NHER vs SAP

[Mark Siddall]

As mst of the work that I do is non-domestic I have little appreciation for some of the finer aspects the day to day ins and outs of energy modleing for domestic situations. What is the difference between NHER and SAP? (Is there a difference?) From the industry perspective, as opposed to purely and AECB stance, is one better i.e. more accurate than the other?

It looks as though both can be approved by building control. http://www.nher.co.uk/

Mark

[Mark Siddall]

Thanks Mike. In a broad sense I'm very aware of the short comings of SAP. I was wondering if NHER offered refinments to SAP rather than a number of bolt-ons.

Mark

[Anonymous]

Sorry, I don't know, but I suspect it is similar to the Hevacomp suite.

[Mark Siddall]

Mike as far as I know Hevacomp is using the EnergyPlus simulation software as the basis of it's calcs. This is way beyond SAP, in fact, as I understand it EnergyPlus is perhaps the most developed dynamic simulation tool to date. HevaComp have spught to give it a nice front end. (Not sure if they have doctored EnergyPlus in some form.)

Mark

[Anonymous]

Mark Are you talking about this one, for Part L1?: descibed on their website as

A new SAP calculation procedure is being published for dwellings and Hevacomp will provide a new SAP calculation program. SAP calculates energy performance and uses a new SAP scale (1 to 100). The dwelling Carbon dioxide emission rate and Environmental impact rating replace the Carbon index. SAP (2005) also includes lighting energy, solar water heating, thermal bridges and renewable and energy saving technologies. Hevacomp's SAP (2005) program will be accredited by BRE.

Or their SBEM simulation software for Part L2? which allows for far more input data

[Mark Siddall]

Hmm. In this respect I'm not sure about HevaComps integration of SAP/iSBEM. If they use the TAS approach they would use dynamic simulation (in this case EnergyPlus), this in turn will highlight the failings of the SAP/BREDEM steady state model. Whereas if they simply integrate the standard SAP/iSBEM model for b.regs certification only then, like IES, the model will be a separate calculation from the dynamic simulation routine (in this case EnergyPlus) and prone to the “normal” inaccuracies of standard steady state models.

[PHPP is not a standard steady state model.]

Mark

[Mark Siddall]

PHPP: Originally all PassivHaus projects required dynamic simulation however what PHI have done is develop a very detailed steady state model using additional parameters that have been derived from dynamic simulation. So it's not dynamic but it is far more detailed than standard steady state models. In fact it is so detailed that it compares well to dynamic models at the PassivHaus performance level i.e. 15kWh/annum.

http://www.passivhaustagung.de/Passive_House_E/PHPP.html

Mark

[Mark Siddall]

Liz,
Interesting. Aware that the CLP is undertaking a line by line analysis of PHPP vs SAP I can't help but wonder whether PHPP and NHER share much commonality. Presumably NHER is not as refined as PHPP? Could NHER be a useful ally in the cause for improved low energy design tools?

Mark

[Mark Siddall]

Methinks that life would be so much easier if it were all in kWh/m2.

Mark

[Anonymous]

This document is however interesting as it shows the NHER rating alongside the SAP rating for new builds.

Now all we need to know is what is behind the conversion to the NHER rating?

Doh, I didn't link the final document did I, here it is:

http://www.nher.co.uk/pages/software/product_sheets/A4%20Builder%20leaflet.pdf

[Mark Siddall]

Thanks Mike.

[Anonymous]

There are three key differences between NHER and SAP:

1) NHER uses degree day data to give regional variation in energy demand, fuel costs etc. – SAP is location independent;
2) NHER includes all energy usage, so it is heating, hot water, cooking, lights & appliances, so giving total fuel costs;
3) NHER permits (at Level 3) matching to fuel bill data to give a good sense of how households are actually living – making it useful as a research tool for fuel poverty.

However at the moment NES (National Energy Services), operators of the NHER scheme, are concentrating on developing the next version of SAP, and the updating of NHER will only take place when that has been completed.

Hope this is useful.

Regards,

Paul Jennings

[Author]

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