MikeSharp01 Posted September 27, 2017 Share Posted September 27, 2017 (edited) Our provisional BC SAP came through at 101 A (6Kw of PV or 107 with the full 8Kw) which makes me very happy. However the assessor told me I could have got two more points if I didn't have the MVHR because of the energy it uses. Can't live without MVHR so was wondering what the collective experience was with SAP and MVHR, can I get a better MVHR (Unit so far in the frame is: Airflow Adroit DV145) what, I wonder, is the conversion from energy use to points (Banded / Algebraic / ?) because I am not sure I will get a much lower figure. Edited September 27, 2017 by PeterW Admin removing bold...... Link to comment Share on other sites More sharing options...
le-cerveau Posted September 27, 2017 Share Posted September 27, 2017 In reality it is over 100 "who cares". SAP is quite arbitrary and favors IMHO efficient gas heating in mediocre insulated houses, and puts a high weighting on renewable at the expense of efficiency. 1 Link to comment Share on other sites More sharing options...
jack Posted September 27, 2017 Share Posted September 27, 2017 32 minutes ago, le-cerveau said: In reality it is over 100 "who cares". Agreed. I think it's nice to hit 100 (ours is 100 or 101 from memory), but I can't see the point in making much effort - or more importantly paying anything more - to go beyond that. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted September 27, 2017 Author Share Posted September 27, 2017 Thanks chaps (assume Chaps) yes I suppose what I wanted to do was save cost if I reduce the PV I could stay above 100 but only, it looks like, if can squeeze down the MVHR as the fabric is pretty much at its limit already. Maybe I could improve air tightness a little, used the PH standard for the preliminary calc, I would expect to do better than that anyway but cannot find the equation linking air tightness and SAP points anywhere. Link to comment Share on other sites More sharing options...
A_L Posted September 27, 2017 Share Posted September 27, 2017 You are not going to get significantly better energy recovery efficiency, perhaps 2% in class leaders but the Specific Fan Power (SFP) is perhaps 50% higher than the best. http://www.ncm-pcdb.org.uk/sap/pcdbsearch.jsp?pid=34 Also what ach@50Pa has the assessor assumed? Link to comment Share on other sites More sharing options...
MikeSharp01 Posted September 27, 2017 Author Share Posted September 27, 2017 14 minutes ago, A_L said: Also what ach@50Pa has the assessor assumed? 0.5 I think. Link to comment Share on other sites More sharing options...
Alex C Posted September 27, 2017 Share Posted September 27, 2017 Its all pretty meaningless as if you have any pv there will be enough power to cover the background use for mvhr during the day anyway. I modelled my own house for SAP and has been mentioned before it is not designed for really efficient houses. The score for a very average house is not really that far away to the score you get from a passivhaus, although the real running costs are likely to be very different. The pretty average new builds down the road from me scored a B, mine is passive spec and scored 101 A. Any buyer is likely to think they are almost the same efficiency Link to comment Share on other sites More sharing options...
jack Posted September 27, 2017 Share Posted September 27, 2017 I do think it's nice to have a three-digit number for your SAP score though Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 27, 2017 Share Posted September 27, 2017 (edited) 5 minutes ago, jack said: I do think it's nice to have a three-digit number for your SAP score though I agree, although it did throw our building control officer into a bit of a wobble, as he'd never seen one over 100 and assumed that 100 was as high as you could get. Edited September 27, 2017 by JSHarris 1 1 Link to comment Share on other sites More sharing options...
jack Posted September 27, 2017 Share Posted September 27, 2017 1 hour ago, JSHarris said: I agree, although it did throw our building control officer into a bit of a wobble, as he'd never seen one over 100 and assumed that 100 was as high as you could get. Well he learned something that day, didn't he? Our SAP assessor was highly experienced, but had never seen a SAP number as high as ours. I suspect that's partly because he does a lot of work for developers! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 27, 2017 Share Posted September 27, 2017 When I emailed the EPC and air test chit to the BCO, this comment was a part of his reply: Quote ...........the air test and EPC results are impressive to say the least................ Later I had an email from the council energy policy officer, asking if he could come around and have a look, as the BCO had emailed him about this odd house in Wiltshire with a silly EPC rating.................... 1 Link to comment Share on other sites More sharing options...
NSS Posted September 27, 2017 Share Posted September 27, 2017 So, if 6Kw gets you to 101 and 8Kw gets you to 107, does it follow that 4Kw would reduce it to 95? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted September 27, 2017 Share Posted September 27, 2017 Our PV is 6.25kWp, EPC is A107. I think I did work out the EPC without the PV, and it was still in band A, but I don't have the file on this laptop to check the actual number. Link to comment Share on other sites More sharing options...
