Heating and ventilation guide

Why a guide is worth it

When mould appears, landlord and tenant almost always argue about the cause: is it the building or the airing? In court you first have to show that the cause does not lie in the fabric of the building. Only then does it come down to whether your tenant aired and heated properly.

A signed guide proves that your tenant knew what was expected. It does not replace an expert report, but it makes the question of how the flat was used easier to answer.

What the guide covers

You only switch on the sections on extractor hoods, new buildings and ventilation systems if they apply to the flat.

• why mould forms and what airing and heating do about it
• humidity: 40 to 60% during the heating season, checked with a hygrometer
• airing properly: short bursts and cross-ventilation, three to four times a day
• heating properly: all rooms, turning the heating down rather than off when away
• removing moisture from cooking, showering and drying laundry
• furniture on outside walls with a 5 to 10 cm gap
• special cases such as new buildings, ventilation systems, airtight windows and holidays
• what your tenant should do on noticing damp or mould
• a checklist with the essentials at a glance

How long to air per month

The colder it is outside, the faster the air is exchanged. The guide therefore names no fixed time. As a rough orientation for short, intense airing, German consumer advice centres and the Federal Environment Agency give these guide values:

• December to February: 5 minutes
• March and November: 10 minutes
• April and October: 15 minutes
• May and September: 20 minutes
• June to August: 25 to 30 minutes

When mould appears

Your tenant must report damp and mould straight away, ideally in writing with photos. The guide also tells them what not to do: do not paint over mould, do not brush it off dry and do not treat larger areas themselves.

Have the cause checked by an expert before you make accusations. If it is provably down to airing, the warning letter about poor ventilation and heating helps.

When to hand over the guide

Ideally you hand over the guide together with the rental agreement and have your tenant sign for receipt. With existing tenants you can do it at any time, because the guide only contains recommendations. A fresh start makes sense at the beginning of the heating season or after new, tighter windows.

If ventilation is also part of the building rules, the house rules refer to it. At handover, the flat handover checklist helps you remember the guide and the other annexes. In CIRO you put the guide, rental agreement and house rules in the tenant portal for download.

How to go about it

1. Enter the names of landlord and tenant, plus the annex number and the date of the rental agreement.
2. Switch on the sections that apply to the flat: extractor hood, new building or ventilation system with maintenance.
3. Enter your email address. CIRO sends you the PDF.
4. Attach the guide to the rental agreement and have your tenant sign for receipt.