Non PassivHaus new homes - Space heating requirements?

[anonymous]

So

 

My aim is to get my existing house to be more efficient, and I'm someone who want to work with PassivHaus principles but not necessarily entirely given you get diminishing returns 

 

Newer houses aim for an air tightness of around 5 or below I believe. Does anyone know how much KwH per square metre they typically use? 

 

I ask, as it should be possible for me to go from an air tightness of 7.6 to 5 quite easily, it not below that (Which is obviously what I'd want, cost permitting) 

[anonymous]

So

 

I've had a quick look see on Barratt Homes, found a new build, and there's quite a few in this postcode area. It isn't my postcode or close to me but I figured Barratt homes would have some new ones even if they're not known for having the best homes about 

 

It seems that they more or less use 35KwH/ Square metre when it comes to heating 

 

So that's something to try and achieve using enerphit 

 

https://find-energy-certificate.service.gov.uk/energy-certificate/0632-2531-7000-0464-4292

 

[joth]

  On 14/12/2022 at 10:56, anonymous said:

 

 

It seems that they more or less use 35KwH/ Square metre when it comes to heating 

 

So that's something to try and achieve using enerphit

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 The enerphit standard is 25kWh/m2/year so if you're doing that you have to achieve that, not some other number. 

You can aim for 35 if you prefer, but that's not an enerphit.

 

(People discuss like they're going for a 1st class honours degree, by renegotiating what score is required to pass)

 

[anonymous]

  On 14/12/2022 at 11:06, joth said:

 

 The enerphit standard is 25kWh/m2/year so if you're doing that you have to achieve that, not some other number. 

You can aim for 35 if you prefer, but that's not an enerphit.

 

(People discuss like they're going for a 1st class honours degree, by renegotiating what score is required to pass)

 

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Tbh I'm looking to use PassivHaus principles as much as possible, and for as it seems worth it regarding costs / benefits 

 

In that sense, air tightness and an MVHR seem key at the very least 

[Adrian Walker]

  On 14/12/2022 at 10:56, anonymous said:

So

 

I've had a quick look see on Barratt Homes, found a new build, and there's quite a few in this postcode area. It isn't my postcode or close to me but I figured Barratt homes would have some new ones even if they're not known for having the best homes about 

 

It seems that they more or less use 35KwH/ Square metre when it comes to heating 

 

So that's something to try and achieve using enerphit 

 

https://find-energy-certificate.service.gov.uk/energy-certificate/0632-2531-7000-0464-4292

 

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As the temp is around 0°C at the moment, heat the house up to say 20°C and see how long it take to cool down and create a graph.  That will give you some idea of the heat losses.  It might be worth getting at airtightness test done.  

[anonymous]

  On 14/12/2022 at 11:49, Adrian Walker said:

 

 

As the temp is around 0°C at the moment, heat the house up to say 20°C and see how long it take to cool down and create a graph.  That will give you some idea of the heat losses.  It might be worth getting at airtightness test done.  

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I've already had my air tightness done yesterday. I'm currently at 7.66

 

He advised me that I could get it below 5 easily, and maybe even lower once I seal up the parts identified in the test. 

[Radian]

  On 14/12/2022 at 11:49, Adrian Walker said:

 

 

As the temp is around 0°C at the moment, heat the house up to say 20°C and see how long it take to cool down and create a graph.  That will give you some idea of the heat losses.  It might be worth getting at airtightness test done.  

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My lazy brain initially told me this might be a very simple way to get an overall U-Value for the house. But then I asked myself how the measured loss in air temperature would relate to the conduction losses through the building fabric and got completely lost. It would be nice to have an average W/(m²K) as a sanity check for the spreadsheet heat loss calcs I've done although they agree quite well with the actual amount of energy I'm having to put in to maintain an indoor/outdoor delta.
 

[SteamyTea]

  On 14/12/2022 at 14:26, Radian said:

It would be nice to have an average W/(m²K) as a sanity check

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Isn't that what Heating Degree Days do?

Allows you to compare on a common basis i.e. 12 or 15⁰C.

[JohnMo]

I thought it may be easy to go back to calculate the u value, but when you start thinking, ventilation rates, MVHR recovery rates would need to accounted for. Did you get solar gain, did you have the oven on, bit of a pain, so stopped thinking about and decided to write the above instead 

[WWilts]

  On 14/12/2022 at 09:00, anonymous said:

Does anyone know how much KwH per square metre they typically use? 

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43 kWh/m2/yr

 

with

Airtightness 3.75 m3/m2.h@50 Pascals

Just an example from real data

75% of that on space heating. Rest on water heating.

Edited December 21, 2022 by WWilts

[anonymous]

  On 21/12/2022 at 19:49, WWilts said:

43 kWh/m2/yr

 

with

Airtightness 3.75 m3/m2.h@50 Pascals

Just an example from real data

75% of that on space heating. Rest on water heating.

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Ah 

 

So around 32.5 KwH / Square metre for space heating which would be an equivalent of 3870KwH a year of space heating for myself 

 

And then also 10.75KwH/sq m for water which means that if my house met that standard I'd need 1290 KwH for water heating 

 

Thanks 

Edited December 21, 2022 by anonymous

[ProDave]

I have resisted posting because this is not a typical developer new house, but my self build, built to largely passive house principles but no attempt to have it analysed let alone certified as a passive house.

