Most buyers look at light, layout and views. The air inside a home, though, decides whether it is pleasant to live in: whether it smells of paint for weeks after the works, whether the corners go black in the second winter, and whether you can ventilate without throwing all the heat out of the window. Here is what is worth knowing — and what to ask when you buy a new-build or freshly renovated flat in Bulgaria.
Paints, varnishes, primers, floor adhesives and some furniture release volatile organic compounds (VOCs). EU law defines them as organic compounds with an initial boiling point of up to 250 °C at standard pressure (Article 2(5), Directive 2004/42/EC). Some evaporate within hours, others over weeks — which is why the first weeks after a renovation are when ventilation matters most.
Directive 2004/42/EC caps the VOC content of decorative paints and varnishes sold in the EU. Under Article 4, the label must state the product subcategory and its limit value in g/l, and the maximum VOC content of the product ready for use. Look at the second figure: the further below the limit, the better.
Current limits (Phase II, in force since 1 January 2010) for the products most used in a home:
| Product | Water-based | Solvent-based |
|---|---|---|
| Interior matt walls and ceilings | 30 g/l | 30 g/l |
| Interior glossy walls and ceilings | 100 g/l | 100 g/l |
| Trim varnishes and woodstains | 130 g/l | 400 g/l |
| Primers | 30 g/l | 350 g/l |
| Two-pack coatings, e.g. for floors | 140 g/l | 500 g/l |
Source: Directive 2004/42/EC, Annex II, Table A.
In practice, water-based products are the norm for walls and ceilings; the real difference is in varnishes for parquet, doors and joinery, where a solvent-based product may legally contain several times more VOCs. The directive does not cover adhesives — for those, look for emissions data in the product's technical sheet.
Formaldehyde comes mainly from wood-based boards (chipboard, MDF) in furniture and built-in wardrobes. Since 6 August 2026, under Regulation (EU) 2023/1464, furniture and wood-based articles placed on the EU market must not exceed 0.062 mg/m³ of formaldehyde in a test chamber. Choosing furniture and certificates is a separate topic; here it is enough to remember that new furniture is another reason to air the home well in the first weeks.
Mould grows where moisture lingers — cold corners, behind wardrobes on external walls, around window frames. The US Environmental Protection Agency (EPA) recommends keeping indoor relative humidity below 60%, ideally between 30% and 50%. A cheap hygrometer tells you a lot within a week.
What helps: airing after cooking, showering and drying laundry; furniture a few centimetres off external walls; a dehumidifier in damp months. If mould returns to the same spot every year, the cause is usually technical — a thermal bridge, a leaking roof or terrace, rising damp on a ground floor — and repainting only hides it.
Radon is a naturally occurring radioactive gas that seeps from the ground and builds up mainly in ground floors and houses. Euratom Directive 2013/59 (Article 74) requires member states to set a reference level for annual average indoor concentration no higher than 300 Bq/m³. Bulgaria's national reference level is 300 Bq/m³ under its Radiation Protection Ordinance, and technical requirements for buildings are set in Ordinance No. RD-02-20-1 of 2019 of the Ministry of Regional Development.
Under the national radon action plan (2018–2022), the Ministry of Health mapped the country in 5×5 km squares. Squares with annual averages above 300 Bq/m³ were found in specific areas — for example around Gotse Delchev, Kresna and Hadzhidimovo, in the Sliven region, Kyustendil and Silistra. If you are buying a house or a ground-floor flat in such an area, a measurement is a sensible step; for a flat on a high floor the risk is far lower.
A heat-recovery unit (рекуператор) brings in fresh air and extracts stale air, passing part of the outgoing heat to the incoming air. The home is ventilated even with windows shut — useful with airtight windows, a noisy street or dust. In new-builds you will see either a central system or individual wall units per room.
If a listing mentions heat recovery, ask:
If you are buying off-plan, see what Acts 14, 15 and 16 mean; if the flat comes as a shell, the second budget before moving in is where to plan low-emission materials too.
A home that smells fresh, has no damp stains and working ventilation shows better at viewings and lets more easily. In our practice, buyers increasingly ask about mould and ventilation at the very first viewing — it pays to have an answer.
Information verified October 2026; general in nature.
If you are viewing a new or renovated home and would like a second pair of eyes, call us or visit our office. We will help you ask the right questions before you sign.
