Is a slight nighttime temperature reduction sensible?

Good day,

first some data about the timber frame house: Kfw 70, heated area (including parts of the basement) approx. 200 sqm, underfloor heating everywhere, brine heat pump, controlled residential ventilation/heat recovery, consumption in 2012 approx. 2500 kWh, location cold region.

I am now considering whether a slight night setback might bring a consumption advantage, even if this is small. I was thinking of a night setback of, for example, 9:00 pm to 5:00 am by 1 degree, controlled with respect to the target return temperature.

What do the experts among you think? Are such considerations worthwhile? Or does the increase/compensation of the target return temperature reduced by one degree in the morning ultimately cost more energy? Are there any experiences/opinions/calculation examples here? Effects on the heat pump, source?

A significant night setback is probably less useful.

Best regards

Your house will then only have cooled down by morning and will have to be heated up again... in the evening you will have the desired temperature again... and it starts all over again.... Savings in the end: nothing... rather more expenses, because the system tries to heat the house up again...

Your house will only have cooled down by tomorrow morning and then has to be heated up again... in the evening you will have the desired temperature again... and it starts all over....

Savings in the end: none... rather more expenses, because the control tries to heat the house up again...

Hello,

I don't believe that the house only "cools down" by tomorrow morning – the heat pump also switches on at night – currently at -5 degrees even 2 or 3 times (from 9 pm to 5 am). We are talking here about only 1 degree lower target return temperature.

I thought it might be more efficient if the heat pump runs longer in the morning to compensate for the setback. I understand that a significant setback doesn't help here. But can one really speak of reheating with just one degree?

Best regards

A technical book states: "The greater the heat storage capacity of the internal building masses and the smaller the heat losses of the building in relation to that, the lower the savings achievable through limited heating operation." In other words: A very well insulated, massive house cannot save anything through nighttime setback because the good insulation and the large storage mass delay the cooling at night. A lightweight and, on top of that, poorly insulated house, on the other hand, can indeed save through nighttime setback.

What is the effect with heat pumps and underfloor heating?

For heat pumps, it is advisable not to perform a setback, especially with air-source heat pumps. With underfloor heating, the reheating must begin correspondingly earlier due to the greater inertia. Accordingly, the savings from the setback are correspondingly lower.

etc.

Hello,

thank you very much for the information.

I am exactly in between
(very) well insulated house, but no storage mass except for the screed…

The inertia is of course correct. I have now set the start time to 7 pm and the end time to 5 am with a reduction of 0.5 degrees in the target return temperature.

Regards