Green Building Forum - SAP 10 is it an own goal?

SAP 10 is it an own goal?

an02ew — Mon, 02 Oct 2023 22:29:26 +0100

Has anyone had experience with the new SAP10?

i am designing and building a small 2 bed detatched bungalow (in total 58m2 int floor) it follows our usual building fabric design:

-insulated raft foundation conncted to EWI connected to EPS loft insulation (totally unbroken insulation element and lots of thermal mass)
-ATness below 0.6 m3/m2
-MVHR (90%)
- 3g window and doors
- 3kW slimjim direct to UFH
-direct cylinder with twin immersion or instant water heaters(budget dependant)

i had this run through the new SAP10 (pre design) and it failed, not due to the fabric efficiency but becuase of the fuel price calc, it seems the only way to get a new building through the new SAP10 is with bolt on PV or ASHP (good news again for installers) In this particular build the budget is very tight and both are costly the ASHP has to low return due to the the low kW/m2/yr and the single occupant has low daytime electrical usage and no EV resulting in a low return value.

IMO SAP10 sends the wrong message, should'nt we be rewarding liftime energy efficient construction methods not short term panels and pumps?

SAP 10 is it an own goal?

fostertom — Tue, 03 Oct 2023 08:55:20 +0100

What's the 'fuel' load split, space heating vs hot tap water? Approx?

SAP 10 is it an own goal?

GreenPaddy — Tue, 03 Oct 2023 09:11:46 +0100

I've just submitted a very similarly sized dwelling for planning, who want to know all about the energy usages etc, so have crossed this bridge, al-be-it not having run SAP yet.

Can't justify a wet ASHP, but for the first time am proposing an air-air ASHP, plus solar panels. There are a number of people on here, who extoll the virtues of air-air, and certainly the Â£500/Â£600 unit costs make it a winner, in my book, for small dwellings (not excluding large dwellings, just more to consider).

Good luck buying a few electric rads for Â£500, or the slimjim and wet UFH. Instead enjoy the A-A's usual SCOP of 4+. As I think Tom was maybe alluding to above, the DHW could be direct elect, but with some solar PV and an excess solar diverter, much of the year would be covered for DHW.

SAP 10 is it an own goal?

WillInAberdeen — Tue, 03 Oct 2023 10:06:49 +0100

Buildings should be rated based on how many tonnes of carbon are emitted, both during their use and during their construction. IMO.

The whole idea of setting EPC ratings for Â£100000 buildings according to Â±Â£100 of fuel cost, is bonkers. It's almost as if the gas boiler lobby had designed it that way!

Fuel cost isn't actually a criteria for new builds in English building regs but the alternative is almost as bad, rating buildings on 'Primary energy' which (surprise!) favours gas oil and coal over electric.

And more nuttiness in Scotland is proposed, where buildings will be rated by space heat losses, irrespective where that heat comes from, or how DHW is heated, thus (surprise!) giving a break to gas oil and coal heating.

The SAP report should show how much of the energy is being used for DHW, should be quite a big chunk of it. Solar for the DHW might bring the SAP under control without massive cost?

Since last year, the English building regs now start off that the building will have PV over 40% of its roof and will have gas for space heating and for DHW, and reasonable fabric U=0.11-0.18.

Using direct electric heating and DHW (= worse Primary energy than gas) and missing out the PV, will set you back a long way, it will be difficult to make up for that with better fabric, even with U<0.1.

You are allowed (Appendix D) to miss out the PV if you use ASHP for space and DHW. This makes some sense because the emissions of a U=0.3 building with an ASHP are better than those of a U=0.1 building with direct electric.

SAP 10 is it an own goal?

fostertom — Tue, 03 Oct 2023 11:56:04 +0100

Leaving out conspiracy in favour of fossil industry, what makes UK Bldg Regs so perennially stupid - even after major revision following criticism? The men at the ministry who design SAP are smart and fully understand PH etc - so why this crack brained UK-centric 'version'? There must be a rationale - what is it?

SAP 10 is it an own goal?

borpin — Tue, 03 Oct 2023 14:03:28 +0100

There is a HP hot water tank out there that I have seen. Not a great COP but better than direct heating. I'd be inclined to use that plus A2A.

I've got a few electric panel heaters and I'm in the process of trying to get a quote for an A2A multisplit to replace them.

I think not fitting Solar is a crime and any new building should be wired for an EV charger! In-roof solar at build stage is minimal additional cost.

