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Stop SAP penalising domestic users of biomass boilers

Posted by Cathy Debenham on 24 October 2014 at 12:09 pm

In an ideal world government departments would speak to each other and harmonise what they are doing. Sadly, those of us who've been around renewable energy for any time know that's often not the case.

We've just had an email that beautifully illustrates the way one department's intransigence can scupper another's good ideas. Dr Neil Ridgway has a biomass boiler. To make his home even greener, he wanted to add solar PV panels. But when he got the obligatory energy performance certificate (EPC) he found that it did not achieve the required level of D - although it would have if he'd had an oil or gas boiler.

"I discovered that because the (RdSAP) software which produces the EPC is not integrated with the MCS/Hetas biomass boiler list, my 93.5% efficient biomass boiler was massively underrated," he said. As a result my EPC rating came out so low that I could not get the higher level of [feed-in tariff] for the PV. I could not go ahead - it simply was not worth the cost."

However, Dr Ridgway hasn't taken this setback lying down. He has set up an epetition calling for there to be one single accurate database. You can sign it here (I have already signed).

He asks: "How is it possible that the EPC energy efficiency rating of oil / gas boilers is better (higher band / score) than biomass boilers, which are considerably more efficient (>90%) & more environmentally friendly (less pollution / less carbon dioxide per year)?"

He explains:

1) Someone within a government department decided that wood pellets will be more expensive than oil & gas. It has been shown that wood pellets are considerably cheaper and the cost of oil & gas is steadily going up in price, whilst wood pellets are not.

2) The software used to generate SAP EPCs has significant problems. Hetas & the Microgeneration Certification Scheme (MCS) have a detailed database of recommended renewable appliances with their tested efficiencies. SAP has it own separate databases, the PCDB for RdSAP EPCs & the SAP Appendix Q database for full EPCs. Hetas & MCS approved biomass boilers are not on the SAP databases & can not be used in generating EPCs - hence incorrect EPCs.

His very simple solution: "Just use one database!"

It makes sense to us. If you agree please sign the petition too.

Photo: Photo Credit: _StaR_DusT_ via Compfight cc

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13 comments - read them below or add one

Jeff B

Jeff BComment left on: 15 November 2014 at 1:01 pm

Cathy - I got a reply from BRE, basically saying the same as the Iain Summerfield comment you published i.e. manufacturers of wood pellet boilers must submit information regarding the efficiency of their equipment in order to get them listed on the PCDB. I subsequently rang the BRE and spoke to the gentleman who replied to my letter; I wanted to check exactly how the process works and I was referred to this link:


Clicking on Database Apllications then takes you to the relevant information.

To me (as a layman) this is not a simple process especially I would think for a non-UK manufacturer, which in the case of wood pellet boilers must mean the majority of manufacturers? I am still not clear though what information manufacturers have to supply to MCS in order to get their equipment MCS accredited and whether this information is the same as that presented to PCDB (the gentleman at BRE did not know either).

My next step is to write to the manufacturer of my wood pellet boiler and see what, if anything, they are doing to get their products listed on the PCDB.



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Cathy Debenham

Cathy DebenhamComment left on: 10 November 2014 at 11:55 am

The following informative comment was left by Iain Summerfield, principal consultant at Kiwa on a Linked-in discussion about this issue:

There seems to be some confusion here. 

We (Kiwa Ltd) administer the boiler submissions to the Products Characterisation Database (PCDB) for BRE. This used to be known as the SEDBUK database and until 2005 was limited to oil and gas boilers. It was then expanded to include biomass boilers, although very few manufacturers registered their products until 2012. The efficiency information is submitted by the manufacturers, our role is to check the evidence provided to ensure that the product is identifiable and that the correct performance figures have been submitted. SAP assessors use the information in the database to produce their assessments. Note that the efficiencies quoted in the PCDB (and SAP) are on a Gross basis, and that manufacturers often quote their efficiencies on a Net basis which is a further source of complication / confusion. 

The main problem faced by SAP assessors is that there are many biomass boilers which are not listed and so the assessors have to use a default number. The default efficiency values from table 4a of SAP2012 are 65% if HETAS approved or 63% if not (for Wood Chip/Pellet independent boilers). Clearly these numbers are quite low. We need to encourage manufacturers to submit the real, measured, efficiency information to the Database rather than lobby for changes to SAP. 

Incidentally, pellet boilers in the PCDB show Seasonal Efficiencies ranging from 77.8% to 89.5%, regular gas boiler efficiencies range from 55.0% to 90.3%. As you would expect, all boiler efficiencies are broadly similar, and condensing boilers have the highest efficiencies. The green credentials of biomass boilers derive from their lower CO2 emissions based on the fuel lifecycle, rather than any efficiency advantage.

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Jeff B

Jeff BComment left on: 4 November 2014 at 5:54 pm

Cathy - ok. Letter went off today.


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Cathy Debenham

Cathy DebenhamComment left on: 4 November 2014 at 11:47 am

Jeff, we'd be interested to hear what response you get.

