Just started a self-build in Dorset. Exciting times!

[NailBiter]

56 minutes ago, SteamyTea said:

This seems like it is going to become interesting, and expensive.

Should be able to chip in with comments every now and again.

I look forward to it.

[AppleDown]

I'd definitely be interested in seeing any drawings or plans you have.

[Moonshine]

36 minutes ago, NailBiter said:

I look forward to it.

 

when are you looking to start on site? (i might have missed you saying) i can imagine the groundworks are going to be pretty big!

[NailBiter]

18 minutes ago, Moonshine said:

 

when are you looking to start on site? (i might have missed you saying) i can imagine the groundworks are going to be pretty big!

We put in the access route this week!

We are now awaiting a second report from the ground investigation team as unfortunately we found some soft deposits but fortunately I'm told the news from the second drilling is positive. The drillers left site on Friday so hopefully only a few weeks till we get the report.

Hoping to avoid a piles or at least to avoid percussive piles, not a great way to introduce yourself to the neighbourhood.

I believe our planning permission is now extant due to the access route and we would be looking to do the reduce level dig once the weather improves somewhat. 

[Moonshine]

1 hour ago, NailBiter said:

Hoping to avoid a piles or at least to avoid percussive piles, not a great way to introduce yourself to the neighbourhood.

 

I am sure the dynamic sampling gave them a bit of the flavour of piling noise.

 

How much earth do you think that you are taking out in the reduced dig? I think ours was about 400t. I hate to think how much yours will be, and the muck away cost! (Assuming you can't lose it on site)

[dpmiller]

14 hours ago, NailBiter said:

High winds (causes frosting of the coil)

 

can someone explain this one to a simpleton please?

[SteamyTea]

12 minutes ago, dpmiller said:

can someone explain this one to a simpleton please

Not easily, but it may be that our (UK) high windspeed are from the south west, which is a more humid wind because it is warmer (close to mean sea surface temperature).

That will increase the dew point temperature, so may cause frosting to happen more often.

There is also the point that when windspeed increases, there are more thermal losses from a building, though these are generally offset but the high outside air temperatures and greater cloud cover which increases night time temperatures.

It may be possible to position an ASHP so that the air outlet faces directly into the wind, this could overpower the airflow caused by the blower.  But even this is highly unlikely as windspeed close to the ground is very low (why it is measured at 10m).

 

If high wind speeds were a real problem, none of the ASHPs in coastal areas would be working, so I suspect that it may be one of those ridiculous statements that pops up every now and again.

[JohnMo]

15 hours ago, saveasteading said:

 

But I agree that being in the sun won't make much difference to an ashp, but being next to a big masonry wall in the sun might be a fair bit better than in a permanently dark and damp alley

Unless you want to cool also, then efficiency drops.

 

So working the argument through

Biggest difference between the OP and the reference property, is the reference property only did DHW for around 1 hour per day. OP will be heating, cooling and DHW, so a different use case.

 

So let's assume the sun exposed, heavily build stone area that's designed to trap the sun's heat, ASHP installed close to a south facing wall to get max perceived gains.

 

Heating by ASHP running with an internal thermostat.

 

Typical nice winters day, cold overnight, zero degs, bright morning, sun out and air temp increases to 7 degs, then by 5pm temp starts to drop quite fast.

 

Overnight the stone area reduces to match ambient air temp of zero, ASHP gets no negative or positive effects from this.

 

Morning air temperature start to rise, stone area remains at close to zero for a prolonged period as sun not high enough in the sky to have any heating effect. ASHP in an area below air temp, negative impact on CoP.

 

Late morning to late afternoon, sun out and heating stone, sun also on house windows warming house, heating clicks off. DHW clicks on and heat pump starts at 2pm. Localised area could warm air flow to ASHP by say 5 degs (if you are lucky), giving a 0.3 CoP benefit. Heating benefit zero as heat pump is off.

 

Early to late evening, temperature outside drop back, some residual heat in stone, but the benefits are marginal, CoP gains for a short period but would guess almost nil.

 

Cooling case case almost the opposite, sun out you need cooling, ASHP is hot sun trap, EER (CoP when cooling), takes a hit. When flowing 12 degs changing air temp from 20 to 25 has a 1.2 negative impact on EER.

 

Another negative is weather compensation becomes screwed up, if the temperature probe becomes exposed to artificial low or high temperatures.