SAP 10 is it an own goal?

djh — Tue, 03 Oct 2023 17:07:56 +0100

Posted By: fostertomwhat makes UK Bldg Regs so perennially stupid

The same thing that makes almost all British committee decisions stupid. Politeness plus vested interests. The smart people who design SAP are more interested in doing something interesting and continuing (i.e. designing an energy modelling system) than in doing something boring and unlikely to lead to further work (i.e. approving some pre-existing system designed by foreign johnnies, don't you know). They're willing to listen to all inputs, in the interest of fairness, and the manufacturers employ people who are fairly smart and who know how to write to give them some input to listen to.

The DHW HP water heaters I have seen involve making two (more) large holes in the exterior wall of my house. Not something I'm comfortable with. All the holes I have were designed in and made during construction.

SAP 10 is it an own goal?

fostertom — Tue, 03 Oct 2023 17:49:43 +0100

Posted By: djhThe smart people who design SAP are more interested in doing something interesting and continuing (i.e. designing an energy modelling system) than in doing something boring and unlikely to lead to further work (i.e. approving some pre-existing system designed by foreign johnnies, don't you know).

I don't think that hangs together. I've met one or two of these, back in the days when trade shows ran top notch seminars on the sidelines, who had expert high regard for PH, just as much as anyone on GBF. If it's vested interests, then that's by ministerial edict, believable from today's chancer-ministers but not credibly from their Labour predcessor(s). Seriously, I think it's a puzzle, not explainable by the usual weary cynicism.

SAP 10 is it an own goal?

Artiglio — Tue, 03 Oct 2023 18:05:59 +0100

My 2p, the rules are probably devised with the volume housebuilders in mind, the goal being maximum output with a simple design, availability of materials, little real training required, can be thrown up quick and most important a decent profit margin when its sold.

SAP 10 is it an own goal?

djh — Tue, 03 Oct 2023 18:25:00 +0100

Posted By: fostertomI don't think that hangs together. I've met one or two of these, back in the days when trade shows ran top notch seminars on the sidelines, who had expert high regard for PH

I'm not sure what your objection is? Sure they can like PH, but it's not very interesting to say "PH it is". Job done.

Instead they can form a committee and take many inputs* and think a lot and discuss a lot and produce something they think is even more suited to the UK situation, and then start to revise it ... (and keep getting paid)

* From volume housebuilders as well as insulation manufacturers etc. Not so much from self builders or architects or ...

edit: FWIW I sat on some British and international technical standards committees, so I have some idea how they work.

SAP 10 is it an own goal?

djh — Tue, 03 Oct 2023 18:43:37 +0100

Actually I've just had a response from the Scottish politician Alex Rowley which says something abou the process:

"... the resources required to have every property verified and certified by Passivhaus Trust approved verifiers are unfortunately not available, and as such an alternative approach needs to be found. My suggestion is to make the Passivhaus standard a requirement through existing building standards and then changing the approach of building standards to verification to appropriately verify that the new standards are being met. The only difference in my proposal is that verification would happen through existing building control measures - albeit, the resources for this may need to be expanded to accommodate new verification requirements."

and there's a link to the working group: https://www.gov.scot/groups/energy-standards-review-scottish-passivhaus-equivalent-working-group/

So it seems the vested interest is the building control people (are they public or private in Scotland?). But given they aren't trained in PH at the moment, it will likely cost just as much to train them and new recruits as it would to increase the number of PH-trained qualified certifiers. JMHO.

SAP 10 is it an own goal?

Peter_in_Hungary — Tue, 03 Oct 2023 19:17:07 +0100

Posted By: djhInstead they can form a committee and take many inputs* and think a lot and discuss a lot and produce something they think is even more suited to the UK situation, and then start to revise it ... (and keep getting paid)

The best committee is a committee of 2 - one of whom is always absent !!!

SAP 10 is it an own goal?

WillInAberdeen — Tue, 03 Oct 2023 20:12:57 +0100

Building Standards are public officials in Scotland (local council staff), but as at present they won't have to do the thermal modelling or airtightness testing themselves, just inspect the certificates issued by the specialists who are hired by the developer. Alex Rowley is an opposition politician, not necessarily representing the government's view on PH enforcement.

SAP is a product supplied by a private company (BRE) so its developers are not the wo/men from the ministry. It's actually supplied to several completely separate ministries in England, Scotland and (sorry idk) Wales and NI for use in different laws (building regs, building stds, EPCs, etc)

To be fair, sounds like the issue in the OP is with the recently-tightened Building regs, rather than with the SAP method itself.

