Passive build - electric heating?

[JohnMo]

14 minutes ago, LeenToo said:

That sounds like a very well thought out system John, thanks for the info.

When you say you charge at night this is building up heat to send around the pipes later in the day or does that actively go into the pipes during the night? Also will it work to cool during the summer , i was under the impression that there would be issues with condensation on the floor if you used it for cooling? Sorry for my non tech knowledge I am slowly being dragged into the 21st century.......

You can use the floor as a storage heater. So a simple thermostat is used to start heat pump during cheap rate electric period, the heat pump just adds heat energy into the floor. Once you get a low energy system the floor becomes quite self regulated. Heat out from the floor is a product of area and delta temperature between it and the room. The closer the dT the lower the output.

 

Summer cooling is similar to heating but it's sucking room heat in from the room. You keep away from condensation issues by flowing relatively high temperature for cooling, my flows vary between 18 and 14ish. This is the side pipe temperature, floor surface temp is a couple of degrees lower than room temperature.

 

Not sure passivhaus ever say you do not need heating, they say you don't need conventional heating systems. People think that means no heating, which isn't correct. The fact that passivhaus state a max heat demand of 10W/m² is purely to allow air heating via MVHR.

 

So our house at around 200m², if Passivhaus certified would need 2kW of heat on the cold design day. Or 48kWh.

[Iceverge]

37 minutes ago, LeenToo said:

Thanks for this, just wondering why you didn't go for UFH from the start ? My initial thinking was that if I am going to build a passive house I wont need heating but I am being disabused of this notion fairly rapidly..........

 

Yeah I was in the same camp. Cost of UFH and ASHP. Stubbornness, cheapness at the time of electricity as backup. 

 

In fairness passivhaus never said houses don't need heating, just that the heat demand is so low it can be provided by heating the MVHR supply. 

 

I would at a minimum put pipes in the ground floor and ducting and wiring for a mono block ASHP. 

 

Just do a couple of UFH pipe runs, you can leave them unconnected and suck it and see to begin with. You'll have the option later too of treating the whole floor like a storage heater on direct electric like  @TerryE  then too.  @terry

[LeenToo]

18 minutes ago, Iceverge said:

 

Yeah I was in the same camp. Cost of UFH and ASHP. Stubbornness, cheapness at the time of electricity as backup. 

 

In fairness passivhaus never said houses don't need heating, just that the heat demand is so low it can be provided by heating the MVHR supply. 

 

I would at a minimum put pipes in the ground floor and ducting and wiring for a mono block ASHP. 

 

Just do a couple of UFH pipe runs, you can leave them unconnected and suck it and see to begin with. You'll have the option later too of treating the whole floor like a storage heater on direct electric like  @TerryE  then too.  @terry

thanks sound advice and really helpful

[LeenToo]

43 minutes ago, JohnMo said:

You can use the floor as a storage heater. So a simple thermostat is used to start heat pump during cheap rate electric period, the heat pump just adds heat energy into the floor. Once you get a low energy system the floor becomes quite self regulated. Heat out from the floor is a product of area and delta temperature between it and the room. The closer the dT the lower the output.

 

Summer cooling is similar to heating but it's sucking room heat in from the room. You keep away from condensation issues by flowing relatively high temperature for cooling, my flows vary between 18 and 14ish. This is the side pipe temperature, floor surface temp is a couple of degrees lower than room temperature.

 

Not sure passivhaus ever say you do not need heating, they say you don't need conventional heating systems. People think that means no heating, which isn't correct. The fact that passivhaus state a max heat demand of 10W/m² is purely to allow air heating via MVHR.

 

So our house at around 200m², if Passivhaus certified would need 2kW of heat on the cold design day. Or 48kWh.

thanks John really appreciate your explanations its helping me get a handle on why i need to factor in a heat pump.....There is a grant for them currently in Ireland so that will take some of the sting out of it........