NSS

Total energy consumption per m2 per annum

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Not been in our new home for a year yet, but have been projecting forward our total energy consumption with the aim of establishing a measure for comparison. Found an interesting article on the OVO Energy site (https://www.google.co.uk/amp/s/www.ovoenergy.com/amp/guides/energy-guides/how-much-heating-energy-do-you-use.html) which is specific to heating requirement, but I wondered if anyone else has (or could) work out their total energy usage per annum as kWh/(m2a) so I can start to gauge how we compare. For the purpose of the calculation, I'm assuming we consume 50% of the solar power we generate (though it may be a little more than that) and adding that figure to the energy imported from the grid.

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All I know is I've just ordered another over £1.2K of oil....

 

Poxy TRADITIONALLY built house! :)

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For comparison, the limit for the passive-house standard for the "Entire Primary Energy Demand" is ≤120kWh/m2.yr (with heating demand limited to ≤15kWh/m2.yr).

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2 minutes ago, Onoff said:

All I know is I've just ordered another over £1.2K of oil....

 

Poxy TRADITIONALLY built house! :)

Ouch!

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6 minutes ago, Dreadnaught said:

For comparison, the limit for the passive-house standard for the "Entire Primary Energy Demand" is ≤120kWh/m2.yr (with heating demand limited to ≤15kWh/m2.yr).

Really? I'd better recheck my calculations as I reckon we'll be looking at a total energy usage of circa 40kWh/m2.yr

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5 minutes ago, NSS said:

Ouch!

 

Yep, TWICE a year that.

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11 minutes ago, Dreadnaught said:

@NSS I should have said that the heating demand limited to ≤15kWh/m2.yr is for space heating only, not to include domestic hot water (DHW).

 

More details here: https://www.passivehouse-international.org/index.php?page_id=150

Yep, I realised that. I'm talking TOTAL energy consumption (space heating/DHW/cooking/lighting/etc/etc) and my projected 40kWh/m2a seems to be correct. Even if I up the assumed use of solar to 75% of annual generation, the total only goes up to about 45kWh/m2a. 

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@NSS sounds like a good figure. Have you modelled your house in PHPP?

 

The most recent iteration of my house (117m² TFA, single story, not yet built) is 49.2 kWH.m2a for Entire Primary Energy Demand. More iterations and re-designs yet to come. Form factor is very poor at 4.69 (largely unavoidable because of planning constraints).

 

image.png.4d28303e2c660b26585776f8f8576df4.png

 

Edited by Dreadnaught
Added form factor

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We import 8,000kWh (all electric) and generate 4,000 in our 330m2 build. Given we only export about 3%, makes our energy demand 36kWh/m2/pa.

 

This is for 6 people, ASHP for DHW, heating and cooling, 2 kitchens, and charging of a hybrid car.

 

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10 minutes ago, Dreadnaught said:

@NSS sounds like a good figure. Have you modelled your house in PHPP?

 

The most recent iteration of my house (117m² TFA, single story, not yet built) is 49.2 kWH.m2a for Entire Primary Energy Demand. More iterations and re-designs yet to come. Form factor is very poor at 4.69 (largely unavoidable because of planning constraints).

 

image.png.4d28303e2c660b26585776f8f8576df4.png

 

No, not modelled it as PH was never a consideration, but pleasantly surprised at how little energy we appear to be using.

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@NSS That's good. What's the shape of the building (form factor, it has a huge effect), fairly compact? Good levels of insulation in the walls, roof and floor? Air tight with MVHR?

Edited by Dreadnaught

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7 hours ago, Dreadnaught said:

For comparison, the limit for the passive-house standard for the "Entire Primary Energy Demand" is ≤120kWh/m2.yr (with heating demand limited to ≤15kWh/m2.yr).

 

Is Primary Demand including losses in generation and delivery (ie covering supply losses back to the resource or power station) or is that number for "energy delivered to the house"?

 

ie Do I have to apply fiddle factors to the numbers I measure at my house, and what are they?

 

Ferdinand

 

Edited by Ferdinand

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Primary energy demand is the measure used, both by SAP and PHPP, and is not just the useful energy readings taken from gas or electricity meters, there are factors applied to fuels/electricity in order to reflect the efficiency of the conversion process from potential energy in the fuel to the useful energy delivered to the house.  This ratio can be quite high for some "fuels", electricity being a good example, where the efficiency of both the power generation system and the distribution system is taken into account when determining the primary energy.  It's primary energy that is used in the PH max allowable figure of 15 kWh/m²/year for space heating.  The passive house standard really needs updating a bit now, IMHO, as we found it pretty easy to hit well under the 15 kWh/m²/year for space heating whilst using electricity as the fuel, which carries a high total energy to useful energy penalty, because of the relatively poor efficiency of the generation and distribution system (which is being revised in SAP, to reflect the increase in renewable and local micro generation in the grid, as being discussed in another thread).

