Heating the construction site in winter

Hello everyone,

we are still renovating an old building from 1920 and are now finally in the third year at the point where the shell (and the new roof) is standing. Since the targets still planned for this year, such as the completion of an extension, completion of the facade, and the start of interior construction, were missed, the shell now stands at about 5° and ~90% humidity. However, the new windows are installed, so except for the hole to the extension (closed with boards and beams), the house is actually reasonably sealed.

Now dry construction is supposed to continue in KW2 2024. Until then, according to the architect, we have to bring the house to a temperature that prevents damage to the dry construction walls and allows interior construction to start.

Can anyone here generally give me tips from their own experience on how to do this most cost-effectively or how they solved the problem themselves? I’m looking forward to all suggestions/experiences, and I can provide more information if needed. Thanks in advance!

The obvious first step would be to close the hole for the extension not just with a few wooden slats, but additionally with Styrofoam or mineral wool. What kind of heating? Is it still there?

Otherwise, there won't be any cost-effective option because everything runs on electricity.

Oil radiators are quite good as frost guards; I wouldn't have dared to run fan heaters 24/7.

Exactly, I obviously wanted to insulate the hole for the extension before starting the work. At the moment, there is no fixed heating installed. As I said, it is a complete shell construction from which absolutely everything had to be removed.

What I still have are about two electric 2.5 kW heaters on wheels. We have three floors (~74m² + ~53m² + ~42m²). Would something like that be an option? How many would I probably need? Depending on the outside temperature, I would only run them as briefly as possible during the day, since the warmth should be kept inside for some time.

How warm does it need to get? Does the drywall installer need a certain temperature or is frost-free enough? If a higher temperature is required, nothing should bypass a large fan heater (the ones with a heavy current connection). Otherwise, I would just set up the two radiators on the lower floors and see how the temperature develops. It will get cool again at the end of the week. Especially cheap, no option is likely to be, since without installation basically only heating with electricity remains.

There should be a chimney. These houses always used to have stoves. Whether that is practical, you will have to see. But I also suspect that heating with electricity is the easiest option here. Yes, it costs, but there is no way around it. I assume you need at least 5 degrees in the house? For processing the materials? Or what do the craftsmen have in mind?