EPCs. What is the future?

[pulhamdown]

Hi.  We built our house in Scotland in 2012, just before the EPC system became compulsory.  So we are not on the Scottish register, but we had an EPC done and it came out as A100.  We just scraped into passiv haus territory, with an airflow reading of just under 0.6 ach, but didn't get it certified.  When we replaced our oil fired boiler with a heat pump, we needed a new EPC for the grant.  So the original EPC was based on the SAP, but the new one was based on the rdSAP for existing homes.  We ended up with a C74.  Clearly something not right.  The system is not fit for purpose, but how on earth can it be changed to make it useful for purchasers?   Perhaps keeping the original EPC based on the SAP, and renewing that every 10 years with appropriate changes taken into account?  The assessor who came to do our second EPC had never seen a "passiv haus" and clearly didn't really get it.  When he saw our EPC of A100, he said there must have been a mistake, and that he'd never given a higher score than C75!  I do realise that the current system faults are mainly down to the methodology of the rdSAP, and I believe there is a plan to change the system sometime next year, but I'm not holding my breath. 

Edited 14 hours ago by pulhamdown
Typo

[JohnMo]

The system just uses people that are happy to cut and paste - sh!te in st!te out. Many assumptions made, but you pay maybe a £100 or less for the EPC - but to do the EPC correctly would take tens of hours. What can we expect? Just treat as a tick in a box and move on would be my advice.

 

Keep your electric bills for a future buyer - way more important than EPC.

[saveasteading]

2 hours ago, JohnMo said:

to do the EPC correctly would take tens of hours.

There  are a lot of useless people doing this, and good too of course.

the test is whether they ask questions and/or give suggestions. interested or its just a job. have some questions.

 

some are just random guys that have been given the task by their employer.

I recall a family purchase and upgrade,  of traditional brick walls and somebody came to assess for the gas or electric company for some reason. He spent 5 minutes making assumptions for 'this sort  of building'. didn't check in the loft. wouldn't listen that we had upgraded the party wall.  I wouldn't be surprised if he thought this was a cushy job and would start his own assessment business. 

[Gone West]

Isn't it possible to fork out a bit more and have a full SAP EPC calculated rather than an rdSAP version.

[SimonD]

8 hours ago, pulhamdown said:

but I'm not holding my breath. 

 

The Future is HEM - https://home-energy-model.co.uk/

[JohnMo]

31 minutes ago, SimonD said:

 

The Future is HEM - https://home-energy-model.co.uk/

More complex but will still be sh!te in.... Same monkeys will just use a different computer program.

[Alan Ambrose]

“At its core, HEM is a building physics simulation. It takes detailed data about a home (its construction, heating system, ventilation, insulation, glazing, orientation, and local weather) and calculates its energy performance at half-hourly intervals throughout a full year.‘
 

Well it’s probably a step forward being single & open source / cloud / written & paid for by the government.

 

It’s effectively UK govt’s answer to PHPP. The usual problems won’t entirely go away though:

 

+ since we have little idea how our current housing stock is built, there will be lots of guessing i.e. ‘assumptions’. So a bit GIGO.

+ we’ll need loads of custom psi calcs if the results are going to reflect the actual heat loss.

+ these are only models and reflect assumptions about how we live in these houses - probably there will be little comparison of actual vs. model (just like EPCs) so the man in the street may pay them very little attention.

 

The 1/2 hour intervals are marketing BS and won’t help the accuracy one bit.
 

Lastly, one of the helpful things about PHPP is its database of real world components - this will be key but a lot of work to replicate.

[SimonD]

1 hour ago, JohnMo said:

More complex but will still be sh!te in.... Same monkeys will just use a different computer program.

 

Sadly, the implementation probably will be. 

[SimonD]

23 minutes ago, Alan Ambrose said:

we’ll need loads of custom psi calcs if the results are going to reflect the actual heat loss.

 

The promise is to use a different cold bridging methodology, probably using FEA tools, so yes a lot of work required, but better than blanket defaults as per SAP currently? If used correctly.....

 

Quote

The resulting heating or cooling demand needed to maintain the zone setpoint

 

But this is interesting, because there is no mention of using BS EN 12831-1:2017 which is the UK standard for designing the space heating load. And this standard has only just been implemented. I wonder if this is going to lead to different standards being used for new builds using HEM that aren't necessarily going to be consistent with BS EN 12831-1. Or is there going to be another poorly considered change to the industry.