[jdadj]

Seems like the article is addressing two orthogonal issues — home insulation and heat pumps. They are suggesting that heat pumps depend on improved home insulation. Why?

Is the idea that heat pumps don’t pack enough punch to replace boilers on their own, and they need to be combined with a more efficient building envelope in order to be sufficient?

[morsch]

Gas heating in old construction heats up the water to 80+C. Heat pumps typically result in lower temperatures. This is not an issue in new construction, which often has floor heating or special radiators. But old construction has radiators that struggle to heat up the interior at these water temperatures -- unless you improve the insulation, which is sensible anyway.

[Gibbon1]

My few thoughts on insulation.

The problem with insulation is retrofitting it is expensive and carries a huge risk because older houses are designed around the idea that they breath.

The current practice of insulating inside the envelope is just so blindly stupid I can't wrap my head around why people think it's a good idea. If you work it out, insulation should go on the outside of the envelop. Think insulated siding and roof panels. Granted I'm now seeing that,

And with insulation you quickly run into the problem that the benefits rapidly diminish while the cost is linear. R30 doesn't save you three times R10.

At some point it's be cheaper to put solar panels on the roof to run a heat pump than add more insulation.

[ClumsyPilot]

> retrofitting it is expensive and carries a huge risk

Because construction industry is shockingly incompetent and corrupt.

Lived in a few newbuilds, they are full of fuckups - walls aren't straight, the hole for a fire sprinkler is not where the sprinkler is, so in case of fire it won't actually work. The hot water plumbing was not up to spec and has discharged a swimming pool of boiling water into someone's apartment, they are lucky no-one died.

They will not get something as complex and humidity control right.

[jibbit]

Yes that’s correct. The heat pump is more expensive to run than the gas boiler it replaces, and can’t match the output.

[pretendgeneer]

That's not true. Heat pumps are cheaper to run than gas heating, I removed my old single room gas heater for a ducted split system total cost reduction was 30% even before Russian invasion caused gas prices to spike. And house is much warmer.

Gas boilers generally produce much hotter water, so the radiators they use tend to be small.

Heat pumps gain more efficiency if you can reduce the output temperature. So running a heat pump at max efficiency through radiators designed for a gas system, won't put out as much heat into the room.

So you have two options, increase the size of the radiators or increase the insulation. It's better to increase the insulation as you gain the benefit of both warmer room and less energy required to heat a room.

[msh]

I think that depends a lot on location dependend prices. I am in denmark and my ehat pump is significantly cheaper to run than the gas boiler that it replaced, even if you compare it with pre ukraine/pre covid gas prices.

[chii]

which begs the question - why would anyone switch from a gas boiler to heat pump then, if they only consider economic utility, and none of the externalities?