back to boxing in the kitchen. An open copper tunnel to the outside is less than ideal with in a house with good insulation and air-tightness!

Removing it would be tricky as it runs down boxing and behind a fitted kitchen unit. Capping both ends would help. I'm also wondering about filling it with some form of insulation. The remaining pipe is around 1.5 to 2m long.

Any suggestions?

Radiators in 2024? Sizing? Actually needed?

Victorianeco — Sat, 06 Jul 2024 09:44:35 +0100

Looking to upgrade radiators in bedrooms, currently single rads in every room.

We will eventually run an ASHP - should we be engineering out the radiators and upgrading the insulation/windows instead? (More costly)

Should we be looking at hydronic plinth heaters instead? Just upgrade to Type 22 radiators the largest we can fit in each room? Maybe look at air to air heating on the landing only?

Spreader plates across joists?

Maybe electric heating instead?

Aesthetically we aren't looking for anything fancy

Ideas appreciated

Hot water cylinder for ASHP?

Victorianeco — Wed, 02 Oct 2024 21:22:56 +0100

My last house had a Kingspan cylinder 210 litres.

We are currently renovating the new house and looking at heat pump and cylinder options under the BUS scheme, but we feel it may be better for us to install the new cylinder ourselves and get the grant just for the heat pump.

What is the best style of cylinder to future proof also? Maybe adding in a feed for PV?

THANKS

10mm pipe for radiators?

Victorianeco — Fri, 27 Sep 2024 19:27:49 +0100

According to the quick sizing table contained in the HVCA central heating design guide 10mm pipe can carry 2500W the limiting factor being the velocity of the water in the pipes. If it exceeds 1.5m/s which is the maximum velocity specified in BS 5449 you will start to get noise problems.

So that you have the whole picture 8mm carries 1500W, 15mm-6000W, 22mm-13000W, 28mm-22000W and 35mm-34000W. For an efficient fast acting system microbore feeds should normally be restricted to runs of no more than one metre and the system pipework reduced as the load reduces.

Would you use 10mm pipe for radiators in a new install for the tails only? Looking to embed them in walls behind skirtings

Should we buy a monobloc

minisaurus — Sun, 15 Sep 2024 12:46:03 +0100

We have an EAHP; it has issues.

I'm considering getting a monobloc, and decoupling the radiator system from the EAHP. So the EAHP is only for hot water & ventilation.

3 questions about monoblocs:

Do they have to stand on concrete? Suitable places at our house are all wooden deck affairs.

Must I have glycol in the radiator pipes in case of stoppages (it can go down to -20 here ...)?

Would it be feasible to just turn the whole thing off in the summer? It's a noise/vibe thing - our outdoor seating area is often completely still & quiet in summer apart from the occasional rustle of Aspen leaves

Underfloor heating to 25C on buffer tank

homdogs — Thu, 05 Sep 2024 18:41:03 +0100

So we have a new UFH system with a wood gasifier/boiler for fuel. The guy who installed the system said we need to heat the water in the buffer tank to 60-70C. It occurs to me, however, that most of the water, for the UFH, is only needed at 25C, and a minimum of water, for showers and at the sinks, would be needed at 60C. Wouldn't it make more sense to have a separate on-demand boiler for showers/sinks and only heat the UFH water in the buffer tank to a much lower temperature, say around 30C?

Changing from gas to electric heating in apartment

Shevek — Thu, 05 Aug 2021 12:37:18 +0100

We currently have a basic gas boiler providing domestic hot water but no central heating. We recently fitted new windows but the walls will remain badly insulated (30-40 mm of PU foam sprayed on external face of internal masonry leaf). However the winter is relatively short and warm here (with lows and highs of 6Âº to 15Âº Dec to Feb).

We're thinking to exchange the gas boiler for a hot water cylinder with integrated air source heat pump (e.g Dimplex Edel, Energie Aquapura Monobloc etc. that can vent directly through the external wall) and fit a few electric infrared or convection panel heaters. (there is EU funding available here up to â‚¬2500 to fit new heat pumps, solar thermal, PV etc.)

But if we're going to the trouble of fitting such a unit and we really want to lower our heating bills then would we be better to fit a heat pump that can also provide central heating?

Problem is I can't find hot water cylinders with integrated heat pumps that can provide this level of output.

We're on the first floor of a 4 storey block of flats and while it might be feasible to fit something on the roof I'd rather avoid that option if we can. First we'd need to get permission, then we need to find a route, it would need to be close enough, and then we'd need to be sure we're not create a noise nuisance for the top floor (the building performs very badly acoustically).