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Jeff B

Jeff BComment left on: 3 November 2014 at 10:28 pm

Linn - ok, thanks. I'll try sending a letter to them and see what response I get!


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Linn Rafferty

Linn Rafferty from JTec Energy PerformanceComment left on: 3 November 2014 at 10:41 am

hi Jeff

it's the B.R.E. rather than OFGEM because BRE maintains and develops SAP, so for the default efficiency to be changed, evidence to support this change must be provided to BRE.

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Jeff B

Jeff BComment left on: 1 November 2014 at 11:00 pm

Mark - our DEA said that the carbon emission for our house was the lowest he had encountered so far (rating = A, 99%), around 0.1 ton of CO2 p.a.! The only thing we could do to reduce energy consumption any further (and achieve a lowly Band C rating) would be to add 4 inches of insulation to the floors i.e. impossible!

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Jeff B

Jeff BComment left on: 1 November 2014 at 10:50 pm

Linn - why the B.R.E. rather than OFGEM?


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Linn Rafferty

Linn Rafferty from JTec Energy PerformanceComment left on: 1 November 2014 at 9:19 am

hI Jeff

I'm not an expert on the MCS list but I think it's because the 'efficiency' values in the two databases are calculated differently. It's a different set of tests that must be done to determine the seasonal efficiency, which is the figure that SAP needs. For sizing a boiler, which means being sure it's sufficient to meet the home's demands on the coldest day, you only need to know peak efficiency.

Unfortunately, it's down to the boiler manufacturers to provide the data to put their products on the SAP database, and if they don't consider it worth their while, they won't do it.

This issue was discussed by Tasha on the yougen blog previously here

This is why I suggest that a pragmatic solution might be to approach BRE as an industry to try to get the default value uplifted.

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Mark Brown

Mark BrownComment left on: 31 October 2014 at 11:21 am

My sympathies. I had a similar issue with Superhome 59 which needed an EPC to get the domestic RHI payments for solar thermal fitted in 2010. I wrote up my experiences here: I never knew the cause of the problem with the RdSAP but my home came out BELOW average on the EPC rating which was incredible for a home that slashed emissions by 90%, reduced costs by 90% and generates 115% of its own electricity. There were contributing factors (other than ignoring our KWB EasyFire wood pellet boiler) and that was the fact the assessor had to ignore the 300mm of loft insulation because the loft was part boarded ("how do we know you haven't removed the insulation from under the boarding?") and our room-over-the-garage had to be treated as a wood framed structure although it was built to the same brick standard as the rest of the house. It is complicated. We still got an good enough EPC for the dRHI but the overall assessment couldn't recommend and further upgrades - we had them all.

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Jeff B

Jeff BComment left on: 30 October 2014 at 5:18 pm

Linn – you are right about the situation for my EPC because my DEA explained that to me when I questioned why he had only given the boiler 2 stars out of 5 for the efficiency rating! What I don’t understand is that surely the boiler manufacturer has already given its efficiency data to the MCS in order for their boiler to be put on the MCS approved list in the first place, so why would they have to do this again? Am I missing something obvious?


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Linn Rafferty

Linn Rafferty from JTec Energy PerformanceComment left on: 30 October 2014 at 10:47 am

It helps to understand the reason for the two databases, I think - it's because the 'efficiency' values in the two are calculated differently.

EPCs must use the SAP 'product characteristic database' which gives the seasonal efficiency of the boiler, not the peak efficiency. This is because SAP is used to calculate energy used in a whole year, not just the energy required in the coldest season, so it reflects how the efficiency of the appliance varies accross the seasons.

BTW there is only one database used in SAP, for both RdSAP and SAP calcs.  Appendix Q is only available to SAP, but it is used for a different purpose - to allow the input of 'innovative' measures that have not yet been included in the main SAP.

If the biomass boiler isn't in the product database (and very few are), the SAP or RDSAP calc must use a default efficiency, which for biomass boilers is quite conservative.  Jeff B - I think this is what has happenned in your EPC.

Of course, the boilers will only appear in the database if the manufacturers apply to have them included, and they have to provide defined evidence from test houses to support the efficiency they claim.

I think one way forward would be for the biomass industry to co-operate with BRE to get the default biomass boiler efficiency increased.  BRE would need evidence to do this, and that's where it gets a bit difficult, but worth contacting them about it.

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Jeff B

Jeff BComment left on: 27 October 2014 at 10:45 pm

Brilliant stuff - petition duly signed! I have a biomass boiler and solar PV panels, the latter being installed over 3 years ago before the EPC rating had any impact, hence my concern is slightly different to Dr. Rigdway's. We have insulated our bungalow to the "nth" degree and consequently have reduced our energy demand for heating/hot water by about a third and yet when we had an EPC done recently for the purpose of registering our new wood pellet boiler for RHI we got a Band D rating, which is clearly absurd! When I looked into the reason it was because the efficiency of the boiler which is deemed to be much lower than it actually is. I would get a higher rating if I changed back to oil - how crazy is that!

Thankfully I have no intention of moving house because if I were a potential buyer, a D rating would mean an immediate look elsewhere!

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