Ventilation Performance

The Critical Role of Adequate Ventilation

Healthy buildings typically require at least 0.5 air changes per hour to mitigate the accumulation of indoor pollutants such as cigarette smoke, carbon monoxide, and solvent vapours, and to manage moisture generated from everyday activities like bathing and cooking. Without controlled ventilation, this moisture can condense on the fabric of the building, fostering an environment conducive to mould and dust mites, and potentially leading to building damage and reduced energy efficiency.

Mechanical Ventilation with Heat Recovery (MVHR)

MVHR systems offer a 24-hour solution to these challenges, circulating fresh air throughout the structure while simultaneously removing excess moisture and pollutants. By extracting heat from stale air and transferring it to the incoming fresh air through a high-efficiency heat exchanger, MVHR systems can recover up to 90% of the outgoing air’s heat, significantly reducing heating costs. Designed to operate continuously, these systems ensure that indoor air quality is maintained without compromising the building’s energy efficiency.

Alternative Ventilation Strategies

Passive Stack Ventilation (PSV): PSV systems naturally channel warm, moist air out through ducts to a vent in the roof, relying on natural air leakage for replacement air. However, the enhanced air-tightness of SIP buildings necessitates that inlet vents remain open, risking over-ventilation and energy inefficiency. PSV does not allow for heat recovery, and the incoming air’s temperature and humidity mirror those outside.

Positive Input Ventilation (PIV): PIV systems pressurize the building by blowing fresh air in, forcing stale air out through any available openings. In airtight SIP constructions, this method may require permanently open extract vents, which could compromise energy efficiency. Some PIV systems mitigate this by heating the incoming air using heat from the roof space.

Extractor Fans: While single-room or multi-room extractor fans can remove moist air from wet rooms, they do not offer a whole-house solution. These fans allow heat to escape and do not provide heat recovery or filtration, reducing the structure’s overall energy efficiency.

Single-room or multi-room extractor fans blow moist air out of wet rooms, allowing heat to escape and lack the power and ability to ventilate, recover heat or filter the incoming air, reducing energy efficiency.

Regulatory Guidelines and Further Information

For buildings constructed with SIPs, ensuring adequate ventilation while maintaining energy efficiency is a balance that requires careful planning and consideration of the specific ventilation needs. Further guidance on ventilation performance requirements can be found within the Approved Document F of the Building Regulations – Means of Ventilation.

Incorporating the right ventilation system into your SIP house can have a profound impact on the health and comfort of its occupants, as well as on the building’s energy consumption and environmental footprint.