Are there any integrated units on the market that can provide central heating?

Convert Pt1000 to NTC 20 k??

john.connett — Mon, 12 Aug 2024 12:10:24 +0100

I am considering changing my solar thermal controller. The existing controller uses a Pt1000 sensor in a roof mounted solar collector. My preferred choice of replacement expects input from an NTC 20 k? sensor. Can anyone suggest an affordable converter?

It would probably be possible to produce something using a https://thepihut.com/products/adafruit-pt1000-rtd-temperature-sensor-amplifier-max31865-ada3648" >PT1000 RTD Temperature Sensor Amplifier, https://thepihut.com/products/adafruit-ds3502-i2c-digital-10k-potentiometer-breakout-ada4286" >DS3502 I2C Digital 10K Potentiometer and a Raspberry Pi Peco or similar if I possessed the necessary making skills.

However, I would prefer a ready made device that wouldn’t frighten a heating installer!

Any suggestions?

PV plus wood burner system: thermal store or vented?

EshanessAl — Thu, 20 Jun 2024 20:12:54 +0100

Hi folks. I’d like to pick your brains on a system for our small 2 bed croft house. We currently have an old Rayburn we are switching for a more efficient boiler cook stove. It’s our main cooker so on every day in winter but not so much in summer. We have 4kW PV but soon will have 7kW with a battery and diverter to immersion. The new stove will output 9kW to water. Currently got a bath and will add a shower. We just need 2 rads.

I can’t decide between a thermal store or vented cylinder. We can only fit about 150L cylinder and have very little head for pressure on a vented system. No radiators yet but planning either 2 radiators or low temperature in-wall heating (like underfloor but in the wall!). the benefit of the thermal store is that the PV could contribute to running the heating, which would be great, and be a good dump for summer days (we still need heating in summer). Plus nice to have mains pressure HW. Vented system would be simpler for plumbing, I’d probably use standard rads, and could add an electric radiator as a summer dump if needed. Shower would probably need a pump.

The stove is rated to work with an unvented system too so that is a possibility, just a bit put off by the fact it needs a registered installer and annual service.

Thermal store would be gledhill or advance appliances. Leaning towards AA as it works in a power cut, which we do get quite regularly in winter. Heard a few negatives on thermal stores needing to be maintained at high temp and dropping quickly with bath or heating. I don’t want to be topping it up from the grid if I can help it.

Thanks in advance!

Optimal Hot Water Settings

Victorianeco — Sat, 01 Jun 2024 11:34:45 +0100

We have just moved into a 1960's detached property

Gravity fed system, gas sytem boiler and hot water cylinder (looks lightly insulated)

Am I right in syaing we should adjust the stat to 50c based on the top exit pipe temperature? Would you then heat it twice a day? Say 5am and 5pm? I have a FLIR camera I can base the temperature on?

The ultimate aim is to replace the system with an ASHP at a later date after insulation, windows etc. etc.

Thanks

Default mode

tony — Sun, 14 Apr 2024 09:03:28 +0100

A friend of mine has solved a problem that we might come across with other people. They have the Eco mode on their boiler, in other words they did not have preheating of the hot water. They were most surprised to hear my boiler come on, and upon investigation found that the Eco mode was off! They realised that this was because the electrician turned the power off when attending to a cooker switch. So what they learned was that whenever someone or something cut the power to the boiler, they will need to switch Eco mode on again when power is restored.

Why to boilers or at least that make default to not eco mode?

Thermal store, adding ufh

rwski — Wed, 14 Feb 2024 14:10:44 +0000

We have 2000l Akvaterm thermal store fed by wood gasification boiler and solar thermal.
Current output is domestic hot water and 3 radiators.
We are going to add ufh.
Does anyone have a plumbing and wiring setup for this that they could share. The important difference to lots of schemes that I see is that adding heat is manual so we don’t want to turn on the ufh when the tank is not hot enough. Everything I look at just sends a call for heat and carries on turning the ufh on…

Ideally we will use heatmiser neo, but at the moment I’m interested in detailed information about what others have done.

Current radiators are just turned on by a thermostat on the tank, if the tank is above the set temperature the pump is turned on.

Thank you!

electric heaters

djh — Wed, 03 Jan 2024 13:27:08 +0000

As I've mentioned before, I use electric resistive heaters to heat my house, because of the low heat demand. I have two: a VEAB duct heater fitted after the MVHR unit, and a radiant heater in the hall. I'm looking for a replacement for the hall heater and not having much luck so far, so I'd appreciate any thoughts you may have.