Scottish government said:

'Some stakeholders have called for SAP and RdSAP to be substantially amended, or
replaced entirely, and an alternative assessment methodology used [PHPP]. This is within
the power of Scottish Ministers, as set out in The Energy Performance of Buildings
(Scotland) Regulations 2008. However, we do not propose to amend or replace the
methodology at this time. This is for three reasons:
â€¢ Firstly, a major update to the SAP and RdSAP methodologies is under
development by the UK Government. We are working with the UK
Government and other devolved administrations to ensure SAP 11 meets the
needs for use in Scotland and have received assurance from the UK
Government that SAP 11 will address many of the concerns stakeholders
have raised about the accuracy of SAP;
â€¢ Secondly, development of a new methodology (and associated ongoing
management work) would need to be undertaken in parallel to the current
methodology. This is because schemes and services that operate across the
UK using EPCs would require the existing methodology to be maintained;
â€¢ Finally, we intend to make clear both on the EPC and in its usage, that the
EPC (and its recommendations) is based on a relatively basic assessment of
the building, and uses standardised values, and so is not a substitute for in-
depth professional retrofit advice."
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17921

SAP 10 is it an own goal?

an02ew — Tue, 03 Oct 2023 20:28:35 +0100

Posted By: ArtiglioMy 2p, the rules are probably devised with the volume housebuilders in mind, the goal being maximum output with a simple design, availability of materials, little real training required, can be thrown up quick and most important a decent profit margin when its sold.

i agree and would hint at a more sinister motive- namely to once agian atificially bolster the renewables sector for polictical gain?

Isnt it stupid to insist on short lived bolt on tech which is harmful to manufacture against the long term benifit of good really quality fabric first construction, and in the process educating the volume building industry and in turn driving down the cost of specialist construction materials.

SAP 10 is it an own goal?

an02ew — Tue, 03 Oct 2023 21:14:55 +0100

Posted By: fostertomWhat's the 'fuel' load split, space heating vs hot tap water? Approx?

Taken from the design SAP

Space heating- 762 kWh/yr (13KWh/m2 /yr)

Water heating- 1411 kWh/yr

SAP 10 is it an own goal?

fostertom — Tue, 03 Oct 2023 21:43:26 +0100

That's quite impressive, puts the 'straight' elect used for heating into perspective, relative to the amount, familiar to most, of elect for (what sounds like) a small user of hot tap water'.

SAP 10 is it an own goal?

Mike1 — Tue, 03 Oct 2023 23:24:39 +0100

Posted By: WillInAberdeenBuildings should be rated based on how many tonnes of carbon are emitted, both during their use and during their construction. IMO.

Fuel cost isn't actually a criteria for new builds in English building regs but the alternative is almost as bad, rating buildings on 'Primary energy' which (surprise!) favours gas oil and coal over electric.

Here in France EPCs are dual-rated for primary energy and CO2 emissions. Whichever scores worst becomes the overall rating. I like the simplicity.

Interesting though that the Primary Energy Factor here is 2.3 (reduced in 2021 from 2.85, which had been set in 1972), so way above the new 1.501 factor in the UK. Principally because the nuclear reactors that provide around 70% of the electricity are only rated 33% efficient. However, the change is enough to tip the balance in the French SAP-equivalent in favour of electricity. It apparently reflects the movement in the generating mix over the next decade or so as nuclear drops to 50% and renewables rise to 40% (which could bring the factor down to closer to 2.1).

SAP 10 is it an own goal?

an02ew — Wed, 04 Oct 2023 07:27:45 +0100

Posted By: fostertomThat's quite impressive, puts the 'straight' elect used for heating into perspective, relative to the amount, familiar to most, of elect for (what sounds like) a small user of hot tap water'.

hey Tom can you explain this, im lost in the abbr.

SAP 10 is it an own goal?

borpin — Wed, 04 Oct 2023 07:47:19 +0100

Posted By: djhThe DHW HP water heaters I have seen involve making two (more) large holes in the exterior wall of my house. Not something I'm comfortable with. All the holes I have were designed in and made during construction.

Yes although I have seem someone just feeding it from internal air instead.

Posted By: WillInAberdeenBuilding Standards are public officials in Scotland (local council staff)

When building my house, I was discussing this with the BC and he was saying it was being privatised so in effect the council was buying the service.