 

 

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23 minutes ago, JSHarris said:

Primary energy demand is the measure used, both by SAP and PHPP, and is not just the useful energy readings taken from gas or electricity meters, there are factors applied to fuels/electricity in order to reflect the efficiency of the conversion process from potential energy in the fuel to the useful energy delivered to the house.  This ratio can be quite high for some "fuels", electricity being a good example, where the efficiency of both the power generation system and the distribution system is taken into account when determining the primary energy.  It's primary energy that is used in the PH max allowable figure of 15 kWh/m²/year for space heating.  The passive house standard really needs updating a bit now, IMHO, as we found it pretty easy to hit well under the 15 kWh/m²/year for space heating whilst using electricity as the fuel, which carries a high total energy to useful energy penalty, because of the relatively poor efficiency of the generation and distribution system (which is being revised in SAP, to reflect the increase in renewable and local micro generation in the grid, as being discussed in another thread).

 

 

 

For future readers, SAP is the model used to create the notional numbers published on EPC Certificates.

 

Ferdinand

 

Edited by Ferdinand

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7 hours ago, Dreadnaught said:

@NSS That's good. What's the shape of the building (form factor, it has a huge effect), fairly compact? Good levels of insulation in the walls, roof and floor? Air tight with MVHR?

Form factor is pretty poor (irregular shape chalet bungalow with multiple gables/dormers). Walls, roof and floor all circa 0.14/0.15. Air permeability of 1.6m3/hm2, Paul MVHR and SageGlass electro-chromic glazing. No gas.

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8 hours ago, Onoff said:

All I know is I've just ordered another over £1.2K of oil....

 

Poxy TRADITIONALLY built house! :)

All I know is I won't have to order oil again :P but I do have to get rid of the oil tank somehow.

Edited by PeterStarck

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31 minutes ago, JSHarris said:

Primary energy demand is the measure used, both by SAP and PHPP, and is not just the useful energy readings taken from gas or electricity meters, there are factors applied to fuels/electricity in order to reflect the efficiency of the conversion process from potential energy in the fuel to the useful energy delivered to the house.  

 

Which is understandable, but 99% of Joe Public couldn't give a toss about how efficient it is to generate the fuel they are using, only caring about how much it costs them their homes.

 

Perhaps part of the problem in trying to convince people to demand more energy efficient homes is that quoting things like SAP, PHPP and EPC calculations go straight over the vast majority of heads.

 

 

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I don't doubt at all that most house buyers probably ignore the EPC.

 

However, I didn't invent the way that SAP, PHPP etc use to compare different fuels, so rather than take another pop at me for just stating fact, why not take it up with the government (in the case of SAP) or the PHI (in the case of PHPP)?  Might be more constructive.

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19 minutes ago, JSHarris said:

... so rather than take another pop at me for just stating fact, why not take it up with the government (in the case of SAP) or the PHI (in the case of PHPP)?  Might be more constructive.

 

I took it as a pop at the people that couldn't give a toss etc, definitely not a pop at you.

 

 

31 minutes ago, NSS said:

Which is understandable, but 99% of Joe Public couldn't give a toss about how efficient it is to generate the fuel they are using, only caring about how much it costs them their homes.

 

Perhaps part of the problem in trying to convince people to demand more energy efficient homes is that quoting things like SAP, PHPP and EPC calculations go straight over the vast majority of heads.

 

I take your point, but an EPC rating of A, B, C etc is supposed to be easy to understand. Maybe people just look at that but it doesn't mean anything to them, whereas digging only a small amount more would let them determine how much the house would cost to heat?

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40 minutes ago, JSHarris said:

I don't doubt at all that most house buyers probably ignore the EPC.

 

However, I didn't invent the way that SAP, PHPP etc use to compare different fuels, so rather than take another pop at me for just stating fact, why not take it up with the government (in the case of SAP) or the PHI (in the case of PHPP)?  Might be more constructive.

How the hell was that a pop at you? 

Edited by NSS

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2 minutes ago, jack said:

I take your point, but an EPC rating of A, B, C etc is supposed to be easy to understand. Maybe people just look at that but it doesn't mean anything to them, whereas digging only a small amount more would let them determine how much the house would cost to heat?

Precisely.

 

 

Edited by NSS

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32 minutes ago, NSS said:

Perhaps part of the problem in trying to convince people to demand more energy efficient homes is that quoting things like SAP, PHPP and EPC calculations go straight over the vast majority of heads.

 

I tend to agree. Joe Public does not give a fig. Even the term Passive House, translated as it is from German, its unfortunate. In my experience, people think it applies to houses only, not other buildings, and invariably implies no heating system at all.

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1 minute ago, NSS said:

Precisely.

 

So as usual, it's people that are the problem!

 

Bloody people! :ph34r:

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Just now, Dreadnaught said:

and invariably implies no heating system at all.

 

Indeed. I was surprised recently when I saw the following comment in a post on a Facebook self build forum:

 

"Our PHPP calcs are showing that our heat demand is above the 15kWh/(m²a) needed to avoid a primary heat source (currently at 21 - probably due to form factor). We don't need to achieve Passivhaus but now conscious that we may need some heat".

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