The current heater is a Stiebel-Eltron IW 180. They don't seem to sell it any more but they do still sell a lower-rated version, the IW 120 < https://www.stiebel-eltron.co.uk/en/products-solutions/central_heating/electrical_heaters/small_heaters/iw/iw-120.html > (I use one of those in a wetroom.) The IW 180 is the same but has 600 W bars instead of 400 W bars. I chose it because it was simple and from a known brand.

It is powered from a fused timeswitch that switches on for the E7 hours from 00:30 to 07:30 when needed. I adjust how many bars are set to come on depending on what the house needs. So it's all manually controlled to date. The hall is on the cooler north side of the house, so the heater heats the hall and lobby and also the stairs and landing above. The MVHR spreads the heat around further.

It has worked pretty well, though the unit has one flaw. It is controlled by a pullcord - once for 600 W, twice for 1200 W, three times for 1800 W and four times turns it off again. But the pullcord exits through a hole punched in the casing that has rough edges, so over time it frays and eventually breaks. I'm getting fed up of dismantling the unit and cutting the cord a little shorter to repair it!

Lately the switch itself seems to becoming awkward, not always switching correctly. Hence my search for a replacement.

My problem is that products have changed (new regulations?) and are 'smart'. So for example I looked at a Dimplex product yesterday, but it is 'smart' and uses a proprietary phone app via wifi. It can't be controlled by a timeswitch because it forgets its network connection details if it loses power :( Other products are only designed for intermittent use or only for outdoor use (whatever that really means?).

So if anybody has ideas as to suitable products or arrangements, I'm eager to hear them.

Pellet boilers

owlman — Fri, 19 Jan 2024 11:36:25 +0000

My ageing logwood gasification boiler may need replacing in the Summer, so I'm considering various options.
The CH system and DHW, ( plate heat exchanger ) are currently fed from the large 2000l accumulator tank. This bit of the overall boiler set up works fine, and I'd like to leave this bit in situ.
The logwood boiler however could do with upgrading, and as I get older a replacement pellet boiler seems to be worth consideration. I'm familiar with how they work and there appears to be a decent choice albeit EU based suppliers. What concerns me is their suitability for batch burn re-charging of such a large store. I can't seem to figure out if they are technically more suited to slower modulating burning more suited to direct connection to a CH system, simple in out, flow and return.
Burning logwood involves the fast, fierce, recharge burn and I wonder if using this methodology every two or three days but running on maximum with a pellet boiler would be unwise.
Does anyone use a pellet boiler with a large re-chargeable accumulator tank, any info would be appreciated. Suppliers I've spoken to either don't know or recon its OK, but then they would say that.

Wood stove: Insulating above the closure plate, is it common? Good idea?

greenfinger — Thu, 14 Dec 2023 16:22:36 +0000

Hi all

I've got a wood burner installed in a builder's opening. Single wall flue into a flexible chimney liner. The thin steel closure plate is higher than the lintel in front - i.e. you can't see it when stood in front of the stove. I therefore often wonder how much heat gets "trapped" in that pocket of space behind the lintel, and subsequently escapes through the closure plate into the chimney void.

So I've been thinking about insulating above the closure plate using mineral wool and wondered what people think to the idea? I've not come across much info of people doing that. Seems sensible to me but perhaps I'm overlooking something.

I did mention it to the chimney sweep when he was last here and he was against the idea. Not sure how much I trusted his opinions though (on that and other things!). One of his concerns was the mineral wool combusting. I told him that in my limited knowledge it's not combustible but he wasn't having any of it!

Any thoughts?

Many thanks

Wood-fired thermal store DHW and UFH system

CJCurry — Fri, 17 Nov 2023 10:57:11 +0000

Good afternoon Green Building Hive Mind.

I'm in the process of renovating my house. It's a stone built, C16th, long, thin, detached off-gas house in the Yorkshire Dales National Park. It's been our family home for several hundred years and I've just taken it on, so it's a bit of a labour of love. It's getting sympathetically double glazed, insulated and generally made as energy-efficient as possible. I'm a tree surgeon and forester by profession, so have almost unlimited amounts of free firewood, which is a resource I'd like to use as my primary heat source. I've removed the very old oil-fired central heating system and designed a new system which I'd like to run by you for comment. Constructive criticism welcome. I've asked my usual plumber but because my needs are a bit non-standard they didn't really get what I'm trying to achieve.