[JohnMo]

16 hours ago, NailBiter said:

Definitely avoid: High winds (causes frosting of the coil), Placement where servicing is hard. Restricted Airflow

Not sure where that snippet came from. An ASHP uses a fan to make high winds local to the heat exchanger to ensure good heat transfer. General wind make no difference to frosting of the coil.

[NailBiter]

2 hours ago, JohnMo said:

Unless you want to cool also, then efficiency drops.

The issue is a lack of power in December and January due to a lack of sunshine. I am totally unconcerned about power demand during sunny months when we need cooling. We only have a 6kw system in our current house and it provides for most of our needs 8 months of the year.

 

 

2 hours ago, JohnMo said:

Biggest difference between the OP and the reference property, is the reference property only did DHW for around 1 hour per day. OP will be heating, cooling and DHW, so a different use case.

Yes true but it isn't just sunny / warm for 1 hour a day. The goal would be to move both our heating demand and our DHW demand to the period when there is minimal difference between the temperature of the inside and outside unit. With DHW this is easy as you can just store hot water. We can also explore oversizing the ASHP slightly. 

The heating is a little harder however. My understanding is we can bank heat from about September / October onwards in the thermal mass of the building. On cloudy / very cold days we may be able to avoid running the system entirely. The goal is to put as few units of energy in during winter whilst preserving stable internal temperatures.

If the council decide to let me have a wind turbine (tall order but you never know) then I will have all the power I need all year round as December / January is typically plenty windy round by me. I asked the architect about this and he didn't seem hopeful however.

 

 

2 hours ago, JohnMo said:

 

So let's assume the sun exposed, heavily build stone area that's designed to trap the sun's heat, ASHP installed close to a south facing wall to get max perceived gains.

This is in response to a comment other than mine, personally I wouldn't install high thermal mass I'd just put it in the sun. If I were to surround it with materials I would be looking for low thermal inertia materials that heat easily in the sun (ever trodden barefoot on lead flashing on a roof in full sunshine?).
 

 

2 hours ago, JohnMo said:

Heating by ASHP running with an internal thermostat.

The ASHP for the UFH does not just use a single internal thermostat. We will be measuring both the air temperature and the floor temperature in each zone and can adjust the heating in each zone accordingly. This will be integrated with our Home Assistant instance and will have knowledge of past conditions, current conditions and future predicted conditions (extrapolated from the past combined with weather).
 

 

2 hours ago, JohnMo said:

Typical nice winters day, cold overnight, zero degs, bright morning, sun out and air temp increases to 7 degs, then by 5pm temp starts to drop quite fast.

 

Overnight the stone area reduces to match ambient air temp of zero, ASHP gets no negative or positive effects from this.

The ASHP does not run at night, we have plenty of heat in the building fabric and we will have several hundred litres of hot water at this point. Plenty for the night and the morning. This is the point the differential between inside and outside temperatures is at its highest and therefore efficiency is at its lowest for running the ASHP.

 

 

2 hours ago, JohnMo said:

Morning air temperature start to rise, stone area remains at close to zero for a prolonged period as sun not high enough in the sky to have any heating effect. ASHP in an area below air temp, negative impact on CoP.

Again I personally wouldn't surround the outdoor unit with high thermal mass / thermal inertia materials, I'd also put it somewhere where it was insolated first thing in the morning (very easy for us on our plot).
 

 

2 hours ago, JohnMo said:

Late morning to late afternoon, sun out and heating stone, sun also on house windows warming house, heating clicks off. DHW clicks on and heat pump starts at 2pm. Localised area could warm air flow to ASHP by say 5 degs (if you are lucky), giving a 0.3 CoP benefit. Heating benefit zero as heat pump is off

Can I get a source on these numbers please? They feel like they might be bum plucked.

If I could get my entire heating demand via solar gain then I wouldn't have any issue with needing to make sure I am efficiently making use of an ASHP in the first place. This is exactly the point I would be putting a good couple hours heat into the building. In a house the size of ours 0.3. CoP benefit is not to be sniffed at. That is nearly a 10% uplift on standard performance.
 

 

2 hours ago, JohnMo said:

Early to late evening, temperature outside drop back, some residual heat in stone, but the benefits are marginal, CoP gains for a short period but would guess almost nil.

