New passivehaus plus project

[Conor]

  On 02/09/2020 at 13:49, ProDave said:

I am reading this thread with interest, but I am puzzled by what seem to me like high energy use figures for a passive house +, i.e mention of 6000kWh per year?

 

My own house that is built to a good standard but never attempted any passive house calculations uses a total, real world measured figure of 1706kWh pa for heating and at about 150 square metres that's 11.37kWh per square metre per year.

 

I do have solar PV which generates more per year than the house uses in space heating, but not quite as much as the house uses for space heating and DHW.

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PH plus standard requires a min of 6000kwh annual generation and a max energy demand of 45kwh/m².... So essentially energy positive buildings.

https://passivehouseplus.ie/passive-house-plus-standard

 

[SteamyTea]

  On 02/09/2020 at 14:25, Conor said:

PH plus standard requires a min of 6000kwh annual generation and a max energy demand of 45kwh/m².... So essentially energy positive buildings.

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Without looking at the details at all, those limits tend to favour larger houses.

 

6000 kWh / 45 kWh/m²  = 133m²

Or about 2.7 times the size of my house.

 

And it is kWh, not kwh.

Edited September 2, 2020 by SteamyTea

[Dan F]

  On 02/09/2020 at 13:49, ProDave said:

I am reading this thread with interest, but I am puzzled by what seem to me like high energy use figures for a passive house +, i.e mention of 6000kWh per year?

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The 6000kWh figure was for generation (not energy usage) for 100m2 footprint.  The other value of 45 kWh/(m²a) is PER (Primary Energy Renewable) which is quite different to heating demand.

[Dan F]

  On 02/09/2020 at 14:37, SteamyTea said:

Without looking at the details at all, those limits tend to favour larger houses.

 

6000 kWh / 45 kWh/m²  = 133m²

Or about 2.7 times the size of my house.

 

And it is kWh, not kwh.

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It's based on projected footprint of the thermal envelope so does not favour large houses.   It does adversly affect bungalows though..

 

Those numbers are a bit mixed up:
-  The 45kWh/m2.a mentioned is max energy demand (PER)
-  The 6000kWh/a that was mentioned is generation for 100m2 footprint.

 

If your house footprint is 50m2, then PV generation required for PH+ would be 3000 kWh/yr.  In the south-east this would require around 9 x 350W south-facing panels.   If PER is closer to 30kWh/m2.a (because of ASHP/WWHRS etc) then this is reduced to 1900kWh/yr and 6x350W panels.

 

[SteamyTea]

  On 03/09/2020 at 00:04, Dan F said:

 

It's based on projected footprint of the thermal envelope so does not favour large houses.   It does adversly affect bungalows though..

 

Those numbers are a bit mixed up:
-  The 45kWh/m2.a mentioned is max energy demand (PER)
-  The 6000kWh/a that was mentioned is generation for 100m2 footprint.

 

If your house footprint is 50m2, then PV generation required for PH+ would be 3000 kWh/yr.  In the south-east this would require around 9 x 350W south-facing panels.   If PER is closer to 30kWh/m2.a (because of ASHP/WWHRS etc) then this is reduced to 1900kWh/yr and 6x350W panels.

 

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Right, may be worth modelling to see what could be achieved with my place.