Essentially, I have a massive 30kw water-jacketed woodburning stove in the big kitchen in the middle of the house. The hope is to burn this fully opened-up for an hour or two on a morning and evening, and keep it ticking over shut down during the day. There are also two smaller stoves with back boilers in the living room and dining room which will be lit in winter. This should fill the 2000l thermal store enough to keep the hot water and underfloor heating topped up constantly - see diagram. If I go away and don't light the stoves, the immersion heaters should kick in, or I'll set them up to be turned on remotely a day before I get back. Equally if the system can't cope with demand, the immersions will take up the slack.

To anticipate a few queries...
-All pipe runs will be in 28mm
-The thermal store is on the first floor and all stoves are on the ground floor, with pipework on a continuous gradient so it should be gravity-fed
-By the time I've finished all the renovations, there'll be seven bedrooms and five bathrooms, with potentially up to 15 people having hot showers when the house is full, hence the wish for a big unvented DHW cylinder rather than a conventional heat-transfer plate from the thermal store.

I'd appreciate it if the with experience of similar systems could sense-check this design for me. Thanks!

UFH Actuators

Diarmid — Wed, 29 Mar 2023 11:26:35 +0100

Currently we have ufh (5 zones) powered by expensive lpg, which will increase to seven after some building work. I'd like more control of the system and believe fitting actuators on the manifold would be the way forward. My question is what would a system to control the seven actuators look like? I'd presumably need 7 thermostats - one in each room...

Understanding air con split unit choices

LouiseSJPP — Wed, 18 Oct 2023 19:05:47 +0100

I'm having a hard time getting to grips with specifying and choosing a reversible split air con unit. It's for my house in northern Spain. Between differing units of heating / cooling capacity (kW, btu/hr, Kcal, Kfrig...), a general reluctance to state electrical power consumption and trying to work in Spanish, I'm a bit lost.
Situated in a ground floor living space of 20m2, the prime function for the unit is to reduce humidity of the house built into a hillside, in a forest.
The second function is to provide background heat. As we spend some months away from home, having a heat source with a drying function to switch on automatically will protect the house when we're not there. When we are there, we have a boiler stove in that space, but at 5kW to room (plus 10 to water which looks after the rest of the house) a bit of heat at the other end of the space will be useful.
The third function is to provide some relief from summertime extreme temperatures and high humidity, as we've had some very unpleasant episodes recently.
The house is double glazed and the thick stone walls seem to provide a reasonable degree of insulation. I'm thinking 1 or 2kW of electrical input giving maybe 2.5 or 5kW of heating / cooling may be about the right size.
Can anyone offer advice, opinion or experience on how to size, where to buy, who might install it.
We're in Valcarlos, Navarra.

Any downsides to replacing regular boiler with combi?

DannySheffield — Tue, 03 Oct 2023 18:41:20 +0100

Our current heating system is a dodgy DIY job (regular boiler, 2 hot water tanks, very odd plumbing). The boiler is a year old.

We need a new bathroom and the fitter has strongly recommended we replace the heating system first as a) it is likely to go wrong and need work which might well involve digging into walls etc, so it's better to do that before we have a new bathroom (and plastering in other parts of the house) done. b) switching to a combi boiler would free up much-needed space in a relatively small bathroom.

I'm aware that we won't be on a gas boiler forever. My question is - is there any benefit to maintaining space for the hot water cylinder in the bathroom on the basis that we might need to move back to tanks if we move to e.g. an air source heat pump? The heating engineer said that's probably 20 years away in our 1930s house. We have a second (120 litre) tank in the crawlspace, which we'd keep either way (just because it's too much hassle to get it out!).

Woodstove back boiler to buffer cylinder, sealed or vented?

LouiseSJPP — Mon, 02 Oct 2023 13:25:46 +0100

This has been discussed before, I see, but many of the information links are now inactive, and my case may be slightly different.

I'm in northern Spain, living nearly off-grid. I'm installing a back-boilered wood burner and wish to connect it to a 6 bar max steel 100 litre cylinder fitted with one coil, situated two floors directly above the stove. This will be the primary buffering circuit, and from there will run the central heating system. I'm intending to use the coil for the heat input to minimise thermal inertia and the water jacket to run the sealed heating system.

The first question is vented or sealed for this primary circuit? Code, in Spain, it seems, calls for sealed. I'm prepared to ignore this if I cannot see a way to guarantee safety without a vented system.

The stove (Flamma 14CS, 15kW, of which 10kW to water) is designed for either. It has a cold water flush in case of overheat. I have no documentation on how this works and frankly, I don't hold much faith in it. Where does it flush to, and if the flush is internal, what drives the flush through the existing pressure in a sealed system??