BC just do not have the resources to monitor the quality of build. Many large builders self certify and do not us the LA BC service.

No quality control results in s^&t build quality.

SAP 10 is it an own goal?

fostertom — Wed, 04 Oct 2023 08:37:59 +0100

Posted By: fostertomThat's quite impressive, puts the 'straight' elect used for heating into perspective, relative to the amount, familiar to most, of elect for (what sounds like) a small user of hot tap water'.

Posted By: an02ewhey Tom can you explain this, im lost in the abbr.

I mean people have an idea of how much electricity goes on their tap water heating, and that it's traditionally almost insignificant compared to what goes on their space heating, and that's why they've use 'cheaper' fuel for space heating but put up with 'expensive' electricity for hot water. Now you've reversed that - space heating is just a 50% add-on to water heating, so if electricity's OK for water heating, just 50% more of same for space heating makes sense.

Not v scientifically rigorous but is a whole new 'common sense'.

SAP 10 is it an own goal?

WillInAberdeen — Wed, 04 Oct 2023 11:19:09 +0100

Posted By: Mike1Here in France EPCs are dual-rated for primary energy and CO2 emissions. Whichever scores worst becomes the overall rating.

Confusingly, there are two different laws in England:
-Building regs for new buildings such as the OP's are now rated on Primary Energy (with metrics for carbon and fabric)
-EPCs for new and existing buildings are rated on Cost (with carbon on the back page that everyone ignores)

They're both enforced using SAP (but different versions) so we get confused between them all. And it's different in Scotland!

Posted By: Mike1Interesting though that the Primary Energy Factor here is 2.3 (reduced in 2021 from 2.85, which had been set in 1972), so way above the new 1.501 factor in the UK. Principally because the nuclear reactors that provide around 70% of the electricity are only rated 33% efficient.

It's bonkers that zero-carbon DHW heated by power from radiation in a 33% efficient power station gets a punitively high Primary energy factor of 3, whereas zero-carbon DHW heated by radiation falling on your own 20% efficient PV panel gets treated as 1.5 (but more if it's located in France), and zero-carbon DHW heated by radiation on your own solar thermal panel scores 0. They're all zero carbon, so why aren't they all rewarded better than coal heating (1.06), which scores better than gas (1.13)?!

Primary Energy made some sense for comparing fossil usage across national economies, but is pretty much irrelevant for comparing houses. Especially over the 100yr lifetime of a new house when the energy mix will change in ways the architect cannot control. The CCC think PE sends out damaging signals discouraging electrification, so have recommended it be ditched in favour of Imported Energy.

SAP 10 is it an own goal?

WillInAberdeen — Wed, 04 Oct 2023 12:07:48 +0100

Posted By: an02ewcan you explain this, im lost in the abbr.

The design is impressively successful in reducing 'fabric' energy, fantastic! That means the biggest problem is now the hot water, which Tom said often gets forgotten when people talk about 'fabric', but needs more attention in new houses now that newer regs have clamped down on insulation etc.

Building regs start off on reducing hot water by specifying WWHR and solar PV. Or you can have an ASHP instead. None of these are really 'fabric' improvements, but that's the nature of hot water.

You can do it another way, so long as you get to the same result, but I can't immediately think how else that would be!

SAP 10 is it an own goal?

an02ew — Wed, 04 Oct 2023 22:14:07 +0100

Posted By: fostertomI mean people have an idea of how much electricity goes on their tap water heating, and that it's traditionally almost insignificant compared to what goes on their space heating, and that's why they've use 'cheaper' fuel for space heating but put up with 'expensive' electricity for hot water. Now you've reversed that - space heating is just a 50% add-on to water heating, so if electricity's OK for water heating, just 50% more of same for space heating makes sense.

Posted By: WillInAberdeenThe design is impressively successful in reducing 'fabric' energy, fantastic! That means the biggest problem is now the hot water, which Tom said often gets forgotten when people talk about 'fabric', but needs more attention in new houses now that newer regs have clamped down on insulation etc.

Building regs start off on reducing hot water by specifying WWHR and solar PV. Or you can have an ASHP instead. None of these are really 'fabric' improvements, but that's the nature of hot water.

This explains the need for expensive bolt on tech (PV,ASHP) to pass the design SAP.

