New passivehaus plus project

[Conor]

35 minutes ago, 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.

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]

15 minutes ago, 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.

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]

9 hours ago, 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?

 

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]

8 hours ago, 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.

 

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]

6 hours ago, 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.

 

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