SAP Test

[Tetrarch]

Our BC Inspector mentioned the requirement for a SAP test on his last visit. As we have built a 28sq m extension with 7.5m of doors and windows plus three 2m x 1m skylights then I suppose he has a point

 

HOWEVER

 

We have demolished our entire solid-brick 1914 first floor and replaced it with a 150mm-insulated timber frame, so we have massively increased the thermal efficiency of the house by dint of this work. Surely we don't have to do a SAP test to demonstrate this as it is blindingly obvious? (n.b. I know that the answer to ALL "surely" questions is always "no")

 

Our work should also increase our EPC, but that wouldn't be difficult as it is currently 4, yep 4, not a typo, and that was with 200mm of loft insulation

 

Regards

 

Tet

[JohnMo]

Basically you need a new EPC or SAP report when you first build or then go on to alter the fabric of the building. Nothing is blindingly obvious. A lot of SAP reports can be shite in, shite out, so make sure they use the correct assumptions i.e. check.

 

Not sure what you mean by a '4' as EPC ratings are A to E?

[Tetrarch]

2 minutes ago, JohnMo said:

Not sure what you mean by a '4' as EPC ratings are A to E?

 

Not exactly - the A to G ratings are just simplifying the presentation of the result. There is an actual numerical score underneath

 

 

Regards

 

Tet

[JohnMo]

So you got a G4 then. 

[nod]

Look on Google There loads of companies that will do a sap report over the phone 

[Redbeard]

Can you no longer just do an area-weighted U value calc? You certainly could before the 2022 re-vamp of Bldg Regs, and I have not heard it's changed (equally I have not heard it hasn't, but a web-hit from 2023 refers to such a calc). The principle is that if your conservatory has >25% of the wall area glazed you have to reduce the other fabric U values to keep the area-weighted U value to what it would be if there was no more than 25% glazing.

[DevilDamo]

That is what the SAP calculation will prove… even though the extension in isolation fails the glazing threshold, the whole house does not. They’re not expensive to have done.

[kandgmitchell]

Don't just get a house sales SAP calc done. It's a specific one that will compare the house with your extension against the house with a "notional" extension of the same size. The proposed should obviously be better than the standard notional one to comply. Actually it can be harder to prove compliance for a modern house than for an older one simply because the contrast in benefit overall, between a highly insulated extension on an old house, is more than one on a house that is already highly insulated.

 

Just explain to a SAP assessor that you need to prove the extension complies even though you have more than 25% floor area in glazing - they'll know what you're after.

[Tetrarch]

I've had a brief scan online and I'm looking at ~£400 to get a SAP calc done. 

 

I ghave ALREADY spent over £3,500 on insulation product for the house refurb. This is proof in and of itself, do I really have to get a SAP calculation done? I've already spent well over £1,000 compensating for the combined mistakes of my Architect and local Planning Department, another £400 for something completely unnecessary is really galling

 

Regards

 

Tet

[kandgmitchell]

Reading the original post again. The simplified method of dealing with glazing in an extension is 25% of the floor area of the extension added to the area of the original openings which are now enclosed should be equal or greater than the total new glazed openings.

 

So, you have a 28m2 extension so at 25% that is 7m2 which is nearly equal to your 7.5m2 of doors. If your original openings equal at least 6.0m2 (3 x 2m2 roof lights) then you're ok. If not then as mentioned by Redbeard you can do an area weighted calculation where you offset the extra glazing with higher levels of insulation to compensate. If after all that, you can't show it works then I'm afraid it's the SAP calculation if BC insist on it.