Chapter 2. Utilities and Heating. Ventilation in a private house: why it matters and which system to choose.

Modern houses are sealed: plastic windows, vapour barriers, tight insulation — great for efficiency, disastrous for air exchange. Without organised ventilation CO₂, humidity and mould accumulate. Especially critical in timber frame houses.

Why a modern house doesn't breathe

Old houses had plenty of leaks giving 0.5–1.0 ACH of natural exchange. A sealed frame house drops to 0.1–0.2 ACH — 5–10× below norm. Overnight CO₂ in a bedroom rises from 400–600 to 2000–3000 ppm: headache, fatigue, poor focus. Humidity hits 70–80% and condensate on cold spots breeds mould.

Ventilation types

• Natural — vents + ducts on stack effect. Cheap but unstable. Not enough alone for a frame house

• Mechanical supply — breezers or central unit with filters and preheater

• Mechanical extract — kitchen/bathroom fans create negative pressure

• Balanced with heat recovery — the best option for continuous Leningrad Region living

How heat recovery works

A recuperator transfers heat from outgoing to incoming air without mixing streams. Plate efficiency 70–90%, rotary up to 92%. Example: outside −15 °C, inside +22 °C. Without recovery you heat air by 37 °C; with 80% recovery — air enters at +14.6 °C, only 7.4 °C to go. 80% savings.

Per 7–8 month season for a 100 m² house, a recuperator saves 8 000–15 000 kWh — 45 000–85 000 ₽ with electric heating. Payback 3–5 years.

Air exchange norms

100 m² house with 3–4 occupants — 200–350 m³/h total.

Equipment and cost

Common mistakes

1. No ventilation at all — design before construction, not after move-in

2. Plastic windows with no supply vents — quiet, warm, but airless

3. Extract with no supply — creates negative pressure, flue backdraft (dangerous with a gas boiler)

4. No bathroom ventilation — humidity, mould, damaged finishes

Consequences of no ventilation

Condensate causes black mould — allergies, asthma, chronic respiratory disease, especially dangerous for children and elderly. Wooden frame structures rot; wet insulation stops working. CO₂ above 1500 ppm cuts cognitive performance by 15–25%. Many "sick building syndrome" complaints are just stale air.

StroyInvest24 plans ventilation at the design stage, integrating ducts into the structure.

See also

• Water underfloor heating: benefits and mistakes

• Frame-house wall insulation

• Sound insulation

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