NSS Posted September 27, 2017 Share Posted September 27, 2017 (edited) 22 minutes ago, JSHarris said: Our PV is 6.25kWp, EPC is A107. I think I did work out the EPC without the PV, and it was still in band A, but I don't have the file on this laptop to check the actual number. So probably circa 101 if only 4Kw, which is still exceptional. My point is that, as @le-cerveau said earlier in the thread, renewable (in this case PV) does seem to have an overly large impact on the SAP calculation. Probably explains why developers stick as few as 2 panels on roofs. In fact, one of my daughters bought a new home last year. Directly across the road from her, a new house built by a different developer has 4 panels fitted on the north facing elevation. Apparently, all the houses of that particular design have 4 panels on the same section of roof, irrespective of the houses' orientation to the sun. Farcical! Edited September 27, 2017 by NSS Link to comment Share on other sites More sharing options...
joe90 Posted September 27, 2017 Share Posted September 27, 2017 Well I finally got my architect to send me a copy of my SAP as designed and apart from some of the details being wrong !!!!!, it assumes an air tightness figure of 7 ( I will be most miffed if it is that bad after all my efforts) and a SAP of 87. Is there a process for getting a "proper" SAP figure , I.e. As built, not in theory making assumptions?. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted September 27, 2017 Author Share Posted September 27, 2017 6 minutes ago, joe90 said: . Is there a process for getting a "proper" SAP figure , I.e. As built, not in theory making assumptions?. As I undersrand it you get an as designed SAP which you need at the start of BC then for final sign off you get the as built. Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2017 Share Posted September 28, 2017 11 hours ago, MikeSharp01 said: As I undersrand it you get an as designed SAP which you need at the start of BC then for final sign off you get the as built. Who supplies this?, do I have to pay again? It would be nice to know ( not that it's a competition or anything ?). Link to comment Share on other sites More sharing options...
IanR Posted September 28, 2017 Share Posted September 28, 2017 (edited) 53 minutes ago, joe90 said: Who supplies this?, do I have to pay again? It would be nice to know ( not that it's a competition or anything ?). Only an Accredited and Registered (with BRE) Energy Assessor can upload the EPC that Building Regs will require, so your as-built SAP will need to be done by that Assessor. If you're going to do a Design SAP then you might as well use the same Assessor as the as-built will use the same calcs and should be a minor update at the end. The Assessor's are not supposed to use someone elses "file", so shouldn't take a home-brew design SAP and produce the as-built from it. I used Pebble Energy. Edited September 28, 2017 by IanR Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2017 Share Posted September 28, 2017 Thanks Ian, I think I will call the assessor and ask what it will cost to do an as built SAP just for my self gratification ( but not if it's expensive?) Link to comment Share on other sites More sharing options...
IanR Posted September 28, 2017 Share Posted September 28, 2017 I was charged £175 for the Design SAP, and £35 to complete the As-built and Register the EPC Link to comment Share on other sites More sharing options...
Gone West Posted September 28, 2017 Share Posted September 28, 2017 13 hours ago, NSS said: So, if 6Kw gets you to 101 and 8Kw gets you to 107, does it follow that 4Kw would reduce it to 95? My preliminary SAP was 101 with 2.8Kw PV and airtightness of 0.6ACH. Apparently if I added a wind turbine it would go up to 104. My airtightness is less than 0.6ACH so I don't know if that will impact my final SAP result. Link to comment Share on other sites More sharing options...
joe90 Posted September 28, 2017 Share Posted September 28, 2017 4 minutes ago, IanR said: I was charged £175 for the Design SAP, and £35 to complete the As-built and Register the EPC I was charged £250 for the design SAP ( the architect was expensive in hindsight as I did all the designing, he just put it on CAD and printed copies for the building regs and builder). Link to comment Share on other sites More sharing options...
Gone West Posted September 28, 2017 Share Posted September 28, 2017 11 hours ago, MikeSharp01 said: As I undersrand it you get an as designed SAP which you need at the start of BC then for final sign off you get the as built. My BCO accepted my PHPP results instead of an as designed SAP. Link to comment Share on other sites More sharing options...
IanR Posted September 28, 2017 Share Posted September 28, 2017 Just now, PeterStarck said: My BCO accepted my PHPP results instead of an as designed SAP. But you still need an EPC for you BC completion Cert... don't you? Link to comment Share on other sites More sharing options...
Gone West Posted September 28, 2017 Share Posted September 28, 2017 Just now, IanR said: But you still need an EPC for you BC completion Cert... don't you? Yes I do. I have had a preliminary SAP and EPC done but I still waiting for my final airtightness result which should be next Tuesday, then I will have my final SAP and EPC. Link to comment Share on other sites More sharing options...
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