If I vent it, I need to choose gravity or pumped. If gravity, protecting against power loss is a null issue. I have a 5m vertical run of flow and return, but the cylinder I already have (Kospel SWK 100) is top-feed to both sides of the coil, which acts a little against gravity flow. I'm guessing if I insulate the vertical flow pipe run and leave the return unlagged copper, it will help maintain the flow.

Either way I understand I need an anti-condensation valve in the primary circuit, and in a sealed system would fit a magnetic filter / charge point and an expansion vessel. Or I could buy a ready-made unit which has these components in it. Plus pressure relief valve, auto-bleed valve and drain point.

Could anyone advise / discuss / guide me please? I need to get this right, I don't want any accidents or a system which doesn't work well.

Background: I was a professional engineer and have a fair bit of plumbing experience, but it doesn't extend to uncontrolled heat sources, hence my wariness and questions.

Edited: there was a typo in the make of stove, here is a link to the relevant pdf::

https://piecepolska.pl/data/UserFiles/Image/Flamma_instrukcja.pdf

They are winding me up!

tony — Thu, 21 Sep 2023 20:49:35 +0100

Room 13m x 6m with suspended un insulated wooden floor, single glazed draughty windows, 380mm solid brick walls and a bay window with French doors and 225 brick walls under the windows and un insulated hipped roof over it. Main room two outside walls.

I said insulate the floor 150mm 100mm batts with 50mm EPS, and IWI 80mm PIR, draughtproofing, secondary glazing, insulate bay roof

What is the difference gas heated 7 days and 7 evenings 21C, night time 14C

Any guesstimates or do we need more info

Helium heat pumps

djh — Fri, 25 Aug 2023 17:42:54 +0100

Has anybody come across helium heat pumps? Are they real? Are they anywhere near production?

Warm air central heating - Options for a low carbon house

PaulEdwin — Fri, 01 Sep 2023 14:09:18 +0100

When we bought our house 12 years ago, I was impressed by the absence of radiators that were a feature of the 1980s warm air heating system. Rising energy costs were to reveal the disadvantages of the system: reliance on gas fuel and the inability to regulate different areas of the house (eg bedrooms). Johnson & Starley are UK manufacturers of warm-air heaters, and they claim that their products will be able to use a future gas mix including 20% hydrogen. This is not an efficient use of energy even if the national gas specification is changed in this way.

I will leave the refurbishment of our heating system for a future owner but wanted to start a discussion to explore how this heating product is best dealt with for a low carbon house.

There are three options that I have thought of, starting with the first â€“ rip out the ducting and replace the gas heater with an air source heat pump and new radiators (and all the new pipework!). This would be a disruptive building operation, not only due to the routing of new pipework, but also the removal of the vertical ducting between ground and first floor would then require substantial redecoration.

Could a heat exchanger replace the gas heater? This would need new heat extraction ducts installed in the loft and ground floor ceiling spaces. The permeability of the building envelope may have to be checked and remedied if leaking. There is also a question of whether the existing supply ducts are correctly sized.

For my third option I wondered if an air-to-air heat pump could replace the gas heater and supply warm or cool air through existing ducts? This would avoid the need for an extraction system as above.

I forgot to mention that we have 8kW capacity solar panels installed on a SSW facing roof.

Air source heat pump issues

Victorianeco — Wed, 02 Aug 2023 21:40:44 +0100

Mitsubishi ecodan 8.5kW system, kingspan 210l cylinder....

Just the last two days it appears my circulation pumps are both stuck on and the pressure relief valve (there appear to be 3) one of which seems to be bypassing water into the tundish....

The temperature seems to be at 57C when it is usually set to 50C...

What's the fault finding process? Never had an issue in 8 years previous, the only thing I can think of recently was draining the heating system to disconnect a rad. But no other issues.

Thoughts please

ASHP + Solar PV

Diarmid — Fri, 04 Aug 2023 19:58:47 +0100

Rather than installing an expensive battery I was mulling over the idea of installing an ASHP and a solar panel array. Currently we heat via UFH powered by lpg (expensive) The house is south facing, 55ÂºN and well insulated. I would have the solar PV feed directed to heat water by default IYKWIM. I'm retired so at home during the day. I realise that between October and April power generation would be limited. Currently consumption about 2000 kWh per year. Thoughts?