 

150 square metres 1.4 air tightness  ASHP under floor heating downstairs only triple glazed and MVHR

 

Last 12 months heating the ASHP consumed 1200kWh so that's 8 kWh of electricity per square metre or about 24kWh of heat delivered.

 

In addition the ASHP has consumed 1000kWh heating the DHW (metered separately to heating usage)

 

And this in the east Highlands where the last week of cold weather that brought the UK almost to a halt, is just a normal weeks weather here in the winter.

[Radian]

  On 14/12/2022 at 09:00, anonymous said:

Does anyone know how much KwH per square metre they typically use? 

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For balance, consider my marginally insulated, air-leaks-like-a-sieve 90's monstrosity = 70kWh/m² pa. for space heating and 30kWh/m² pa. DHW 🤦‍♂️

[MikeSharp01]

  On 21/12/2022 at 22:10, Radian said:

For balance, consider my marginally insulated, air-leaks-like-a-sieve 90's monstrosity = 70kWh/m² pa. for space heating and 30kWh/m² pa. DHW

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Commiserations, that's 10kWh/m2 more for DHW than @ProDave, assuming a COP of 3, and he is three occupants IIRC🤔

[Radian]

  On 21/12/2022 at 22:28, MikeSharp01 said:

Commiserations, that's 10kWh/m2 more for DHW than @ProDave, assuming a COP of 3, and he is three occupants IIRC🤔

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Thanks. But three occupants here as well. All with rather long hair 😎

[SteamyTea]

My daily mean, so far this year, is 7.9 kWh/day, 2781 kWh for the year to date.  I use around 3 kWh/day for DHW and about 1 kWh a day for the rest.

So 4 kWh/day for space heating.  House is 50 m².

So total energy works out at 55.6 kWh/m².Year.

Heating is 28.2 kWh/m².Year.

Those number will go up a little for the last few days of the year, but not much.  Yesterday I used half the amount I did the same day last week.

I have just got in from the Montol and it is 10°C in town.  Ansom my bird.

 

[MikeSharp01]

  On 21/12/2022 at 23:16, SteamyTea said:

I have just got in from the Montol and it is 10°C in town

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Looks like fun and why would you not like your bird? (or is 'bird', not the rather old school (c 1300) word meaning 'girl', something in Cornish I have missed)

[Onoff]

  On 22/12/2022 at 07:15, MikeSharp01 said:

Looks like fun and why would you not like your bird? (or is 'bird', not the rather old school (c 1300) word meaning 'girl', something in Cornish I have missed)

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https://matadornetwork.com/abroad/15-slang-phrases-youll-need-know-cornwall/

[MikeSharp01]

  On 22/12/2022 at 07:58, Onoff said:

https://matadornetwork.com/abroad/15-slang-phrases-youll-need-know-cornwall/

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This might be some sort of Cornish cultural appropriation as 'Bird' (meaning girl / young woman) was around in the 14 century although tracing its use up to the 1960s when it seems to have seen a resurgence looks tough. Naturally in the hands of @SteamyTea , in the way that bulls**t baffles brains, it could mean almost anything - but we digress from the core topic of this thread. 

 

Back to PHPP - which tells me what our home should need (Treated Floor Area TFA = 140m²): Heating Demand = 9.993 kWh/(m²a) & DHW = 22.4 kWh/(m²a) (Based on 2 person occupancy)

[SteamyTea]

  On 22/12/2022 at 08:43, MikeSharp01 said:

meaning girl / young woman)

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Generally used as a greeting or farewell for someone that you know.  Girls often call their male friends Bird, but boys use it for both male and female.

[MikeSharp01]

  On 22/12/2022 at 08:50, SteamyTea said:

Generally used as a greeting or farewell for someone that you know.  Girls often call their male friends Bird, but boys use it for both male and female.

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Very 'Now'! 

[SteamyTea]

  On 22/12/2022 at 09:12, MikeSharp01 said:

Very 'Now'! 

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Always been trendsetters down here.  Shop in Padstow was the first place to sell Crocs.

[WWilts]

  On 14/12/2022 at 11:20, anonymous said:

an MVHR

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MVHR compulsory if you have excellent airtightness (in practice, likely to be compulsory if you achieve 2 m3/m2.h@50Pa)

If your house remains leakier than that, consider Vent Axia Tempra heat exchange fans to replace your existing extractor fans. Background mechanical ventilation without the expensive retrofit of ducts etc

Edited December 22, 2022 by WWilts

[anonymous]

  On 22/12/2022 at 14:57, WWilts said:

MVHR compulsory if you have excellent airtightness (in practice, likely to be compulsory if you achieve 2 m3/m2.h@50Pa)

If your house remains leakier than that, consider Vent Axia Tempra heat exchange fans to replace your existing extractor fans. Background mechanical ventilation without the expensive retrofit of ducts etc

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The only extractor fan I've got is in my en suite / kitchen tbh 

 

Other than that, I have no trickle vents, though I do have some vents underneath the loft part in the attic 

[JohnMo]

Sound like you need a ventilation strategy, before you start making improvements other your house will start to turn black and your CO2 levels raise, all which will make an unhealthy home.