3 ms·

A large percentage of homes in the UK are not and cannot reasonably be insulated well enough for heat pumps to work. I don't quite understand why I can't just

by throwaway22032 3y ago

A large percentage of homes in the UK are not and cannot reasonably be insulated well enough for heat pumps to work. I don't quite understand why I can't just run a heat pump 2-3x more powerful, but apparently that's not the done thing.

Maxion 3y ago
Can you elaborate on the insulation part? My understanding is that if you have a poorly insulated house you just need more heat energy to keep it warm, I.e. a larger heat pump.
- throwaway22032 3y ago
  That's my logical understanding as well. I'm wondering whether it just ends up being significantly more expensive than gas heating so no-one talks about it.
  - pdonis 3y ago
    > it just ends up being significantly more expensive than gas heating Bingo.
  - tomthe 3y ago
    A heat pump is much more effective if you only have a small temperature difference [0]. If your house is well insulated and you have underfloor heating, you can heat your house with 40°C (sorry for European units) water to keep it warm inside. If you have poor insulation and small heating elements, you need much hotter water (>60°C). A heat pump can have a carnot efficiency (theoretically achievable efficiency) of >10 to warm water from 20 to 40 degrees, but only ~5 if you have to heat it from 20 to 60 degrees (not sure about the numbers, but you get the idea). [0]: https://energyeducation.ca/encyclopedia/Carnot_efficiency https://energyeducation.ca/encyclopedia/Carnot_efficiency
Gasp0de 3y ago
The problem lies in the radiators. Heat pumps can not "lift" the temperature more than 30-40 degrees Celsius without getting inefficient. So at -5°C outside, you can only warm water up to 35°C. At this temperature, your old radiator doesn't transfer enough energy from the 35°C warm water to the 20°C room. You would need to either heavily insulate your house or replace the radiators.
ZeroGravitas 3y ago
This would be more convincing a reason if the new builds over the last couple of decades had been fitted with good insulation and heat pumps. Since they dragged their heels on that low hanging fruit, I'll suggest they've not really even tried to make it work elsewhere. (There have been some improvements so I don't want to get carried away, but there's also estimates of many Billions wasted by not doing what was obviously a good idea at the time). Also, recent real world experience suggests more older buildings than you think will work. Britain doesn't get that cold for that long and modern heatpumps and insulation techniques are pretty good.

Maxion 3y ago

Can you elaborate on the insulation part? My understanding is that if you have a poorly insulated house you just need more heat energy to keep it warm, I.e. a larger heat pump.

throwaway22032 3y ago
That's my logical understanding as well. I'm wondering whether it just ends up being significantly more expensive than gas heating so no-one talks about it.
- pdonis 3y ago
  > it just ends up being significantly more expensive than gas heating Bingo.
- tomthe 3y ago
  A heat pump is much more effective if you only have a small temperature difference [0]. If your house is well insulated and you have underfloor heating, you can heat your house with 40°C (sorry for European units) water to keep it warm inside. If you have poor insulation and small heating elements, you need much hotter water (>60°C). A heat pump can have a carnot efficiency (theoretically achievable efficiency) of >10 to warm water from 20 to 40 degrees, but only ~5 if you have to heat it from 20 to 60 degrees (not sure about the numbers, but you get the idea). [0]: https://energyeducation.ca/encyclopedia/Carnot_efficiency https://energyeducation.ca/encyclopedia/Carnot_efficiency

Gasp0de 3y ago

The problem lies in the radiators. Heat pumps can not "lift" the temperature more than 30-40 degrees Celsius without getting inefficient. So at -5°C outside, you can only warm water up to 35°C. At this temperature, your old radiator doesn't transfer enough energy from the 35°C warm water to the 20°C room. You would need to either heavily insulate your house or replace the radiators.

ZeroGravitas 3y ago

This would be more convincing a reason if the new builds over the last couple of decades had been fitted with good insulation and heat pumps. Since they dragged their heels on that low hanging fruit, I'll suggest they've not really even tried to make it work elsewhere. (There have been some improvements so I don't want to get carried away, but there's also estimates of many Billions wasted by not doing what was obviously a good idea at the time). Also, recent real world experience suggests more older buildings than you think will work. Britain doesn't get that cold for that long and modern heatpumps and insulation techniques are pretty good.