In this case the SAP assumes an occupancy 1.9persons and a average daily HW useage 54L/day- is this an assumed figue by the assessor or fixed by SAP? What if the DHW system was based on instantainous heating (electric showers, under sink water heaters etc) not stored HW maybe this would reduce the useage? and reduce the yearly KWh

SAP 10 is it an own goal?

Mike1 — Wed, 04 Oct 2023 23:21:46 +0100

Posted By: WillInAberdeenIt's bonkers that zero-carbon DHW heated by power from radiation in a 33% efficient power station gets a punitively high Primary energy factor of 3, whereas zero-carbon DHW heated by radiation falling on your own 20% efficient PV panel gets treated as 1.5 (but more if it's located in France), and zero-carbon DHW heated by radiation on your own solar thermal panel scores 0...

...The CCC think PE sends out damaging signals discouraging electrification, so have recommended it be ditched in favour of Imported Energy.

Yes, the system and the factors used are based more on politics than physics. And I agree that using cost is extra mad!
I missed the CCC's recommendation on Imported Energy - will have to look that up - thanks!

SAP 10 is it an own goal?

an02ew — Sun, 08 Oct 2023 13:05:32 +0100

Update.

Following another discusion with the SAP assessor (Paul Taylorson) and some realtime adjustment of the SAP10 software to removing the bath and DHWc, now using direct water heating to an electric shower and undersink water heaters we have reduced annual DHW kWh usage from 1411 to just 442, alas this still fails the SAP assesment unless renewables are added. the fails is due to the current high cost of electric skewing the running cost figues.

i wonder how much a saving PV or ASHP makes against its purchase, instalation and service cost vs good old 240v on such a low energy demanding home?

SAP 10 is it an own goal?

djh — Sun, 08 Oct 2023 17:58:43 +0100

I think PV can be made to pay for itself still (but I'm not sure as I haven't bought any recently) by careful selection of tariff and sizes and maybe replacing some roof covering with PV. ASHP is just a cost for low users. But if adding some PV means you can build and otherwise you can't then it's a no brainer?

SAP 10 is it an own goal?

an02ew — Sun, 08 Oct 2023 20:30:47 +0100

Posted By: djhBut if adding some PV means you can build and otherwise you can't then it's a no brainer

yes, But that means that every new build house in England will have to have PV, can you imagine what this will do to the industry in the next 6 month? MSC installers will be stetched to breaking point and big spec building companies bulk purchasing panels and inverters.

SAP 10 is it an own goal?

WillInAberdeen — Sun, 08 Oct 2023 22:14:42 +0100

Posted By: an02ewthe current high cost of electric skewing the running cost figues

Don't really understand the background here?

New builds have to comply with Building Regs, which don't care about the running costs - they're based on (primary) energy consumption in kWh, not Â£.

The only place where energy costs are assessed is for the EPC after the house is finished, but that only matters if the property is rented, and the target is a C which should be easily met here?
Is there another reason the assessor is looking into prices and costs?

An EPC uses the 'Standardised' electricity prices, 16.49p/unit for SAP10 or 13.19p for rdSAP. This year's higher market prices shouldn't come into it. You can also use the E7 rate of 9.40p but would need a cylinder for that.

TBF there are lots of requirements in planning and building regs that are a cost on the first owners that won't pay back during their period of ownership. I suppose they're required to stump up for the good of wider society, over the whole lifetime of the house! Or something.

There's an argument that PV panels are more usefully deployed in solar farms than on rooftops - but that's not in tune with the public mood!

SAP 10 is it an own goal?

Mike1 — Sun, 08 Oct 2023 23:17:19 +0100

Posted By: WillInAberdeenThere's an argument that PV panels are more usefully deployed in solar farms than on rooftops - but that's not in tune with the public mood!

The French 2021 Climate & Resilience Law requires PV panels (or a green roof) to be installed on all new & renovated commercial buildings >500mÂ², over all car parks >500mÂ², and over all office buildings >1,000mÂ². Seems like a good place to put them.

SAP 10 is it an own goal?

Peter_in_Hungary — Mon, 09 Oct 2023 08:17:05 +0100

Posted By: WillInAberdeenThere's an argument that PV panels are more usefully deployed in solar farms than on rooftops - but that's not in tune with the public mood!

Except that PV on my roof gives me a disconnection from the vagaries of energy pricing that isn't there in someone energy co. solar farm, especially here where I am on annual reconciliation and after the first year (EV and all) it looks like the annual elec. bill is that they pay me about a fiver (excess export over import).