Reinforcement mortar for facade insulation at current temperatures

Hello everyone,

In 2 weeks we will have our prefabricated house placed on our prefabricated basement and want to insulate the half of the basement that is not in contact with the earth this Saturday. The basement is downhill and the earth-contacting side has already been insulated. Now I am wondering how to best attach the perimeter boards of the lowest row as well as the remaining insulation boards. To even out the irregularities on the bitumen membranes (for sealing the prefabricated joints), I thought of using reinforcing adhesive/mortar. Unfortunately, these have processing temperatures starting from +5 degrees. From STO I found StoLevell FT. This would work from +1 degree but is very expensive at 40€/25kg.

Do you have any ideas on how I can attach the insulation boards at temperatures from +1 to +9 degrees?

The boards must be attached by calendar week 3 of 2019 because the screed will be done then. But since temperatures are more likely to drop than rise, I would like to complete this work beforehand.

Oh yes, one more piece of information. The basement is a purely utility basement.

Many thanks in advance!

You are left only with the mush that is approved for +1, or you have exactly the time when there are no cold nights. Here (400m above sea level) it currently does not drop below 5°C at night either. I would still work with the standard stuff there. At +1 it's a tricky thing, it depends on how many hours after processing you have the +1 and what the temperature was directly during processing.

I have now found an adhesive for insulation boards that works down to -5°. It also compensates for slight unevenness. This should work too, right?

Somehow it usually works (no guarantee for this statement!) I would generally use material from a single source and stay within the respective system of the manufacturer.

Please also note that the adhesive is suitable for bituminous substrates. If the unevenness is too great, the substrate should first be leveled and then the panels glued. At 5 degrees substrate, material, and drying temperature, I would still process "normal" goods.