Almost nil != nil so it would depend on the cost to site it in a insolated location vs in the shade as to cost / benefit.

Besides by this time the heat pump is off again because the internal / external temperature differential is high again.
 

 

2 hours ago, JohnMo said:

Cooling case case almost the opposite, sun out you need cooling, ASHP is hot sun trap, EER (CoP when cooling), takes a hit. When flowing 12 degs changing air temp from 20 to 25 has a 1.2 negative impact on EER.

Cooling is not a concern for multiple reasons. Mostly the heat capacity of the building but also the fact it is mostly solar powered. When there is cooling demand there is available power. I know there is no such thing as a free lunch which is why I'm trying to shift demand from when I don't have spare power (winter) to when I do (9 months of the year).

 

 

2 hours ago, JohnMo said:

Another negative is weather compensation becomes screwed up, if the temperature probe becomes exposed to artificial low or high temperatures.

This is a solved problem, the manufacturers worked out you can place the sensor in a sensible location and run the fan at full quickly before taking a reading. It is all detailed in one of the links above. 

Edited March 6 by NailBiter

[NailBiter]

3 hours ago, dpmiller said:

 

can someone explain this one to a simpleton please?

I don't know how to share this with you but I'm lucky enough to get journal access as part of my job. Your local library / university / pirate paper repository will have access to a copy https://www.tandfonline.com/doi/full/10.1080/1023697X.2017.1313134

[Thorfun]

17 minutes ago, NailBiter said:

If I could get my entire heating demand via solar gain then I wouldn't have any issue with needing to make sure I am efficiently making use of an ASHP in the first place.

Thats actually a thing……it’s called Passivhaus 😉

[NailBiter]

3 minutes ago, Thorfun said:

Thats actually a thing……it’s called Passivhaus 😉

Sure and if we were talking about a Passivhaus that would be a fair enough point but we aren't.

It came down to wanting more glazing than the passivhaus standard would allow.

Edited March 6 by NailBiter

[saveasteading]

3 minutes ago, NailBiter said:

If we were talking about a Passivhaus

But the principles apply. Play with them.  Avoid their gimmicks for the last 1/2% improvement, and other fads. 

A lot of people on here have aimed for 'close to passivhaus' standard, in their own terms.

In my opinion. Low and slow ashp, with the units positioned for aesthetics. 

No windmills.

Consider future solar panels, by putting a cable duct in.

But mostly, quality design detailing and construction, which trump everything else and are hard to achieve, so read other people's issues on BH for what to look for.

[Nickfromwales]

21 hours ago, NailBiter said:

Apologies but with it being so important to get right I will have to listen to the accredited professionals.

I would take a blend of both.
 

There are a lot of very well versed individuals on this forum, and I for one have zero ‘credentials’ to relate to building a certified passivhaus. 
 

However, I recently engaged with a PH certified architect, 25 years of PH design experience, and I got my design in at 88% efficient vs his 87%. He asked me a lot of questions, I gave very robust and reasonable replies, he conceded and the client then changed the MVHR design (well, the entire MEP design) and supplier on my say-so (and agreed to accept they’d lost £1k on the 1st design deposit).

 

A PH certified home builder now builds differently, after 30 years of PH experience, after meeting me and hearing how I have approached creating homes that consider M&E etc and how we’ve integrated things on other clients previous builds. 
 

In terms of qualifications, I have a clean driver license, that’s it. But I do have bucketloads of tenacity, a passion for what I do, and an unquenchable thirst for knowledge. 
 

Most of the stuff I’ve learned has come from exchanges here, with invaluable input, argument, reason, and real-life data (there’s a HUGE amount of it here if you want to spend some time digging).

 

One PH certified architect overlooked insulation in the foundations (😮), also didn’t have any clue about MVHR or space heating. Credentials coming out of every orifice, none that they understood or practiced well afaic. 💩 
 

I’d rethink your confidence in ‘all that glitters’, as only a select few turn out to be gold…  but I certainly do hope you have some of the best at hand. You’ll need it, as there’s a LOT to correlate and execute correctly at yours.

[NailBiter]

17 minutes ago, saveasteading said:

But the principles apply. Play with them.  Avoid their gimmicks for the last 1/2% improvement, and other fads. 

A lot of people on here have aimed for 'close to passivhaus' standard, in their own terms.

