Whilst not personally having built any - I've SAP assessed a lot.

It depends on how you want to build. You *could* get a building to achieve Code 4 with worst allowable U-values for all elements and your roof covered in PV to achieve the Co2/energy emissions saving - not recommended by any means, but doable.

I would personally suggest making the building as well insulated and air tight as you possibly can afford as a first step (Energy Saving trust enhanced accredited details are a good step to assist with this). Then depending on what heating strategy you chose to adopt, add a decent MVHR system and renewables to the mix as required.

Either way, get a Code assessor and SAP assessor involved at earliest stages, as you can miss out on code credits if various issues not considered early enough to be incorporated. Code Assessor will require an accredited energy assessor to have done the calculations.

On a related note, Building regulations L1A 2010 is about to be published (by end of April), SAP 2009 has just been published and Code for Sustainable Homes 2010 is about to finish it's consultation.

Come October, the Code, reg's and SAP will be very different to present - so if you are not intending to register the job until after October, the required values may be very different to those required currently.

Posted By: SigaldrySAP 2009 has just been published

but

Posted By: SigaldryCome October ... SAP will be very different to present

What's SAP 2009 if it's just about to be re-written for Oct?

So - first sight of the definitive new regime is out - what does it look like? Any of the old deficiencies and inconsistencies dealt with? What about RDSAP?

I saw a main contractor offer the client 3g windows as a no extra cost option over dg --- not quite 0.7 but getting close

If they could do it so can we all.

"Apart from the relatively poor air leakage, these kind of numbers are getting close to PassivHaus. I didn't think that code 4 was this stringent?"

This is code 4 without renewables no? lower the spec and you need to pile on the pv/heat pumps is the order of the day - or so i understand it

Thanks all. This is all very very helpful.

I do not like the idea of going for the cheapest solution (now) as as time goes on it look more and more foolish.

Are we really looking for the minimum route?

@ Fostertom

RDSAP (Appendix S) currently unchanged (use SAP 9.83) - apparently they will look at amending this for October (or thereabouts).

@Markbennett, Bampton & Neilu et al

Spec as I presented for current code 4 is as noted, a non renewables led approach using the current documents - as I also noted, renewables can reduce this spec considerably.

For achieving Code 4, Solar hot water and MVHR help considerably, PV even more so, but as I understand it is expensive.

Enhanced details do help considerably under curent SAP - I would note that floor U-value on the EST guidance document are a bit on the poor side - quite easy to achieve a lower value compared to most of the other solutions. It’s a reasonable document in most respects.

I agree, 0.70 triple glazing will likely be expensive and not as easy to get hold of - but some people do ask for no renewables solutions... The whole calculation process is a trade-off, obviously if you improve one thing sufficiently, you can relax another. Likewise if you rule out some options, you will need to do more elsewhere.


Heat Pumps do make it considerably easier to get code 3 and 4 currently (the ‘Code 4 loophole’), this ignores however the considerably higher overall emissions compared to a gas or biomass approach and the higher costs to the end user associated with using electric heating. You also lose any credits within the code for low NOx emissions.

Heat Pumps do have their place in saving energy (cost and emissions), particularly where the alternative is electric heating of other types as it is considerably cheaper and more efficient than for example night storage, or panel heaters with dual immersion.

If over time we can drive down the emissions associated with producing electricity, Heat Pumps will be a strong tool and a better bet than at present. For now I tend to suggest that they are a good idea if electric is the only alternative on site, or if the electricity they will consume can be provided on site via PV or wind power.

If every housebuilder only does the minimum necessary to achieve Code 3 compliance currently (or L1A 2010 compliance based on consultation SAP and consultation L1A) using air source heat pumps to help make it easier to get dwellings to pass, but otherwise the least they can possibly get away with, then overall the amount of CO2 emissions from housebuilding will go up – not down.

Done lots of modelling using consultation SAP, consultation code for sustainable homes (Fabric Energy Efficiency targets seem too easy to achieve) and consultation Approved Document L1A.

(Consultation CfSH sets out Fabric Energy Efficiency requirements with mandatory levels required for given code levels, which means that a certain standard of fabric will be required to be achieved to hit the mandatory requirements as well as the CO2 emissions / Energy targets).

However as these are all consultation documents (with the exception now of the recently published SAP 2009), whatever I tell you based on that work could be wrong - I haven't seen the final L1A 2010 document yet.

The party walls issue for instance has changed between consultation version and final version. (Now party walls in the target are set at 0.00 W/m²K, whereas the target was set at 0.40 W/m²K for consultation reference specification). Under the consultation documents and cSAP, full filling the cavity and thereby stopping heat loss though the party wall cavity up into the loft space would result in a reasonable chunk of your 25% improvement over L1A 2006 levels being achieved. The result of the change from target of 0.40 changing to 0.00 means that developers will need to solve the party wall issue and then still have to undertake various other measures to make up the 25% improvement. This follows the scottish building standards consultation proposal to that particular measure.

The proposed change in Low Energy Lighting to minimum 75% (whereas using current regulations/SAP 2005 the figure is set within SAP at 30%) will immediately save a fair amount of CO2 emissions/Electricity costs as Low Energy Lighting was proposed in consultation document to be 'tradeable' as far as Dwelling Emission rate calculation is concerned.

However - as noted - I don't now know for sure what is in and what's not.

I can say that using the consultation software and documents L1A 2010 compliance seemed easier than current Code for Sustainable Homes level 3 25% improvement over L1A 2006 DER. Equally Code 4 under the consultation seemed a lot easier than under current reg's/SAP CfSH Level 4.

Well SAP 2009 is based on a monthly calculation rather than yearly and various information from SAP 2005 has been updated, thermal mass now taken into account (low thermal mass actually works out in SAP 2009 consultation at least as better for emissions) - but as I don't know which particular anomolies you are talking about, it's hard to comment on whether they have been fixed.

I would guess that it's probably more accurate than it was before for calculating potential emissions.

At it's heart it is still based on standard occupancy and standard behaviour, so won't represent actual emissions/costs for real people living in a house in their own particular way of living; But it does serve as a reasonable comparison tool to determine whether a given house with its own particular specification is likely to be better or worse for cost and environmental impact than another.

Thanks Matt