Complying with the Part L when building a low energy build

fclauson

Wanted to start a new thread - complying with Part L and low energy

What lee way is their to prove compliance with the law in a low energy build and prehaps fail at DEAP.

Given the two threads here and here where this was started to be discussed but was a tangent to the original thread I thought a new thread with this as as specific item might be useful

If you are a 25Kw/M2 house - but you are not achieving your 10Kw/M2 renewable (you want to have a multifuel stove for aesthetics and perhaps a gas boiler for quick response) what latitude could one/should one/could one get to the actual planning act which states

(b) providing that a reasonable proportion of the energy consumption to meet the energy performance of a dwelling is provided by renewable energy sources;

Obviously DEAP is defacto and PHPP seems to be accepted (although you could argue you can have a non complient PH house quite easily)

So -
What is reasonable ?
What have people found to be acceptable to the BER certifier ?

sydthebeat

Firstly, dont get too confused with BER and this regulation.

in essence they are two separate things. The only co-relation with the two is the fact that the software used to provide a rating is the same software that is used to check compliance with building regs. So then not to confused the issue from here on in, lets not refer to the acronym BER.

The individual "building regulations" certifier is the one who has the final call on this.
As with every other building regulation, there is a de-facto method to show compliance which are the TGD's (Technical guidance documents). Once you step outside these de-facto compliance methods, its down to the person proposing compliance ie the builder / client to prove that compliance is met or improved upon in some other manner.

In this particular case the de-facto compliance is prescribed as 10kwh/m2/yr heating energy and 4kwh/m2/yr electrical energy.

The obvious problem is that the regulations is based on a per sq m basis rather than a ratio to energy demand.

What a certifier is to consider 'reasonable' is really up to the individual as its their professional reputation and more importantly, their professional indemnity insurance which is on the line. So its 'reasonable', in my opinion, for a certifer to demand the prescribed amounts.

fclauson

So sydthebeat - I always value you input

The regulation is clear - its about showing a resonable proportion

TGD Part L 1.2 must be making reference that if the property is built to regs then a resonable amount would be 10 Kwh/M2.

It is silent on if the build is built to better than regs

The reference regulation build figure for my build is 123 Kwh/M2 - using DEAP - and hence to meet the 10Kwh/M2 figure I need to deliver about 8% of my energy demand from renewable. That’s classed as reasonable.

If as my build is it comes as at say 21Kwh/M2 – again using the DEAP modelling - then why could one not argue that 4.2Kwh/M2 (i.e. 10%) is a reasonable contribution from renewable rather than having to achieve 10Kwh/m2 which is just shy of 50% from renewable via the defacto method

Both figures are arrived at using the IS EN 13790: 2004 model