In my opinion. Low and slow ashp, with the units positioned for aesthetics. 

No windmills.

Consider future solar panels, by putting a cable duct in.

But mostly, quality design detailing and construction, which trump everything else and are hard to achieve, so read other people's issues on BH for what to look for.

We are building with passivhaus principles in mind, it would be rather foolish of us to have paid extra for a passivhaus trained architect and not to do so.

The above was in reply to someone who suggested we could get all the heating demand from an hour of sunshine in winter. I wish that were the case but it simply isn't unfortunately. 

Apologies if I came off a little blunt with them but how does someone with little to no knowledge of our build guess the time of day our thermostat clicks off? It simply isn't possible to even have an educated guess at that.

 

Very good tips about fabric first, we are definitely taking that approach. Thanks so much for the recommendation of the timber framing company. We have spoken with them and they are doing a quick turnaround quote for us which we will have on Friday (very impressive!). I really do appreciate you taking time out your day to share that with us.

Edited March 6 by NailBiter

[JohnMo]

51 minutes ago, NailBiter said:

My understanding is we can bank heat from about September / October onwards in the thermal mass of the building. On cloudy / very cold days we may be able to avoid running the system entirely.

Wish it was true. It would be nice, my 57 tonnes of concrete floor and about 65 tonnes in the walls would beg to differ.

[JohnMo]

56 minutes ago, NailBiter said:

Can I get a source on these numbers please? They feel like they might be bum plucked.

I don't bum pluck numbers, CoP numbers for different flow temps and outside temps.

 

With this I will bow out and let you dream on.

 

 

[MikeSharp01]

23 hours ago, JohnMo said:

Wikipedia, is a site any tom dick or Harriot can upload too. Nothing scientist about that site. If I wanted to upload and say the world is flat and made of chocolate I could

You could but you would soon either have it overwritten or asked to provide your evidence / citations/ references. I dimly recall it was compared with encyclopedia brittanica and its veracity score was similar. 

[SteamyTea]

27 minutes ago, NailBiter said:

Apologies if I came off a little blunt with them but how does someone with little to no knowledge of our build guess the time of day our thermostat clicks off? It simply isn't possible to even have an educated guess at that.

Pop up the plans and the specifications and we will all know how far off we all are.

[SteamyTea]

1 hour ago, NailBiter said:

I don't know how to share this with you but I'm lucky enough to get journal access as part of my job. Your local library / university / pirate paper repository will have access to a copy

Or you can just copy and past the text and post.

 

What is your job?

[NailBiter]

4 minutes ago, SteamyTea said:

Pop up the plans and the specifications and we will all know how far off we all are.

The plans and the information I've given already would identify me and our address. I've sent a few renders privately to a few people that responded here. I will do the same with the plans once the latest changes are incorporated.

I'd love to just stick them up here but I really don't want it indexed on Google / Wayback and here forever. If I could just share them with the people replying (or set a minimum level to see them e.g. full member) I would. 

[NailBiter]

41 minutes ago, JohnMo said:

Wish it was true. It would be nice, my 57 tonnes of concrete floor and about 65 tonnes in the walls would beg to differ.

 

Ok that's interesting to know thanks, if I remember correctly your build is Durisol? It must still take a significant time to heat and cool that mass though? 

[NailBiter]

43 minutes ago, JohnMo said:

I don't bum pluck numbers, CoP numbers for different flow temps and outside temps.

 

With this I will bow out and let you dream on.

It isn't so much a case of dreaming on as much of a case of trying to get the maximum efficiency from installed systems. As has repeatedly been pointed out this house is large but that means even small efficiency savings can have a large impact.

I'm slowly discovering how much conflicting information is out there and it is hard to know what to do.

I really appreciate you citing your data source, I don't mistrust anyone in particular but data wins arguments.

Edited March 6 by NailBiter

[JohnMo]

32 minutes ago, MikeSharp01 said:

ou could but you would soon either have it overwritten or asked to provide your evidence / citations/ references. I dimly recall it was compared with encyclopedia brittanica and its veracity score was similar

I worked with a guy that used to use Wikipedia as a reference tool, for marine engineering project He started quoting something he found on there in a large meeting, unfortunately the information was duff and he was nearly sacked. Internet is awash with rubbish information, you need to do your due diligence to verify stuff.