ᐅ Multi-day Power Outage as Currently Experienced in Berlin: Risks for Heating Systems and Water Pipes?

Good day!

As you probably know from the news, there is currently an extended power outage in the southern part of Berlin, which started on Saturday and is expected to last until Thursday. This makes me wonder: what impact does a multi-day power outage have on building systems when outside temperatures are below freezing?

Let’s assume that a house in an unprepared state would no longer be habitable by usual standards. The fresh water system can be drained, and the local water supplier can be asked to shut off the supply line in the street. This should take care of that aspect. But what about the circulation water in the heating system? It’s unlikely that every radiator or underfloor heating loop can be completely drained reliably.

How long does it take for a well-insulated house, constructed with materials that have good thermal mass, to freeze enough that there is a risk of heating pipes bursting? The consequences would be severe, potentially requiring the removal of the screed…

So, let’s assume minus ten degrees Celsius (14°F) and a week without power. Are there any experience reports from previous events?

Matthias

Pianist schrieb:

So I wonder: what effects would a multi-day power outage at below freezing outdoor temperatures have on the building services?

On the property itself: none at all.

Pianist schrieb:

You can’t reliably completely drain every radiator or underfloor heating system.

You don’t have to. A regular draining process is perfectly sufficient.

Pianist schrieb:

How long would it take for a well-insulated house, built with materials that have good thermal mass, to become so thoroughly frozen that there is a risk of heating pipes bursting? The consequences would be severe, up to having to remove the screed…

Since that scenario doesn’t occur (because you are draining the system), it remains theoretical.

Pianist schrieb:

So let’s assume minus ten degrees and a week without electricity. Are there any practical experiences from past events?

Very roughly (and it can be calculated), the indoor temperature in such a house would drop to about 2–5°C (36–41°F) after around two weeks. It could take perhaps another two weeks for frost to penetrate deep enough to cause damage.
Why? Because heat always comes in through the ground slab or basement, effectively "heating" the house from below. Plus, the sun plays a role. When the sun is out, the interior warms up quickly. Especially in the screed (above the ground slab/basement), which has a very high thermal storage capacity, temperatures remain well above freezing for much longer. Also, there must be enough water in the pipes to expand at all. Moreover, the material would need to break (and the screed applies counterpressure).

I would consider the risk of burst pipes about as realistic as a meteorite hitting your roof.

In the end, this is more of an analysis that has to refer to a specific house.

• For KfW 40 standard, I wouldn’t worry at all and wouldn’t take any immediate action. These houses often have an emergency power supply via the solar system and battery, so they might not even notice it...
• For KfW 55, with appropriate technology, it will be similar – in any case, I also wouldn’t take any action there.
• For standard new builds, I would personally start by heating internally using existing systems (wood stove?) or additions (gas or kerosene heaters), but otherwise wouldn’t do anything.
• For all other buildings, from my point of view, a general statement is nonsense – for example, we have a house from the late 1990s with a solar system, battery, and emergency power supply that can also be fueled externally (generator). I would simply continue living there. Otherwise, I support the last two paragraphs from @nordanney, although I would replace the meteorite with a frozen disposal ball from an airplane...

PS: And yes – I would be more cautious with ventilation in that case...

PPS: After a death in the family and a multi-year legal dispute, we experienced a water damage after three years caused by a frozen heating pipe in a genuine old building from the 1930s... so even there...

But if nothing ever happens, then you actually wouldn’t need to drain the system, right? I had thought about draining the system in the summer and replacing the fill with something frost-resistant.

The fundamental question is also in what way and with what goal you prepare. Whether you leave the house in such a situation to at least avoid serious damage, or whether you create a fallback option that allows you to stay living in the house. For that, you would probably need a power input point that is accessible from outside, like a red 32A CEE socket (male), and a manual switch to isolate the house from the public grid. Then you could connect a diesel generator. The next question would be whether you keep such equipment permanently or only rent it if needed...

For a new build, I would definitely give serious thought to what a good overall concept could look like. Even with photovoltaic panels and a 10kWh battery storage, you would quickly reach your limits... (even if you do without cooking)

Jesse Custer schrieb:

- For KfW 55 standard with appropriate technology, it will be similar – in any case, I wouldn’t do anything there either.

- For typical new builds, I would personally start by heating internally using existing technology (wood stove?) or additional options (gas or kerosene heaters), but otherwise not take any further action.

Where is the real difference (apart from minor details)? Everything new complies with the Building Energy Act, which is almost comparable to KfW 55 (KfW 55 requires a better thermal transmittance value, while the Building Energy Act has stricter individual component requirements) and KfW 40 is uncritical in this regard. Of course, backup power with photovoltaics/storage and/or a wood stove is great.

But thanks to the generally very stable electricity supply, you will only rarely risk being without power for more than a few hours.

nordanney schrieb:

But thanks to the overall very relaxed electricity situation, you would only rarely face the problem of being without power for more than a few hours at a time.

Tell that to those affected...

Although I also believe that the situation where I live in Berlin is not as severe as it is there, experience shows that perpetrators are extremely well informed and know exactly where they can cause the most damage.