Multi-fuel vs Wood Only (and "Hybrids") when just burning wood...

greenfinger — Sun, 06 Aug 2023 18:33:46 +0100

Hi

Sorry to return so soon with another wood stove question... This time it's about multi-fuel (MF) vs wood only (WO) stoves. From the reading I've done, there seems to be mixed opinions on whether a WO stove performs better than a MF stove, when burning wood only.

****Open Grate****. One of our shortlist stoves is the ACR Earlswood III and Astwood II. Both are MF and have grates with permanently open slots. See below for pics. The stoves tick a lot of boxes for us, but the grate puts us off. The manufacturer has said that it won't affect performance, so long as there's a good bed of ashes. But logic and the opinions of some on the net would perhaps suggest otherwise.

****"Hybrid"****. I used the term "Hybrid" in the title to refer to stoves like the Clearviews and Woodwarm Fireviews (others too I'm sure), which have riddling grates which can be put into a closed position and provide a flat bed. But there's still gaps between the bars so it's not a truly solid bed. And whilst the primary air can be closed (at least I know it can on the Woodwarm), I'm not sure if that totally prevents air getting through. A Woodwarm Fireview Eco is a contender.

****Wood Only.**** Another contender is the Dik Geurts Ivar 5. True wood only burner with vermiculite bricks on the bottom.

Any thoughts on the three types and how relevant or important the grate/base situation is for wood only, would be most appreciated. And just to add, I've read that a bonus of the MF and Hybrids is that the Primary Air coming in beneath the grate can be very helpful getting the fire going. Yet on the other hand, a WO without the grate and ashpan means a larger firebox.

Over to you guys!

Many thanks

ASHP insulated pipe under/up through concrete beam & block floor?

john.connett — Tue, 01 Aug 2023 15:48:02 +0100

I am considering replacing my Viessmann Vitodens 200-W gas system boiler with a Vitocal 200-A Monobloc ASHP. The indoor unit of the ASHP is almost identical in size to the gas boiler. Much of the electronic and plumbing connections should be able to be reused. Great!

Problem: The boiler is in the kitchen at the front of the house and the outdoor unit of the ASHP would need to go in the back garden. How to connect them with Uponor Ecoflex Thermo Twin HP, a large diameter insulated pipe for hydraulic, electrical and electronic connections?

The house was built in 1995 and has a concrete beam & block ground floor. My ideal solution would be to run the pipe under the house and up through a core-drilled hole in the kitchen floor. There is a kitchen unit close to the boiler and if it surfaced under that it would be almost invisible except for possibly some boxing at the back of a cupboard.

The excellent technical support at Uponor suggest that it is technically feasible but cannot identify a contractor that could do the work. They are only aware of contractors that undertake commercial/industrial projects.

The core drilling is feasible (although I don't know the Building Regulations aspects). I know that builders have put basements and wine cellars under existing houses. Others have sprayed thermal insulation under suspended floors. If a drain under my house broke I imaging there would be somebody that could fix it.

I really want to avoid the disruption of moving out furniture, ripping up carpets and floorboards and running large bore, insulated pipes up the outside and through the fabric of the house. If I can't avoid that aggravation I might just scrap the whole project!

With heat pumps set to become a common replacement for gas boilers, insulated pipe connections under the ground floors of houses without basements doesn't seem such an outrageous solution.

Has anyone achieved something similar?

Square stove in corner - how close to solid plastered wall without risking blowing?

greenfinger — Mon, 31 Jul 2023 13:30:15 +0100

Hi all

We're looking to have a wood stove installed. It will go into the corner of a room, at 45 degrees to the walls. Both walls are external, cavity, with plastered block / brick on the inside.

One installer has said so long as the two back corners are 100mm minimum from the walls, there won't be a problem with blowing the plaster.

But another has said it is best to follow the stove guidelines for distances to combustibles (even though the wall isn't combustible; but to prevent blowing) - which in our case would be 400mm.

Quite a difference! Would anyone mind sharing your thoughts on which sounds most realistic?

Many thanks

wet underfloor heating

maxsm — Sat, 14 Jan 2023 18:47:52 +0000

Hi all, just hoping for some advice on wet underfloor heating. I live in a 60s bungalow and the install would be in a flat-roof single story 'annexe' which is connected to the main property. My home is very poorly insulated and heated by a gas boiler and radiators but I'm currently speaking to architects with the aim of extending the property and bringing my energy usage right down (a new well-insulated roof and wrap around external insulation finished with render). The wet UFH in the annexe is a test to see if I would like it throughout the rest of the property.

How deep will I need to dig down to end up with a new floor at the same level as the current concrete floor?

