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Preliminary SAP great but could be better


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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 by PeterW
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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.

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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.

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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

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5 minutes ago, jack said:

I do think it's nice to have a three-digit number for your SAP score though B|

 

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 by JSHarris
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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!

 

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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....................

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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 by NSS
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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?.

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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 ?).

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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 by IanR
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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.

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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).

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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.

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