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Should I insulate the flow and return on my rad circuit?

 
Air Source Heat Pumps (ASHPs)
Last Post by AdamK 1 day ago
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 AdamK
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Topic starter 29/03/2025 2:18 pm  

not sure if i should insulate the 28mm flow and return that goes to the radiator circuits. they are quite a long 8m approx. L shape run with other rads coming off them. im just worried once the water runs a further 6m or so in 22mm and 15mm there wont be much heat left.

This topic was modified 2 days ago by Mars
This topic was modified 2 days ago by AdamK

   
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bontwoody
 bontwoody
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29/03/2025 3:02 pm  

I would as I would like the heat to be emitted in the room primarily but there is a school of thought that thinks as long as the heat is going into the house it’s not that important. Obviously if the run is in the loft then insulate. 

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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 Old_Scientist
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29/03/2025 3:45 pm  

As @bontwoody says, if they are inside the heated envelope of the house then it becomes a question of whether it is more beneficial for more of the heat to reach the radiators in question.

Another consideration for not insulating, is that with low temperature heating systems (e.g, ASHPs), we are trying to maximise the size of our emitters, and those pipes when uninsulated increase the amount of heat the system can emit into the property, so there are benefits there besides just the cost savings on the insulation. They probably act as an additional radiator in the system.

Is it possible to try running uninsulated to start with, and then add insulation later if the affected rooms are too cold? Or would adding insulation later not be possible due to pipe placement? Someone smarter than I will probably be able to calculate how much heat would be lost on your 28mm run to see if it's worthwhile insulating or if it's going to be insignificant.

I have not insulated mine because I'd rather maximise the emitter size, and I'm already struggling with a narrow dT so the more heat I can dissipate before the return flow makes it back to the heat pump, the better (e.g, it may help me go from a dT of 3C to 3.5C)

 

This post was modified 2 days ago 2 times by Old_Scientist

Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 3.645kWp solar (south facing), Fox ESS inverter.
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.


   
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bontwoody
 bontwoody
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29/03/2025 5:50 pm  

@old_scientist good point about increasing the size of the emitter!

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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 AdamK
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Topic starter 30/03/2025 11:10 am  

my worry is most of the 28mm and 22mm runs are in the kitchen ceiling so quite a bit of heat is going into the corner of the house where we dont sit most of the time. there is a bedroom above one half of the kitchen, but there is some fibre glass insulation in this ceiling/floor area as was once an external roof before the bedroom was built over it, the rest is under an upstairs bathroom.


   
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bontwoody
 bontwoody
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30/03/2025 11:18 am  

@adamk I think I would insulate as much as I could then.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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 AdamK
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Topic starter 30/03/2025 12:13 pm  

this is a rough diagram of the pipe runs, beyond the 28/22mm runs it drops to 15mm to rads. for scale the Kitchen is about 5.3m x 3.2m.

Screenshot 2025 02 25 165155
This post was modified 2 days ago by AdamK

   
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 AdamK
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Topic starter 30/03/2025 2:15 pm  

red is 28mm orange is 22mm.


   
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