After digging down I understand the layer order will be: 300mm insulation - DPM - concrete - 60mm wet UFH in screed - 15mm engineered wood floor. Is this in the correct order? Am I missing any layers? What thickness will the concrete be?

In the short-term the wet UFH will be powered by a gas combi-boiler but I may end up with an air source heat pump and/or solar water heating in the future. Is there anything in terms of plumbing/thermostat set-ups I should do now to ensure the UFH is compatible with my future energy plans?

Hope all that makes sense, any advice much appreciated, thanks

Air-source vs ground-source heat pumps - 2023 edition

lineweight — Mon, 26 Jun 2023 11:03:26 +0100

At this moment in time is there any kind of broad consensus on when a ground-source heat pump should be considered for domestic houses?

My understanding is that some years ago, there was a quite big gap between the efficiency of AS and GS, but that this has closed considerably in the meantime.

Meanwhile, GS remains a fair bit more expensive to install.

So, is GS something that is only worth even thinking about on larger new-build projects, ones where a garden area is available, and ones where the budget is fairly generous?

Or are there other scenarios where it's worth consideration?

Heat Pump Questions

mitchino — Tue, 13 Jun 2023 11:09:59 +0100

I think our oil fired Worcester Bosch External Combi is on the way out. A replacement including installation would be Â£4500-5000.

I'm wondering whether now is the time to get a heat pump, as it looks like we can apply for grant funding from the Scottish Government of Â£7500 plus another Â£1500 because we are in a rural area.

Initial Questions:

The oil combi is the 25/32 kW model. What size of heat pump would we need?

I assume we would need an air to water heat pump - can the water tank be located outside of the house - we have a lean-to outhouse, can it go in there?

How far from the tank can the heat pump be located, and is this best positioned in a sunny spot with little wind?

The house has 15 radiators, plus two woodburners which we light when we want save oil. We would want keep the radiators, installing underfloor heating would be too much to deal with. If possible we would like to also avoid having to double the size of the radiators. Is there a system that we could get that would just be a straight swap with the oil combi?

Is it a condition of the grant application that the house has to have a certain level of insulation etc? Some parts of the house are well insulated, other areas are not.

As I said, just replacing the oil combi would be up to Â£5000. Roughly, what would be the cost of a heat pump and tank installation before the grant is taken into consideration?

Anyone with recent experience doing something similar?

Future heating of old houses

PeterWat — Fri, 24 Mar 2023 17:23:16 +0000

Been wondering about the right course of action for home heating.

Background is living in a 1920s house - detached, semi-rural position, mostly solid brick walls; double glazed and some loft insulation; suspended timber ground floors. So far, bills for our gas CH/gas cooking/gas DHW are still not horrendous. Two advantages we have are south facing main windows, so a lot of solar gain; and one small woodstove, costing nothing to run (as we have a firewood source, coppiced and processed ourselves, seasoned when cut, stored for minimum 2 years under cover and well ventilated).

We have so far resisted going for expensive EWI and floor insulation. Partly because this would be very difficult and disruptive (and would cover up period features), and partly because we may be moving anyway; and the trend locally is for developers to demolish and rebuild (or gut and massively extend) many older houses that come on the market. So any retrofit insulating we did might have a very short life.

All that said, our gas boiler is over 15 years old and the decision is either (1) replace like with like; or (2) spend more on a heat pump. The latter would be doing the "right" thing - by current national advice - but is it?

On (2) all the usual advice says no - not worth doing unless the house is super-insulated as well.

Am wondering, however. In our situation, might it be worth considering an ASHP that would be considered undersized; keeping the existing radiators; and topping up heat in cold weather by plug in convector heaters? An expensive option, but would it remain so?

In the UK, conventional wisdom (at least, in the chattering classes) suffers from a deeply ingrained belief (dating from the 1950s) that gas heating is cheap, electric is expensive. I wonder though if this will soon be all wrong? Solar and wind power costs are tumbling but electricity seems likely to stay expensive due to the high costs of maintaining back-up generation (or energy storage) for periods of low generaion by renewable sources. On the other hand, the costs of fossil fuel power (or natural gas replacement by hydrogen) may get even more expensive. (For climate reasons they certainly ought to be).

Alongside all that, construction materials- and wage- inflation is simultaneously making effective insulation much more expensive.

So in future, might it become a valid strategy to leave some older, period houses poorly insulated, use a smallish ASHP for background heat, and bite the bullet of topping up with old-tech plug in heaters to heat key rooms on cold days?

Obviously not the ideal solution from a climate perspective - but in the (post mid-century) future we may have surpluses of renewable electricity, with significant consequences for relative prices.

MVHR recommended suppliers.

gustyturbine — Thu, 08 Jun 2023 08:11:21 +0100

Hi all, I know that many of you lovely people have installed MVHR systems. Would anyone recommend the company they used? Any self installers that found it straight forward and would make that financial saving again? any tips that need sharing to help me along my way? MVHR is a new system for me so I'm looking forward to it. Many thanks all.

One of the big six is suggesting they can help, then suggested air con

tony — Fri, 12 May 2023 18:05:37 +0100

Buildings should be designed so that they donâ€™t need air cooling, to suggest air con in the same breath as reducing things is nuts

Thermal Store with Back Boiler Stove

Dan Barlow — Wed, 10 May 2023 09:32:18 +0100

Hi All, Ive recently install a thermal store connected to a gas boiler and back boiler stove and im having a few teething problems which hopefully someone with more grey matter than me can assist with....

Its a 210L Advanced Appliances multi fuel thermal store, its connected to Ideal 40kW combi boiler which also still supplies some of the hot taps and a fairly old 14kW (5 to room, 9 to water) Hunter Herald stove. The TS runs my central heating (radiators and underfloor) and the remainder of the DHW (mainly the bath). I will use the immersion heaters too once solar is fitted.

All seems to be working generally as it should it terms of controls, when the stove is lit the pump runs and depending where the thermostats are set the boiler switches off.
However the TS is suppose to operate at 75-80 degrees according to the instructions, but im struggling to get it up to that temperature using the boiler or the stove, 60-65 is more realistic. The boiler is set on max temperature (80 degrees) but unless i run it flat out for hours on end the TS seems happier at around 65 degrees.

Im not sure if i was expecting too much from the back boiler stove but even after several hours with a good fire the output temperature is still only 60 degrees. The TS has a blending valve which controls the flow back to the stove which according to the instructions should be set at 55-60 degrees. It is a multifuel stove so maybe im not getting anywhere near the maximum output burning wood and would need to burn coal which im reluctant to do. Ive experiments with various pump speeds for the stove pump and also tried closing the valves to the heat leak radiators which is plumbed between the flow and return but im still not able to achieve more than 60 degrees.

Any help or advice would be much appreciated

Details of the Thermal Store:

https://www.youtube.com/watch?v=UX1O1kcvo1Q&t=13s

https://www.advanceappliances.co.uk/product/70-multi-fuel-universal-thermal-store-sfuts/

Barn conversion - Heat pump w/ Ducted warm air heating vs. Wet UFH

TigoDog — Fri, 28 Apr 2023 16:34:15 +0100

Hi all,

I'm helping my dad convert a 19th century hay barn into a 3 bed home that he'll live in. We're aiming for Band A EPC, so a very high level of insulation and air tightness, if not quite PassivHaus standard.

We effectively have a blank slate, so I'm interested in the GBF hive mind's opinion on the best heating solution. We are expecting to use an air-source heat pump, and I know the most commonly done method is an air-to-water system, heating water for UFH and general use. However, there is no existing wet heating system and I'm interested in air-to-air systems, particularly ducted systems (not wall mounted units). My thinking is that it should be more efficient to use the warm air created by the ASHP to heat the home directly, rather than losing energy in converting warm air to warm water. Also, UFH is expensive to install and ducted air should be cheaper(?). I'm also interested in how it could interact with Mechanical Ventilation. I imagine it would add complexity, but for the money I've seen quoted for UFH, I'd guess you could get a very high-end warm air/ventilation setup.

I know warm air systems were wide spread in residential buildings in the 70s - but were not popular as I understand it. They are common in commercial buildings (HVAC) and I assume they have come along way in the last 50 years, but most contractors I speak to seem to be pushing wet UFH. I'm trying to understand if this is just 'what they're used to' installing, more profitable, or if it is genuinely a better solution.

I appreciate he'd need a separate solution for hot water if we use the warm air system. He has space for solar, or if not, would an electric water heater would do the trick, or would that negate the efficiency gains? I've seen this system which does both in another thread, but according to the Daikin installer I spoke to, it isn't yet available in the UK market. https://www.daikin.eu/en_us/product-group/air-to-air-heat-pumps/multiplus.htm

My dad is relatively open to both options, but I wouldn't want to push something on him that doesn't work well, or 'feel nice'.

The barn is in the South of England (Berkshire). I include plans, which I have permission to post.

I'd welcome your opinions, or alternatively suggestions of contractors that can help.

Thanks in advance!